Grasses, Easy and Hard

by Carl Strang

Grasses are a pain. I thought that Carex sedges would be my big botanical challenge this year, but they are a breeze compared to grasses. As in all groups, you have to wrestle with the plants and identification keys to get a grip on what the authors of those keys are talking about. They’re not all so difficult, however.

This grass was refreshingly straightforward. All those long hairs, and the little round 1-flowered spikelets, pointed the way to old-field panic grass, Panicum implicatum.

Growing beside that grass in Mayslake Forest Preserve’s north savanna was another that was more challenging.

I had watched as this delicate looking plant developed, and some finally produced their first anthers, so I pulled a stem to identify.

Looking back, I can see that I learned a lot from this grass, but only after much frustration, quitting at least three times and stubbornly going back for more. I found that it had a tuft of cobwebby hairs buried inside the flower, pointing to Poa as the genus, but that tuft was very small compared to the obvious one in Kentucky bluegrass, which I had identified earlier.

The reproductive parts are contained within tiny leaflike structures called lemmas, and the number of veins on the lemmas, how distinct they are, and whether they have hairs on them are important characters to distinguish species in this genus. It took a while to get there, and I had to lean on a lot of other features, but ultimately I came up with Canada bluegrass as the ID. Its scientific name is Poa compressa, and the stem indeed is very flattened out as that label suggests. I hope it gets easier with experience. If nothing else, having learned to identify these species, they reduce the list of possibilities next time.

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