A Brief Analysis of the Role and Methods of Cold Vernalization in Cymbidium goeringii

Orchids that need vernalization are those in the bud stage; orchids that have not produced flower buds do not need vernalization. A large temperature difference between day and night is a necessary condition for good bloom quality. Vernalize in sunlight, bloom in shade, tall stems and good quality (this suits natural vernalization in the Jiangsu-Zhejiang region); if vernalizing indoors as in the north, shade vernalization is recommended (temperature controlled at 1-12°C, with a temperature difference of about 10°C for about 40 to 50 days), then bloom in light (the "bloom in light" here does not mean direct sunlight either; diffuse light is best, ensuring Cymbidium goeringii temperatures of 8-20°C and Cymbidium faberi temperatures of 10-23°C, preferably not exceeding 25°C)

In the north, vernalization is generally carried out during the period from Minor Snow to Major Cold! Vernalization means "freezing" orchid plants with flower buds (Cymbidium goeringii, Cymbidium faberi) at below 10°C and above 4°C (can go to above 0°C) for 30 days, so that the flower buds can open normally. Place budded orchid plants in a place without sunlight for vernalization; after a month, bring them into an air-conditioned room and gradually raise the temperature; do not go straight to 24°C. On day 1, 16°C; after 2 days, 18°C; after 4 days, 20°C; after 6 days, 24°C (temperature and timing depend on the condition of the flower buds). Of course, there should be some humidity as well. During the warming process, it is best to expose them to little sunlight, so the stems will grow straight.

Regarding the vernalization of Cymbidium goeringii, orchid masters through the ages have all attached great importance to adequate vernalization of Cymbidium goeringii. They advocate keeping orchids at low temperatures of 0-10°C in winter, especially during the period from Major Snow to Major Cold, with a day-night temperature difference maintained at around 10°C, so as to accumulate sufficient nutrients for the flower scapes to grow tall and open after spring. Adequate vernalization and an appropriate temperature difference are necessary conditions for promoting the flower scapes of Cymbidium goeringii to grow tall and for the bloom quality to be right, fully respecting the natural flowering characteristics of Cymbidium goeringii. If there is not enough vernalization during the bud stage, and not enough relative humidity when the scapes are growing, forcing them to open will defeat the purpose, and the bloom quality will be greatly reduced. The substantive issue argued is that Cymbidium goeringii must undergo low-temperature vernalization in order to bloom and produce good blooms. This article attempts, from daily orchid-growing practice and some individual cases, to briefly discuss how Cymbidium goeringii can likewise produce good blooms without undergoing vernalization; it is not intended to overturn the theoretical views of predecessors and fellow orchid growers, still less to presume to discuss orchid-growing lore here with predecessors and fellow growers. The aim is mutual exchange and common improvement, seeking common ground while reserving differences. Criticism and correction are welcome for anything inappropriate or mistaken.

The author began growing orchids on a balcony in 2000, and has dabbled in Cymbidium goeringii, Cymbidium faberi, Cymbidium ensifolium, Cymbidium sinense, and Cymbidium kanran. The varieties can be said to be quite mixed, but the author is especially fond of Cymbidium goeringii and Cymbidium faberi, particularly liking the delicate fragrance when Cymbidium goeringii blooms, filling the whole house with scent and refreshing the heart. Over several years of orchid growing, the author continuously learned orchid-growing knowledge from orchid masters, covering cultivation, watering, fertilizing, potting medium, sunlight, ventilation, and other aspects, and in the process gradually came to know that Cymbidium goeringii needs low-temperature vernalization to bloom.

Around New Year's Day 2005, the author visited a local veteran orchid grower. This man loved orchids as his life throughout his life, and the author benefited greatly from him; now the old gentleman has passed away, which is deeply saddening. When we talked together about the vernalization of Cymbidium goeringii, the gentleman said, look at my Song Mei blooming right now, the bloom form is very proper, the flowers are delicately fragrant, the flower scapes are about 10 cm, and it has not undergone vernalization. During the day our temperature is around 20°C, after midnight around 16°C (central heating; at night the temperature is sometimes the same as during the day), and from 5 a.m. the heat is released, with the temperature rising back to around 20°C, sometimes reaching 23°C at noon, with humidity of 30-45 degrees. It has no way to experience the tempering of low temperatures, and is basically the same as the ambient temperature in your home. If the heating were turned off and the temperature controlled lower, there would be no problem with it blooming in time for Spring Festival (February). Letting nature take its course is better; I never artificially control the temperature. What needs to be explained here is that even with the heating off, the nighttime temperature in this room would not be lower than 10°C, and during the day it would reach 18°C, with a day-night temperature difference of about 8°C, because the heating in the other rooms is all on. The gentleman's orchid potting medium was entirely local mountain pine-needle soil, grown on an indoor balcony. In spring and autumn, watering once every 10-15 days, with direct sunlight; in summer, depending on the weather and temperature, sunlight no longer reaches indoors; in winter, watering once a month, using tap water, with direct sunlight. The fertilizer was made by composting fish scraps, peanut meal, rice-washing water, and the like, applied to the roots once every 10-15 days in spring and autumn; in summer, depending on temperature and weather, no fertilizer when the temperature exceeds 30°C, and no fertilizer on rainy days; chemical fertilizers were never used. Seeing the balcony full of lush, verdant orchids, I sincerely admired the gentleman's orchid-growing skill.

Using pure pine-needle soil (formed on the mountain under pine trees where fallen pine needles rot and mix with the soil) to grow orchids is something the author has tried, mainly because moisture is hard to control, especially in the plum rain season, when with high temperature and high humidity there were many times when everything was lost; the author's Xiaotaohong, Dafugui, Jinqi, and a wild-collected Cymbidium faberi butterfly flower (20 plants) and others long ago returned to the western paradise. Although they were not famous varieties, they had after all followed the author for many years, and seeing the small shoots sent out by the old remnant of Xiaotaohong left on the balcony was heartbreaking. After this painful lesson, the author no longer dares to use pure pine-needle soil. Now a mix of 70% planting stone + 30% pine bark (or pine-needle soil) is used as the potting medium. In spring, autumn, and winter, full sun; Cymbidium goeringii and Cymbidium faberi in front, Cymbidium sinense and variegated-leaf types behind; after May they are moved to the rear open-air balcony, where they can see sunlight before 9:30 and when the sun is about to set in the afternoon, exposed to wind and rain, and after heavy rain sprayed with thiophanate-methyl. The fertilizer is made by the author's own composting of fish scraps, peanut meal, rice-washing water, and pig bones; occasionally expired milk or sour milk is used directly to water the roots, and the effect is fairly good. Over several years there has also been quite a harvest. (Doubt one: orchids like cleanliness, and this composted fertilizer water stinks unbearably and is nauseating, and if the "returning-soul water" is not applied the next day, the stench is left to slowly disperse.) Last autumn, I moved the orchids from the north balcony (open-air) into the indoor south balcony, wanting to verify what the old gentleman said, that Cymbidium goeringii likewise blooms without undergoing low-temperature vernalization. I divided the orchids into two groups. One group, with flower buds, was placed on the south balcony, with the temperature controlled at minus 2°C to 15°C and humidity at about 30-50 degrees, vernalized until the end of Major Cold; the other group, without flower buds, was placed indoors, with the temperature at about 15-20°C and humidity at about 30-40 degrees. Among them, one pot of budded Yinguansu, one pot of budded Daxuesu, and one pot of budded Xiaoxuesu were managed indoors. From late January 2008, the vernalized Yuhudie and the non-vernalized Daxuesu, Xiaoxuesu, and others bloomed one after another, reaching full bloom at Spring Festival. After careful comparison, whether in terms of flowers or scape height, there was no major difference. What the author did not expect was that Longzi, which had always been grown indoors, produced 4 flower buds above the soil in late February, and Daxuesu and Xiaoxuesu each also produced one flower bud (Doubt two: it had already bloomed at Spring Festival, with two flower scapes each for Daxuesu and Xiaoxuesu; can it bloom repeatedly in one season?). At first I took them for shoots, because most varieties of Cymbidium goeringii and Lianban have already passed their flowering period; would they now produce flower buds? The Longzi buds had already opened their mouths, giving off a faint delicate fragrance, and the scapes were also growing taller day by day. Now the indoor temperature is 16-23°C and humidity is about 30-45 degrees, while the outdoor temperature is 29°C. Whether indoors or outdoors, the temperature and conditions for vernalization are no longer present.

In summary, as long as water, fertilizer, temperature, humidity, light, and so on are appropriate, windows are opened on time for ventilation, and there is a certain day-night temperature difference, Cymbidium goeringii, Cymbidium faberi, and the like can likewise produce blooms that satisfy us without undergoing low-temperature vernalization.

Zhang Zhiqiang