Observations: “You Have the Care Down, and Now It’s the Feeding”

By definition, the main appeal of carnivorous plants lay in their ability to reverse the standard arrangement of who eats whom. Sadly, while serious enthusiasts can appreciate the fluting grace of a Sarracenia leucophylla trap or the dropping allure of its blossoms, all most people care about is that the plant catches and digests insects and other prey. That’s a start, but this is only one of the merits of raising carnivores. This aspect is also what gets most of them killed.

Let’s take a look at the most famous and most abused carnivore of them all, the Venus flytrap. Millions of flytraps are grown every year, thanks to the miracle of sterile tissue propagation. Many of these sell in grocery stores, hardware stores, home improvement centers, and any number of other locales, where they’re generally set up and neglected until they sell. It’s no fault of the proprietors, mostly because nobody bothers to pass on any information on proper care. Even with those nurseries and vendors who take the time to explain the basics of proper water and light, it’s hard to get past the lurid reputation of flytraps and their alleged dietary voraciousness. This means that no matter how many times a salesperson emphasizes the proper feeding of a flytrap, the customer usually rushes home and promptly fills every last trap with captured flies, earwigs, grasshoppers, cats, and chunks of stew meat.

That’s what kills the flytrap.

Much of the problem with working with carnivores of all sorts is trying to rewire people into realizing that pets, livestock, and crops aren’t little humans. The same mindset that causes someone on medication to take double the standard dose because “if a little is good, then more is better” usually leads to overfeeding of dog, lizards, birds, and carnivorous plants. Just because a Nile monitor will eat whenever food is offered doesn’t mean that it should eat a full meal every day, and just because a Venus flytrap has an open trap doesn’t mean it needs to be stuffed with protein. Under most conditions, when left out in the open, flytraps do a perfectly good job at capturing their own prey without assistance,and that means two to ten traps waiting for prey while one processes a recent capture.

The reason why carnivores have such problems with abundance involves their general habitat and environment. All carnivores live in marginal habitats, always lacking in nitrogen and potassium in a form usable by plants. This could be rain forest or jungle that receives incessant precipitation, such as the Nepenthes pitcher plants. For the flytraps, and all of the other carnivores of North America, the main habitat is stressed both by regular rains that wash away nutrients and regular brush fires that sterilize the soil and vaporize compounds containing nitrogen and other volatile gases. Instead of living in symbiosis with nitrogen-fixing bacteria, the way mesquite trees and red clover do, the carnivores catch their nitrogen and potassium on the wing, so to speak. Their prey also bring essential trace elements that also tend to be washed away or destroyed, and all of this gives a carnivore a strategic advantage in survival in habitats where few other plants have a chance.

The other critical aspect of carnivorous plant care involves a suitable amount of light, as discussed elsewhere, because carnivorous plants aren’t catching and digesting prey for energy the way carnivorous animals do. Instead of cracking fats and other compounds in their prey for energy, carnivorous plants utilize light in the same manner as any other plant for the production of sugars and starches, but also to produce the essential enzymes necessary to digest proteins. Many animals chew or tear their prey to increase the surface area of their meals exposed to enzymes in saliva, stomach fluids and bacterial action in the intestines, and many animals such as spiders and venomous snakes inject digestive fluids into their prey, helping to speed the process. Birds and crocodilians can’t chew, so they further grind their food with stones in their gizzards. Not a single carnivorous plant has the ability to chew, so they have to stick with prey small enough to be processed quickly, before it has a chance to rot. Snakes that eat prey too large for their stomachs, or that remain too chilled for proper digestion. ultimately vomit up the remains.

Venus flytraps that catch prey too large to handle can’t puke up their meals, and they can’t move somewhere warmer and brighter to finish digestion, so the trapped prey rots, ultimately killing the trap and sometimes the entire leaf. Since the leaf is still necessary for photosynthesis, if the flytrap’s already only getting a marginal amount of light, that leaf loss may kill the whole plant.

Some carnivores have ways around this situation, but most of those options are distasteful to humans. The cobra plant Darlingtonia produces no enzymes of its own, but it makes a home for both midge larvae and beneficial bacteria that break down trapped prey. Sarracenia and Heliamphora of all sorts provide homes for rotifers, mosquito larvae, and other animals that digest prey by proxy. Animals as large as frogs and spiders regularly raid carnivore traps for large prey and then defecate into the traps, thereby preventing rot and disease while getting a meal, and the huge-trapped Nepenthes bicalcarata even grows homes for predatory ants within its stems, so the ants will dismember and process prey, The most extreme example is the obscure sticky-leafed carnivore Roridula, which has no ability to digest prey on its own. However, it has a symbiotic relationship with at least one species of ambush bug: the plant snags and immobilizes prey, the ambush bugs kill and devour the prey, and the plant’s leaves catch the bug feces and absorb the available nitrogen.

Sadly, the poor Venus flytrap, because it seals its traps shut when catching prey, has no such options. This is why anyone keeping flytraps has to be particularly careful if feeding by hand is necessary. As a general rule, tips for feeding Venus flytraps also apply to other carnivores in cultivation, and they’re remarkably easy.

  1. As tempting as it is to do so, do NOT feed your carnivore as soon as you get it home. You’ve just purchased a new carnivore from the store or via mail order? You might end a long journey with a hearty meal, but that’s the last thing your plant needs before it’s adjusted to its environment. If you want your plant to live, get it situated into its new locale. If it’s going to be an indoor plant, get it potted and into a sunny window or under a suitable plant light. If it’s outdoors, put it into its hanging pot or into the greenhouse. In both cases, leave it alone. Don’t take it to school to show off. Don’t put it in the living room for a couple of days so friends and family can see it. Most importantly, don’t feed it at all until you see new growth, usually in about two weeks to a month, and holding off until a whole new leaf with trap grows from the crown of the plant is even better.
  2. Don’t forcefeed the plant. If you’re in a situation, such as in an office environment, where your plant is unlikely to snag prey and where letting prey loose might encourage harsh words from others, handfeeding is unavoidable. The trick is always to underfeed. Always remember “small prey in small portions” when feeding carnivores. Many will let you know if you’re pushing the limit: sundew and butterwort leaves will blacken and rot if they’re getting too much food, Sarracenia pitchers will grow large brown spots if too much prey is collecting too quickly in their throats, and Nepenthes pitchers will simply shrivel and turn brown. If one trap or leaf shows these signs, then this could be a minor accident, but if all of them start dying, cut back on the food NOW.
  3. Watch the temperature. It’s obvious that carnivores from temperate locales are more resistant to cold than tropicals, and some varieties, such as Darlingtonia and all of the Heliamphora, need much cooler temperatures than others. The two absolutes are that almost all carnivores stop digesting prey below 50° F (10° C), so don’t try to feed carnivores when the average daytime temperature goes below this. With carnivores that need an annual winter dormancy for survival, this restriction is even more important, because feeding a trap or leaf as the poor plant is trying to slip into dormancy is a great way to spread mold and fungus, and both of those could kill the plant before it ever has a chance to revive in spring.

    Alternately, even plants that survive in harsh heat (the Lithops stone mimics of South Africa and the saguaro cactus of Arizona are prime examples) shut down photosynthesis when the ambient temperature exceeds 90° F (32° C), and carnivores aren’t exempt from this. Many of Australia’s sundews form tubers during summer, when the heat is too much for active growth, and revive when autumn rains return. Most of the Sarracenia will stop producing traps and produce photosynthetic leaves called phyllodia when the temperatures get too high, and most of Australia’s Stylidium triggerplants wait to produce their carnivorous flower scapes once summer’s heat has broken. Even Venus flytraps exposed to high temperatures will cease to function for as much as a week, as the traps temporarily convert back into standard photosynthetic leaves. If you try to feed your flytrap via a new trap and it won’t accept food, check the temperature and try to lower it if at all possible. For the record, most temperate carnivores can tolerate temperatures up to 100° F (37° C) for a short time, but they don’t like them.

  4. Ask friends and bystanders to leave the traps alone. After about four triggerings, whether or not the trap actually captures prey, Venus flytrap traps stop functioning and become nothing but photosynthetic leaves. This can happen accidentally, if the trap keeps getting set off by prey too small to be trapped or prey too strong to remain inside. In captivity, though, the main cause is from smartalecks who want to demonstrate how the traps operate by tripping them over and over. (This, incidentally, also applies to triggerplant flowers, as they’ll only fire about four or five times before becoming a female flower and becoming nonfunctional.) If you want your flytrap to stay healthy, don’t set off traps to demonstrate their abilities to your Aunt Phil unless you’re adding prey.
  5. Finally, DO NOT FEED YOUR CARNIVOROUS PLANT MEAT, RAW OR COOKED. Yes, the labels on far too many carnivorous plant containers in grocery stores and home improvement centers read “Will even eat hamburger!” This is actually a very sly way to get you to keep buying new carnivores as the previous ones keep dying. Yes, the general definition of a carnivore is an organism that eats meat. Yes, some of the big Nepenthes pitchers can capture and eat vertebrates as big as rats. Humans can also chew and swallow plastic, but a regular diet of Styrofoam is just as lethal to you as hamburger is to your Venus flytrap.
    Now, many authoritative guides to raising carnivores give this advice, but almost none give a reason as to why. Most insects are relatively fat-free, gram for gram, compared to large vertebrates, so the carnivores generally don’t need enzymes for digesting fat. When your flytrap catches a ladybug or spider, what fat was in the prey remains on the shell left behind when digestion finishes and the trap opens, where it acts as bait for opportunistic hunters. Now, take a quick look at the fat content of your hamburger meat: even the “ultra-lean” brands are still about seven to ten percent fat, and typical hamburger is closer to 30 percent fat. Go ahead and fry up a batch of the hamburger that you’d serve to your flytrap and note how much grease collects in the pan. A lot more than you expected, eh?

    (Now, at this time, you may point out that many large carnivorous plants catch vertebrate prey from time to time. Sarracenia will occasionally catch tree frogs, even if most are ones that died of natural causes and fell into the trap. As discussed before, though, any carnivore big enough to catch even the smallest vertebrates usually has lots of cooperative organisms that don’t have a problem with digesting fats. The Venus flytrap, also as discussed before, doesn’t have that option, so knock off the meat. Stay away even from such fat-free fish foods such as scraped beef heart, and while it’s fun to watch Cape sundews wrapping around little bits of chocolate, ask yourself how often they’d be catching cocoa butterflies in the wild.)

Remember: small prey in small portions, and don’t go crazy. Your flytrap or pitcher plant won’t be able to thank you now, but just wait until it blooms next spring.

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