Introducing Proboscidea louisianica

As with any standard garden, 2011 had such promise for the Triffid Ranch. As with any standard garden, 2011 proceeded to make fools of us. We’re not losing whole crops out here the way West and Central Texas are, but that’s mostly because I had the opportunity to invest in a near-tripling of the previous rainwater cache, and that’s the only reason why half the plants aren’t dead. Many of the experiments were utter failures, and others survived for a short time before collapsing in the freeze in February or the early stages of the June drought. Not all has been a failure.

Surprisingly, the biggest success this summer wasn’t in the usual contenders. It’s been a banner year for exotic Capsicum peppers (including surprising successes with Bhut Jolokias, still considered one of the world’s hottest), and I’m getting ready to start more in preparation for this autumn. The real surprise, though, was with a species I was told was extremely hard to start: Proboscidea louisianica, also known as the unicorn plant or the devil’s claw.

Proboscidea louisianica, the devil's claw

As Stewart McPherson notes in his book Carnivorous Plants and Their Habits, Volume 2, Proboscidea is problematic. In many ways, it appears to be carnivorous, as it attracts and captures various small insects on the bottoms of its leaves. However, nobody has found evidence either of actual digestive enzymes being produced by the plant, or of an animal proxy (as with the South African plant Roridula that does the digesting in the plant’s stead. McPherson notes that the leaves and stems secrete a considerable amount of mucilage, with an odor that attracts mosquitoes and fungus gnats. I’ve also noted that under UV light, the leaves have a very high fluorescence: even more so, in fact, than its blooms. P. louisianica may not be a full carnivore, but it’s definitely leaning that way.

Anyway, after being warned repeatedly by such authorities as Peter D’Amato that getting Proboscidea seeds to germinate was very difficult, I looked on with my usual hubris, said “Let me give it a shot,” and ordered a package from the International Carnivorous Plant Society seed bank. Due to weather fluctuations and prior commitments, I wasn’t able to sow them until the end of May, and I suspect that a consistent soil temperature of above 75 degrees F (23.88 degrees C) for at least thirty days is a major factor. Next winter, I plan to experiment with heat pads intended for sprouting tomatoes and peppers, in order to remove the possibility of light influencing germination.

The plants themselves were stunted somewhat by the dryness, but 14 out of 16 seeds sprouted, with 12 plants alive today. Throughout May and June, they produced large numbers of pink, yellow, and white flowers, which bore markings resembling a mouth with teeth. These were exceedingly popular with both bees and wasps, with both jostling each other for pollen. By the beginning of July, the first fruit formed, which helped explain the common name “unicorn plant”. The pods look much like okra pods, but with a long, thin extension at least as long as the rest of the pod. As they matured, they split from the tips of the extensions, explaining the other common name: devil’s claw.

Proboscidea louisianica seed pods

A quick note to anybody interested in CGI effects for film or video: I’ve been joking all summer that devil’s claw pods look more like an early ship design proposal for the Nineties science fiction show Babylon 5 than anything floral in origin. Have fun.

Devil's claw seed pod

Most articles on Proboscidea suggest that the seed pods evolved to take advantage of Pleistocene megafauna, such as mammoths and ground sloths, for seed distribution. It’s easy to understand why. Most devil’s claw seed pods have two prongs, but occasionally they’ll show four. At the tip of each prong is a very strong and very sharp claw, which have no problems with snagging on fur, hair, clothing, and bare skin. Even though the direct evidence is lacking, the surmisal appears to be sound, as these dried seed pods are ridiculously strong as well, and could drop off kilometers away from where they were picked up by an inattentive mammoth.

Devil's claw interior

The interior of the seed pod, though, is just as interesting. Each pod noted so far has four seeds that hang very loosely on the inside of the pod. Those tend to break free with the slightest jostle, such as from the removal of a pod from the plant stem, and scatter on the ground immediately underneath. (If you’re trying to collect seed from your own plants, I highly recommend putting a plastic bag around the seed pod before trying to remove it.) The others, as shown in this photo, remain locked inside for a time, and are gradually shaken free. As McPherson suggests, this not only allows the plant to drop seed in a known area amenable for Proboscidea growth, but also to take it far beyond its original range. This helps explain why Proboscidea ranges throughout the southern and southwestern US, into Mexico, and down into South America.

Now, most accounts of Proboscidea note that the unripe seed pods are edible, but I haven’t taken the chance to find out. That may come later: as with tomatoes, Proboscidea seems to die back slightly in extreme heat, but produces buds that expand later when growing conditions are more suitable. This fall, I’ll get to find out if this hypothesis is accurate. More details will follow as the year continues.

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