Betula

This large handsome birch can reach 30m with a trunk 1 metre in diameter in its native habitat in the Far East. It is used there in plywood and by the furniture industry but is also a beautiful park tree. The leaves are slender, long and oval, and the branches droop attractively. The bark varies from white to cream, silvery or even pale red, exfoliating showily from the trunk and large branches in broad strips. In old age the bark becomes impressively thick.

The climate in costata birch’s native range closely resembles that in Finland, as does its habitat. The species seems to grow successfully here, although there are differences depending on seed provenance. Mustila has obtained seed direct from north-east China and South Korea. The Korean species grown in European nurseries is mainly Erman’s birch (Betula ermanii). 

The bark and shoots of yellow birch give off a strong smell of wintergreen when rubbed or crushed. The trunk is yellowish or silver-grey, without much tendency to peeling. The long leaves are noticeably larger than either of the two Finnish species, and resemble hornbeam (Carpinus) leaves, lying along the branches in layers. This is a showy species, especially in its autumn colour, when it gleams in the sunshine like a raised group of yellow azalea. The common name comes either from this yellow autumn foliage, or from the yellowish bark, or perhaps even from the yellowish colour of the wood, which is highly valued for carpentry.

Native to eastern North America, it grows to 25–30m in the northern parts of the broadleaf forest belt but fails to achieve these dimensions when planted in Finland. The specimens at Mustila date from the early 1900s and have grown well. Only two of these old trees are left, the third of the group having been destroyed in a storm in 2009. A new generation of this species was planted in the 1970s. Seed was collected on expeditions from Mustila in 1996 and 2002 from excellent northern provenances which should produce trees even better suited to Finnish conditions. Yellow birch is one of about a dozen American broadleaf species which should be more widely used in Finnish public landscaping.