Tips on telling blunt-flowered rush Juncus subnodulosus from sharp-flowered rush Juncus acutiflorus, which is much more common in Herefordshire
The photo shows some differences in ‘jizz’. Sharp-flowered (L) has dark-chestnut perianths and capsules, blunt-flowered distinctly paler ones (though note much darker at fruition than at the very pale flowering and bud stages). Flower clusters are more slender and attenuated in sharp-flowered and blobby in blunt-flowered and the latter often has some branchlets directed vertically downwards. It is possible to convince yourself that you can see the diagnostic longitudinal septae of blunt-flowered when you are in fact looking at sharp-flowered because of the difficulty of splitting the leaf clearly. The longitudinal septae in blunt-flowered are very clear and should look like this:
Take the time to confirm, as in so many cases, with a x20 hand lens. (If you don’t have one, get one!!) The names are well-given and, as usual, Stella Ross-Craig (1906-2006) comes up with the goods. Here are her superb illustrations from Drawings of British Plants. As in all rushes the flowers are like miniature tulips with six tepals (petals and sepals jointly adopting very similar shapes). Those of the blunt-flowered are blunt, those of the sharp-flowered sharp, gradually tapering to a narrow point which is reflexed outwards and even hooked-in in some and often all of the tepals. This last point is important as a third species, jointed rush Juncus articulatus often resembles sharp-flowered rush even more than blunt-flowered rush. Perhaps subject for another post, but in a nutshell that is a lower growing plant with almost black tepals and fruit and rather less acutely-pointed tips which do not bend and hook.
Correct identification of blunt-flowered rush is especially important in Herefordshire as it is not only a rare plant with us but one of ecological significance: we lie squarely on the overlap of the M22 and M23 mire-types (probably with an unpublished variant of our own) and all records help us to evaluate the nuances of this situation.
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