What are the latest cultivation methods for potted poinsettia

Poinsettia, also known as ivory red, laolai jiao, Christmas flower, etc., is an evergreen shrub plant of the genus Euphorbia in the family Euphorbiaceae, native to Central America, widely cultivated in tropical and subtropical regions, and cultivated in most provinces, autonomous regions and municipalities in China, commonly seen in parks, botanical gardens and greenhouses for ornamental purposes. Its stems and leaves used as medicine have a detumescence effect. Now let us take a look at the cultivation methods for potted poinsettia!

Growth habits of poinsettia

Poinsettia is native to the Taxco region of Mexico in Central America, and was introduced to the United States in 1825 by Joel·Poinsett, the first U.S. ambassador to Mexico. It is a short-day plant and likes warmth. The suitable temperature is 18-25℃, 18-24℃ from April to September, 13-16℃ from September to April of the following year, and the winter temperature should not be lower than 10℃. It likes moisture, and poinsettia is relatively sensitive to water. During the growing period, it only needs sufficient water supply. It likes sunlight, and during the stem and leaf growth period it needs sufficient sunlight to promote rapid and luxuriant stem and leaf growth.

Propagation methods of poinsettia

1. Cuttage: The cuttage propagation of poinsettia mainly includes semi-hardwood cuttings and softwood cuttings, as well as old root cuttings. Regardless of which cuttage propagation method is used, poinsettia cuttings should preferably be cut in the early morning. This is because at this time the water content of the cuttings is relatively sufficient. When cutting the cuttings, the cut should be smooth, and the split epidermis and xylem should be trimmed off to avoid water accumulation and rot, which would affect healing and rooting.

2. Layering: Poinsettia generally uses the air layering propagation method, and the layering time is preferably from April to July. Select lignified branches, generally healthy and plump branches from the previous year, and perform ring-barking on a smooth part. The width of the ring bark should be similar to the thickness of the branch at the ring-barking site, generally 3-4 cm is suitable. After layering, roots generally grow in about two months. At this time, it can be cut off and planted in a pot, thus forming a new plant.

Cultivation methods of poinsettia

1. Soil: Poinsettia likes loose soil with good drainage. Generally, use 3 parts vegetable garden soil, 3 parts humus soil, 3 parts leaf mold, 1 part decomposed cake fertilizer, and add a small amount of cinder for mixed use.

2. Temperature: Poinsettia likes warmth and fears cold. In mid-to-late September each year, move it indoors and strengthen ventilation so that the plant gradually adapts to the indoor environment. In winter, the indoor temperature should be maintained at 15℃ to 20℃. At this time, it is exactly the period of bract color change and flower bud differentiation. If the room temperature is below 15℃, the flowers and leaves will develop poorly. After mid-December, it enters the flowering stage, and ventilation should be gradually increased.

3. Light: Poinsettia likes sufficient light and is strongly phototropic. It is a short-day plant. It should receive sufficient light throughout the four seasons, and this is even more important during bract color change, flower bud differentiation and flowering. If light is insufficient, branches are prone to leggy growth and susceptible to diseases, and flower color is dull. If placed in a dark place for a long time, it will not bloom and will shed leaves in winter. In order to advance or delay flowering, light can be controlled. Generally, give 8 to 9 hours of light per day, and it can bloom in 40 days.

4. Fertilization: Poinsettia likes fertile sandy soil. In addition to adding organic fertilizer and horseshoe slices as base fertilizer when potting and repotting, during the growing and flowering season, apply once every 10 to 15 days a 5-fold diluted fully decomposed sesame paste residue liquid fertilizer. After autumn, 0.3% compound chemical fertilizer can also be applied once a week for 3 to 4 consecutive times to promote bract color change and flower bud differentiation.

5. Watering: Poinsettia is not tolerant of drought, nor of waterlogging. Watering should be flexibly controlled according to the weather, pot soil and plant growth conditions. Generally, watering should be done to keep the pot soil moist without water accumulation, but watering should be reduced after flowering. Watering should be even to prevent excessive dryness or moisture, otherwise it will cause the lower leaves of the plant to turn yellow and fall off, commonly known as “bare legs”, or uneven branch growth.

6. Pinching: About 3 weeks after planting poinsettia, the root system has grown, and pinching can be carried out at this time. When pinching, leave 4-6 leaf nodes, raise the temperature to a daytime temperature of 28-30℃ and a nighttime temperature of 23℃, and frequently spray to increase humidity. After lasting about two weeks, when buds are seen growing, then slowly lower the temperature to 25-28℃ during the day, and lower the humidity as well. During this period, according to the uniformity and fullness of the plant, carry out a second pinching, supplement nutrients, and combine with dwarfing agent treatment.

7. Pruning: Around Qingming Festival, repot the dormant old poinsettia plant, cut off old roots and diseased and weak branches to promote the sprouting of new shoots. During the growth process, pinching is needed twice, the first in late June and the second in mid-August. During cultivation, heavy fertilization and heavy watering should be controlled, especially before the plant shape is set in autumn. When branches grow 20 to 30 cm, begin shaping and bending, with the purpose of making the plant shape compact, the flower heads neat and evenly distributed, and improving ornamental value.

8. Plant height control: During the cultivation of poinsettia, plant growth regulators must be used to dwarf the plant height in order to achieve the requirement of consistent height for commercial flowers. In addition, maintaining consistency of day and night temperatures during cultivation is also crucial, and tracking and monitoring should be carried out at any time. When the day-night temperature difference exceeds 3℃, after sufficient pinching, spray 750 to 1000 ppm chlormequat 1 to 4 times to inhibit stem leggy growth.

Pest and disease control of poinsettia

1. Gray mold

[Symptoms] Gray mold mainly occurs in winter, exactly during the flowering season of poinsettia. Once there is continuous rain and dampness without sunlight, it can harm poinsettia inflorescences, bracts, leaves and branches. Generally, water-soaked lesions first appear from the inflorescences. Afterward, the lesions are covered with a layer of pathogen conidia, and the pathogen continues to spread to the bracts. In the early stage on the bracts, water-soaked faded spots appear, and later gradually expand into irregular shapes. The pathogen then spreads to the branches, producing yellow-brown to brown lesions on the branches. In the later stage, the lesions are obviously sunken and dark brown, and in severe cases the lesion areas become dry and withered.

[Control] By utilizing the closed characteristics of the facility, create an ecological environment with high temperature and low humidity to control the occurrence and development of gray mold. At night, indoor humidity in the facility is often higher than 90%. After pulling up the covering in the morning, immediately open the ventilation openings to ventilate and remove moisture, reduce indoor humidity, and control disease development with a lower temperature. After 9 o'clock, when the indoor temperature rises rapidly, close the ventilation openings to quickly raise the indoor temperature to about 32℃.

2. Root rot

[Symptoms] It generally occurs more severely in high-temperature seasons, and is also very likely to occur when the cultivation soil has high water content. In the early stage, the plant shows wilting. If the stem base is examined at this time, a light brown constriction can be seen, but the infected plant shows no rot or hydrolysis. Later, the lesions gradually spread upward, and the wilting gradually becomes more serious. The stem lesions are slightly sunken and yellow-brown. In the later stage, the tissue at the lesion disintegrates, causing the plant to wither and die due to severe water deficiency. Sometimes the whole plant becomes water-soaked and yellowed, eventually rotting and dying. White hyphae can be seen near the ground, and in severe cases they can spread to the cultivation soil. When the roots are affected, root rot often occurs, initially affecting the normal growth of the plant, and in severe cases causing death.

[Control] ① Implement crop rotation: rotate every other year in lightly diseased fields, and rotate every 3-5 years in heavily diseased fields. ② Deep plowing and soil improvement: increase application of organic fertilizer, reasonable irrigation and drainage, and enhance disease resistance. ③ Strict seed selection: eliminate unqualified seeds. Treat seeds with 50% carbendazim wettable powder at 0.5% of seed weight. ④ When disease occurs, spray the stem base of peanuts with 50% carbendazim wettable powder 1000-fold solution, using 25-30 kg of liquid per mu each time.

3. Leaf spot

[Symptoms] Leaf spot occurs more severely mainly in spring and summer, and the lesions mostly begin on old leaves. In the early stage, purple-red to brown small spots appear on the leaves. The lesions are nearly circular to irregular, and later gradually expand. Most lesions can heal with each other to form a large lesion. In the later stage, the center of the lesion gradually turns gray-brown. In severe cases, the lesion tissue becomes gangrenous, causing the leaves to twist and dry up.

[Control] ① Remove diseased tissue in time and burn it in a centralized manner. ② Crop rotation (soil can be changed in greenhouses). ③ Do not spray water on the plants. ④ Begin spraying from the early stage of disease occurrence to prevent the disease from expanding and spreading.

4. Whitefly

[Symptoms] Adults and larvae of whitefly like dense and shaded environments. They gather on the upper leaf backs of poinsettia and suck sap with piercing-sucking mouthparts, causing leaves to fade or develop chlorotic spots, affecting photosynthesis and leading to poor plant growth. The honeydew excreted by the insects often causes sooty mold. Adults are attracted to yellow.

[Control] Whitefly is most vulnerable as newly mobile larvae, followed by newly emerged adults, which are sensitive to pesticides and suitable for spray control. Whitefly generally occurs in large numbers under high temperature and low humidity, with the peak period from late September to late November. The optimal control period is late September, and the spraying time is 6-10 a.m.