Dionaea muscipula

A trap that counts touches

Each leaf ends in two hinged lobes edged with stout bristles, and the inner face of each lobe carries three trigger hairs ^[11]. A single touch does nothing. According to Flora of North America, the hairs must be touched twice in close succession before the trap snaps, in under a second, and this double requirement keeps raindrops and debris from setting it off ^[2]. Laboratory work by Böhm and colleagues puts the window at roughly 15 to 30 seconds between the two electrical signals that a touch produces. The same study found that the plant only switches on its digestive genes after further stimulation, with about five signals needed for strong expression, which is what a struggling insect supplies ^[12].

This fits two pieces of ICPS advice. Traps given dead food have to be massaged so they seal and digest ^[7], and a trap that is not stimulated enough will reopen after about a day with the food undigested ^[13]. The ICPS feeding page suggests a piece of rehydrated bloodworm about a third the size of the trap ^[13]. A trap that closes on nothing simply reopens the next day, so triggering it out of curiosity is harmless; the ICPS checklist even treats closing speed as a health check, with slow closure pointing to a leaf that is too young or too old, or to too little light ^[8]. More on this in traps not closing.

Individual leaves last only a few months, and a healthy plant keeps producing new ones while the oldest turn black ^[8]. See why traps turn black for when blackening is a problem.

What the plant looks like

The plant is an evergreen rosette growing from a bulb-like rhizome made of fleshy leaf bases, and it keeps its leaves rather than forming a tight overwintering bud ^[11]. Petioles are winged, and the trap faces range from green to bright red. Flora of North America notes that petiole length varies with both genes and growing conditions, and that strong sun often, but not always, brings out the red ^[2]. White flowers appear on a leafless stalk in late May and June in the wild ^{[11, 2]}.

Cultivated forms differ mainly in these traits. The ICPS guide describes ‘B52’ as keeping short petioles all year, ‘Justina Davis’ as making no red pigment at all, and ‘Korean Melody Shark’ as having long petioles that take up space. Many plants put up tall, narrow-stalked leaves in spring as flower stalks emerge ^[7].

Fire-maintained savannas of the Carolinas

The wild range is small. The US Fish and Wildlife Service describes a historical range within about 161 km (100 miles) of Wilmington, North Carolina, with the largest populations in wet pine savannas and flatwoods of the Outer Coastal Plain and smaller ones in Sandhills seeps ^[3]. Flora of North America records it at 0 to 100 m and notes that in this corner of the Carolinas it grows alongside at least 16 other carnivorous plant species, the highest diversity of carnivorous plants known anywhere ^[2].

Fire is the key habitat factor. NatureServe summarizes research suggesting the plant declines when fires come less often than every three years, because woody plants move in and shade it; it also cites soils with a pH of about 3.9 to 4.5 ^[4]. Plants found in Florida, New Jersey and Washington are introductions, not native populations ^[2].

Law and conservation status

North Carolina made the taking of wild Venus flytraps or their seed a Class H felony in 2014; the only exception is a permit signed by the landowner and carried on site ^[5]. Federally, a 2016 petition led to a full status review, and in July 2023 the Fish and Wildlife Service concluded that listing under the Endangered Species Act was not warranted. Its finding counted 18 populations in moderate to high condition holding nearly 865,000 plants, and named fire suppression and other habitat loss as the primary threats, with poaching and small population size as added stressors ^[3].

Other assessments are less reassuring. NatureServe ranks the species G2G3, counts 74 extant natural occurrences with roughly 880,300 plants, and cites an estimate that up to 70% of historical sites have been lost ^[4]. IUCN has also assessed the species for its Red List, in an assessment published in 2000; see the assessment for its category ^[14]. International trade falls under CITES Appendix II, which exempts seeds and sterile tissue-culture flasks ^[6]. The Fish and Wildlife Service asks buyers to purchase only plants grown from tissue culture ^[15]; see buying plants legally.

Dormancy: two positions, two situations

The sources agree on outdoor plants. A plant outside where its growing point will freeze must already be dormant, or be moved to shelter ^[9]. The ICPS guide says fully dormant plants can survive a week frozen solid if they are kept from drying out, and that in USDA zones 7 and 8 the risk comes from unusually cold winters and early or late freezes ^[7]. NC State Extension describes the wild dormancy as running from November into early spring, triggered mainly by shortening days, and recommends at least 10 weeks at about 2 to 10 °C (35 to 50 °F) for plants given a dormancy, with protection from hard freezes below about −7 °C (20 °F) outdoors ^[10].

Indoor plants are where the sources part ways with the older books, which the CPN article says assumed every flytrap needs a winter rest ^[9]. The ICPS guide states that Venus flytraps under strong lights need neither a terrarium nor dormancy, and that putting one in the refrigerator for dormancy is wasted effort ^[7]. It shows plants that have grown indoors under lights for more than 10 years ^[7], and its author names strong light and regular feeding as the keys to growing them that way ^[9]. The Extension article accepts this for plants under dedicated grow lights but expects windowsill plants to go dormant on their own ^[10].

Both the ICPS guide and the Extension article warn against moving plants back and forth between regimes ^{[7, 10]}. The dormancy guide covers the outdoor method in detail.

Feeding, repotting and new plants

Plants that catch nothing need feeding. The ICPS recommends live insects or rehydrated dried bloodworms and warns never to fertilize the soil ^[8]. Well-fed plants grow fast and need repotting every year or two, when they hit the pot edge or the soil turns salty and new traps die before opening ^[9]. The ICPS checklist also suggests removing flower stalks so the plant does not spend energy on them ^[8]; see Venus flytrap flowering.

Repotting is the time to make new plants. Leaf bases pulled from the old part of the bulb and set into peat and sand can be separated as small plants after about five months ^[16]; the steps are in leaf pullings. Seed is slower: the ICPS guide says a seedling can take five years to mature without regular feeding, and that commercial nurseries propagate selected plants by tissue culture instead ^[7].