Why Do Perennials Return Each Spring?

ByKen

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This article answers the question why do perennials return each spring using two sources: a review of dormancy release and bud break in perennial plants, and a University of Wisconsin horticulture article on plant dormancy. The short version is that perennials are built to stop growing in fall, to hold still through winter, and to restart when the season signals spring. The sections below explain the cycle, the role of cold and day length, the hormones involved, and what the sources do not cover.

Quick answer

  • Perennials go dormant in fall, which is a built-in pause in growth rather than a sign of death.
  • Cold exposure over a period of time is needed before growth can resume in many perennials.
  • Abscisic acid holds buds in dormancy, and the level falls over winter until growth-promoting hormones can take over.
  • Warmer days and longer light in spring restart growth, and existing plants survive winter to resume growth.

Perennials run on a yearly cycle

The review points out that “Unlike annual plants, perennial woody plants undergo a repeated cycle of growth, dormancy, and recovery.” The Wisconsin article makes the same point in everyday terms: “Every fall we see trees, shrubs, and herbaceous plants go dormant as winter approaches and wait for them to resume growth when spring arrives.”

The cycle is dependable. The Wisconsin article says that “the dormancy process is very dependable, as both existing plants and seeds in the soil survive to resume growth after winter fades away.” The phrase “existing plants” matters here, because it means the plant that returns is the one that was already in the ground, not a new seedling.

The review describes the seasonal order in woody plants. “In order to survive harsh winter conditions, perennial trees in the temperate and frigid regions enter a dormant state and cease growth in late summer after vigorous growth in spring and summer.” The article adds that this dormancy and the release from it are “crucial for the adaptations of woody plants and their survival in the natural environment.”

How dormancy starts in fall

The review says that “In late summer, buds of perennial plants cease their growth and enter a state known as bud set which is induced by disadvantageous environment such as short daylength.” Shorter days are one of the main signals. The review also states that “The cessation of growth and establishment of dormancy in trees are mainly induced by short day length.”

Once the buds are dormant, they carry a hormone load that keeps them still. The Wisconsin article explains that “In late fall, dormant buds in trees and shrubs have elevated levels of abscisic acid to keep them dormant.” It describes the hormone as “Often called the dormancy hormone,” which “inhibits any growth processes from starting at incorrect times.”

The review describes the stages in more detail. It says that “The cycle of plant dormancy and active growth has been proposed to include the transitions between endodormancy and ecodormancy.” Endodormancy is the deeper stage. The review notes that “Once endodormancy is established, active growth cannot be restored by promotive conditions unless endodormancy state is broken by long-term low temperature rather than merely the presence of low temperature.”

That last point explains why a warm spell in mid-winter does not wake a perennial. Only a long enough cold period moves the bud out of the deeper stage, which the review describes as breaking endodormancy.

Why cold is needed before spring growth

The Wisconsin article states plainly that “True plant dormancy requires exposure to a cold period to resume active growth.” It adds that this “ensures winter survival and avoids growth starting during mid-winter mild weather.” The article ties this requirement to winter survival.

The timing of the cold is also specific. The article says that “Bud dormancy is broken by exposure to a certain minimum temperature over a required period.” It also says that “Extreme cold is not required, and an unusually cold spell in winter does not accelerate the process.” The count is the length of the cold period, not the depth of one freeze.

The review agrees that a prolonged period is what matters. It says that “After experiencing a prolonged cold period during winter, trees release dormancy and reenter ecodormancy at the end of winter.” Only after that does the bud respond to warmth. The review then states that “upon exposure to promotive conditions, trees will initiate bud break and subsequently engage in active growth.”

The review also gives a cellular detail that supports this pattern. It says that “Under low-temperature conditions prevalent in winter, the expression of fatty acid desaturase genes in trees is induced to reduce the saturation of membrane fatty acids, thereby maintaining membrane fluidity.” In plain terms, the cells adjust their membranes to keep them fluid. The review does not say this adjustment is the trigger for spring growth, so it should be read as part of winter survival.

How spring restarts growth

Spring growth depends on more than warmth. The review says that “Although rapid growth in spring is induced by warmer temperature and longer day length, the reactivation of plant growth is primarily triggered by prolonged periods of low temperature, so long-term low temperature is like a signal that prompt trees spring is approaching.” This is a useful way to read the timing: winter cold tells the plant that spring is coming, and warmer days then speed up growth.

The Wisconsin article gives the same sequence in its own words. Abscisic acid “levels slowly drop until reaching a level that can be overcome by growth promoting hormones.” It then says that “Increasing light and accumulating warmer days of spring raise growth hormone levels, thus plant growth resumes.”

The review adds gibberellin to the picture. It says that “The content of GA in trees is synthesized and downregulated in response to short day conditions,” and that this “indicating that GA may regulate the release of tree dormancy.” The wording of the review is cautious, and the link between gibberellin and dormancy release is described as a possibility.

Abscisic acid has a role in the review too. A study cited there suggests that “ABA negatively regulates poplar dormancy release.” The review therefore fits with the Wisconsin article: abscisic acid holds dormancy, and its reduction is part of what allows release.

Genes behind the timing

The review describes the regulators in more detail for poplar. It says that “Photoperiod and temperature are key regulators in the bud dormancy and break cycle.” Among the genes it covers, one is described this way: “EBB1 acts as a positive regulator of bud break.” The review also says that “PttEBB1 is induced under low-temperature conditions, where it represses ABA to promote the expression of EBB3.”

These gene details are dense, and most come from one tree genus. The review’s own captions say the regulatory networks are “based on studies from poplar.” A reader should treat them as a model for how the timing works in woody plants, not as a list of genes that every perennial shares.

The review also shows that species differ. In apple, the text says that “apple dormancy is induced by low temperature rather than short-day photoperiods.” So the trigger for dormancy is not identical in every perennial, even though the broad sequence of fall dormancy, winter cold and spring growth is shared.

Why the plant comes back from the ground

Perennials return because the parts that matter most survive winter. The Wisconsin article says that “both existing plants and seeds in the soil survive to resume growth after winter fades away.” For a perennial, the crown, roots and buds are the living core. The Wisconsin article applies that survival to existing plants in the ground.

The review notes that growth resumes in a particular order. Once buds are released, they “initiate bud break and subsequently engage in active growth.”

How we chose these sources

We picked one review article on dormancy release and bud break in perennial plants, and one extension article from the University of Wisconsin on plant dormancy. Both URLs were requested directly with curl, and each returned HTTP 200 on 2026-10-28. The review covers woody perennials in temperate and cold regions. The extension article covers trees, shrubs and herbaceous plants at a general level. Neither source is a retail page.

What we could not verify

The review is focused on woody plants and on poplar in particular. Its gene-level material comes from one tree genus, and it does not give a single model that covers every perennial. The extension article gives the general sequence but does not give timing for any region or any plant. Neither source gives a number of cold days for a named perennial, so this article does not offer one.

What the sources do not say

The sources do not describe how to protect a perennial’s crown through a specific winter, and they do not say when to remove winter mulch. They also do not give a fertilizer schedule for spring regrowth. For those practical questions, the guides on how to prune perennials and how to fertilize perennials cover the care side, which these two sources do not address.

Frequently asked questions

Why does a perennial not grow during a warm spell in January?

The Wisconsin article says that dormancy “requires exposure to a cold period to resume active growth,” and that this “avoids growth starting during mid-winter mild weather.” The review adds that once endodormancy is established, growth “cannot be restored by promotive conditions” until a long cold period breaks it.

Is a perennial dead when its top growth disappears in fall?

No. The Wisconsin article says that “Every fall we see trees, shrubs, and herbaceous plants go dormant as winter approaches and wait for them to resume growth when spring arrives.” The plant is paused, and the living parts stay in place.

Does more cold always mean an earlier spring?

No. The Wisconsin article states that “Extreme cold is not required, and an unusually cold spell in winter does not accelerate the process.” The process depends on a required period at a minimum temperature, not on one very cold event.

What is abscisic acid in this process?

Abscisic acid is the hormone that keeps buds dormant. The Wisconsin article describes it as “Often called the dormancy hormone,” and says that its “levels slowly drop” over winter until growth-promoting hormones can take over.

Do all perennials respond to cold in the same way?

No. The review says that in apple, “dormancy is induced by low temperature rather than short-day photoperiods,” which shows that the triggers can differ between species.

Sources

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