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Mick Crawley

12 Jul, 10 tweets, 5 min read

Genera of Poaceae: Molinia. This is one of the last of the really important grasses to come into flower. It dominates huge areas of wet heath in the uplands, it's abundant in fens, and forms the understory of wet Betula pubescens woodland in the lowlands.

Molinia is in Key A of Stace's genera of Poaceae, because its ligule is a dense fringe of hairs.

First we eliminate lots of hairy ligule plants that are easy to identify: Zea mays, Sorghum, Tragus, Cenchrus, Setaria and several finger grasses (Dactyloctenium, Cynodon, Eleusine, Chloris). The first important question is spike or panicle. It's narrow but obviously the latter.

The next question: is it a Miscanthus (left) where the spikelets are in pairs, or are the spikelets not in pairs (right). Not in pairs (right), so on we go.

Another easy one now: is it a pampas grass (Cortaderia selloana (left) or C. richardii (right))? Nope. Onwards.

Is it a reed (Phragmites or Arundo) with a long tuft of silky hairs from the rachilla or the back of the lemma (left), or not (right). No silky hairs (right).

Now look closely (X10) and count the number of florets per spikelet. Is there 1 or more than 1 ? Sod's Law has reared its head again, because Molinia can have 1, 2, 3 or 4 florets per spikelet, so Molinia appears in both branches of the key. It doesn't matter which way we go.

Is the lemma awned (left) or awnless (right). It's awnless

Does the lemma have 1 vein (left) or 3-5 veins (right). It has 3-5 (right)

Is it a perennial with lemmas 3mm long or longer ? Yes and yes. So we have Molinia. The species M. caerulea (Purple Moor-grass or Flying Bent) is popular with some garden designers, and there are several cultivars commerically available.

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More from @crawley_mick

Mick Crawley

@crawley_mick

10 Jul

Cudweed season is upon us (Gnaphalieae: Asteraceae). What makes these plants so tricky to identify is that their general woolliness hides all the bits that are important for ID. The other thing is that they are now split up into seven different genera

Let's look at how the genera are separated to begin with. I know it’s illegal, so you need to get the land-owner’s permission to uproot one of your plants. Is it an annual (left) or a perennial (right, with short rhizomes). The only perennial genus is Omalotheca.

The hard work starts with the annuals. Use your tweezers to free up at least one capitulum, and open it up to see inside. Find the marginal flowers (easier said than done). See if they have receptacular scales or not (illustrated with scales).

Read 17 tweets

Mick Crawley

@crawley_mick

6 Jul

Here are the answers to the grass quiz. Don't worry about not knowing species in habitats you don't visit. I suggest you visit each of your local habitats in turn and make a point of finding, pressing and closely observing the species you didn't get right. Let me know your score.

roadside
1) Arrhenatherum elatius
2) Dactylis glomerata
3) Poa trivialis
4) Festuca arundinacea

waterside
1) Phragmites australis
2) Phalaris arundinacea
3) Glyceria maxima
4) Alopecurus geniculatus

Read 13 tweets

Mick Crawley

@crawley_mick

1 Jul

While the grasses are still in reasonable condition, it might be a good idea to take stock of where you have got to in your quest. The plan is to revise the most important species in the form of a quiz (with answers later in the week).

I’ll show you 4 of the most important grasses from each habitat in turn, starting with roadsides. To keep track of the answers, I'll number them like this: 1 = top left, 2 = top right, 3 = bottom left, 4 = bottom right.

Waterside grasses next.

Read 13 tweets

Mick Crawley

@crawley_mick

20 Jun

Key to the common species of Agrostis. You should collect underground parts and dissect a spikelet before beginning the key to determine whether the palea is large or small (more or less than 2/5 of lemma length). We shall start with the species with larger paleas.

Select a spikelet from the very top of the inflorescence. If the back of the lemma is hairy (left) and there is a sticking-out awn, you have Agrostis castellana (much planted in commercial grass seed). Hairless (right) is something else.

Look at the ligule on the upper-most culm leaf. If it is small (0.5-1.5mm) you have the widespread and abundant Agrostis capillaris. Larger ligules (2-6mm) are something else.

Read 7 tweets

Mick Crawley

@crawley_mick

20 Jun

Genera of Poaceae. Agrostis. When you see a grass with a big open panicle like this (left) with tiny spikelets that look as if they might contain just 1 floret (right), your mind should turn to the genus Agrostis.

Agrostis is fiddly because the flowers are so small and tricky because it is essential that you bring back the underground parts from the field. You need to dissect the spikelt and expose the lamma and, crucially, the palea

Then, with some carefully cleaned underground parts, you need to say whether the plant has rhizomes (left) or stolons (right).

Read 7 tweets

Mick Crawley

@crawley_mick

20 Jun

Here is one of my candidates for ‘most elegant of all British grasses’. It’s Apera spica-venti, and has a droopy, shining golden inflorescence, made up of tiny spikelets with ridiculously long awns.

It stands about 1m tall, and its considerable height means that the individual spikelets (less than 3mm long) look even smaller than they are. The awns can be up to 4 times this length (they are as much as10mm long and are seldom less than 5mm).

Apera is one of the genera where there is just 1 floret per spikelet, hidden completely by the glumes (Key F in Stace, with companions like Agrostis and Polypogon)

Read 6 tweets

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