What is the relationship between bud withering and vernalization?

Up to now, the so-called "vernalization" or "vernalization effect" of Cymbidium goeringii and Cymbidium faberi in orchid circles remains a vague and confused concept...

The reason for this confusion is that the botanical term "vernalization" or "vernalization effect" borrowed by orchid circles no longer carries its original definition, but has been extended to specifically refer to the need for a certain degree of low temperature during a certain period after the formation of Cymbidium goeringii and Cymbidium faberi flower buds and before the flowers open - a "vernalization" or "vernalization effect" in a special sense. This is how most orchid growers understand or accept the "vernalization" or "vernalization effect" of Cymbidium goeringii and Cymbidium faberi - that is, they believe that if there is no low temperature of a certain degree during a certain period after the formation of Cymbidium goeringii and Cymbidium faberi flower buds and before the flowers open, the buds cannot open smoothly, normally and perfectly...

On the other hand, because orchid growers cite the original botanical definition of "vernalization" or "vernalization effect" when explaining what "vernalization" or "vernalization effect" is, and due to differences in understanding, some orchid growers equate the "vernalization" or "vernalization effect" specifically referred to in orchid circles with the botanical "vernalization" or "vernalization effect" - this view often blames the failure of Cymbidium goeringii and Cymbidium faberi to produce flower buds on the absence of "vernalization" or "vernalization effect"...

At the same time, because orchid growers in the south have successfully worked out a set of practices for making Cymbidium goeringii and Cymbidium faberi bloom under natural temperature conditions lacking low temperatures, some orchid growers misinterpret some means of promoting, preserving and improving flowers other than low temperature conditions as "vernalization" or "vernalization effect"...

All of this often leaves new orchid growers at a loss when dealing with the issue of "vernalization"...

In order to clarify these relationships, one must first understand "vernalization" or "vernalization effect" in the botanical definition...

The so-called "vernalization" or "vernalization effect" in the botanical definition refers to the phenomenon that a certain low temperature condition must be met to prompt a plant to complete "flower induction", form a "flower primordium", and then develop complete floral organs. Conversely, if there is no corresponding low temperature condition, flower buds simply cannot form. This is "vernalization" or "vernalization effect" in the botanical sense...

However, the formation of flower buds in Cymbidium goeringii and Cymbidium faberi does not require low temperature conditions. On the contrary, it occurs in the summer when temperatures are very high...

Some orchid growers have raised the question of whether the winter temperature several months before flower bud formation affects flower bud differentiation. Although this question remains to be further verified, from the information currently available, it can basically be ruled out. This is because in Guangdong and Guangxi, southern Fujian, Hainan, Hong Kong, Macao and Taiwan, and other places where winter temperatures do not reach vernalization conditions, Cymbidium goeringii and Cymbidium faberi are not unable to form flower buds under natural temperature conditions; rather, after budding, the buds wither or the flowers produced are of poor quality...

From a botanical point of view, Cymbidium goeringii and Cymbidium faberi (as well as Cymbidium tortisepalum and Cymbidium tortisepalum var. lianban, etc.) are not "vernalization plants"...

What orchid circles call "vernalization" is something that happens after flower bud formation. The so-called "vernalization period" of Cymbidium goeringii and Cymbidium faberi is more accurately a "dormancy period" or "winter dormancy period" entered after flower bud formation to inhibit physiological growth (vegetative growth) to meet the needs of further reproductive growth, and a certain low temperature condition precisely caters to this "dormancy period"...

But at the same time, this low temperature condition is not the only condition for Cymbidium goeringii and Cymbidium faberi physiological growth (vegetative growth) to enter the "winter dormancy period" or "dormancy period". Many years ago, orchid growers in Taiwan fully demonstrated this by using measures such as withholding water and reducing humidity under 15-20°C temperature conditions to "force" budded Cymbidium goeringii into a physiological growth dormancy period and obtain perfect blooms the following year...

In summary, what orchid growers often refer to as "vernalization" or "vernalization effect" is fundamentally different from "vernalization" or "vernalization effect" in the botanical definition, and can only be called "vernalization-like" or "vernalization in a broad sense"...

Strictly speaking, borrowing the term "vernalization" to describe the need of Cymbidium goeringii and Cymbidium faberi for low temperature to a certain extent after budding, thereby achieving perfect bloom performance the following year, is not very appropriate. However, since it has been said this way for so many years, let us tentatively call it "vernalization-like" or "vernalization in a broad sense" here...

We know that vernalization in the general sense refers to the induction and promotion of flowering in overwintering plants by low temperature, that is, if a plant does not experience this low temperature period, it cannot complete the initial differentiation of flower buds...

In 1918, German botanist G. Gassner discovered that rye has winter and spring types. Spring rye does not need to go through a low temperature period to head, so it can be sown in spring. Winter rye, however, needs to go through a low temperature period of 1-2°C before and after germination to head, so it must be sown in autumn. In 1928, Soviet agronomist Trofim Lysenko discovered that winter varieties of cereal crops, if not exposed to low temperature, remain in the tillering stage for a long time without jointing or flowering. If seeds of rye, wheat and barley are sown in a snow-covered field and subjected to a period of natural freezing, they can joint and flower. If just-germinated winter cereal seeds are frozen at 0-5°C for a certain number of days before sowing, they can joint normally no matter when they are sown. He and his colleagues applied this low temperature treatment method to agricultural production and called it "vernalization"...

In fact, the discovery of the "vernalization phenomenon" and the method of low temperature treatment of germinated seeds were not the first innovations of the Soviets. In northern China, as early as the Northern Wei Dynasty, the "wheat sweating method" recorded in Qi Min Yao Shu by Jia Sixie (putting germinated winter wheat seeds in a jar and placing them in a 0-5°C environment for low temperature treatment for 40-50 days before spring sowing) had long been widely used by the people, about 1400 years earlier than the Soviets...

Why is it said that the "vernalization" of Cymbidium goeringii and Cymbidium faberi is actually a kind of "vernalization-like" or "vernalization in a broad sense"? This is because by the so-called "vernalization period" of Cymbidium goeringii and Cymbidium faberi, their flower buds have already grown, that is, flower bud differentiation has already been completed, and what is needed is only a preparatory period for flower opening with relatively low temperature conditions within a certain period of time. Without this low temperature preparatory period, the flower stem often shrinks and the flower posture becomes listless...

As ornamental plants, the quality of the bloom is crucial for orchids, so in order to appreciate a perfect bloom, budded Cymbidium goeringii and Cymbidium faberi must have a sufficient low temperature period...

One point needs to be distinguished: budded Cymbidium goeringii and Cymbidium faberi, if not subjected to a period of low temperature, generally only show the so-called "early spring opening" phenomenon, and will not develop stunted buds, dry buds or rotten buds...

If stunted buds, dry buds or rotten buds do appear, apart from the fact that too high a temperature and other factors prevent vegetative growth from "braking" and the remaining nutrients of the orchid plant cannot meet the needs of rapid bud growth under high temperature, causing the buds to dry up, most cases are due to physical damage to the buds (such as bruising, scorching, freezing, smothering, water and fertilizer damage, infection damage). Another important reason is that the vegetative growth of the orchid plant, after being relatively stalled, unexpectedly restarts...

For a plant to flower and fruit, the first thing that must be completed is the transition from vegetative growth to reproductive growth. That is, after a period of vegetative growth, the plant can sense external signals (low temperature and photoperiod) and produce flowering stimulants. The flowering stimulants are transported to the shoot apical meristem, where a series of induction reactions occur, causing the meristem to enter a relatively stable state, namely the floral determined state. A plant that has entered the floral determined state possesses the ability to differentiate flowers or inflorescences, that is, it has completed so-called "flower induction". After completing flower induction, the shoot growing tip of the plant undergoes morphological changes; the meristematic cells in the surface layer of the growing tip divide rapidly, causing folds to appear on the surface of the growing tip, forming flower primordia at the places where leaf primordia originally formed, and then differentiating the primordia of the various parts of the flower on the flower primordia. This process is flower organ formation. Flower organ formation also requires suitable internal and external conditions, including light, temperature, water, fertilizer and physiological conditions, and only in this way can the entire flowering process be completed...

After the "flowering process" of Cymbidium goeringii and Cymbidium faberi is completed, the "floral organs" undergo further growth and development and then emerge above the pot surface in the form of a "flower bud". At this point, the orchid plant has basically completely entered the reproductive growth stage. After entering the reproductive growth period, its vegetative growth will be in a relatively stalled stage...

So what are reproductive growth and physiological growth (vegetative growth)...

Simply put: budding → flowering → seed setting is reproductive growth, while tillering → leaf opening → becoming a plant is physiological growth...

The reproductive growth and physiological growth of orchids generally do not proceed simultaneously and in parallel, but with a certain emphasis. When reproductive growth is underway, physiological growth is inhibited; when physiological growth is underway, reproductive growth is likewise inhibited. This is a kind of "survival wisdom" gradually evolved by orchids in their tens of millions of years of contest with nature based on the overall coordination of natural conditions and nutrient allocation...

In practice, it has been found that the early reproductive growth period of an orchid plant can be terminated. If at this time external factors cause the orchid plant to suffer unexpected stimulation (such as abnormal temperature rise, application of excessive nitrogen fertilizer, chemical stimulation, and repotting, etc.), the orchid plant will restart vegetative growth, which often leads to the interruption of its reproductive growth. In this case, even flower buds that have already formed will ultimately wither due to the interruption of reproductive growth...

There is also a relatively common situation: when the flower bud appears too early, because the external temperature is still relatively high at this time, the physiological growth of the orchid plant is difficult to inhibit (that is, the vegetative growth mentioned above cannot "brake"), which likewise triggers the interruption of its reproductive growth and ultimately leads to "flower bud withering"...

However, the later reproductive growth of the orchid plant (such as the "emergence from the sheath" of Cymbidium goeringii bud tips and the "bud alignment" period of Cymbidium faberi) cannot be terminated. At this stage, no matter how harsh the external environment or how few roots and damaged leaves the orchid plant itself has, as long as the orchid plant still has a breath left, it will carry flowering through to the end...

In the traditional orchid cultivation of Jiangsu and Zhejiang, potted plants that have already budded are generally not repotted after autumn unless there are special circumstances; in Di Yi Xiang Bi Ji, Zhu Kerou once said: "When Cymbidium goeringii is finished and Cymbidium faberi comes, do not plant it hastily when you find it; keep it until after Qingming before planting, and if planted early the flowers still will not open." The ancient orchid growers also first "dried them in storage" rather than potting directly for robust wild-collected Cymbidium faberi with buds that had not yet entered the "bud alignment" stage...