Wednesday, July 2, 2014

One Man's Milkweed, Another's Poison

I understand that there are biologists, both amateur and professional, who curse Carl Linnaeus for his Latin-infested taxonomic classification system, and I am sometimes among them.  I personally am quite thankful that someone else spent a lifetime pulling apart flowers and describing floral sex organs, because I don't possess the most minute fraction of the patience required.  On the other hand, all the Latin is a bit off-putting.  Today, however, I guess if Linnaeus hadn't been such a stickler for reproductive organ detail, I'd never have been able to identify the new wildflower in my untamed prairie backyard.  Well, Mike Haddock, the genius behind helped quite a bit as well.  Being able to look at a collection of native flowering plants grouped by bloom color and month of bloom is a big aide to those of us who can't count stamens.

This new find is Whorled Milkweed, or Asclepias verticillata L. as it was known to Linnaeus.  I'd never have guessed that this perennial was related to my ubiquitous Asclepias tuberosa because it is not my nature to stare lewdly at flower parts;  I look at leaves, and commonly fail at identification because leaf shapes are reborn again and again in different plant families.  Look, for example, at the leaves of Whorled Milkweed.  I would think those thin leaves resemble a coreopsis family member, but their whorled pattern around the stem is responsible for the species name. Surprise, surprise, the favorite habitat of this one to three foot tall plant is a place in dry prairies with chalky or limestone soils, so my yard is as much of an Eden for Whorled Milkweed as it is for me.  I'd just never seen it before.

Whorled Milkweed, also known as Horsetail Milkweed, grows in colonies just as depicted in the photograph to the left, and it is poisonous to livestock.  Luckily, it tastes so bad that it is rarely consumed from the pasture.  Whorled Milkweed, as other milkweeds, may contain cardiotoxins and neurotoxins, and dosages as low as 0.1% to 0.5% of body weight may cause death in hooved animal species.  The toxins are not inactivated by drying; thus the biggest danger to livestock is the feeding of hay containing the plant.  Clinical signs include profuse salivation, incoordination, seizures, and gastrointestinal upset and death may occur 1-3 days after ingestion.  So, all in all, the presence of this plant in my backyard may not be so exciting as it first seemed.  I need to remember not to cut my backyard for hay to feed to the donkeys, and I may have to watch that the dog doesn't take a bite of the plant, but otherwise I'm glad that Whorled Milkweed is back in my prairie.  

1 comment:

  1. I discovered whorled milkweed by accident the 2nd summer we were here - and now the occasional plant or two have grown into a couple nice sized patches. This plant has really (pardon the pun) grown on me! Individually, it is just a wimp, but in a colony I find it graceful and attractive.

    I'm aware of its toxicity to livestock, which makes me cringe a little as I let it grow in the Back 5, but I console myself that grazers avoid it because of its taste. I guess there would just be spraying to do before we'd ever be able to hay.

    I've seen monarchs nectar at the blooms, but I haven't found any monarch caterpillars growing on it. To be fair, though, monarch cats are pretty rare these days in general.


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