Author: Luca Parolin
Photo: Luca Parolin
Reading Time: 10 min
Those who approach the world of carnivorous plants for the first time are often surprised—and
sometimes worried—when, with the arrival of autumn or winter, some plants begin to “die”: leaves
turn yellow, traps dry out, and growth comes to a halt.
What may initially seem like a problem is in fact a natural and indispensable process: dormancy.
Understanding dormancy is essential not only for growing carnivorous plants correctly, but also
for avoiding common mistakes that can compromise their long-term health
What is dormancy (and why is it so important)?
Dormancy is a period of vegetative rest during which the plant drastically slows down or
completely stops its growth. It is an evolutionary response to unfavorable environmental
conditions, particularly:
• low temperatures
• reduced daylight hours
• decreased availability of insects
In many temperate plants, the transition from winter to spring is not random but is tightly
regulated by environmental signals. Among these, chilling requirements and the accumulation of
growing degree days are essential for synchronizing vegetative and reproductive development.
The chilling requirement, or chilling units, corresponds to a range of low temperatures—typically
between 0 and 10 °C—during which the plant slows its growth and accumulates energy reserves.
Growing degree days measure the accumulated heat necessary for phenological development
During dormancy the plant is not inactive, but instead concentrates its energy in vital organs—
rhizomes, roots, and buds—to survive the winter and restart more vigorously in spring. Skipping
this period is equivalent, for the plant, to never sleeping: at first it may appear “active,” but over
time it weakens and eventually declines
For temperate carnivorous plants such as Dionaea muscipula, Sarracenia, Drosera, and
Pinguicula, this mechanism is fundamental. Winter cold allows them to:
• complete dormancy without metabolic stress;
• accumulate sugars and other reserve substances in the rhizomes;
• regulate plant hormones necessary for the production of new traps and flowers;
• ensure a vigorous restart in spring.
In other words, dormancy is not merely a period of inactivity: it is an essential biological process
that synchronizes the plant’s life cycle with the environment and ensures long-term health.
Dormancy in the most common temperate carnivorous plants
Commonly known as the Venus flytrap, Dionaea muscipula is probably the most famous
carnivorous plant, but also one of the most misunderstood. With the arrival of the first autumn
chills, it naturally enters dormancy: growth slows, traps gradually become smaller, and many
leaves die off completely. It is not uncommon for beginners, observing this change, to think the
plant has died—sometimes even throwing it away or bringing it indoors for protection—without
realizing that this is a completely normal process. During winter, only a low, compact rosette
remains visible, while the underground rhizome stays perfectly alive. Skipping this rest period is
harmful: a Dionaea that does not enter dormancy weakens year after year and eventually dies
prematurely.
Sarracenia is a genus of North American carnivorous plants adapted to well-defined seasons and
cold winters. With the arrival of autumn, they enter dormancy: growth stops, many pitchers
produced during summer turn yellow and gradually dry out, and in some species they are
replaced by non-carnivorous leaves called phyllodia. Even if the aerial part is drastically reduced,
the underground rhizome remains alive and healthy. As with Dionaea, forcing a Sarracenia to
remain active during winter by keeping it indoors in warm conditions leads to progressive
weakening and increasingly poor growth in subsequent years
Temperate sundews, such as Drosera rotundifolia, D. intermedia, and D. anglica, exhibit one of
the most evident forms of dormancy. As temperatures drop, the carnivorous leaves disappear
completely and the plant forms a hibernaculum—a small, compact, protected bud that encloses
the vital tissues. During winter, the plant may appear completely absent or dead, but in reality it is
simply enduring the most unfavorable period of the year. In spring, with rising temperatures and
increased light, the hibernaculum opens and produces new, fully functional carnivorous leaves.
Temperate European and North American butterworts show a particularly interesting type of
dormancy. In autumn, the summer carnivorous leaves are gradually replaced by a compact
rosette of non-carnivorous leaves, often thicker and closer to the ground. This transformation is
completely normal and represents a survival strategy against cold temperatures and reduced
insect availability. Even though the plant’s appearance changes dramatically, its root system and
growth center remain alive. A proper dormancy period is essential not only for overall plant health,
but also for good flowering in the following season
Practical Tips for Cultivation During Dormancy
• Gradually reduce watering (keep the substrate only slightly moist)
• Ensure cool temperatures (0–10 °C for many species)
• Leave the plant outdoors or in a cold, bright environment
• Remove only completely dried parts
• Be patient
Mistakes to Avoid
• Bringing the plant indoors to warm conditions
• Continuing to fertilize or feed the traps
• Exposing the plant to complete darkness
• Letting the substrate dry out completely
• Artificially stimulating growth
Do all carnivorous plants go dormant?
Not all carnivorous plants require a winter rest: the main difference depends on their native
habitat. Tropical and subtropical species such as Nepenthes, Heliamphora, Cephalotus follicularis,
many Utricularia, and some Drosera (for example, Queensland sundews) originate from
environments where temperatures remain relatively stable year-round and there is no true winter.
These plants are therefore adapted to continuous growth: vegetative metabolism and the
production of leaves and traps do not stop, even during the “cooler” months of their natural
habitat. Growth may slow slightly if conditions become less favorable, but they never enter true
dormancy. Conversely, attempting to force a rest period in these tropical species—by exposing them to very low temperatures or drastically reducing light and humidity—can be harmful, compromising their
metabolism and overall health. For these plants, the key is to provide stable and consistent
conditions of temperature, humidity, and light to encourage continuous, vigorous growth.
Subtropical species and partial dormancy
Some particularly hardy subtropical species can also be grown at cooler temperatures during winter, inducing a kind of partial dormancy. Subtropical Drosera come from regions with relatively mild climates year-round. These plants do not require mandatory dormancy, but under certain conditions—especially when temperatures drop slightly in winter or light levels decrease—they may slow their growth or reduce the production of new carnivorous leaves. This slowdown is natural and not a cause for concern: the plant remains perfectly alive. However, forcing a prolonged artificial rest at very low temperatures can be risky. Keeping these plants in mild, humid conditions instead allows them to be grown in an active vegetative state all year. Some species, such as Drosera capensis, are very hardy and can tolerate temperatures close to freezing, while others are much more delicate and should not be exposed to harsh cold.
Summer dormancy
In addition to the typical winter dormancy of temperate species, some Drosera have developed the opposite strategy, known as summer dormancy, linked to climates characterized by hot, dry summers. This adaptation is typical of groups such as tuberous Drosera, many petiolate Drosera, and some pygmy Drosera, mostly native to Australia. In these environments, the most critical period for survival is not winter, but summer, when high temperatures and drought make active growth impossible During summer dormancy, the aerial part of the plant may be drastically reduced or disappear entirely: in tuberous Drosera, survival relies on underground tubers, while in petiolate and pygmy species the growth center enters a quiescent phase with a strong metabolic slowdown. During this period, the plant suspends the production of carnivorous leaves and focuses on conserving the energy reserves needed to face the next favorable season. A distinctive feature of pygmy Drosera is the production of gemmae—structures for asexual propagation that generally form during the most favorable season and represent not only a means of reproduction, but also a survival strategy. From a cultivation perspective, it is important to recognize that pygmy Drosera do not require an obligatory cold dormancy, but benefit from seasonal management that respects their natural cycle. With the return of more favorable conditions—usually milder temperatures and increased moisture—the plant resumes active growth. Cultivationally, it is essential to respect this natural cycle: keeping these Drosera constantly wet and stimulating growth during summer can lead to rot and decline. In this case as well, dormancy is not a problem, but an essential evolutionary strategy that ensures the plant’s survival in its natural habitat.
In conclusion
Dormancy is not a problem to be solved, but a natural process to be respected.
Understanding it means growing carnivorous plants that are healthier, longer-lived, and more
vigorous over time.
