It has been a great spring for blackthorn blossom. The dark spiny branches have been densely covered with flowers, perhaps because of the warm summer of 2018. They may yield a good crop of sloes, which are usually sparse hereabouts.
Blackthorn Prunus spinosa is conspicuous most of the year, occurring in dense thickets which spread by suckering. In the winter the better-lit parts of these thickets can be seen to be plastered with lichens, which like its nutrient-rich bark (photos 1-2). They are mainly grey-green fruticose species such as the beard lichen Usnea spp., Ramalina farinacea and the appropriately-named Evernia prunastri (photo 3).
The star-like flowers (photos 4-5), although short-lived, are very attractive to early nectar-seekers such as the white-tailed bumblebee Bombus lucorum s.l. photographed at Inverkirkaig by David Haines (photo 6). The same blackthorn thicket also harbours a singing blackcap most years; Gwen Richards heard one there on 24th April 2019.
The leaves are a favourite with the caterpillars of butterflies and moths, with over 180 species recorded from blackthorn in the British Isles. In the summer they sometimes bear densely-clustered marginal galls caused by the mite Eriophyes prunispinosae. I am not sure whether these have been found locally; something to look for later.
In autumn the leaves turn a pale yellow, painting the thickets gold (photos 7-8). The sloes, when they occur, are quite persistent, especially the distorted ones known as ‘pocket plums’; these have been galled by the fungus Taphrina pruni, and were noted at Glenleraig on 12th November 1995 and again at Inverkirkaig on 22nd October 1996.
The wealth of blossom reminded me that this is a scarce tree in Assynt, mapped in the Flora from only nine tetrads, mainly around the coast, usually on roadsides and often on south-facing banks. Although almost ubiquitous in England, Wales and lowland Scotland, it becomes very scarce in the north-west, and has not been found north of Assynt, except for an isolated old record from Faraid Head.
I was prompted to check the local records, which are now available on a large spreadsheet containing all those of local plants, and found at least three sites that do not appear in the Flora (map 9). There is a stand along the front boundary of a derelict garden in Drumbeg (NC1232) and the very conspicuous thickets along the north side of the B869 at Rhicarn (NC0725 and 0825) appear, oddly, not to have previously been logged. In Lochinver there is a small stand along the wall opposite the Newsagents (NC0922) and the seaward ends of the thickets beside the road up to Achins at Inverkirkaig (NC0719) were not noted until 2017.
I wonder if there is more blackthorn lurking around the north side of Loch Inver or anywhere else in the parish? I have noticed, in passing, a possible patch near Clashnessie. Most of the sites are suspiciously close to human habitation. But, given its thorniness and tendency to spread, why would anyone plant it? There is also a small patch far from habitation on the south face of Cnoc na Sroine, above Loch Borralan (NC2611), which we found in August 1998, but have not revisited since.
Ian M. Evans