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.
Of the big ligule species, Agrostis gigantea (left) has rhizomes and A. stolonifera (right) has stolons. When mature, the inflorescence of A. stolonifera becomes narrow like a folded-up umbrella, but the panicle of A. gigantea remains spreading.
There are 3 native species with shorter paleas. The very distinctive Agrostis curtisii looks more like a fescue than a bent. It has hair-like, blue green leaves held in dense tussocks, and grows on lowland heaths in south and southwest Britain.
The last two species are impossible to separate accuratelty without good underground material. Agrostis canina is a wetland plant with abundant stolons and no rhizomes (left). A. vinealis is a plant of dry heath and rocks with rhizomes and no stolons (right). Awns are no help.
If the glumes are bigger (3-4mm) you have Agrostis vinealis (below), but often they are smaller than this (2-3mm) and overlap with A. canina (glumes 1.7-3 mm). There is no getting away from it. You need to get your fingernails dirty and come up with either stolons or rhizomes.
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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.