Sweet Vernal Grass

CMG (or rather Andrew) is on a roll today – with our third posting:

Sweet Vernal Grass Anthoxanthum odoratum.

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Identifying grasses can be tricky.  There are some very good guides available, like this one:

http://www.countrysideinfo.co.uk/grass_id/index.htm

and since grasses make up a large proportion of what is growing in a meadow, it’s desirable to be able to recognise most of the common ones.  We’ve always assued that the one that’s flowering now is sweet vernal grass, but then we though we should check in a bit more detail.  By looking through a hand-lens at the ligules and auricles – see page 3 on the link above – we’re mildly reassured that in our field the main grass that is currently flowering is indeed Anthoxanthum. However, if anyone disagrees having looked at the photos – please tell us!

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This species of grass was the subject of some research on the Park Grass Experiment at Rothamsted, which had some surprising results.  Park Grass is one of the longest running field experiments in the world, and you can read about it here:

http://www.era.rothamsted.ac.uk/Park

Research done in the 1970s showed that plant populations could show local adaptations to a changing environment over a relatively short time period. Populations of Anthoxanthum odoratum grown from seed sampled from plots with different pH survived better and were higher yielding when grown in soil with pH like their ‘home’ environment.  This means that in only 40 years, the plants in two plots only 30m apart had evolved to be more suited to the particular conditions in their own plot than they were in the other plot.  This was surprising because (like all grasses) Anthoxanthum is wind pollinated, and it is also self-incompatible which means one individual flower can’t pollinate itself; so it would be expected that there is considerable gene flow between the plots on the experiment as well as within them.  It was found that there were inherited differences in the timing of flowering between plants on adjacent plots that could reduce the gene flow.  It’s amazing that such adaptations can happen in only a few decades.

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