Common Alder

 

On the slope from the towpath to Hilly Orchard bridge is a beautiful young alder tree, conical in shape, which, in its old age (by 2060), should grow to around 25m. Early in the New Year you can already see the pretty purple catkins.

January 17th 2024

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February 15th 2024

The longer dangling ones are males (and will be covered with yellow pollen in the spring), while the much smaller ones are the females. (Alder trees are monoecious, ie the male and female flowers are on the same tree).

Once fertilised the female catkins will transform into small cones, first green then turning red-brown and opening in the autumn to release their seeds to be carried by the wind.

July

Last year's cones are still on the tree, and you may be lucky enough to see a finch searching for a forgotten seed.

Redpoll enjoying the last of the seeds in March

Bees benefit from the trees’ nectar and pollen, and look out too in summer for the wonderful caterpillars of the alder moth, Acronicta alni, which are striped yellow and black.

Besides the catkins and old cones, now you can also see the flat purple-grey leaf buds on short stems.

Rescued from the leaf litter in January

The Alder in May 2023

In spring the leaves will emerge, growing long and dark green with serrations and often an indented tip. Later in the year these may be peppered with lots of small holes, thanks to the adults and larvae of the metallic-blue alder leaf beetle.

Alder leaf beetle in May on Hazel by the pond

The tree also goes under the name Black Alder as the bark becomes very dark with age.

Bark of the young tree

This is a native species, though others such as the European Grey Alder have now been introduced. All Alders have nodules on their roots where nitrogen-fixing bacteria Frankie alni live, these convert nitrogen from the air into valuable nitrates for the trees and other plants growing in the soil. As alders like wet ground they are frequently used for flood mitigation planting. You can spot more alder trees growing by the canal and in the playing field copse where the ground is often saturated.

Further information and images

The Woodland Trust - Alder

The Conservation Volunteers – Common Alder

Forest Research – Common or Black Alder