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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This is what Ashurst looks like in a ‘ragwort year’. There are more than 10 flowering individuals per square metre.
This is what Ashurst looks like this year (1 August 2023). There’s not a single ragwort plant in sight.
So what is going on ? Between 1980 and 2019 ragwort numbers fluctuated dramatically but there were no extended periods of very low plant densities (less than 1 m-2). Since 2020 we’ve seen 4 consecutive years with exceptionally low numbers.
Identifying rushes. The three annual species of Section Tenageia can be tricky to tell apart. The common species is Juncus bufonius (left) and the two rarer species are J. foliosus (upper right) and J. ranarius (lower right).
They all have flat or inrolled bifacial (grass-like) leaves on the stem (the basal leaves are typically withered by flowering time). The diffuse panicle is interspersed with leaf-like bracts and each flower has 2 small bracteoles.
Juncus foliosus is the easiest to identify: its leaves are more than 1.5mm wide (left) and the seeds have longitudinal ridges (x20, right A).
Identifying rushes. The reason why our 31 Juncus spp. are so tricky to identify is that the genus is so complicated botanically. It’s worth starting by looking at each of the 10 Sections that are represented in UK, just so that you can see the issues involved.
Identifying grasses. It’s obviously a Brome, but which Brome is it ? First, we need to identify the genus (i.e. is it Bromus, or Bromopsis, or Anisantha or Ceratochloa ?). This is the lower half of Key H on p. 1033.
#6 Are the lemmas strongly keeled on the back (left) or not (right). Definitely not keeled, so on to #7
#7 Always a tricky one. Annual or perennial? Look at the roots and check for the absence of rhizomes. See if there are any non-flowering shoots. No rhizomes and no sterile shoots, so annual is the best bet. On to #10.
Seaside Grass Quiz. This is arranged by habitat (sand-dune, dune slack, rocks & shingle, cliff and tidal mud-flat) then by plant size within habitat (big, medium, small). Answers tomorrow.
Grass revision quiz. Waterside and wetland grasses. The are just 10 species in this quiz, reflecting the ecological fact that rushes, sedges and other Cyperaceae are more numerous than grasses in this habitat.