Orchid Cultivation Guide: Key Points for Growing Orchids Through the 24 Solar Terms

OrchidCultivation: Orchid Care Through the 24 Solar Terms

The Earth takes 365 days, 5 hours, 48 minutes and 46 seconds to complete one revolution around the Sun, and also rotates once every 24 hours. Because the plane of the Earth's orbit is not aligned with the equatorial plane but maintains a certain tilt, the position wherethe four seasonssunlight strikes the Earth directly differs throughout the year. In the Northern Hemisphere, when the sun shines directly at 23.5 degrees north latitude, it is astronomically called the Summer Solstice; when the sun shines directly at 23.5 degrees south latitude, it is called the Winter Solstice; the Summer Solstice and Winter Solstice indicate that summer and winter are already at their midpoints. When the sun shines directly over the equator twice a year, these are the Spring Equinox and Autumn Equinox respectively, marking the midpoint of spring and autumn, and on these two days day and night are equal in length. The solar terms that reflectthe four seasonschanges are: Start of Spring, Spring Equinox, Start of Summer, Summer Solstice, Start of Autumn, Autumn Equinox, Start of Winter, and Winter Solstice, 8 solar terms in total. Among them, Start of Spring, Start of Summer, Start of Autumn, and Start of Winter are called the “Four Starts,” meaningthe four seasonsare beginning. Those reflecting temperature changes are: Minor Heat, Major Heat, End of Heat, Minor Cold, and Major Cold, 5 solar terms. Those reflecting weather phenomena are: Rain Water, Grain Rain, White Dew, Cold Dew, Frost's Descent, Minor Snow, and Major Snow, 7 solar terms. Those reflecting phenological phenomena are the four solar terms: Awakening of Insects, Pure Brightness, Grain Buds, and Grain in Ear.

The twenty-four solar terms are unique to China and were mainly established for agricultural production, so they also have universal practical significance for orchid cultivation. Below they are introduced solar term by solar term. As for the cultivation techniques for orchids in each solar term, fellow orchid growers are invited to express their own views and exchange ideas.

I. Start of Spring

Since the Qin Dynasty, our country has always regarded the Start of Spring as the beginning of spring. The Start of Spring is divided astronomically, while in nature and in people's minds, spring is warmth, birdsong and fragrant flowers; spring is growth, plowing and sowing. In climatology, spring refers to the period when the five-day mean temperature is 10°C to 22°C. When the Start of Spring arrives, people clearly feel that the days have grown longer and the sun warmer. Temperature, sunshine and rainfall are often at a turning point in the year at this time, tending to rise or increase. Early spring crops grow faster, and when rapeseed bolts and wheat joints, water consumption increases, so timely irrigation and topdressing should be applied to promote growth. Agricultural proverbs remind people: “When Start of Spring and Rain Water arrive, rise early and sleep late.” Preparations for main spring plowing also begin. Although “spring” has begun, most areas of the basin will still see frost, and in a few years there will even be scenes of “white snow, thinking spring's colors are late, deliberately flutters through the courtyard trees as flying flowers.” These climatic characteristics should all be considered when arranging agricultural production. Where do people often love to search for signs of spring? In the buds peeking out on the willow branches, “tenderer than gold, softer than silk”; in the little grass in the soil eager to emerge, waiting for “the spring wind to blow and bring it back to life”; and the people working hard in the fields to win a new harvest are creating true spring with their own hands.

For orchid enthusiasts in the Jiangsu-Zhejiang area, orchids during this period are still in the “vernalization” stage. Keep the temperature above zero (minimum nighttime temperature above zero, maximum daytime temperature below 12-15 degrees), basically do not water, or just slightly moisten along the edge of the pot. Do not let the north wind blow directly onthe orchid plants。

II. Rain Water

The meaning of the Rain Water solar term is that rainfall begins and the amount of rain gradually increases. In the Yellow River basin, the birthplace of the twenty-four solar terms, before Rain Water the weather is cold, with snowflakes flying but rarely the sound of pattering rain. After Rain Water, temperatures generally rise above 0°C, snow gradually decreases and rain gradually increases. But in the warm Sichuan Basin, even in deep winter, rainfall is not rare. During this period in our province's basin, the five-day mean temperature is mostly above 10°C, peaches and plums are in bud, cherry blossoms are blooming, and climatological spring has truly arrived. Except in a few years, the frost period also ends at this point. Grafting fruit trees and afforestation are timely now. After the winter drought, the basin often has spring drought, especially in the western basin where “spring rain is as precious as oil.” In agriculture, attention should be paid to preserving soil moisture and irrigating timely to meet the water supply during the critical period when wheat is jointing and booting and rapeseed is bolting and flowering. The western Sichuan plateau and mountainous areas are still in the dry season, with low air humidity and high wind speed, making forest fires easy to occur. In addition, cold waves can cause sharp temperature drops and blizzards, which are extremely harmful to old, weak and young livestock. All of these require special attention and prevention. Time passes easily, the seasons urge people on, and “the whole year's work depends on a good start in spring.” Management of early spring crops and preparation for main spring plowing should both be carried out promptly, striving to make this year better than last.

For orchid enthusiasts in the Jiangsu-Zhejiang area, there will be some rain or sleet during this period, and attention should still be paid to keeping warm. As temperatures gradually rise, water along the edge of the pot to thirty percent (stopping before water comes out of the bottom of the pot). Since the climate is not yet stable and cold air still moves south, do not let the orchid plants stay outside overnight. Note: when flower buds are shooting up stems, do not fertilize.

III. Awakening of Insects

The Awakening of Insects reflects natural phenological phenomena, and its meaning is: spring thunder rumbles, awakening the hibernating animals dormant in the soil. At this time, temperatures rise relatively quickly, and most areas of the Yangtze River basin gradually have spring thunder. In the western basin and southern Liangshan Prefecture, spring thunder can also be heard for the first time during Rain Water and Awakening of Insects in normal years; while in the northwestern basin, except in a few years, thunder generally does not occur until Pure Brightness. When Awakening of Insects arrives, most areas of our country enter the busy spring plowing season. Truly: the seasons wait for no one, and every moment is worth a thousand in gold. During the Awakening of Insects solar term in our province's basin, the average temperature is generally 12°C to 14°C, more than 3°C higher than during Rain Water, making it the solar term with the fastest temperature rise of the year. Sunshine hours also increase noticeably. However, because cold and warm air alternate, the weather is unstable and temperatures fluctuate greatly. In the Yangtze River valley area of the southeastern basin, in most years during Awakening of Insects temperatures remain stable above 12°C, favorable for rice and corn sowing; in other areas, low-temperature weather with daily mean temperatures below 12°C often occurs for more than 3 consecutive days, so early sowing should not be done blindly. Although temperatures rise rapidly during Awakening of Insects, the increase in rainfall is limited. In the central and northwestern basin during Awakening of Insects, total rainfall is only about 10 millimeters, and after the usual winter drought, spring drought often begins to appear. At this time, wheat booting and rapeseed flowering are both in periods of relatively high water demand and are sensitive to water requirements, so spring drought often becomes an important factor affecting early spring crop yields. Afforestation should also take this climatic characteristic into account, and after planting, watering should be done frequently to strive to improve the survival rate of saplings. During Awakening of Insects, spring light is bright and everything is renewed. Through careful observation and accumulation of phenological knowledge, it will be helpful for arranging farming activities according to local conditions.

From agricultural proverbs we know that “at the first thunder of Awakening of Insects, snakes and insects crawl out,” and although spring is already in the air, orchid plants still cannot leave the house. Choose a sunny, windless day to spray insecticide once (pay attention to concentration). Note: orchid plants that have not left the house cannot be fertilized; if fertilized, orchid leaves will certainly develop scorched tips. WhenCymbidium goeringiihas finished blooming, promptly prune it off;Cymbidium faberiwhen flower buds are shooting up, pay attention to water control (do not splash water on flower buds or leaf centers)

IV. Spring Equinox

The Spring Equinox is one of the solar terms reflecting the changes of the four seasons. In ancient China, the custom was to use Start of Spring, Start of Summer, Start of Autumn, and Start of Winter to indicate the beginning of the four seasons. The Spring Equinox, Summer Solstice, Autumn Equinox, and Winter Solstice are in the middle of each season. On the day of the Spring Equinox, sunlight shines directly on the equator, and day and night are equal in length everywhere on Earth, so in ancient times the Spring Equinox and Autumn Equinox were also called “day-night division,” and there is a folk proverb, “Spring Equinox and Autumn Equinox, day and night divide equally.” After the Spring Equinox, overwintering crops in most areas of our country enter the spring growth stage. In central China there is an agricultural proverb, “At Spring Equinox the wheat rises, every moment is worth a thousand in gold.” Temperatures continue to rise in all parts of our country, but generally not as quickly as during the period from Rain Water to Spring Equinox. In late March, the average temperature is mostly 13°C to 15°C in the northern basin and 15°C to 16°C in the southern basin. In most plateau areas the snow and ice have already melted, with ten-day average temperatures of about 5°C to 10°C. In the river valley areas of the Jinsha River and Anning River in southwestern China, temperatures are highest, already averaging around 18°C to 20°C. In the basin, except for the marginal mountain areas, in about seven or eight out of ten years the daily mean temperature steadily rises above 12°C, favorable for sowing crops such as rice and corn, and very suitable for afforestation. However, around the Spring Equinox the basin often experiences a relatively strong cold air intrusion, with temperatures dropping significantly and the minimum temperature falling below 5°C. Sometimes small cold air masses follow one after another, creating several consecutive days of low temperature and overcast rain, unfavorable to agricultural production. Based on this characteristic, full use should be made of weather forecasts and sowing should be done at the right time by seizing the end of the cold spell and the start of the warm one.

Although literally the Spring Equinox means spring is already half over, in fact for the Jianghuai basin spring has only just begun, with occasional “sudden heat” and frequent cold spells; it is the time when temperatures are most unstable, so orchid plants still do not leave the house (in the morning they can be placed under the eaves to sunbathe). For orchid plants that were not sprayed at “Awakening of Insects,” carry out one spraying to remove insects and wash the leaves (note that water must not be too much and must be drained before nightfall). Do not fertilize.

V. Pure Brightness

Pure Brightness is a solar term that represents phenological phenomena, containing the meaning of clear weather and luxuriant vegetation. On the day of Pure Brightness, there are folk customs such as spring outings, cold food, and tomb sweeping. As the saying goes: “Pure Brightness ends snow, Grain Rain ends frost.” When Pure Brightness arrives, the basin's climate is warm and spring is at its fullest. But around Pure Brightness, cold air still intrudes from time to time, even causing the daily mean temperature to remain below 12°C for more than 3 consecutive days, causing rotten seedlings in middle rice and dead seedlings in early rice, so rice sowing and transplanting should avoid the end of warm spells and the start of cold ones. In the western Sichuan plateau, livestock are weakened by the harsh winter and insufficient forage, so strict precautions are needed against the harm to old, weak and young livestock from strong temperature drops after the beginning of spring. “During Pure Brightness the rain falls thick and fast” is the Tang Dynasty poet Du Mu's portrayal of spring rain in Jiangnan. But as far as Sichuan is concerned, this is not the case. Especially in the western basin, which is often in a spring drought period, rainfall in early April is generally only 10 to 20 millimeters, less than half that of the Jiangnan area; although the eastern basin has more spring rain, rainfall in early April is generally only 20 to 40 millimeters, and natural precipitation is also insufficient for agricultural production, requiring supplementary water stored from the previous year. In addition, April is the month with the most hail in Liangshan Prefecture in the whole year, so defense against hail disasters should be strengthened.

Pure Brightness, pure and bright, the weather begins to warm. The Jiangnan region enters spring, while the Huanghuai basin still has cold spells. Orchid plants begin to sprout. Note: plants that have sprouted can be watered; plants that have not sprouted should still be kept mainly moist. Do not fertilize.

VI. Grain Rain

As the saying goes: “Rain brings a hundred grains to life.” With sufficient and timely rainfall, grain crops can grow vigorously. This is the meaning of the Grain Rain solar term. During Grain Rain in the Sichuan Basin, “poplar flowers fall and the cuckoo cries,” willow catkins drift down, cuckoos call at night, peonies burst into bloom, and cherries turn red and ripe; the natural scenery tells people that late spring has arrived. At this time, temperatures in the basin rise relatively quickly. In late April the average temperature, except in parts of the northern and western basin, has already reached 20°C to 22°C, more than 2°C higher than in mid-month. In the eastern basin there are often one or two days with high temperatures above 30, making people begin to feel the heat. The low-altitude river valley areas of southwestern Sichuan have already entered summer. The basin's climatic characteristic of relatively high spring temperatures is favorable for taking early measures in main spring crop cultivation. The suitable temperature for sweet potato transplanting is 18°C to 22°C, which can already be met at this time. Experience in the old drought areas of the basin proves that sweet potatoes planted early after Grain Rain can, before the summer drought, have their vines and leaves cover the beds, enhancing drought resistance and achieving high and stable yields. In the eastern part of our province's basin, rainfall is relatively abundant at this time, with late April rainfall of about 30 to 50 millimeters in normal years. The first heavy rain of the year generally occurs during this period, favorable for rice transplanting and the seedling-stage growth of corn and cotton. But in the rest of the basin, rainfall is mostly less than 30 millimeters, requiring irrigation measures to reduce the impact of drought. In the western Sichuan plateau and mountainous areas, the dry season continues, with precipitation generally only 5 to 20 millimeters. Rainfall around Grain Rain in the basin often “steals in with the wind at night, moistening things silently,” because “night rain in the Ba mountains” occurs most often in April and May. “In Shu the sky often has night rain, and by morning the river railings are already clear.” This weather of night rain and daytime clearing is quite suitable for the growth of main spring crops and the harvest of early spring crops.

Spring has truly arrived, and the time for orchid plants to grow desperately has come. The nutrients in last year's potting soil are no longer enough for the needs of the orchid seedlings. You can apply light nitrogen fertilizer for the first time. (1. Growth-promoting fertilizer)

VII. Grain Rain

As the saying goes: “Rain brings a hundred grains to life.” With sufficient and timely rainfall, grain crops can grow vigorously. This is the meaning of the Grain Rain solar term. During Grain Rain in the Sichuan Basin, “poplar flowers fall and the cuckoo cries,” willow catkins drift down, cuckoos call at night, peonies burst into bloom, and cherries turn red and ripe; the natural scenery tells people that late spring has arrived. At this time, temperatures in the basin rise relatively quickly. In late April the average temperature, except in parts of the northern and western basin, has already reached 20°C to 22°C, more than 2°C higher than in mid-month. In the eastern basin there are often one or two days with high temperatures above 30, making people begin to feel the heat. The low-altitude river valley areas of southwestern Sichuan have already entered summer. The basin's climatic characteristic of relatively high spring temperatures is favorable for taking early measures in main spring crop cultivation. The suitable temperature for sweet potato transplanting is 18°C to 22°C, which can already be met at this time. Experience in the old drought areas of the basin proves that sweet potatoes planted early after Grain Rain can, before the summer drought, have their vines and leaves cover the beds, enhancing drought resistance and achieving high and stable yields. In the eastern part of our province's basin, rainfall is relatively abundant at this time, with late April rainfall of about 30 to 50 millimeters in normal years. The first heavy rain of the year generally occurs during this period, favorable for rice transplanting and the seedling-stage growth of corn and cotton. But in the rest of the basin, rainfall is mostly less than 30 millimeters, requiring irrigation measures to reduce the impact of drought. In the western Sichuan plateau and mountainous areas, the dry season continues, with precipitation generally only 5 to 20 millimeters. Rainfall around Grain Rain in the basin often “steals in with the wind at night, moistening things silently,” because “night rain in the Ba mountains” occurs most often in April and May. “In Shu the sky often has night rain, and by morning the river railings are already clear.” This weather of night rain and daytime clearing is quite suitable for the growth of main spring crops and the harvest of early spring crops.

Orchid plants are growing vigorously, and fungi and insects also begin to show their power. Spray the second disinfection and insecticide treatment of the year. One week later, apply the second bud-promoting fertilizer to encourage new shoots to sprout as much as possible.

VIII. Grain Buds

Most of the twenty-four solar terms can be understood from their names, but Grain Buds is somewhat puzzling. Originally, Grain Buds means that summer-ripening crops such as wheat are filling out and milking, and the grains begin to plump up. Agricultural proverbs of the Sichuan Basin give Grain Buds a new meaning: “If Grain Buds is not full, the field ridges dry and crack”; “If Grain Buds is not full, Grain in Ear does not matter.” “Full” is used to describe the abundance or shortage of rainwater, pointing out that if the fields cannot store enough water at Grain Buds, the field ridges may dry and crack, and even at Grain in Ear rice cannot be transplanted. Because “at Start of Summer and Grain Buds it is exactly time to transplant rice,” and “rice seedlings rush to Grain Buds, grain rushes to autumn,” Grain Buds is exactly the season suitable for rice transplanting. Whether the summer drought in the basin is severe or not has a direct relationship with the amount of rice transplanting area; and whether transplanting is early or late is closely related to the level of rice yield per unit area. In the central and western basin, winter drought and spring drought often occur, and heavy rain comes relatively late; in some years the heavy rain does not arrive until June, and at the latest even as late as July. In addition, rainfall during the Grain Buds solar term in normal years is not much, averaging only about 40 millimeters, and natural rainfall cannot meet the water demand for transplanting rice, making the summer drought in the central basin, where water sources are scarce, even more severe. As the saying goes: “Storing water is like storing grain,” and “Preserving water is like preserving grain.” To resist drought, in addition to improving farming and cultivation measures and accelerating afforestation, special attention must be paid to storing and preserving water in the previous year. However, attention should also be paid to the possible continuous overcast and rainy weather, which affects the harvest and drying of early spring crops. In the western Sichuan plateau and mountainous areas, the rainy season has mostly begun by this time, crops are growing vigorously, and everything is flourishing. Orchid and cymbidium flowers have finished blooming, and vigorous plants and diseased seedlings can be repotted and transplanted. New plants are already half-height; apply the third fertilizer (root-promoting fertilizer). The root-promoting fertilizer should be mainly phosphorus and potassium to encourage new seedlings to develop roots.

IX. Grain in Ear

Grain in Ear represents the ripening of awned crops such as wheat, and is a solar term reflecting agricultural phenological phenomena. When Grain in Ear arrives, the wheat harvest season in the Sichuan Basin is already over, and the transplanting of middle rice and sweet potatoes is nearing completion. In most areas middle rice has entered the regreening stage, with tender green seedlings full of vitality. The poetic line “The east wind dyes three thousand qing, and the folded egret flies over with nowhere to rest” vividly depicts the beautiful scenery of the fields at this time. When Grain in Ear arrives, middle rice in the basin that has not yet been transplanted should be transplanted promptly; if delayed further, because temperatures rise, the vegetative growth period of rice shortens, and the growth stage is also prone to drought andpests and diseases, so the yield will certainly not be high. Sweet potato transplanting must also be completed before the Summer Solstice at the latest; if sweet potatoes are transplanted too late, not only will the impact of drought worsen, but when autumn comes and temperatures drop, it will be unfavorable for tuber expansion, and the yield will also decrease noticeably. This is the reasoning behind the agricultural proverb “At Grain in Ear, transplant busily.”

The weather is clear and mild; shading begins to be needed. Watering can be done by spraying, irrigating, soaking, or sprinkling, but before temperatures drop at night it must be drained. (Determine water amount according to the growing medium.) Pay attention to rain protection and insect prevention. Provide ventilation as much as possible.

X. Summer Solstice

On the day of the Summer Solstice, sunlight shines directly on the Tropic of Cancer, and it is the longest day of the year in the Northern Hemisphere. In various places in Sichuan, from sunrise to sunset is mostly about fourteen hours. Although the Summer Solstice has the longest day and the highest solar elevation angle, it is not the hottest time of the year. This is because the heat in the near-surface layer is still continuing to accumulate at this time and has not yet reached its maximum. After the Summer Solstice, agricultural production in our province's basin enters the field management period because crops are growing vigorously and weeds, pests and diseases spread rapidly, while plateau pastoral areas begin the golden season of abundant grass and thriving livestock. At this time, rainfall in the western basin increases noticeably, causing the distribution pattern of rainfall in the basin since the beginning of spring, with more in the east and less in the west, to gradually change to more in the west and less in the east. If there is a summer drought, it can generally be expected to be relieved at this time. In the past thirty years, although the number of large-scale floods in the western basin in late June has not been many, their severity has been relatively serious. Therefore, special attention should be paid to preparing for flood control. The Summer Solstice solar term is the solar term with the most rainfall of the year in the eastern basin, after which it is often controlled by the subtropical high, bringing summer drought. To enhance drought resistance and win an agricultural harvest, in these areas, seizing and storing rainwater before the dog days is an important measure. After the Summer Solstice, the ground heats strongly and air convection is vigorous, so thunderstorms are often easily formed from afternoon to evening. This kind of thermal thunderstorm comes suddenly and leaves quickly, with a small rainfall range, and people call it “summer rain separated by field ridges.” The Tang Dynasty poet Liu Yuxi, in Sichuan, once cleverly used this weather as a metaphor to write the famous line, “In the east the sun rises, in the west it rains; though one says it is not clearing, there is clearing.” Ventilation is the first essential. Entering summer, shading, ventilation and water mist measures should all advance together, with attention paid everywhere. Apply complete fertilizer (growth-assisting fertilizer) to help spring shoots become mature plants and to develop autumn shoots and flower buds. Fertilizer should be light, and fertilizing and watering can be changed to early morning and evening.

XI. Minor Heat

Green trees give dense shade; Minor Heat has arrived. During Minor Heat in the Sichuan Basin, the average temperature is about 26°C, already midsummer, and it feels quite hot, but it has not yet reached the hottest time. In mid-July in normal years, in the low-altitude river valley areas of the southeastern basin, concentrated periods with daily mean temperatures above 30°C and daily maximum temperatures above 35°C can begin to appear, which is unfavorable for hybrid rice heading and flowering. In addition to fully considering this factor in advance in crop layout, corresponding remedial measures should be taken for fields already transplanted. In the northern part of the western Sichuan plateau, frost and snow can still be seen at this time, equivalent to the scene of early spring in the basin. Around Minor Heat, the western basin enters the season with the most rainstorms; in normal years the number of rainstorm days in July and August can account for more than 75% of the whole year, generally about 3 days. In places with greater topographic relief, mountain torrents often break out, even causing mudslides. But in the eastern basin, after Minor Heat, because it is often controlled by the subtropical high, there are many consecutive clear and hot days, and the summer drought period begins. This climatic characteristic of drought in the east and flooding in the west in our province's basin has a great relationship with agricultural abundance or failure, and drought-resistance and flood-control measures must be taken separately as early as possible to reduce harm as much as possible. Around Minor Heat, all parts of our province enter the season with the most thunderstorms. Thunderstorms are a violent weather phenomenon, often accompanied by strong winds and rainstorms, and sometimes hail, easily causing disasters, so attention must also be paid to prevention.

Entering the height of summer, ventilation and cooling are the first essentials. When dry, water thoroughly. Do not fertilize.

XII. Major Heat

Shu means hot. It indicates that this is the hottest solar term of the year. Generally speaking, the Major Heat solar term is the period in the basin with the most sunshine and the highest temperatures of the year, the period in the western basin with the most abundant rainfall, the most common thunderstorms, and the most concentrated days with high temperatures above 30°C, and also the period in the eastern basin when high temperatures above 35°C occur most frequently. High temperatures around Major Heat are originally a normal climatic manifestation, because higher temperatures are favorable for main spring crops to flower and fill grain, but if temperatures are too high, crop growth is instead inhibited, and the seed-setting rate of rice drops noticeably. After the dog days begin in the western basin, light, heat and water are all at their annual peak, and the three promote one another, forming good climatic conditions for the growth of main spring crops, but attention must be paid to flood control and drainage. In the eastern basin at this time, high temperatures and long sunshine are often accompanied by little rain, which not only limits the advantage of light and heat but also aggravates the adverse effects of summer drought on main spring crops. To resist summer drought, in addition to paying attention to storing water earlier, crop cultivation measures should also be improved according to the climatic characteristics of the eastern basin, basing everything on “early” in order to seek advantages and avoid disadvantages. The sweltering Major Heat is the season when jasmine and lotus bloom. The refreshingly fragrant jasmine becomes more intensely fragrant as the weather gets hotter, giving people a clean and fragrant enjoyment. The noble lotus, unafraid of scorching sun and sudden rain, opens in the morning and closes in the evening; poets praise it as “lotus reflected in sunlight is especially red.” The vigorous height of summer is nurturing a harvest.

Major Heat is muggy; pay attention to ventilation. There are occasional thunderstorms, so it is best to let them get little rain. Office workers can bring orchid plants indoors and use a fan for ventilation. Orchid plants enter high-temperature dormancy; water less (control water to temper the plants) and do not fertilize (fertilizing will certainly cause scorched tips).

XIII. Start of Autumn

“On the day of Start of Autumn, cool wind arrives” clearly links the Start of Autumn with cooler weather. It can be seen that the Start of Autumn is the beginning of cool autumn. Because latitudes and altitudes differ from place to place, it is actually impossible for all places to enter autumn on the same day of the Start of Autumn. According to the climatological standard that spring and autumn are when the five-day mean temperature is between 10°C and 22°C, in our country, except for places with higher latitudes and altitudes, most places have not yet entered autumn at the Start of Autumn and are still in the midst of hot summer. Even in most areas of the Northeast, at this time one still cannot see autumn scenery with gusts of cool wind and drifting yellow leaves. For the Sichuan Basin, located in the central subtropical zone, the heat in August is still heavy in normal years. Climate data statistics show that the basin does not enter autumn until mid- to late September; in plateau and high mountain areas where it is winter all year round, or where winter is long and there is no summer with spring and autumn linked, one cannot say when autumn begins. After the Start of Autumn, late rice joints and boots, cotton bolls crack and open, and field management must not be relaxed at all; middle rice and summer corn enter the grain-filling and maturity stage, and precautions must be taken against hail, strong winds and rainstorms. In the eastern and western basin, drought-resistance and flood-control work should continue to be done respectively. In the basin after the Start of Autumn, although the season is still midsummer, “ten days after Start of Autumn, everything turns yellow,” and a golden “autumn” is about to arrive.

The autumn sun is like fire; pay attention to strong shading. Change watering to the evening, and it must be drained before dawn. Before the sun comes out, no water droplets should remain on the leaves, otherwise black spots are easily sunburned onto them. Water more, do not fertilize.

XIV. End of Heat

End of Heat is a solar term reflecting temperature changes. “Chu” contains the meaning of hiding and ending, and “End of Heat” indicates that the hot summer days have ended. The average temperature is generally about 1.5°C lower than at Start of Autumn, and in some years in late August there may be low-temperature weather with daily mean temperatures below 23°C for more than 3 consecutive days, affecting hybrid rice flowering. However, because at End of Heat the region is still basically controlled by the summer monsoon, weather with maximum temperatures above 30°C in the west and above 35°C in the east still often occurs. Especially in low-altitude areas along the Yangtze River, in years when the summer drought continues, people feel even more the lingering power of the “autumn tiger.” In the western Sichuan plateau, autumn is at its fullest at End of Heat; above 3500 meters altitude it already presents early winter scenes, pasture grass gradually withers, and frost and snow increase day by day. End of Heat is the early part of the period when rainfall distribution in our province's basin changes from more in the west and less in the east to more in the east and less in the west. At this time rainfall in the central basin is often the second highest point of the year, greater than at Major Heat or White Dew. Therefore, to ensure farmland water use in winter and spring, water storage during this period must be earnestly carried out. In plateau areas, from End of Heat to Autumn Equinox there will be continuous overcast and rainy weather, unfavorable to local agricultural and pastoral production. At this time in our province's basin, it is also the busy season for harvesting middle rice. In ordinary years during the End of Heat solar term, sunshine in the basin is still relatively abundant; except in the western basin, there are not many rainy days, favorable for cutting and drying middle rice and for cotton bolls opening. But in a few years there are also situations like those described in Du Fu's poem, “The dog days have just passed, and the blazing sun turns into continuous rain,” with autumn continuous rain arriving early. Therefore, special attention should be paid to weather forecasts, full preparations should be made, and every fine day should be seized to do a good job of rush harvesting and drying without missing the opportunity.

Shade against the sun. Water must not be cut off (water mist, water jars). Protect against rain, and do not let plants be cold-rained on endlessly during continuous autumn rain. Apply phosphorus-based flower-assisting fertilizer to encourage early development of flower buds.

XV. White Dew

Dew is formed when water vapor condenses into droplets on the ground or on near-ground objects due to falling temperatures. Therefore, White Dew actually indicates that the weather has already turned cool. Among the climates of the twenty-four solar terms, White Dew has the obvious characteristics of rapid temperature decline, the beginning of continuous rain, and a sharp decrease in sunshine, profoundly reflecting the seasonal transition from summer to autumn. During White Dew in normal years, the average temperature is about 3°C lower than at End of Heat, and in most areas the five-day mean temperature successively falls below 22°C. According to the climatological standard for dividing the four seasons, the sequence begins to enter autumn. Autumn rain in the basin mostly occurs from White Dew to before Frost's Descent, most in the middle and lower reaches of the Min River and Qingyi River, and relatively less in the central basin. Although the agricultural proverb “When White Dew is excessive, every day you walk on slippery roads” cannot be used to forecast weather based on whether it rains on the day of White Dew itself, generally there is indeed often a period of continuous overcast rain around White Dew; moreover, from then on rainfall in the basin mostly has the characteristics of low intensity, many rainy days, and frequent continuity. Correspondingly, during White Dew in the basin, sunshine decreases sharply by about half compared with End of Heat, and the decreasing trend continues until winter. The above climatic characteristics during White Dew are unfavorable for late rice heading and flowering and for cotton bolls bursting, and also affect the harvesting and turning-drying of middle rice, so the agricultural proverb says, “When White Dew weather is clear, grain and rice are as white as silver.” Only by fully understanding the climatic characteristics of White Dew and adopting corresponding agronomic measures can the harm of autumn rain be reduced or avoided. On the other hand, water should also be stored promptly when it rains, especially since White Dew in the east is another solar term with relatively abundant rainfall after Grain Buds and Summer Solstice, so a good opportunity should not be missed.

The summer heat gradually fades, but the autumn sun is still harsh. Pay attention to shading. Water at dawn and dusk. After entering autumn, nitrogen fertilizer is prohibited (otherwise scorched tips and rotten leaves will inevitably result and become unmanageable).

XVI. Autumn Equinox

The Autumn Equinox is a solar term representing seasonal change. On the day of the Autumn Equinox, the sun is at 180 degrees of celestial longitude, and sunlight shines almost directly on the equator, with day and night almost equal in length. At this time, the five-day temperature in the Sichuan Basin generally drops below 22°C, entering cool autumn. “One autumn rain, one spell of cold.” Wave after wave of southward cold air meets gradually weakening warm, humid air, producing rain again and again, and temperatures fall again and again. In the northern part of the western Sichuan plateau, the daily minimum temperature drops below 0°C, and one can already see the magnificent snowy scene of swirling flakes flying everywhere and the earth wrapped in plain silver. After the Autumn Equinox, rainfall in our province decreases noticeably, and rainstorms and heavy rains generally rarely occur; however, the number of rainy days instead increases somewhat, often with continuous overcast rain, and the nighttime rain rate is also relatively high. The famous line by the Tang Dynasty poet Li Shangyin, “Night rain in the Ba mountains swells the autumn pool,” vividly depicts the climatic feature of many nighttime rains in Sichuan in autumn. In our province's basin and Liangshan Prefecture, autumn has much continuous rain and severe wet damage, greatly affecting autumn harvest, autumn plowing and autumn sowing. It is necessary to seize clear weather to harvest and dry, arrange drainage to prevent waterlogging, and do a good job in the quality and progress of the “three autumns” production. At the same time, full use should also be made of the meteorological conditions of autumn's overcast rain, scarce sunshine and relatively good soil moisture to seize the opportunity to carry out large-scale afforestation and strive to improve the survival rate of saplings.

Autumn is high and air is crisp; the year's results (shoot production rate) are already before your eyes. Flower buds have also emerged from the pot surface one after another. Thinning buds appropriately is acceptable. Water in the morning and evening; do not water unless dry, and when watering, water thoroughly.

XVII. Cold Dew

In ancient times, dew was regarded as a sign that the weather was turning cool and cold. In mid-autumn during the White Dew solar term, “dew condenses and turns white”; by late autumn at Cold Dew, it is already “the dew air is cold and about to condense” into frost. At this time, temperatures in all places continue to fall. The daily mean temperature in the basin is mostly below 20°C; even in areas along the Yangtze River, the mercury column can hardly rise above 30°C, while the minimum temperature can drop below 10°C. In the western Sichuan plateau, except for a few low river valleys, the five-day mean temperature is generally below 10°C, which by the climatological standard for dividing the four seasons is already winter. Frost spreads for a thousand li and snow drifts for ten thousand li, utterly different from the autumn scenery of the basin. During Cold Dew in normal years, rainfall in the basin also decreases day by day. The western basin is mostly around 20 millimeters, while the east is generally about 30 to 40 millimeters. Continuous rain is very frequent, from morning to evening, drizzly and fine, affecting “three autumns” production and becoming a disastrous weather type in our province's basin. The climatic characteristics accompanying continuous rain are: high humidity, much cloud cover, little sunshine, many overcast days, and foggy days also increase noticeably from then on. However, whether the autumn continuous rain is severe or not directly affects the progress and quality of the “three autumns.” For this reason, on the one hand, weather forecasts should be used to seize clear days for harvesting and sowing; on the other hand, effective farming measures such as deep trenches and high beds should be adopted according to local conditions to reduce wet damage and improve sowing quality. In plateau areas, around Cold Dew is one of the seasons when snow damage is most severe; accumulated snow blocks traffic and harms livestock production, so attention should be paid to prevention. ⟦69 Jiangnan is in full golden autumn, north of the river there is already frost, and the north has begun to snow. China is truly vast, and it cannot be generalized. Pay attention to “being mindful at every moment” and handle things as needed. In the north, cold-resistance fertilizer can be applied; in the south, wait a few more days.

In Jiangnan the golden autumn still holds, north of the Yangtze frost has already appeared, and in the north snow has begun to fall. China is truly vast, and no single rule fits all. Note to "pay attention at every moment" and handle things as needed. In the north, cold-resistance fertilizer can be applied; in the south, wait a few days.

XVIII. Frost's Descent

The Frost's Descent solar term contains the meaning that the weather gradually turns cold and frost begins to fall. In the Sichuan Basin, which is farther south in latitude, the average temperature is mostly around 16°C, and there are still three solar terms before the first frost date. In the river valley areas of the southern basin, frost is not seen until deep winter. Of course, even at places of the same latitude, because altitude and topography differ and the temperature and humidity of the air in the surface layer differ, the first frost date and the number of frost days also differ. From a scientific point of view, the saying that “dew condenses into frost” is inaccurate. Frozen dew formed by dew droplets freezing is hard small ice beads. Frost damage refers to the phenomenon of crop freeze injury caused by a sharp drop in temperature, and the damaging temperature varies with crop, variety and growth stage; for frost to form, the temperature of the ground or ground objects must drop below 0°C, and the water vapor content in the air in the surface layer must reach a certain level. Therefore, when frost damage occurs, frost does not necessarily appear, and when frost appears, frost damage does not necessarily occur. However, because the temperature when frost is seen is already relatively low, if cooling continues, it can easily lead to frost damage. After Frost's Descent, our province's basin begins to harvest and dig sweet potatoes in large quantities. If harvesting is too early, the tubers have not yet fully expanded, which affects yield; but if harvesting is too late, they may suffer early frost damage, and the tubers will be frozen and deteriorate, not storing well, so timely digging of sweet potatoes is important. The great Northern Song literary figure Su Shi wrote in a poem: “A thousand trees are swept into one expanse of yellow, only the hibiscus blooms alone.” The Sichuan Basin has a mild climate; during Frost's Descent, the fields are green, oranges are yellow and tangerines are green, autumn chrysanthemums compete in bloom, and hibiscus trees bloom in profusion, dressing the fertile “Land of Abundance” even more gorgeously.

The weather gradually turns cold, and northern cold currents begin to invade the south. Shading can be omitted. When the weather is cold, do not pour water over the top of the plant; water slowly along the edge of the pot in several rounds to prevent “false thoroughness.” If there are autumn pseudobulbs, the last closing fertilizer of the year can be applied.

XIX. Start of Winter

Speaking of “winter,” one naturally thinks of cold. “Li means beginning,” indicating that winter starts from then. “On the day of Start of Winter, water begins to freeze and the ground begins to freeze.” Nowadays, people often take biting north wind and cold frost and snow as symbols of winter. Our province's basin also has little frost and snow, so in climatology the day of “Start of Winter” is not fixed as the beginning of winter in each place; instead, temperature is used to divide the seasons, that is, a five-day mean temperature below 10°C is winter, which better matches the phenological landscape at the time. During Start of Winter in our province's basin, it is still in the busy “three autumns” period, with average temperatures generally 12°C to 15°C. The continuous rain has already ended. Climatic conditions are suitable for transplanting rapeseed. Wheat with a shorter growth period and stronger spring habit should also be sown promptly, because in the later part of Start of Winter there are often strong cold air intrusions, and temperatures often drop considerably; if temperatures are low after sowing, seedling emergence is slow and tillering insufficient, which will affect yield. When the daily mean temperature is below 15°C, sweet potato growth gradually stops, and it should be harvested promptly. In a few years in the northwestern basin, early frost has appeared at Start of Winter, so cellars should be dug even earlier to avoid freeze damage. In plateau areas, this is already the dry season, humidity drops rapidly, and wind speed gradually increases, so high vigilance must be maintained against forest fire risk.

Cold air attacks frequently, and there is already a trace of chill. Orchid plants can successively (according to variety) be moved indoors. Reduce watering; after drying thoroughly, water sixty percent. Do not fertilize.

XX. Minor Snow

Minor Snow indicates the starting time and degree of snowfall. Snow is a product of cold weather. During the Minor Snow solar term, the northern part of the Sichuan Basin begins to enter winter. “The lotus is gone, no longer holding up rain covers; the chrysanthemum is withered, yet still has frost-bearing branches,” already presenting early winter scenes. Because to the north there are the Qinling and Daba Mountains as a barrier, blocking cold air intrusions and blunting the severity of cold waves, the basin's “warm winter” is pronounced. The number of snow days in the whole year is mostly below 5 days, much fewer than in the middle and lower reaches of the Yangtze River at the same latitude. Before Major Snow there is very little chance of snowfall; even in deep winter, one rarely gets to admire the enchanting scene of “a thousand trees and ten thousand trees blooming as pear flowers.” Because in winter the near-surface air temperature in the basin often remains above 0°C, accumulated snow is even less likely than snowfall. Occasionally, although the sky shows “flurries swirling,” no “broken jade and scattered pearls” are seen on the ground. However, in the cold western Sichuan plateau, snowfall generally begins in October in normal years. In the northwestern plateau, the number of snow days in the whole year can reach more than 60 days, and in some high-cold areas snowfall is possible throughout the year. During Minor Snow, the first frost is generally visible in the northwestern basin, and precautions should be taken against the harm of frost to crops. In the northern parts of Ganzi and Aba prefectures, the minimum temperature is mostly around minus 15°C, and cold-proof and warm-keeping work for livestock should be done well.

Orchid plants are moved indoors; water less, and prune dead branches and withered leaves. For diseased and weak orchid plants, repot, wash the roots, and replant using “revival soil.” Clean, scrub and disinfect the orchid room.

XXI. Major Snow

"Major Snow" indicates that snowfall begins to increase at this time. The Sichuan Basin has a mild winter climate with little rain or snow; the average temperature is about 2°C to 4°C higher than that of the middle and lower reaches of the Yangtze River, and rainfall accounts for only about 5% of the annual total. Occasional snowfall mostly occurs in January and February; snow covering the ground is rarely seen even once in three to five years. If one could witness the earth blanketed in white snow and green trees adorned with silver and jade, it would often be an unforgettable delight. "A timely snow promises a good harvest" is a farming proverb widely circulated in our country. In the north, a thick, loose layer of snow is like a quilt covering wheat to keep out the cold. The nitrogen compounds contained in snow are 4 times more than in rain; after the snow gradually melts and seeps into the soil, it can increase the nitrogen in the soil, which is easily absorbed and used by crops. Snow water has a low temperature and can freeze to death pests overwintering in the surface layer, also bringing benefits to agricultural production. However, in the south, if a clear night follows snow, the ground loses more heat, and freezing damage may occur, causing some losses to crops such as peas and broad beans. In our province's basin, the average temperature is still mostly 8°C to 9°C, and wheat and rapeseed can still grow slowly, so field management needs to be strengthened to prevent freezing damage. During Major Snow, precipitation in the basin is mostly below 15 mm, and in the western part of the basin it is even less than 5 mm, already a period of "winter drought." At this time, the basin's climate also features frequent fog, and December is generally the month with the most foggy days. Fog usually appears in the early morning when the night is cloudless or nearly cloudless, which meteorology calls radiation fog. As the saying goes: "Nine out of ten fogs mean clear weather." Fog mostly dissipates before noon, and the afternoon sunshine feels especially warm.

In the orchid room there is nothing much to do; pay attention to controlling water. With short days and long nights, one may read by lamplight and study orchid cultivation. Keep notes on the year's orchid work. Clean out empty pots and potting medium, and prepare to select and buy wild-collected orchids.

Twenty-two, Winter Solstice

The Winter Solstice is a solar term divided according to astronomy, called in ancient times "short day" or "shortest day." On the day of the Winter Solstice, the sun is at 270 degrees of celestial longitude, and sunlight shines almost directly on the Tropic of Capricorn, making it the day with the shortest daylight in the Northern Hemisphere. In our province, from sunrise to sunset there is not quite 10 hours. After the Winter Solstice, as the Earth moves along its orbit around the sun, the zone of direct sunlight gradually shifts northward, making daylight gradually longer and night gradually shorter in the Northern Hemisphere. Although on the Winter Solstice the sun's altitude is lowest and the duration of sunshine is shortest, and the ground absorbs less heat than it loses, the heat accumulated over the long period before is still continuing to dissipate, and the temperature near the ground has not yet dropped to its lowest, so this is not yet the coldest time of the year. After the Winter Solstice, although days gradually lengthen and nights gradually shorten, in the short term it is still short days and long nights, and the heat the ground absorbs each day is still less than what it loses, so the temperature does not immediately rise. Among the people it is customary to begin "counting the nines" from the Winter Solstice, with every nine days as one "nine." Around the "third nine," the heat stored in the ground is at its least and the weather is also coldest, hence the saying "cold in the third nine." In astronomy, the Winter Solstice is taken as the beginning of winter, which for most regions of our country is obviously too late. During the Winter Solstice period, the average temperature on the western Sichuan plateau is generally below 0°C, and in the Sichuan Basin it is only about 6°C to 8°C. However, in the low-altitude river valley areas of southwestern Sichuan, even in the locally coldest first ten days of January, the average temperature is still above 10°C; it may truly be said that autumn departs and spring remains level, with no winter throughout the year.

Getting through winter is easy in Jiangnan; in the north, pay attention to keeping warm. In indoor orchid rooms in natural environments, pay attention to controlling water. Northern greenhouses must guard against dryness. You may use a soft brush to gently wash the orchid leaves.

Twenty-three, Minor Cold

Cold means chilly, and Minor Cold indicates the degree of cold. As the saying goes, "cold in the third nine." The "third nine" mostly falls from January 9 to 17, which also happens to be within the Minor Cold solar term. But this is only a general rule; in a few years Major Cold may also be colder than Minor Cold. And in the winter of 1975, still fresh in people's memory, the solar term with the lowest temperature was actually Major Snow! In our province's basin, winter warmth is pronounced; in deep winter in January, east of the Three Gorges frost and snow invade together and freezing often occurs, with the lowest temperature around minus 10°C. Yet in the northern part of the basin, the lowest temperature is seldom below minus 5°C, and in the southern part of the basin low temperatures below 0°C are even less common. The coldest area in our province in deep winter is the northern part of the northern Sichuan plateau, where the lowest temperature can reach about minus 30°C, with severe cold and frozen ground, and dripping water turns to ice. The low-altitude river valley zone of southwestern Sichuan is the warmest place in our province in deep winter, with an average January temperature of about 12°C, and only in very few years may low temperatures below 0°C occur. In addition, the inversion effect is very pronounced, so tropical fruits such as bananas and mangoes can grow well. The winter minimum temperature in the basin is not low, which is favorable for spring production and also suitable for developing diversified undertakings. The citrus, which "receives the command not to move, and grows in the southern land," generally requires a minimum temperature not lower than minus 5°C and an annual temperature above 15°C for growth; most areas in the basin can satisfy this, and subtropical plants are almost all available. Sichuan is known as the "Land of Abundance," and its uniquely favorable climatic conditions should be a very important factor.

In deep winter, a vat of water may be placed in the orchid room. On the one hand it increases the humidity of the orchid room; if thin ice is seen on the water surface, the temperature must be raised to keep warm. Water less and prohibit fertilizing.

⟧ Twenty-four, Major Cold

Like Minor Cold, Major Cold is also a solar term indicating the degree of coldness of the weather. Although modern meteorological observation records show that in most parts of our country Major Cold is not as cold as Minor Cold, in certain years and in a few coastal places the lowest temperature of the whole year still occurs within the Major Cold solar term. During Major Cold, the average temperature in our province's basin is mostly 6°C to 8°C, nearly 1°C higher than during Minor Cold. The proverb "Minor Cold and Major Cold, cold into a ball" shows that the Major Cold solar term is also a cold period of the year. Therefore, continue to do a good job in protecting crops from the cold, and special attention should be paid to protecting livestock so they pass the winter safely.

For certain crops, an appropriate low temperature is needed during a certain growth period. Wheat and rapeseed with strong winter habit require a relatively low temperature to pass through the vernalization stage, otherwise they cannot grow and develop normally. In our province's basin, winters are warm year after year, and wheat and rapeseed sown too early often grow too vigorously, jointing and bolting ahead of time, greatly weakening their cold resistance and making them prone to damage from low-temperature frost. It can be seen that selecting crop varieties according to local conditions, sowing and planting at the right time, and adopting effective measures to promote and control growth are an important link in achieving high yields.

Minor Cold and Major Cold are the periods with the least rain of the year. In an ordinary Major Cold solar term, rainfall increases only slightly compared with the earlier period, with most areas of the basin receiving 5 to 10 mm, and the mountainous area of the western Sichuan plateau generally only 1 to 5 mm. Although the difference in rainfall between the eastern and western parts of the province is not great, the east has dense clouds and heavy fog while the west has brilliant sunshine, so the weather is utterly different. The basin is dry in winter, and overwintering crops consume relatively little water during this period, so the contradiction between farmland water supply and demand is generally not prominent. However, "Do not complain of bitter cold and snow; snow comes to leave wheat for next year." When rain and snow are scarce, timely irrigation in different regions according to different farming habits and conditions is undoubtedly of great benefit to the growth of small spring crops.

Winter is at its fullest, and spring is about to arrive. Flower buds are stirring restlessly; moisten slightly and prohibit fertilizing. When sunning in the morning, pay attention to turning the pots. The flower buds of tender green varieties must be protected with paper sleeves.