Alnus glutinosa - Common Alder Trees
Alnus glutinosa, the Smooth or Common Alder, is a bushy deciduous tree that can grow well over than half a metre a year in the worst quality soils and just loves waterlogged terrain.
It has broad, serrated leaves with a blunt, rounded triangle shape and in winter it is covered in decorative male and female catkins, like bright green streamers and baubles respectively, each fading to a rusty brown as the winter draws to a close. Its autumn foliage is a simple pale yellow.
Alnus glutinosa is a classic pioneer tree that is often used in reclaiming sites with especially poor soils, mainly due to its ability to support bacteria in nodules in its roots that fix nitrogen from the air into the soil, improving it for other plants.
Although it is fairly short lived - about 120 years - it will last much longer when coppiced and was an essential tree during the industrial revolution for three main reasons.
- The wood is very water resistant and was used for many jobs where timber would be constantly wet.
- It was quite grease proof, easy to carve and light weight - perfect for making clogs, which were the equivalent of today's steel toe capped boot.
- It made gunpowder grade charcoal and picked up the name Black Alder as a result.
Growing Alnus glutinosa: it likes to spread its seeds by water and they often sprout in riverbank mud. Clumps of old Alder that have lost their central stem and formed thickets of side shoots, found on wet ground by water are some of Britain's most untouched habitats, making good nesting sites for birds and providing vital shelter for some of our more exotic dragonflies and amphibians. The nearest relative of
Common Alder, the
Grey Alder, shares all the same traits and grows slightly faster. Its American cousin, the
Red Alder is also a good choice to use in conjunction with Common Alder.
Planting Alder Alnus glutinosa
Alnus glutinosa will grow anywhere except acidic peat or shallow, chalky soil. It is tolerant of alkaline earth and, along with willow, is the best tree for waterlogged ground. However, it does not need an abundance of water and is equally happy on drier, stony ground. It is very demanding about light and we recommend that you plant it where it will have no competition from adult trees. If you want to use it to improve the soil in preparation for other trees, you should be able to plant them at the same time as Common Alder will outgrow most other trees, especially on poor soil. Alnus glutinosa should reach about 20 metres, 60 feet.
If you are unclear about the way standard trees are sized, take a look at our Guide to Standard Tree Sizing or you can go back to our main standard trees page.
You can buy smaller, hedging sized Alder trees here.
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