Birch

Birch is a tree in the birch family. Birches are hardy and can be found anywhere in the Northern Hemisphere.

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Foto: CC0 Public Domain
  • Leaf and sap of the birch is not poisonous.

Birch (Betula) is a tree in the birch family (Betulaceae). Birches are hardy and can be found anywhere in the Northern Hemisphere.
It is best to prune the birch in the fall and winter when the sap flow has almost stopped. In the spring just before the leaves emerge, the sap flow is very strong and the tree may bleed when pruning.
Birch occurs naturally in swamps and other moist soils. Birches are pioneer plants: they quickly occupy open spaces in the forest.
Birches are not demanding when it comes to soil.
Like beech, birch lives in symbiosis with soil fungi. The fly agaric (Amanita muscaria), in particular, is often found on birches.

Bugs

Birch catkin bug, photo: Aiwok – CC BY-SA 3.0

Leaf damage, yellow spots, and holes: birch catkin bug (Kleidocerys resedae).

recognize bugs on birch
Parent bug with eggs, photo: Bj.schoenmakers – CC0 Public Domain

Slight damage to leaves and seeds: parent bug (Elasmucha grisea).

Aphids on the leaves: linden aphid (Eucallipterus tiliae). This aphid secretes honeydew on which sooty mold forms.

Snail-like caterpillars, larva of the oak slug sawfly eats mesophyll from leaves
Larvae of the oak slug sawfly on an oak leaf, photo: Rasbak – CC BY-SA 3.0

About 1 cm small, dark-tinged, slimy snails eat the mesophyll between the veins of the leaves. This causes the remaining mesophyll to turn brown and the leaves may drop: snail-like caterpillars (larvae of the oak slug sawfly – Caliroa annulipes).

recognizing birch sapwood borer feeding tracks
Row of holes on the trunk of a birch, photo: CC0 Public Domain

On the trunk, a series of holes develop longitudinally: the birch sapwood borer (Scolytus ratzeburgi).

Fungi & diseases

Witch’s brooms, photo: MPF – CC BY 2.5

A motley collection of outgrown twigs: witch’s broom (Taphrina betulina).

Birch polypore, photo: Fred Bastemeyer

A 10 to 30 cm large rusty brown or gray fungus on the trunk: birch polypore (Piptoporus betulinus).

Nectria canker, photo: MarkusHagenlocher – CC BY-SA 3.0

Wild growth and overgrowth on the trunk: nectria canker (Neonectria ditissima).

recognize sooty bark disease
Dark brown spots on the trunk caused by sooty bark disease, photo: Arie de Vreugd

Dark brown to black spots on the bark, early leaf fall and dried branches in the crown: sooty bark disease (Cryptostroma corticale).

recognize chaga
Chaga on the trunk of a birch tree, photo: Aurelijus Banelis, CC BY-SA 4.0

A black, irregular thickening develops on the trunk. Size ranges from 4 to 40 cm in diameter and 10-15 cm in thickness: chaga (Inonotus obliquus).

Other

Birch bleeds profusely after pruning: pruning took place during or just before the leaf emerges. The bleeding is barely stemmed.

Fly agaric, photo: CC0 Public Domain

Fly agaric is often found under birches.

recognize foam on trunk of trees
Foam on the trunk, photo: Monique Beers

In early spring, foam appears at the base of the trunk: tree foam.