Orchid Vernalization Tips: How to Help Orchids Vernalize Better

In 1918, Gassner studied the phenomenon that low temperature can promote plant flowering. In 1935, a Soviet geneticist proposed the concept of vernalization, pointing out that the process in which low temperature induces plant flowering is called vernalization.

Orchid growers in Guangdong and Taiwan, China, all say that Cymbidium goeringii and Cymbidium faberi can produce flower buds locally, but few can bloom with good form, and the buds often wither soon after appearing. This is caused by insufficient vernalization, and now many growers, after mastering the mechanism of vernalization, have been able to successfully make vernalized orchids bloom with good flower form.

I. The effect of vernalization on orchid flower form

Cymbidium goeringii, Cymbidium faberi, Douban orchid, Cymbidium tortisepalum, Chunjiang orchid, Songchun orchid and others belong to the low-temperature vernalization type of plants, and their growth and development processes all place certain demands on temperature conditions, especially in the qualitative transformation process from vegetative growth to reproductive growth. The vernalization phenomenon of the above orchids has long been widely accepted by orchid growers, but at present the physiological mechanism of their vernalization is generally mentioned only briefly, which leaves many orchid growers confused. Therefore, the term "vernalization" sometimes makes orchid growers feel quite bewildering.

Some views hold that vernalization activates the genes in the plant body that determine the continued differentiation of flower buds, ultimately leading to a series of physiological processes, thereby causing the meristem at the tip of the orchid bud to transform into a flower primordium in a specific region. Some researchers believe that during low-temperature induction, changes occur in the plant's proteins, nucleic acids and so on, thereby producing specific mRNA and rRNA. Therefore, it can be considered that low-temperature conditions have some necessary connection with nucleic acid metabolism in the orchid body. For example, during asexual division propagation, cells of the orchid plant that have completed the vernalization effect can transmit vernalization information through division, that is, daughter cells that have not yet perceived the vernalization effect can perceive the vernalization effect of the mother cell. Another view holds that under low-temperature induction, the so-called "vernalin" is produced in the plant body; the precursor of this substance is an intermediate product under low-temperature conditions, while under high-temperature conditions, "vernalin" is in an inactivated state. When under certain temperature conditions, this intermediate product is converted into a stable substance, namely "vernalin". 

According to the state of the plant body when the orchid perceives vernalization, it is called plant body vernalization. According to the quantitative relationship of the plant's response to the low-temperature effect of vernalization, if low-temperature treatment is not carried out, it can only cause the plant's flowering time to be delayed or the number of flowers to decrease, ultimately leading to less than ideal flower form.

II. The optimal temperature and time for orchid vernalization

The time for orchid plants to complete vernalization varies with species, variety and specific temperature. The temperature range through which plants pass vernalization also varies with species and variety; usually this temperature range is 0-10°C, among which 0-7°C is suitable for the vast majority of those requiring vernalization. The vernalization temperature for Cymbidium tortisepalum is 5-15°C. At this temperature, Cymbidium goeringii, Chunjiang orchid, Cymbidium tortisepalum, Songchun orchid and Douban orchid generally need 20 days to be satisfied, while Cymbidium faberi needs about 30 days to be satisfied.

Whether the vernalization of orchid plants can be successfully completed depends not only on temperature conditions; in addition, after vernalization, certain light conditions are still required for flowering. In many cases, although the plant body is within a suitable vernalization temperature, if the treatment time is too long, the degree of vernalization will instead be somewhat weakened; this phenomenon is called "over-vernalization". If the plant is placed at normal temperature before its vernalization process has completely ended, the vernalization effect will be weakened or completely disappear; this phenomenon is called "devernalization". 

III. The effect of vernalization on winter buds

After effective vernalization, the effect on orchid plants causes the pseudobulbs of nearly mature spring shoots to enter the final maturation stage, and their vegetative growth gathers energy; for example, winter buds generally show new roots emerging before the buds emerge from the soil, and the new shoots are plump and strong. From the surface, apart from the accelerated growth rate of flower buds, the plant appears to enter a period of growth rest. When the weather warms up in early spring, because the winter buds laid a solid foundation early on, there is no pause period after they emerge from the soil, allowing the shoots to mature by late May to early June, and most will have second-generation shoots emerging; with proper management, a third generation of autumn shoots will appear.

Conclusion:

For orchids with obvious vernalization introduced to the south and north, in order to make the flower form bloom well, local orchid growers indeed need to find ways to provide a certain vernalization period. The best choice is air-conditioning cooling. Some orchid growers place Cymbidium goeringii and Chunjiang orchid with flower buds in the refrigerator for vernalization, but the operation may have been improper and failed to achieve ideal results. In heated areas of the north in winter, the temperature in some orchid growers' homes is too high, and some orchid growers move Cymbidium goeringii with flower buds into the bathroom and close the door, so that heating cannot enter and an imagined vernalization effect is achieved, but this also fails because the vernalization standard cannot be met.

In the Yangtze River basin, using natural temperature for vernalization is the most ideal, and orchid growers do not need to worry about it every year, but they must prevent over-vernalization. Ideal vernalization will make the flower form display its biological blueprint, with a more extended flower stalk, more elegant flowers, and an overall appearance that is even more enchanting.