Family: Papilionaceae
Common Name: Kowhai

Widely distributed in temperate regions of the northern hemisphere, this genus of 50 ever-green and deciduous trees and shrubs also includes a few species from New Zealand. Mostly open, many-branched trees, they have alternate, feathery leaves and drooping clusters of pea-type flowers in spring or summer, followed by bean-like seed pods. They make good shade trees or lawn specimens.

Species

S. chrysophylla, zone 10, from Hawaii, is a compact, deciduous shrub, to 3 m (10 ft). The leaves are composed of a number of pairs of leaflets, and the bright yellow flowers are borne in short clusters.

S. japonica, Japanese pagoda tree, zone 5, from central China, is a lovely, deciduous tree, growing up to 20 m (65 ft). The leaves are composed of blueish leaflets and the cream flowers are borne in long trusses. The timber, bark and fruit yield a yellow dye. Cultivar 'Pendula', weeping pagoda tree, with drooping branches, is sometimes grafted onto standards; 'Tortuosa' has twisted branches.

S. microphylla, zone 8, from New Zealand, is an evergreen tree, growing to 5 m (16 ft). The leaves, comprised of small, dark green leaflets, have a fern-like appearance. The flowers, mostly deep yellow in colour, are borne in dense clusters in summer. 'there are many popular cultivars, such as 'Earlygold', 'Goldies Mantle' and 'Goldilocks'.

S. prostrata, zone 8, is a low-growing or upright shrub, also from New Zealand, which may be 60 cm to 3 m (2-6 ft) high. The flowers range from orange to brownish yellow and occasionally bright yellow.

S. tetraptera, Kowhai or New Zealand laburnum, zone 8, is New Zealand's national floral emblem. Reaching up to 12 m (40 ft), though generally smaller, this tree develops a slightly pendulous habit. The leaves are comprised of large numbers of silky, gray-green leaflets, is borne on interlocking branches. A profusion of golden yellow flowers are borne in drooping clusters, in spring.

S. tomentosa, silverbush, zone 10, is a tall shrill) or small tree with loose clusters of pale yellow flowers.

Cultivation

Sophoras are suitable for cool climates, but will tolerate hot conditions if they receive enough water in summer. Most prefer moist, well-drained soil, but will grow in sun or partial shade. Any tender species (zone 10 in list) can be grown in an intermediate green-house in frost-prone climates. Propagate from seed when ripe, in a garden frame, or from semi-ripe cuttings in summer, with basal warmth.

Climate

There are species suited to various climatic zones.