What are these alien-looking lower Hudson flora/fauna?
December 6, 2010 4:03 AM   Subscribe

While walking beside the Hudson in Poughkeepsie last July, I noticed that the ground was littered with these spiky, alien-looking black "shells." They're mostly hollow, and have a "wingspan" of about 1-1/2 inches. What on earth are they?
posted by ROTFL to Science & Nature (15 answers total) 3 users marked this as a favorite
Best answer: Water caltrop, invasive species from Asia. AKA 'Bat Nut' or 'Devil's Head' seed pods. UBC Botanical Garden Thread, Wikipedia.
posted by cobaltnine at 4:15 AM on December 6, 2010 [2 favorites]

Response by poster: Thank you, cobaltnine! Funnily enough, I was calling them "Devil's Toenails" in the absence of a real name. Guess I wasn't far off....
posted by ROTFL at 4:26 AM on December 6, 2010

Response by poster: And now a follow-up question: How did they get all over the walkways by the shore? They weren't washed up on a beach; these walkways were about 8 feet above water level, along a retaining wall. I looked up "trapa natans" (the scientific name) and I didn't see any explanation for how they would be brought up out of the water.
posted by ROTFL at 7:31 AM on December 6, 2010

They could have been left there by someone who was eating them, or planned to eat them.
posted by Logic Sheep at 7:59 AM on December 6, 2010

Response by poster: Possibly, Logic Sheep. They weren't in piles, though; they were scattered widely and randomly across about 150 ft of waterfront.
posted by ROTFL at 8:07 AM on December 6, 2010

Wikipedia says they're an invasive species from Vermont to Virgina, so they may have grown there as well.
posted by Logic Sheep at 8:36 AM on December 6, 2010

My thought would be one has a bag, is walking along the beach eating them, and tossing the shells as they are eaten. Ergo your distribution.
posted by cobaltnine at 9:19 AM on December 6, 2010

Bat cocoons.
posted by elder18 at 9:38 AM on December 6, 2010

Response by poster: Well, I've been Googling, but I can't figure out how you eat the dang things. These were totally intact "shells" -- a few of them appeared to be crushed, but most were intact, so there was no way anything could have been removed from them. Do people just eat the foliage? Or is it possible that birds harvest them and then sometimes get scared away before they can eat them?
posted by ROTFL at 9:38 AM on December 6, 2010

Any chance they got there by a flood?
posted by buttercup at 10:53 AM on December 6, 2010

Best answer: And now a follow-up question: How did they get all over the walkways by the shore?

I worked as a volunteer with US Fish and Wildlife last summer on a water chestnut eradication program and we removed tons of water chestnut from a local creek. As much as we tried no to, we left behind many seeds up on shore. There may have been a local Riverkeeper or other organization doing a hand-pull of water chestnut in the area where you were, and they may have pulled the weeds but left some seeds behind.

The other (possibly more probable) reason that you would see them is that their seed dispersal depends upon downstream transport in flowing water. As fall arrives, the green stems wither and detach, leaving the spiky seeds to roll downstream and stick to some other place. It's likely that the Hudson overtopped its banks and some of the seeds were left on the floodplain.

Whatever you do, don't throw them back in the water. It's a really expensive, time-consuming and long term process to get rid of these things.

Also, these are not the same water chestnuts that you get in Asian cuisine. I don't think anyone is eating them.
posted by kuujjuarapik at 11:11 AM on December 6, 2010 [1 favorite]

Response by poster: Thanks, kuujjuarapik -- both for your volunteer work and for your answer. No worries about throwing them back, since my 5-year-old boy and I were both enthralled by the things and collected dozens to take home. What's really amazing about them is how different each one is. They're like little goth abstract sculptures.
posted by ROTFL at 11:48 AM on December 6, 2010

They're edible (there's a bin of them in the produce section at most of the Asian markets around here), but apparently should not be eaten raw.
posted by Lexica at 7:01 PM on December 6, 2010

What, then, is the correct way to dispose of these invasive little gremlins, to be sure they don't have any progeny? Can they just be tossed out with the kitchen garbage, or do they need to be burnt to a crisp or otherwise decimated?
posted by exphysicist345 at 7:17 PM on December 6, 2010

Best answer: They may indeed be edible, but they are still very distinct from the ones that you would get in a Chinese restaurant stir-fry. That chestnut is Eleocharis dulcis from China. The invasive is Trapa natans from Europe. Still edible according to your link, but not likely to be harvested as such in the US without a major change in demographics. No demand, no human harvest impact, still a problematic invasive species.

The correct way to dispose of them (according to USFWS in my area) is composting. We sent about 17 dumptruck loads to a composting facility where they were arranged in windrows, to be later sold for commercial compost after several months or when they were no longer deemed a threat. But a landfill would be acceptable, they will hopefully degrade before reaching another waterway. Really that is all it takes, just keeping the seeds out of waterways. I have a few on my shelf because they are so good looking, and I don't foresee anyone chucking them into a river when I'm gone. Maybe I'll leave a note.

The trick was to harvest the green chestnuts before they had a chance to disperse their seeds, and dispose of them then. That way the plant would have used most of its energy to produce bountiful seeds, but not be able to transfer that energy into the next generation. It is a long term effort, and each year we hope to see new growth decline until they disappear. But hope is a crappy strategy and nuking from orbit is not environmentally sound. So it will be pulling them out by machine or hand until they're gone.

It looks like there are plans underway to do the same in the Hudson in the next few years.
posted by kuujjuarapik at 8:02 PM on December 7, 2010

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