2017 May 24

When I photographed this grass stalk beside the road on June 28, 2016, any grasses that hadn’t been mowed had mostly grown to their full heights (this one was almost three feet tall), and were mature enough to make their seed heads.


Waiting for them to mature is really useful for telling grasses apart, because most of them have very similar leaves and stalks, but very distinctive seed heads. This one, for example, is quite obviously quackgrass, Elymus repens, also known as Couch grass, twitch, dog grass, witch grass, and several other common names


The seed head has separate florets that are enclosed in glumes that zigsag up the stalk.


The leaves are fairly broad for a grass, and are particularly good for that trick where you take a blade of grass, clamp it between your thumbs so that there is a little air passage around it, and then blow across it to make a loud screeching noise.


Quackgrass is a very hardy plant, as can be seen from the way that it was muscling its way up through the pavement on the shoulder of the road. It is a perennial that mostly spreads by rhizomes, which are roots that travel horizontally just below the surface of the ground and periodically send up new plants. It is not native to North America, although it was (accidentally?) introduced way back in the 1600s and so has had a lot of time to spread.

Quackgrass is an noxious weed, it tends to crowd out a lot of other plants, particularly crops like corn, wheat, and oats. The rhizomes make it particularly hard to get rid of, because if you pull it out it just comes back up from the roots, and if you plow it just tears the rhizomes into pieces and spreads them around, where they produce new plants. For a long time, the most effective method for controlling it in fields was to let the field lie fallow for a year while you went out and tilled it maybe once a month, which eventually used up the ability of the rhizomes to resprout. But, this meant that the field had no cover for an entire year, leaving it wide open for erosion and loss of topsoil, so it wasn’t exactly optimum.

Which is why, back in 1974, Monsanto introduced the herbicide glyphosate, under the trade name Roundup. The original use of this was to clear the quackgrass (and similar plants) out of fields where they had taken over. The procedure was still to let the field go fallow for a year, but instead of plowing and cultivating, the plants were just allowed to grow until they were going well. Then, the glyphosate was sprayed on. The key feature of glyphosate is that it is absorbed by plant leaves and then translocates throughout the entire plant. It then interferes with the synthesis of certain amino acids that the plant needs to grow, and so it dies. And unlike other herbicides, it kills the whole plant, roots and all, and so the quackgrass rhizomes die as well. It binds to soil particles so that it isn’t readily available to plant roots, and breaks down in the environment pretty quickly (anywhere from a week to maybe 200 days, depending on bacterial activity). As a result, within a few weeks of applying to a field, all of the weeds are dead and the farmer can now cultivate the field and plant whatever crop is desired. It even made it possible to use “minimum tillage” agriculture, where the field is not plowed, and the crops are planted directly in the mulch, which greatly reduces soil erosion.

Of course, now glyphosate is used in a lot of other ways, some of which people take exception to. But finally making it possible to get rid of quackgrass once and for all was its first real “killer app”.

One Response
  1. June 5, 2017

    It looks a lot like wheat, so I did a quick Google search to see if you could turn it into flour. In case of a zombie apocalypse, you just might.

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