Thursday, 7 October 2010

Arrhenatherum elatius - False Oat-grass

Arrhenatherum at Langcliffe churchyard 2009 late Sept
I have a love-hate relationship with Arrhenatherum elatius

Sometimes I feel like instead of calling it "Arrh  enatherum,", I could call it "Arrh anathema"
(Anathema means detested person or object).
"Arrh...". anyway.

On the other hand elatius (which means "tall" in Latin) sounds like "elated" . Hey, I feel elated and happy!

Read on to find out about the dilemma with this plant,

Before nearly every course I teach, I search for its big, jolly spikelets, easily recognisable by their one long awn per spikelet. I am so grateful when I find them.
It is easy for students to open the big spikelets and find the different parts of the grass flowers.

It is a very common grass - If you live in the UK I am sure some will grow very near you

This article will help you to learn to recognise it.
It is a tufted plant.
It is growing at the edge of my garden - in full flower. I have just been weeding it on 6th October!. Here is the root.. freshly picked from the garden 30 minutes ago..
Note how knobbly the shoot base is. And at the point where the roots emerge there is a rusty orange colour. 90% of Aarrhenatherums have this rusty orange colour at the shoot base.

 Arrhenatherum elatius spikelet
Labelled Arrhenatherum spikelet

Here is a spikelet open, with the translucent paleas back to back, the white feathery stigmas poking out, and a dark purple anther visible.

I now paste the article I wrote last October in the North Ribblesdale Parish Magazine -comprising three parishes - Langcliffe, Stainforth and Horton in Ribblesdale

October’s grass:  False Oat-grass Arrhenatherum elatius

Did you know that you can still see a big grass in flower in each of our three churchyards in October?

Yes – have a look for a tall grass at the borders of Horton, Stainforth and Langcliffe churchyards and you’ll find a few flowering shoots of False Oat-grass – Arrhenatherum elatius. Its Latin name “elatius” mans tall.

Arrhenatherum at Stainforth 
I have a “love-hate” relationship with this grass -. First the bad bit – it grows well when there is no or little mowing or grazing. So we see it on our road verges and on the railway. It can start to swamp out smaller species. I used to carry out botanical surveys of grasslands in Humberside and sometimes I found small fields – that still had some traditional hay meadow meadows flowers - but which were being taken over by this grass as they were being neglected and not both cut for hay and grazed by cattle.

On the positive side, False Oat-grass has big flowers that are easy to dissect and it can be found in flower from early May to (at a stretch) December – so it’s an excellent plant to show people.

Arrhenatherum at Horton in Ribblesdale
In grasses, if the flower-head is branched it is called a panicle, and the “blobs” on the panicle are called spikelets. In False Oat-grass the spikelets have two flowers and they are big - 1.5cm long. You can recognise false oat grass because it is the only common grass with one long bristle (awn) per spikelet. The papery scales on the outside of a spikelet are called glumes. If you pull these off, then you are left with the two flowers. The individual spikelets only open for a few hours as in the pictures below when conditions are right, and then you can see the beautiful feathery stigmas.

The awns have a kink/sharp bend in them when they are dry and the awns arise in the middle of the back of the lemma. this is a feature of a group of grasses known in English as "Oat grasses" or as subtribe Aveninae

The emerging leaf is rolled. the bases of the leaf blades are slightly uneven.

Tussock in early morning
What vegetation type does abundant Arrhenatherum indicate?

If the verge/railway/field has Arrhenatherum growing nearly everywhere, the vegetation type in the National Vegetation classification is MG1 - Mesotrophic Grassland number 1.- Which is a very common grassland type usually of low conservation value.

The picture on the right was taken in early morning in late August 2010 in a field that has had very low grazing over the past few years. The leaves die an orangy brown

It can be found in well lit areas at the edge of ungrazed woodlands.

If the same grass is found growing on ledges on our limestone cliffs with other rare plants it then counts as a rare community of high conservation importance  MG2.

Go out for a walk and check if you can find a tall grass still flowering on waste ground with big spikelets - and if you suspect it is Arrhenatherum, check the root shoot junction for the rusty orange colour.

Well, go out for a walk anyway.


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