Curly birch (Betula pendula var. carelica (Mercklin) Hämet-Ahti) is a special variety of silver birch, known for its hereditary and unique, highly decorative curly-grained and brown-figured wood. It is the most highly-prized variant of native trees in the Nordic countries.
Curly birch occurs naturally, but it is rare, growing only in Northern Europe and some parts of Eastern and Central Europe. In Finland its natural distribution area covers the southern part of the country.
Curly birch wood is the result of abnormality in the functioning of the cambium, which in turn is caused by a hereditary mutation. As a result, the annual rings and the orientation of wood tissues become wavy in appearance and the pith rays become dilated.
Morphology of curly birch
Curly birches display a wide range of morphological variation from crooked multi-stemmed bush-like individuals to straight and single-stemmed trees. Single-stemmed trees with abundant protuberance formation and rich curly wood configuration with brown figures are suitable for turning and therefore commercially the most valuable.
Curly birch wood
Curly birch wood can be highly decorative due to its curly-grained and brown figured pattern, in the best cases including hologram-like reflections. The cross-section of a curly-grained birch stem shows V-shaped patterns, which can form a pronounced and closed ”curly flower” configurtion.
When the bark is peeled off, the surface of the stem has a decorative granulated appearance with small oblong swellings and depressions. A longitudinal tangential cut shows a lens-like configuration.
The wood density and hardness of the wood of curly birch is greater than those of normal silver birch. Curly birch is well suited for turning, but long pieces of this wood tend to bend and twist as massive items.
Logs and veneers of curly birch have traditionally been used in interior decoration, furnishing and paneling, e.g. offices, banks, luxury homes, ships and high-end cars. Wood of smaller dimensions is used by artisans when making highly valued products as gifts, souvenirs, tools annd furniture.
Silviculture of curly birch
Silvicultural management of curly birch has to be done with great care, starting from plantation establishment, through branch pruning and correctively timed selective thinnings to final cutting at the age of 35–45 years. Succesful curly birch management requires special expertise, significant effrot, and economic investments from the forest owner.
Changing markets of curly birch wood
Cultivation of curly birch has a long tradition in Finland. Interest in commercial cultivation of curly birch has, however, significantly increased during the past 30 years with some 7000 hectares having been planted by 2025. These stands will soon start reaching the end of their rotation. Small-dimension wood from thinnings is already now available in abundance. Harvesting curly birch wood from cultivated, certified stands does not endanger the rare individuals in natural forests.
The significantly increasing availability of this exceptionally beautiful wood resource makes it possible to develop new products based on this, now cultivated variant. The wood is suitable also for use in premium products of high-class design.
More information about this special tree variety can be found in attached literature review on curly birch.
