Species Focus- Alder (Alnus glutinosa)

Species Focus- Alder (Alnus glutinosa)

Blog by Ciara Laverty

The alder is a hardy, native tree species that thrives in wet conditions. It is found growing along riverbanks, on the edges of ponds and the Lough Neagh shoreline. This common species is quite easy to identify- leaves are dark green and rounded in shape with serrated edges.


The alder is monoecious, which means both the male and female flowers are found on the same tree. The male catkins are about 5cm long, and eventually turn yellow. Whereas the female catkins are green and oval in shape. The female catkins are pollinated by wind and by winter harden into woody cones. These will open and the seeds within are dispersed by wind and water.

From time to time alder cones can be infected by a fungal plant pathogen Taphrina alni or “Alder Tongue Gall”. This causes a strange, tongue like growth on the alder cones. They appear green at first before turning orange or red in colour and will eventually turn brown. These galls release spores which will infect neighbouring alder trees. 

Alder 4

Alder is an important food source for a number of bird species. Finches like siskin, redpoll and goldfinch will readily feed on the small seeds within the alder cones. As the trees shed their leaves, look up into the highest branches to glimpse the impressive acrobatics of these small birds as they hang from the thinnest twigs while prying the seeds from their cones.

male siskin (1)

Historically, Alder was an important tree on the island of Ireland. In his book Ireland’s Trees: Myths, Legends and Folklore Niall Mac Coitir describes how Alder wood was used to make charcoal and containers like bowls while the bark and catkins were used to make black dye. It was also considered a tree of war and death due to the wood turning a blood red colour after being cut. Bronze age shields made from Alder wood have been found in various parts of the country.

Alder 6

Reas Wood and Farrs Bay have been designated a Special Area of Conservation (SAC) for the presence of Alder and Ash wet woodland. Unfortunately this type of habitat is now rare within Europe. Both of these sites have public access and I highly recommend paying them a visit and experience this rare, wet woodland habitat for yourself!

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