I was recently down at FLS land by the shores of Loch Maree. As well as common alder (Alnus glutinosa), I was surprised to see at least two other alder species present.
As Italian alder (Alnus cordata) is quite a distinct looking species and grey alder (Alnus incana) is the only other alder species I had heard of being used in Scottish forestry, I had initially supposed that was what I was looking at must be grey alder.
But no…
I now think there are two species present (as well as common alder). (Unfortunately, an error came up when I tried to post this as new users can only embed one media file so I may have to repost pictures in the replies section.)
A small scrubby species with small serrated leaves and buds which seem too pointed to be grey alder - my best guess is green alder (Alnus alnobetula)?
A much larger tree, with large pointed leaves, slightly recurved at edges and apparently too large to be grey alder - my best guess is red alder (Alnus rubra)?
See replies for image.
As I’m new to these species, it would be great to hear what others think. This is my first post on the hub, so also let me know if this is not the kind of thing to be posted on here.
Could well be red alder for the larger one, I believe there is quite a bit of it about. I’m trialling it on our croft as a fast growing coppice species.
I’m not familiar with green alder but we do have grey here, which is more shrubby and also suckers, a handy id feature.
There’s also Sitka alder to add to the mix… It’s used up in Shetland but I’m not aware of it elsewhere. Grows as more of a multi stemmed tree up there.
I agree that these are American alders - red and green (A.rubra & A.viridis). Red alder has that slightly incurved leaf margin, which is a useful i.d. feature. Red alder was used quite extensively by FC and planted in some surprisingly remote places (e.g. Loch Shiel). It is seriously invasive as it is very vigorous and lacks most of the natural pathogens associated with common alder (hence the biodiversity it supports is likely to be more limited). I’ve not seen so much green. Most of these alders can hybridise, and some of the resultant offspring are fertile. There is also nothofagus by Loch Maree. In 2010 I didn’t find any exotic alder on the Loch Maree islands, but it would be interesting to see how far/fast they are spreading. Sitka and W hemlock have been seeding onto the islands, probably from this plantation, as there are more invasives on the southern and western islands which makes sense given the prevailing wind direction. So alders could also colonise this way. I’d be very wary of planting these species in places where they can escape into the wild or hybridise with native alder.
