Grey Alder Trees - Alnus incana

Alnus incana - Speckled Alder / Grey Alder Trees

Alnus incana, the Grey Alder, (or Gray Alder, if you like) is an extremely fast growing deciduous pioneer treea happy Grey Alder can zoom up a metre a year during its first decade. Quite conical at first, it broadens out with age. Grey Alder is distinguished from Common Alder by its slightly speedier growth and the downiness of its new leaves and stems. It has modest yellow autumn foliage and wonderful long male catkins and round female catkins that decorate the tree from February until the leaves appear. The pock marked, pale grey bark is smooth, developing vein like wrinkles with age. It has a strong suckering habit, which is great news for all sorts of wildlife that take shelter in the dense mass of stems. The Alders are arguably the best trees for reclaiming sites with terrible soils, from closed rubbish dumps to former industrial zones, they are able to thrive thanks to their root's ability to fix nitrogen from the air, just like clover does. They add more nitrogen to the soil than they need, enriching it for other plants. Alnus incana will grow just about anywhere that it gets plenty of light, including very waterlogged, marshy ground - they especially love gravelly terrain next to rivers. They are an ideal tree for improving watery habitats, quickly throwing up a wind break or binding loose soil and preparing the ground for other trees to follow. Grey Alders generally don't live more than 100 years, although older specimens do often lose their central trunk and carry on as side shoots until competition for light finishes them off. Alnus incana will reach about 20 metres, 60 feet.

Planting Alder Alnus incana

Only acidic peat and chalky soil will present a problem to Grey Alder, absolutely any other soil type, wet or dry, will be fine. What Alnus incana needs is all the sunlight it can get - it has evolved to thrive on soils that other trees would struggle with in order to have the sun to itself. We recommend ensuring that it has full sun for at least three quarters of the day. If you are planting Grey Alder in conjunction with slower growing trees that will eventually be taller, you may plant them at the same time. The Alder will zoom up and be outgrown in due course, improving the soil all the while. If you want some variety, you can combine Alnus incana with its cultivar Aurea or with the Speckled Alder.

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.