Betula maximowicziana Regel

With its large Tilia-like leaves, densely lenticillate platinum bark, and clusters of long fruiting catkins in spring, Betula maximowicziana is one of the most distinctive and immediately recognisable of the birches. The species was described in 1865 by Eduard Regel from a specimen collected by Carl J. Maximowicz (1827–1891) on Hokkaido (Yezo) during his expedition to Japan in 1860–1864. The name initially used by Regel, B. maximowiczii, is illegitimate, having already been used by Ruprecht for B. dahurica – Regel published the replacement name B. maximowicziana in 1868. In Japan the species is planted commercially as a major timber-producing tree. Japanese fisherman are supposed to have used the bark for torches that would light easily even when wet (Curtis’s Botanical Magazine 1910).

Betula maximowicziana belongs to a northeastern group of tree species of Japan and north-east Asia that has few species in common with the Sino-Himalayan region (Ran, Wei & Wang 2006) and appears to have been isolated from its close relatives in subgen. Acuminatae since at least the Tertiary period. Although the species shares its elongated leaf teeth and long, cylindrical, clustered fruiting catkins with the other species in subgen. Acuminatae, it differs from them in its autumn, rather than summer, fruiting period and its much thicker male catkins.

Tsuda & Ide (2005) describe Betula maximowicziana as a long-lived pioneer species of cool temperate forests with relatively little genetic diversity but some differentiation among populations, which suggests that the populations have been through significant bottlenecks in the past with episodes of small population size. The species occurs naturally at lower altitudes than B. pendula subsp. platyphylla (Osumi 2005; Tabata 1966), and appears to be more drought tolerant than many other birches – Coder (1999) includes only this species and B. nigra in a list of drought tolerant trees for the southeastern United States. Natural regeneration of Betula maximowicziana depends mainly on the previous year’s seed production, but the species has been shown to have a persistent seed bank with over 16% of buried seed being viable after six years (Osumi & Sakurai 1997). This means that there is always seed present in the soil, even in years when no seeds are produced, to take advantage of any disturbance which provides favourable conditions for seed germination (Tsuyuzaki & Goto 2001).

Betula maximowicziana was introduced to cultivation in Britain in 1888, when J. H. Veitch sent seed from Hokkaido. A further introduction was made in 1893 from seed sent from Hokkaido by way of the Arnold Arboretum – a plant raised from this material was figured in Curtis’s Botanical Magazine (1910). A celebrated tree planted in 1894 at Grayswood Hill, Surrey, was supplied by the French nursery Lemoine of Nancy (Bean 1976). The species is now fairly common in cultivation and seems to be easy to grow in temperate areas of the British Isles and North America (Clarke in Bean 1970; Santamour & Lundgren 1996). It is easily propagated from seed and is quick growing. It appears to be almost totally self-incompatible, and only a single hybrid tree is known (see B. × dosmannii)

The lone specimen of Betula maximowicziana in the Hergest Croft Arboretum, Herefordshire produces large quantities of non-viable seed when growing in the presence of many other birch species, suggesting that hybridisation with species of other subgenera is uncommon.