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Alder

Some ancient peoples thought this tree was evil because its wood quickly turned red when cut, as if bleeding.

Alder leaves

Alder (Alnus glutinosa) leaves

About Kew's alder trees

Kew's alders are mainly planted at the margins of the lake, ensuring they benefit from the watery habitat they prefer.

Take a closer look

  • The shape of a mature alder can make it look like a deciduous conifer. To add to the illusion, it has catkins that look very much like pine cones. The leaves, however, are an oval shape and look nothing like any conifer.
  • Alder leaves are round with an indent at the tip. As autumn turns to winter you'll notice that they remain green long after the leaves of other trees have fallen.

Tree biology

Alder is an important ‘coloniser’ – growing in areas of new ground before other species. It can do this because the bacteria that live among its roots can 'fix' nitrogen from the air, so enriching the soil for other plants.

The edges of streams and rivers alders make good habitat for nesting otters. They can build their ‘holts’ among the roots of the alder, creating an underwater entrance to protect their cubs from predators.

Cultivation and uses

Alder wood is hard and durable in water. Historically, boats, jetties and underwater supports have all been made of alder wood. It is said that Venice was built on alder wood piles.

Before the use of coal, alder was also coppiced to produce small timber for making charcoal, especially for metal working and making gunpowder. Traditionally alder wood was used for the soles of clogs as worn in Lancashire.

Quick facts

  • Scientific name: Alnus glutinosa
  • Family: Betulaceae
  • Place of origin: western Asia, North Africa and Europe; this tree is native to Britain
  • Conservation status: Common
  • Date planted: 1959
  • Height: 10 m. Can grow to 20 m in ideal, wet conditions – on drier soils it grows as a bush.