The weather has been strange in North Texas, but not as strange as it was last year. That said, we’ve had odd fluctuations in both temperature and humidity, with mixed results among the carnivores. The flytraps and butterworts love the available prey, and they can’t complain about surprisingly cool mornings. The Sarracenia, though, are having a few problems, and it’s because they’re a little too good at their jobs.
For the uninitiated, this is the throat of a North American pitcher plant hybrid, Sarracenia spp.. For a lot of insects, this is one of the last things they’ll ever see. The hood on top secretes nectar that attracts everything from gnats to wasps, and the throat of the pitcher produces even more. On good days, you can actually see wasps hanging on with their rearmost pair of legs, desperately trying to keep their balance and not fall in. If they do, well, they aren’t getting out. The nectar contains a drug called coniine, getting the bug drunk in small doses and becoming lethal in large ones, so that only improves the odds that they’ll slip.
Unlike the other plants worldwide that garner the name “pitcher plant”, Sarracenia are a bit more aggressive in retaining prey. Sarracenia shares with its distant cousins a wide throat area lined with wax, so dislodged insects that lose their grips slide inside. Like their cousins, the throat is shaped so that any bug that tries to fly out finds that it’s actually pulled deeper into the plant’s trap. (This isn’t completely true, as some insects and their larvae regularly feed on larger relations that can’t escape. However, we’re talking about the majority.) About a third of the way down, though, the inside of the pitcher is lined with sharp and strong downward-pointing hairs, and I can attest from bloody experience as to their strength and sharpness. (Let’s just say that cutting a damaged pitcher in half lengthwise and running your finger the wrong way up the pitcher interior isn’t exactly like running your finger up a bandsaw blade, but the effect is much the same.) Trapped bugs get a choice: fight the flow of the hairs and get punctured, or keep going down. Ultimately, the bugs run out of “down”, and that’s when the plant secretes digestive enzymes and breaks down the doomed critter. The plant absorbs needed nitrogen and phosphorus, and the vermin census in the immediate vicinity is down by one.
As just about everyone who ever keeps Sarracenia is concerned, the plants are absolute pigs. In particularly lively periods for bugs, the pitchers can literally fill to the rim, with insects falling in and then crawling right out over the corpses of their brethren. In more insidious cases, though, one can see these strange burn spots on the pitcher sides, looking as if someone took a lighter to the trap. Beginners understandably panic about a blight or other disease and start spraying, but the real reason is a bit more insidious.
To find out more, you have to give whole new meaning to “peeking under the hood”. With a gentle touch, it’s possible to bend the hood back and take a look inside. (Afterwards, wash your hands, and make sure that you don’t put your fingers in your eyes or mouth before doing so. I’ve never had a problem with coniine toxicity, but that’s probably because I don’t take risks with the same active ingredient that makes hemlock-cooked hot dogs so tasty.)
And here’s the problem. The previous few days saw two major factors that affected this Sarracenia: ridiculously dry days and ridiculously moth-filled nights. The relative humidity outdoors reached as low as 15 percent, meaning that the plant couldn’t produce its digestive fluids as quickly as it would have liked. Since Sarracenia don’t have teeth or other structures to increase the surface area exposed to enzymes, the trapped moths, and there are a lot of moths down there, started to rot before the plant could digest them. If the rot is bad enough, it burns the inside of the leaf, working its way out, leading to those scars on the outside of the trap.
Now, this can happen in different circumstances, usually involving extremely low temperatures or lack of sunlight. In this case, it was caused purely by low humidity combined with especially intense sun due to that lack of humidity. (The sun was intense enough to give some of my cactus sunburn, and it helped keep me inside until dark.) Either way, the affected pitchers themselves will die, ultimately, but the portions that didn’t burn will continue to take advantage of the nitrogen bounty and pass that to the rest of the plant. By September or October, this will be a very, very happy pitcher plant.
As an aside, when watching Sarracenia in the wild or in collections, keep an eye open for other interlopers. When I was first exposed to Sarracenia when living in Tallahassee a decade ago, I noted the number of green tree frogs that camped out in the pitchers. It’s a very handy relationship for both plant and frog. The frog has a place to hide from predators, and prey comes to it instead of the other way around. The plant effectively gets a set of teeth, as the frog snatches prey too large for the plant to digest effectively and then uses the pitcher as a toilet afterwards. The plant certainly isn’t complaining about getting its nitrogen pre-chewed, and if the frog dies of natural causes, then the plant gets a bit more. Other animals will take advantage of the situation, particularly spiders, but you’d be amazed at the variety. I regularly get baby Hemidactylus turcicus geckos that stalk both Sarracenia and Nepenthes pitchers in search of an easy meal, and they also don’t complain about having a good hiding locale in the middle of the day. I’ll just start worrying when I find fence swifts and other lizards in there, too.