Winter Carnivore Cleanups – Venus Flytraps

Backstory: it’s January, we don’t have any distractions, and the plants need us. Therefore, it’s time to discuss methods to clean up carnivorous plants for spring. For details, go back to the beginning.

By the middle of January, if you’ve decided to avoid the surefire ways to kill your Venus flytrap (Dionea muscipula), it should be dormant. Between the shortened days and cooler temperatures, if you haven’t forced it to stay active, it’s catching every photon it can get in its quest to turn sunlight and water into starch, in order to have enough energy on standby to get it through the next growing season. If outside temperatures went well below freezing, then most of the traps would be frosted off and blackened, but a core in the center of the plant will remain green. If it wasn’t exposed to that much cold, the long-stemmed traps it produced during spring are all or mostly dead, leaving a small cluster of short-stemmed traps close to the soil. Some of those traps may still close if triggered, so don’t trigger them: recent research suggests that a flytrap uses marginally more energy to reopen a trap than it would gain from that trap’s photosynthesis. Besides, it has few if any insects to catch this time of the year, and it wouldn’t have enough energy to produce the digestive enzymes it would need to consume them anyway. All we’re going to do here is clean them up a bit now, so as to avoid disrupting them when they’re coming out of dormancy in spring. (“Spring” in this context is defined by the date where generally the risk of late frost has passed. In the Dallas area, that date is usually around March 17, although we’ve had occasional later freezes all the way into the beginning of April. For the most part, though, the recommendation of flytrap dormancy stretching from “Thanksgiving to St. Patrick’s Day” holds, with the first new growth starting around then and the first blooms appearing by the middle to end of April.)

For this exercise, the following tools or their analogues are highly recommended:

  • Garden mat or old towel
  • Isopropyl alcohol, bottle or wipes
  • Hand cloth or paper towels
  • Spray bottle filled with rainwater or distilled water
  • Narrow garden shears or garden scissors
  • Long tweezers or alligator forceps
  • Tamper

Everyone raising carnivorous plants has at least one story about Venus flytraps being thrown out by January because “I thought it was dead,” either by their hand or that of a loved one, and it’s a bit understandable. In the photo above, you can see three Venus flytrap cultivars: “King Henry” (left), standard flytrap (center), and “Aki Ryu” (bottom), and they’re way past their summer prime. The long-stemmed traps of summer and fall are all dead, and any latent color is now prominent. The Aki Ryu in particular looks dead, mostly because it blends in with the soil, but all three still have their central core alive and photosynthesizing. Leave them alone and keep them moist, and you should see the first new traps growing from the center, and maybe even new plantlets growing off the roots, by the vernal equinox. There’s no reason why we can’t clean up everything a little bit and make sure everything is okay right now, though.

The first thing to do is to remove any weed seeds before the plants get established in the spring. Grass seeds tend to turn up in sphagnum moss, and any plant exposed to the outdoors has a chance of seeds blowing in on the wind or transported by birds. Since the preferred soil mix for Venus flytraps is extremely acidic and nutrient-deprived, this tends to encourage the growth of opportunists such as clover and violets, and it’s much better to get them out now than later when they’ve choked out the flytraps half to death. When doing so, try to use forceps: they’re much more effective than fingertips at pulling out the entirety of a weed seedling instead of leaving the roots to come back later.

As with most carnivores, a good gauge for flytraps is “if it’s brown and dry, get rid of it.” Dead leaves aren’t going to revive, so snip them off with scissors and remove them. As tempting as it may be, do NOT try to yank or pull off dried leaves, as they tend to be stronger than the plant’s roots. Even if you don’t uproot your flytrap, you’ll still cause it damage which could lead to opportunistic infestations or infections, so take the effort to cut them off and remove the temptation.

And now for a bit of plant anatomy with this freshly trimmed model. Each leaf is separated into two lobes (the two sides of the trap) and the stem, officially known as a petiole. The petiole will perform some photosynthesis, but the overwhelming amount of photosynthesis is done with both lobes of the trap. On the edges of the trap can be seen the trapping hairs or cillia, and in the center of each lobe, in an equilateral triangle, are the sensory hairs that cause the trap to close.

(Fun fact: those sensory hairs are bioelectric generators, based on research published in 2020. Moving any hair generates a microelectric charge which dissipates after about 10 seconds, so either two hairs have to be tripped at once or any two hairs tripped within ten seconds to build up a charge that sets off specialized cells at the trap hinge and causes the trap to close. Well, the trap closes most of the way: prey that’s too small to be worth the effort are able to squeeze out and prey too large can just pull themselves out, and if the trap was accidentally set off by a passing animal or a torrential rain, the trap will reopen within a day or so. But if the prey hits the trap’s Goldilocks zone, though, that critter repeatedly brushing against the sensory hairs causes the trap to seal shut and release digestive enzymes, and the soon-liquefied prey is absorbed by the plant through glands all over the trap surface. Three to four days later, the trap opens up again, leaving the indigestible portions of the prey on the lobe surface to help attract spiders and ants in search of an easy meal.)

Thanks to the power of selective breeding, flytraps don’t just come in green. Several flytrap cultivars are all-red, with chlorophyll concealed with a red pigment. As you can see here, the red pigment is much like a suntan: give an “Aki Ryu” flytrap insufficient sun, and the whole plant will go the same green that appears here where dead leaves covered the live leaf surface. Because of this deep brick red coloration in dormancy, be especially careful not to cut off living leaves while attempting to remove dead ones.

Every once in a while, a flytrap will retain its long-stemmed traps into spring. Note the concave shape of the traps on the long stems: at this point, these traps are now nothing but photosynthetic surfaces, and almost always, no force on earth could get them to close, no matter how many times their sensory hairs are stimulated. So long as they stay alive, they keep transferring energy to the main plant. If it really bothers you, snip these leaves off as well, but this isn’t necessary.

(As a bonus, in the photo above, check out the spot on the trap on the bottom right. That used to be a young jumping spider, that was either attracted by an insect carcass in the trap or just happened to step in the wrong place while searching for prey. A surprising number of spiders get caught in flytraps, which suggests that the spiders are able to see into the ultraviolet spectrum far enough to see the UV-fluorescing patches on each trap lobe.)

Now time for a Before & After. In the “Before,” it would be understandable to assume that this flytrap was dead or at least dying. Only a couple of tiny traps are visible from underneath dead leaves, and the plant sure looks as if it’s about ready to kick it at any time. Let’s withhold judgment, though, until all of those dead leaves are out of the way.

What a difference a cleanup makes. This is the same plant without stems and leaves in the way, and without the violet seedlings that would have choked it out in spring. Technically, these are the same plants, as three plantlets to the right of the main plant are themselves getting established. Treat a flytrap right and give in the growing conditions it needs, and that one plant will clone itself over and over and ultimately fill this whole globe in a few years. If it becomes necessary to repot this flytrap, right now is a perfect time to do so, as it will be subject to a lot less stress when dormant than it would be if it were at the height of summer growing.

Finally, carnivores purchased from commercial greenhouses, or even carnivores grown in close proximity to others, have a tendency to pick up benevolent hitchhikers. Many sundews and bladderworts readily spread seed as far as they can during blooming season, and some of their progeny may show up in flytrap pots. In this case, we have two species: the sundews (probably Drosera spatulata or D. tokaensis) are pretty obvious, but barely visible are the tiny leaves from a terrestrial bladderwort, probably Utricularia subulata. Some carnivorous plant enthusiasts are adamantly opposed to these hitchhikers and will remove them at any opportunity, while others look at them as getting an additional carnivore for free. That’s completely up to you. Considering that these sundews won’t survive a cold winter, and that the bladderworts aren’t coming close to competing with the flytraps for room or prey, removing them is probably more trouble than it’s worth, and the brilliant canary yellow blooms of a good-sized U. subulata colony in spring are a welcome surprise.

To be continued…

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