Wild Proboscidea in Oklahoma

I’m just back from a 10-day research trip to Oklahoma. I’ll have more pictures to post soon, of all kinds of cool things. One of the most surprising and interesting things I discovered on the trip was Proboscidea – not the mammalian order of elephants and their relatives, but the genus of plants with wacky seed pods native to the Americas.

I say I “discovered” Proboscidea, but all I mean by that is that I became aware of their existence – a personal discovery rather than a scientific one. People have known about them for a long time, and indeed Native Americans have been using the plants and even semi-domesticating them for millennia. The plants have several common names, including “ram’s horn” and “unicorn plant”, but they appear to be most commonly referred to as “devil’s claws”, and that is the name they’re known by in the Oklahoma panhandle.

The weird horns on the seed pods are adapted to snag on the limbs of passing critters, especially large ungulates, and cling there. As the animals wander around, they spread the seeds by either shaking them out of the pods or crushing the pods underfoot. Either mechanism works – the seeds and the pods they grow in are both incredibly tough, and a lot of gardeners find that the seeds don’t germinate well unless they’ve been scarified or even cracked open like sunflower seeds. Or so the internet tells me. I don’t have any direct experience of growing Proboscidea yet, but from pods too damaged to make good souvenirs I collected a couple dozen seeds, which I will attempt to germinate later this spring.

I accidentally got some personal experience with their typical mode of dispersal. I collected a double handful of undamaged seed pods and passed most of them out to students on our field trip, saving only a couple back for myself. I put those two in the back seat of Rich Cifelli’s truck, on top of my coat. By dinnertime it was dark and I’d forgotten about them when I reached into the back seat to grab my coat. As I walked toward the camp, I felt something dragging on my pant leg – it was the two devil’s claws, which had gotten tangled with each other and with me when they’d fallen out of the truck. I’d stepped on one and cracked the tip off of one of its horns, but the other pod, shown here, was completely undamaged. The seed pods are essentially made of springy wood and it takes a lot to damage them. This one rode home in my carry-on luggage, with the horns held at a 90-degree angle to the pod by a stack of books.

I didn’t put any scale bar in these photos – of course – but if you’re curious, this particular seed pod is almost exactly 12cm tall, wide, and long (~5 inches).

One final point – I assumed that the genus name Proboscidea referred to the obvious similarity of the dried seed pods’ horns to the tusks of mammoths. But some of the online sources I’ve seen suggest that the name relates to the proboscis shape of the green, unsplit pods. I’ll try to track down the original description to find out which interpretation is correct, but whatever the answer, it’s pretty interesting that the same part of the same plant could look like both an elephant’s trunk and its tusks at different points in its development.

If you’d like to read more about Proboscidea, the most complete source I’ve found online is this page by Wayne Armstrong at Palomar College – in particular check out the photos of green seed pods that have not yet split open, which looks like fat green beans. There’s more useful information on this page and in the comments on this one. If anyone knows of better sources, or has personal experience growing devil’s claws, please let me know in the comments.