Common / Black Alder Trees

• Common name: Common Alder, Black Alder
• Latin name: Alnus glutinosa
• Native: Yes
• Sold as: Bareroot standards at 6/8cm and 8/10cm girth
• Mature size: More than 12m tall, in time to 25m, and 4 to 8m wide. 20 to 50 years to full height
• Shape: Broadly conical when young
• Catkins and cones: Catkins in late winter, before the leaves. Small woody cones that last through winter
• Best soil and site: Wet, poor and heavy ground: clay, loam or chalk, moist or badly drained. Full sun. Exposed or sheltered
• Nitrogen fixing: Yes
• Pruning: Can be coppiced or pollarded
• Hardiness: H7, hardy in the severest British winter
• Delivered: Bareroot only, November to April. Collection from Castle Cary also available

Common Alder is the native tree of riversides and wet ground, a fast, conical deciduous tree to about 25 metres with catkins in late winter and small cones that feed birds. Bacteria in its roots take nitrogen from the air, so it grows on poor, wet soil where other trees fail. Full sun.

Common / Black Alder Trees

Common or Black Alder, Alnus glutinosa, is a native tree that loves growing in wet, boggy soil. Young plants are slender and have a narrow canopy; mature old trees can spread quite a bit.
It has mid-green leaves that last until the end of autumn before they turn yellow. The yellow spring catkins develop into seed-bearing cones in the autumn, which are food for small birds. The catkins are wind-pollinated, and provide a source of protein-rich pollen for bees early in the year, when there isn't much else available, however, it's also a famous trigger for hay fever.

Common Alder trees can reach a mature height of about 25 metres.

These standard trees are the largest size that we deliver; you can also buy Common Alder saplings.
Browse our other alder trees or all our garden trees.

Growing Common Alder

It needs a sunny location on pretty much any soil, but if the site is really dry and drought prone, Italian Alder is a better choice. It won't grow on a beach, but it'll be fine quite close to the coast within reach of some salty winds. It does like chalk, but it doesn't like any rocky location (chalk or otherwise) with shallow topsoil.

Note on Alder roots: Alder has invasive roots that can break old water pipes and damage the foundations of old buildings or walls. 15 metres away from vulnerable structures is a safe distance to plant Alder. New build, concrete foundations aren't at risk.

History & Trivia

It is a classic pioneer tree that is often used to prevent riverbank erosion and to reclaim sites with especially poor soils, due to the bacteria living in nodules in its roots, which fix nitrogen from the air into the soil, improving it for other plants over time, especially as the tree ages and dies, or is pruned.

A concoction of the inner bark, simmered overnight in vinegar, was used to make an insecticide to kill lice and scabies mites, and was also used as mouthwash.

The timber is rot resistant and was widely used for foundations, clogs, and guttering in the past: most of central Venice is built on piles and platforms of alder, along with elm, oak, and poplar. It is good for smoking foods, especially fish.

Standard trees are measured by their girth in centimetres 1 metre above ground level: their trunk's waist measurement. Unlike sapling trees and hedge plants, standards aren't measured by their height, which will vary quite a bit both between and within species.
So, a 6/8cm standard tree has a trunk with a circumference of 6-8cm and an 8/10 standard has a trunk 8-10cm around. This measurement makes no difference to the tree's final height.
On average, standard trees are 2-3.5 metres tall when they arrive, but we cannot tell you precisely how tall your trees will be before we deliver them.

Planting Companions

On drier ground choose Italian Alder instead; Grey Alder is the tougher cousin for cold and poor sites. By water, the other natural choice is one of the Willows. For a mixed native planting, see our native trees and trees for wildlife. Dust the roots with Rootgrow as you plant.

Why Ashridge?

Ashridge has sold trees since 1949 and is a Which? Best Plant Supplier 2025. Your Alder comes as a bareroot standard, lifted while dormant, and like for like a bareroot tree is larger and better value than a potted one. It is guaranteed for 12 months.

Frequently Asked Questions

Will Common Alder grow in wet or boggy ground?

Yes. That is what it is for. Alders thrive in poor, wet conditions, and this one grows in badly drained soil. It is the native tree of riverbanks.

What does nitrogen fixing mean?

Alders make their own fertiliser. Bacteria living in nodules on the roots take nitrogen from the air, so the tree grows where others starve and improves the soil for its neighbours.

How big does a Common Alder grow?

To about 25 metres tall and 4 to 8 metres wide, taking 20 to 50 years to reach full height. Your young tree will be narrow and conical.

Can you coppice or pollard an Alder?

Yes, both. Cut to the ground or to a short trunk, an Alder grows away again. If you want smaller plants to coppice, buy the saplings and not these standards.

Do birds eat Alder cones?

Yes. The small woody cones hang on through winter, and siskins and redpolls feed on the seed inside them.

When are Alder trees delivered?

Bareroot only, from November to April, while the trees are dormant. On average your standard tree will be 2 to 3.5 metres tall when it arrives.