- Name also: Moor Birch, Hairy Birch
- Subspecies: Downy Birch or White Birch (ssp. pubescens), Mountain Birch (ssp. czerepanovii)
- Family: Birch Family – Betulaceae
- Growing form and height: Tree with a single trunk or shrub with several main stems. 2–20 m (6.5–65 ft.), usu. 8–20 m.
- Flower: Small, greenish to brownish, lacking perianth. Inflorescences dense, pendent catkins formed by numerous, 2–3-flowered cymes. Male and female flowers in separate inflorescences.
- Leaves: Ovate, short-pointed, serrate (with sawlike margins), often hairy beneath. Always green at emergence. Autumn colour yellow to orange.
- Buds: Narrowly tapering, rather small, brown, sometimes greenish.
- Fruit: Small, winged achene.
- Habitat: Moist coniferous and mixed forests, spruce swamps, eutrophic fens, ditches, shores, field and road margins.
- Flowering time: April–June. Flowers when coming into leaf.
The genus Betula comprises some 40 species, both trees, shrubs, and dwarf shrubs. The trunks of birches are covered with white or darkish, often papery bark. They flower when coming into leaf in the spring. The small flowers are unisexual, the inflorescence a catkin-like, dense compound cyme.
Downy birch, also known as white birch, is a very variable tree. Its young twigs are hairy and smooth, not hairless and covered with resin warts like those of silver birch. It has serrate leaves, not doubly serrate like silver birch. Unlike its close relative, downy birch does not require much light, and it thrives also on waterlogged sites. Downy birch is also a pioneer species, especially in Northern Finland. In the fjeld district in the far north mountain birch (ssp. czerepanovii) dominates. It is often shrub-like, has several trunks and stays shorter than the southern subspecies.
Tough and flexible timber of downy birch is good for making furniture. Leaves can be used as tea and in herbal medicines, and sap as a stimulating drink in spring.