Sunday, 15 April 2012

Poa trivialis - Rough Meadow-grass

Grass of the Month for April 2012
(See other months' grasses)

Poa trivialis grows

  • beside woodland footpaths, 
  • in gardens, 
  • in species rich hay meadows, 
  • in damp meadows that have been so heavily fertilised that they hold little else except Ryegrass and Poa trivialis
  • beside streams
  • in nettle patches 
  • on roadside verges

Vegetatively, Poa trivialis is easy to recognise.
Well I think so
The above plant found on a woodland footpath makes a flattened tuft. If growing in a meadow you might  find just individual fine shoots threading through the sward, with the emerging leaf folded and the blades folded, and the sheaths compressed.

Can you see how the narrow shoots Trail along the ground? - they are Tiny and Trivial.

The shoots are very compressed. They lie flat against the ground and look Trampled on.

The underside of the blades are shiny (when folded, it is only the undersides that you see). With raindrops, they are so shiny they almost Twinkle

Get it?
Tiny, Trivial,  Trailing shoots that look Trampled on and have Twinkling undersides to the blades
Twinkling for Twivialis.

If there is sufficient light, the sides of the sheathsl  facing the light are Terra-cotta coloured (plum coloured), whilst the blades are Tree green  (Tree green means bright mid green - not bluish as in Poa pratensis or whitish as in Poa annua)

Later in the year some of the trailing shoots might root so then they become stolons.

The blades are  Tapering and thus Triangular - like a long isosceles triangle

The above photo of two vegetative blades is useful because as well as showing the tapering nature of the blade, it shows the characteristic vegetative features of nearly all Meadow-grasses:- tramlines (two central grooves) the boat shaped tip (with imagination).

It also show a  SHORT ligule.

"Short ligule?" you ask. "Doesn't Poa trivialis have a long ligule - to distinguish it from the short ligule of Poa pratensis?"

Answer:- the flowering shoot of Poa trivialis has a long ligule, but the vegetative shoots have short ligules.

Poa trivialis growing on the bank of the river Laver
near where it joins the Skell. Note Ground  Elder. see how they trail

The flowers?
They come out in May-July and  have "Christmas-tree panicles, just like the other Poas.  - It is the vegetative trainling shoots that are so distinctive...
But the flowering shoots, which start to grow in April,  grow vertically (even before the flower pokes out), and higher up the shoot they have LONG ligules, and rough sheaths - Hence the name    "Rough Meadow-grass"

Can you remember all the Tr adjectivies for Poa trivialis?
Trilling. Triumphant - Tremendous - trivialis - and the other ones?

(See other months' grasses)

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