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Alnus - Growing Guide
Alnus - Growing Guide
Stone Lane Gardens, near Chagford in Devon, has a national collection of around 30 Alnus species (as well as birch). In spring the size and variety of catkins on the different species is amazing for those who can find time to leave the A30 for just a mile or three.
Sadly, as yet, Burncoose only offers three of the rather more common European alders which grow wild in poor wet soils normally near rivers, streams and ponds. They can therefore form an important part of the government’s carbon neutral drive to plant more trees in the UK in such locations. If you create a new pond or have a boggy area in your garden which floods it is very likely that, before long, seeds of Alnus glutinosa, common alder, will arrive and germinate naturally. Alnus cordata, Italian alder, and Alnus incana, European or grey alder, may well not be far behind in some locations as all three of these species of alder are well established in the UK.
Alders have male and female catkins on the same tree. They are yellow-brown and 3-4in long. Female catkins are smaller and develop into persistent cone-like green fruits which turn brown when ripe and are buoyant in water. A. cordata and A. incana will tolerate drier soils and all three species can be pruned back hard to only a few feet in height periodically if you want to grow alders as an effective windbreak.
They can be propagated easily from seed or form hardwood cuttings set in the cold frame or in a soil bed over winter.
Alnus incana ‘Aurea’ is the only genuinely ornamental variety of alder which we currently offer from time to time. This makes a good freestanding small tree with bright yellow leaves in spring that mature to light green. This tree grows up to 40ft in height eventually which is rather less than the other three species can achieve in maturity.