Arthraxon hispidus

Earlier this year, September 14th to be exact, while driving a gravel road through a section of the Mark Twain National Forest I noticed a dramatic change in the structure of the roadside vegetation. My brain instantly weighed my desire to stop and investigate against my need to get some real work done. Before I could make up my mind, my foot hit the brake. It always does.

What I had seen was a large colony of grass that superficially resembled Microstegium vimineum in overall stature and habit. However, the inflorescences more closely resembled Bothriochloa bladhii.

Luckily, I had my copy of "Steyermark’s Flora of Missouri" (Yaskievych 1999) riding shotgun. A quick run through the keys gave the name Arthraxon hispidus.

I had heard of this grass before, though I had never seen it. It occurs rather sporadically throughout the eastern U.S. and is more common in the southeast (Kaufman and Kaufman 2007). Vegetatively, it is readily identified by its clasping leaves (similar to Dichanthelium clandestinum) and strongly ciliate leaf margins.

Arthraxon hispidus is native to Japan and Eastern Asia. The first record of its occurrence in the U.S. came from Pennsylvania in 1877 (Yatskievych 1999). As with its gross morphology, it seems to prefer the same habitats as Microstegium vimineum; mesic to wet disturbed sites in open forests and floodplains. The most likely mode of dispersal seems to be from logging equipment and trucks, also similar to Microstegium vimineum. I don’t know that this grass has great potential for invasion in Missouri, but it was dominating the roadside where I found it for 50 or 60 meters and appeared to be spreading into the surrounding pine woodland. This county record represents the fifth county it is known from in Missouri (as of 1999). Regardless, the accumulated effects of several weak invasives can be as detrimental to a local ecosystem as one strong invasive, if not more so. Let's hope it behaves itself.
------------------------------------------------------------------------------------
Kaufman, S.R. and W. Kaufman 2007. Invasive Plants: Guide to identification and the impacts and control of common North American species. Stackpole Books. Mechanicsburg, Pennsylvania.
-------
Yatskievych, G. 1999. Steyermark's Flora of Missouri. Conservation Commission of the State of Missouri. Jefferson City, Missouri.

Comments

  1. Great, just great. Just what our sad little pine woodlands need now...

    ReplyDelete
  2. That's a new one for me. It appears to be known from two counties in Indiana along the Ohio River. While those ciliate-margined, broad leaves are pretty cool-looking, I hope I never see this grass around here. It sure looks like it could become a problem given the way it is growing. You should write a note on your recent important finds, including this one. It's important to get the word out about these invasives before they get too out of control.

    ReplyDelete
  3. Invasive species are a lot like cancer under America's health care system. Early detection in the key, but no one can afford to go to the doctor.

    ReplyDelete
  4. Arthraxon was first described for the state in beautiful Forest Park in St. Louis. As such, I have had my eye on it for a few years now and don;t think it is going to be a huge problem. It certainly seeks out disturbed areas, but seems to just loll around. It doesn;t seem to spread very rapidly or persist in the face of competition. Luckily, we have plenty of disturbance in the Park, so we have kept our populations. I sure hope I didn;t spread it anywhere, and I will definitely let you know if and when the populations explodes!

    ReplyDelete
  5. I sure hope Steve is right about it behaving itself except in disturbed habitats. I've not seen it before, but I'll be keeping an eye out! Thanks for letting us know about it, Justin. What county was it in?

    ReplyDelete
  6. I found it in Phelps County. A few weeks later I saw two populations of it in Arkansas (Ouachitas). They were relatively small and restricted to disturbed areas along the trail. From what I can find about it, it seems to be more of a problems in floodplains than uplands.

    ReplyDelete
  7. Ha! Look where I ended up while looking for info on Microstegium vimineum! I'll have to start watching for Arthraxon hispidus too!

    ReplyDelete
  8. Interesting, in Australia it is listed as a threatened species and grows sparsely in paddocks and adjoining bush. It does not seem to be as vigorous as the pictures you have shown.

    There is currently work being done to translocate from areas where new highways are proposed. It is amazing how a threatened species in one place is a weed in another.

    ReplyDelete

Post a Comment

Popular posts from this blog

JUNCUS BRACHYPHYLLUS AND THE CASE OF THE MISSING PRAIRIES

Carex aureolensis

The Elymus of Imagination