Monday, September 2, 2013

Plant story: the amazing buffalograss, Buchloë dactyloides


buffalo grass, Buchloë dactyloides
stand of buffalo grass, Buchloë dactyloides
grass family, Poaceae. Area is about 1 square yard.
  Buffalograss is one of my favorite plants. Grasses get walked over a lot, with people not even trying to tell them apart. One of buffalo grass's strengths might be recognizability. Once you learn what it looks like, it is easily recognized. The leaves are narrow green ribbons. The plant sends out runners which root and let it spread. It never grows more than 8-10" (20 cm) tall. You never have to mow a buffalo grass lawn.
herd of bison
herd of bison (old bad photo)
  For clarity I should state that I'm talking about Buchloë dactyloides, the buffalo grass that is native to the high plains of North America. There is a tall (3', 1 m) grass in southern Africa called foxtail buffalo grass which I have seen labelled "buffalo grass" online. I don't mean that buffalo grass. And, apparently South Africa and Australia call Stenotaphrum secundatum buffalo grass or buffalo lawn grass. In the U.S., the usual name for S. secundatum is St. Augustine grass. I don't mean that buffalo grass either. I mean the North American native buffalo grass Buchloë  dactyloides.
buffalo grass, Buchloë dactyloides
buffalo grass, Buchloë
 dactyloides,
closer view, area less than 1 square
foot. The grass blades are about 4"
tall.

  (I have no idea why there are dots, an umlaut, over the e. There are two syllables there, though: Buk lo ee).


   The "buffalo" in the name of the buffalo grass refers to the American bison, Bison bison, popularly called the buffalo. Buffalo grass, Buchloë dactyloides, apparently owes its distribution to the bison. And it contributed to the bison's success. In sum, they have a mutualistic relationship aiding both, even though they are grass and grazer.




buffalo grass,
buffalo grass, Buchlöe dactyloides
spreading on dry ground
   Buchloë dactyloides's nearest relatives are several species of little grasses found only in northwestern Mexico. In comparison, even before humans started cultivating it, buffalo grass was found from Mexico to the Canadian prairie provinces, from the east side of the Sierras to the edge of eastern forests in Wisconsin south to Louisiana. A very successful little grass.

    Why is it so much more widespread than its relatives? Probably because bison like to eat buffalo grass. As a food for bison and cattle, it is hard to beat buffalo grass. Buffalo grass is nutritious. (more info). Furthermore, it is nutritious wet or dry, fresh or frozen. Other prairie grasses store any nutrients they have accumulated during the year in their roots over the winter, so the late fall and winter prairie hay is really straw, with little food value for animals. Buffalo grass keeps the nutrients in the leaves. If a bison digs down through a foot of snow to find buffalo grass, it gets a good meal.

buffalo grass, seed capsules
buffalo grass, seed capsules
    Meanwhile, buffalo grass makes a hard seed pod, usually called a bur, up to 1/4 inch (1/2 cm) in diameter containing four seeds. The bur develops just off the ground amid the leaves (red arrows in the photo to the right). The grazing animal gets the bur with its mouthful of grass. It might bite the bur, which will probably kill the seeds, but it may swallow the little lump whole. The bur can withstand the digestion of the complex stomachs of bison and cattle, and it will be deposited, alive and well, in a nice moist, nutrient-rich heap of dung. Not an attractive spot to the rest of us, but a perfect spot for a germinating grass seedling.

     Jim Quinn of Rutgers demonstrated experimentally that buffalo grass seeds germinate much better after being eaten by bison.

buffalo, American bison, Bison bison
buffalo, American bison,
  Bison bison 
   So, where the buffalo roamed, there went buffalo grass, carried along in the animals' guts. The relatives that are found only in Mexico aren't continuously nutritious and don't hide their seeds among their foliage.

    Feeding the bison and being transported by them has made Buchloë dactyloides one of the dominant plants of North American grasslands.



(You can find buffalo grass as Buchloë  dactyloides and Bouteloua dactyloides. Same plant. The systematists don't agree.  I'll explain what's going on in another post. Until the experts sort it out, both names are okay.)

Comments and corrections welcome.

References
Quinn, J. A., D. P. Mowrey, S. M. Emanuele and Ralph D. B. Whalley. 1994. The "foliage is the fruit" hypothesis:  Buchloe dactyloides (Poaceae) and the shortgrass prairie of North America. American Journal of Botany 81(12): 1545-1554. (source of the details of the buffalo grass- bison mutualism) 

Weaver, J.E. Prairie plants and their environment. A fifty-year study in the midwest. University of Nebraska Press, Lincoln.

Kathy Keeler, A Wandering Botanist
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2 comments:

  1. Is this the same (or similar) buffalo grass that's used as a xeric lawn? I've always wanted that stuff...

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    Replies
    1. Yes! It is widely planted as a water-efficient lawn grass. I was just thinking I should have said that. Thank you!!!

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