Esprit Bonsai International – August 2019

38 - EspritBonsaiInternational #101

Botanical^

Profile

Classification

Family: Betulaceae

Genus: Betula

Species: Betula pendula

Typical and progressive transition between white, smooth bark

and the blackened, cracked bark of a mature silver birch.

On these pioneer species,
the young slender branches
grow directly from the
trunk towards the light.

A speedy

pioneer

Silver birch

Identifiable by its lovely and

unparalleled light-coloured

bark, silver birch grows in all

types of environment.

Author:

Louis-Victor Bourdeau

S

ilver birch (also known as warty birch) is a

Eurasian species and is easily recognisable

by its smooth, white bark. It is a deciduous

tree and its Latin name, Betula pendula refers to

the pendulous, “weeping” aspect of its vegetation.

When the tree is very young, the bark is brown

and smooth that turns white, and then with age, it

becomes progressively dark grey and rough and

cracked.

Slightly sticky leaves

The young branchlets are glabrous, slender and

pendulous and carry little resinous warts, which

shed thousands of droplets onto the windscreens

of cars when they are parked under birch in leaf.

Measuring between 3 and 7 cm (1¼ and 2¾ in.)

long, the leaves are simple and alternate and some-

times a little sticky. They turn yellow in autumn

giving a luminous atmosphere to birch forests – the

last grand burst of light before the night of winter.

The buds are small and sticky. In spring, they are

a very light green.

It is a monoecious species with male and female

flowers (catkins) on the same tree. In mid-summer

the pollen of the male catkins is dispersed by the

wind onto the female catkins, which after inse-

mination, slowly mature and transform into scaly

pods that carry numerous, seeds. When the cat-

kins break open at the end of summer, the almost

weightless seeds are easily scattered in the wind.

At subalpine level

Silver birch is very similar to pubescent birch

(Betula pubescens), commonly known as downy

birch, and both species share part of the same

geographic range. As its name suggests, downy

birch bears smooth, downy shoots, whereas those

of the silver birch are hairless. Their habitat is the

same but the leaves are slightly different. The two

species can hybridise, but it is rare and no issue is

possible from the fruit of a hybridised plant.

Silver birch has an immense range covering

almost all the northern regions of the Eurasian

continent – from Ireland to eastern Siberia. It is

found in the northernmost limits for deciduous

trees and is one of the few species that can grow

at subalpine levels.

Downy birch is the archetype of the pioneer

species with all its characteristics. It colonises any

open space; it is not fussy about the type of soil,

and it can tolerate the lowest temperatrues. It is