Aspen and White Poplar
The aspen is a forest tree, occurring widely throughout the whole of Europe, and extending beyond the Arctic Circle in the north. In central Europe it grows in lowland and on mountains up to and above 1000 metres; it is most plentiful, however, in hill country, coppice forests and forests which are clear-felled.
It reaches heights of 25 to 30 metres and has a sparse, highly placed crown. The bark is smooth and coloured greenish grey, but old trees have fissured blackish bark at the lower part of the trunk. The buds on the twigs are lustrous-brown and sharply pointed. The aspen is a dioecious species (male and female flowers on separate trees). It flowers in March and the tiny seeds, imbedded in cottonwool-like hairs, are shed in late May. The leaf stalk is long and flattened, and even a slight breeze sets the leaf in motion. The aspen is a light-demanding tree and does not require rich soil.
Of the Asian cypresses, the one most commonly found in Europe is the sawara cypress (Chamaecyparis pisifera Sieb et Zuec.), which has a great number of ornamental forms.
The juniper is extremely adaptable to various climates and grows in most of Europe and a large part of Siberia. It grows in poorer, drier soils and thus may be found both on dry limestone slopes as well as in damp, acidic soils, both on lowland and on mountains. It requires ample light for good growth, however, and therefore generally grows in pastures, margins of woods, heaths and non-fertile soils. It occurs mostly as a shrub, less frequently in tree form, growing to a height of 10 metres. Its sharp, prickle-pointed leaves are slightly grooved, and have a whitish band on the upper surface.
The white poplar propagates also by means of root suckers growing from the lateral roots, often as far as twenty metres from the trunk.
The white poplar grows in regions with a mild climate. It requires abundant light and ample moisture, and stands up well to flood water and slightly acidic soils. It is very attractive as an open- grown tree in water meadows, and, because of its vast root system, is used also to strengthen sand dunes. In intensive forest management it is being replaced by cultivated forms of black poplars. The wood is soft, and used to make cellulose and for turnery. The pyramidal form from Turkestan, known as Populus alba pyramidalis (syn. bolleana), often makes its appearance in parks.
