Identification notes
One of three similar-looking taxa that have sometimes been grouped as the ‘Racomitrium canescens aggregate’, R. ericoides is now considered distinct enough to merit recognition at species rank. This species, R. canescens and R. elongatum differ from our other Racomitrium species in habit, normally forming short turfs rather than tufts or cushions on the ground (less often on rock). They all have matt-looking leaves and stems with numerous, short stubby branches. They are also slow-growing, weakly competitive species that favour dry, barren ground that dries out periodically, such as on gravelly tracks or dry mineral soil in disused quarries. R. ericoides is more of a calcifuge than its close relatives.
Of the three, only R. ericoides and R. elongatum have a nerve which clearly reaches into the leaf tip. R. ericoides is a common species but it’s always best to check candidate material to rule out R. elongatum. R. ericoides has a hairpoint of variable length – usually short and sometimes entirely absent.
Under the microscope, check for rectangular, thin-walled marginal cells just above the alar groups. 💡 These cells are at the extreme base of the leaf and often remain attached to the stem when leaves are pulled off with forceps. Find leaf bases with intact alar cells (enlarged, egg-shaped non-sinuose cells) and look at the margin immediately above to confirm the identity. There is a good image below.
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