Thursday, June 28, 2012
An almost-native ornamental grass
Species name: Deschampsia cespitosa
Common name: tufted hair-grass
Here's one example of a plant where the difference between "native" and "naturalized" has been blurred over the years. Technically speaking, the tufted hair-grass is native to the western coast of North America but it had been transported to the eastern coast centuries ago. It is now naturalized to a very similar habitat on the eastern coast; so much so that it's difficult to distinguish it there from a native grass because it thrives in communities with other native eastern grasses. In fact, this plant does incredibly poorly when planted on its own so there's definitely some sort of synergistic effect when it exists in grasslands. The idea is that in pure culture (that is, when the plant is growing on its own away from other native grasses) it doesn't possess the full community of symbiotic fungi in the root system of the plant that it requires, and so can't acquire nutrients as well as it can when grown in a grassland community. An interesting idea, but I'm not honestly sure if anyone has looked at this phenomenon with this particular plant in detail. And like animals, every plant is different! Reasoning for a lack of optimal growth in one plant species can't always be applied to another species even in the same habitat. Currently, the tufted hair-grass is not at immediate risk for population decline, however the habitat that it thrives in is becoming encroached by urban sprawl. There might be a time in the very near future that this is a species that's threatened or at risk.
In general, I really don't like trying to identify grasses since you almost always need a complicated identification key and a microscope. There are a few exceptions that I'll highlight later this summer, but this is one of the exceptions of the smaller ornamental garden grasses. If you run your fingers along the blades of grass of this species, one direction will feel like you're being cut by thousands of little razor blades (trust me, it's not pleasant!) while running your fingers the other way will feel smooth as silk. If the blade of grass feels that way and it has big tall seed heads that turn brown before the grass does AND you're in North America, then you've got the tufted hair-grass.
Interesting factoid: a closely related species to this grass, Deschampsia antarctica, is one of only two flowering plants on all of Antarctica!