Tsuru Collection 鶴 • No. 062

Why do tea plants enter dormancy?

In winter, some tea plants appear to suspend their growth. Yet, beneath the scales of the buds, the plant is not simply “asleep.” It is undergoing a succession of physiological states that are already preparing for the return of new shoots.

In some tea plantations, winter profoundly transforms the garden.

The tea plants remain green. They do not necessarily lose their leaves like a deciduous tree. Yet, the young shoots harvested to make tea slow down, and may then stop developing.

From the outside, the phenomenon seems simple: it is cold, so the plant no longer grows.

The reality is more interesting.

In Camellia sinensis, bud dormancy corresponds to a set of mechanisms that allow a perennial plant to adapt its growth rate to the seasons. Temperature plays a role, but it does not act alone. Day length, cultivar, the physiological state of the tea plant, its reserves, and many internal signals also contribute to the process.

And above all: a bud that does not grow is not necessarily in the same state as another immobile bud.

This is where our journey begins.

1. Can a perennial tea plant really enter dormancy?

Yes.

The tea plant is a perennial woody shrub with evergreen foliage. In many regions, it therefore retains a significant portion of its leaves during the unfavorable season.

But perennial does not mean permanent growth.

What particularly interests the tea producer are the meristems contained in the buds: they are what will produce the future shoots, and then the young leaves that can be harvested.

When seasonal conditions change, these buds may interrupt their active development.

Winter dormancy then constitutes an adaptation that allows growth to be synchronized with a more favorable period.

2. Sleeping or simply unable to grow?

This is probably the most important distinction in this entire article.

Plant physiologists distinguish several forms of dormancy depending on the origin of the growth blockage.

Paradormancy

The bud is restrained by another part of the plant.

A classic example is a lateral bud held in dormancy by the dominance of a shoot located above it. If the inhibitory signal disappears, this bud can resume its development.

Endodormancy

Here, the lock is within the bud itself.

Even if you immediately place the plant in apparently favorable conditions, the bud will not necessarily start again.

Its internal physiological state must first change.

Ecodormancy

The bud has regained the physiological ability to grow, but the environment still prevents it.

Cold, for example, can keep a bud in this state even though it would be able to restart if temperatures became sufficiently favorable.

This distinction completely changes the way we look at a garden in winter.

Two apparently immobile tea plants may actually be at different physiological stages.

3. What triggers dormancy in the tea plant?

Two environmental signals constantly reappear in research on tea plant dormancy: temperature and photoperiod, that is, the daily duration of light.

As the unfavorable season approaches, days shorten and temperatures drop.

For the plant, these variations provide information.

Historical studies on the tea plant have proposed short days and sufficiently low temperatures as being associated with the onset of winter dormancy. But it would be misleading to derive a universal threshold from this that applies to all gardens in the world.

Behavior varies notably according to:

• the cultivar;
• latitude;
• altitude;
• local climate;
• garden management;
• and the thermal history experienced by the plant.

A tea plant grown in a subtropical region with a pronounced cold season therefore does not necessarily follow the same calendar as a tea plant grown in a warm climate that allows for much more continuous growth.

This is also one of the reasons why speaking of the “annual cycle of the tea plant” as if it were identical everywhere would be an oversimplification.

We had already encountered this diversity in the Tsuru No. 009 dedicated to the harvest seasons.

4. What does the bud really do during this period?

Saying that the tea plant “sleeps” is convenient.

Biologically, however, the word can give a false impression.

A dormant bud is not a dead piece of plant.

Transcriptomic analyses conducted on tea plant buds have shown major changes in the activity of thousands of genes during the different phases of dormancy and the return to growth.

Researchers have notably observed changes concerning:

• hormonal signaling;
• regulation of the cell cycle;
• carbohydrate metabolism;
• stress responses;
• communication between cells;
• regulation of gene expression.

In other words, visible immobility masks complex biological activity.

The tea plant may no longer be producing a shoot that can be seen lengthening every day, but its bud is changing state.

5. Do hormones hold the key?

They are part of the key.

Recent research on Camellia sinensis particularly highlights changes in the signaling pathways of several plant hormones.

Abscisic acid, often abbreviated ABA, is regularly associated with the maintenance of dormancy and responses to cold or stress.

Conversely, during the resumption of growth, certain pathways related to gibberellins—GA—as well as cytokinins and auxin change.

However, one should not imagine a simple switch:

ABA = sleep / GA = awakening.

The reality involves much broader regulatory networks.

Studies published in 2026, for example, identified a regulatory module in the tea plant involving the CsWRKY21 and CsDREB17 factors in dormancy and bud break. Cold and ABA participate in this regulation.

Other studies also show changes associated with hormonal pathways, regulatory proteins, cell cycle activity, and energy metabolism.

Breaking dormancy therefore appears to be a true physiological transition, not simply the result of a thermometer exceeding a specific temperature.

6. How can cold both stop and prepare growth?

This is one of the most interesting paradoxes.

Cold first contributes to the cessation of active growth and the establishment of the winter cycle.

But a prolonged period of low temperatures can also contribute to the change that leads some buds from endodormancy to a state where they will be able to grow again.

Once this transition is complete, the bud may find itself in ecodormancy.

It is ready.

But the environment is not yet.

When temperatures become favorable again, growth can then resume quickly.

This is an essential difference between:

7. What happens when the tea plant “wakes up”?

When conditions become favorable, the bud gradually enters a bud break phase.

Metabolism intensifies.

Cells resume their activity of division and expansion.

Reserves accumulated in the plant can be remobilized to the developing young tissues.

The tea plant then operates according to a source and sink logic.

Organs capable of providing resources—mature leaves, stems, roots, and accumulated reserves—feed the young buds, which become powerful “sinks” of carbon and nutrients.

At the beginning of the spring resumption, this mobilization of reserves helps support the new shoots before their own photosynthesis can fully contribute to their development.

Then appear the tissues the producer is waiting for:

bud, first leaf, second leaf…

The harvest cycle begins again.

8. Is this what explains the reputation of spring harvests?

Only partly.

Spring harvests often follow a period of slowdown or dormancy in regions where winter is pronounced enough.

The young shoots then develop under particular conditions of temperature, light, water availability, and growth rate.

Depending on the regions and teas, the first spring harvests may exhibit chemical balances different from those observed later in the season.

This contributes to their characteristic sensory profiles and also explains their high commercial value in certain production traditions.

But beware of an overly attractive conclusion:

The final quality also depends on the cultivar, terroir, precise weather conditions, harvest date, picking standard, and above all, processing.

A remarkable tea remains the result of a chain of factors.

To understand this point further, you can find the Tsuru No. 059 dedicated to altitude and the Tsuru No. 009 dedicated to the harvest season.

9. And the famous First Flush?

The term first flush refers to the first major growth spurt or first harvest period after the resumption of vegetation, its precise use varying according to the producing regions.

It is particularly well known for Darjeeling teas.

However, the expression does not mean:

“leaves that have slept during the winter, and are therefore necessarily superior.”

It first places the harvest in a vegetative calendar.

The sensory and commercial value of a First Flush then comes from the set of conditions that shaped this growth and the work carried out after picking.

This is an important nuance for understanding harvest mentions without turning them into absolute quality labels.

10. Do all cultivars wake up at the same time?

No.

And this difference greatly interests breeders and producers.

Cultivars may exhibit different behaviors regarding:

• dormancy depth;
• its duration;
• bud break date;
• the growth rate of young shoots;
• tolerance to low temperatures.

Recent molecular studies precisely compare cultivars exhibiting different dormancy periods and resumption dates.

This characteristic can have considerable economic importance.

An early cultivar can allow for a faster harvest in spring.

But earliness also carries a risk.

Very early bud break can expose particularly fragile young tissues to a late frost event.

Being the first to start again is therefore not always an absolute advantage.

Here we find a principle already encountered in the Tsuru n°008 dedicated to cultivars: no interesting trait ever exists independently of its environment.

11. Can climate change disrupt this clock?

This is now an important question for perennial crops.

The calendar of spring depends heavily on thermal conditions.

Milder winters, earlier temperature rises, or unusual alternations between warm and cold periods can change the phenology of woody plants.

In the tea plant, the question is complex because several effects can overlap.

A warmer spring can advance bud break.

But earlier growth can also be exposed to late frost.

Conversely, in certain situations, a major change in the winter regime could change how the physiological needs related to dormancy are met.

The answer will depend heavily on the regions and cultivars.

It would therefore be incorrect to summarize the situation as:

"warmer = better harvest"

or

"cold winter = better tea".

The plant responds to a succession of conditions, not to an isolated temperature.

What we will remember

Tea plant dormancy is not a simple absence of growth.

It corresponds to a succession of physiological states during which the bud changes profoundly, even when nothing is visible to the naked eye.

Temperature and day length contribute to the calendar, but the cultivar and the plant's internal state also matter.

During the winter, a bud can go from true endodormancy to a state where it is physiologically ready to start again but remains held back by external conditions.

Then comes bud break.

Reserves are mobilized, cellular activity resumes, and young shoots appear.

A few weeks later, some of these shoots will become the first harvests of the year.

Dormancy therefore does not create great tea on its own.

But in many terroirs, it is one of the invisible chapters that precede the leaf we will eventually find in our cup.