Plant of the Month: January

Rubus cockburnianus 'Goldenvale' Common name: White-stemmed bramble Family: Rosaceae Vital statistics Height and spread: 14m (46ft). Form: Deciduous shrub. Soil: Well-drained, moderately fertile. Aspect: Full sun to partial shade. Hardiness: Fully hardy.

Rubus cockburnianus 'Goldenvale' @ Rosemoor

There is an impressive stand of this superb plant growing at the lower end of the Foliage and Plantsman's Garden, where its stunning (but extremely prickly!) arching white stems are shown off to excellent effect.

Rubus

This varied genus of at least 250 species of deciduous or evergreen prickly shrubs, climbers and a few herbaceous perennials is found in a range of habitats from coastal sand dunes to thickets, woodland, forest and mountain slopes throughout the world. The name Rubus is the Latin name for blackberry, bramble and raspberry.

The leaves are alternate and entire, lobed, palmate or pinnate with three or more often toothed leaflets.

Flowers are pink, white, red or purple and borne in racemes or panicles and are saucer- to cup-shaped with four or five petals.

Some species are grown for their edible fruits, including R. idaeus (raspberries) and R. fructicosus (blackberries) along with hybrids between these.

Ornamental species are grown for their flowers, foliage and winter shoots, and are an attractive addition to a shrub border. Prostrate species such as R. tricolor provide good ground cover.

Rubus cockburnianus

This strong-growing, thicket-forming deciduous shrub is a native of China and was named in honour of members of the Cockburn family who lived in China. It was introduced by Ernest Wilson in 1907 and has arching, prickly purple shoots with a brilliant white bloom in winter.

The leaves are attractive, pinnate and fern-like and up to 20cm (8in) in length, with five to nine, diamond-shaped or ovate-lance-shaped leaflets. The leaflets are mid-green above and white and hairy beneath, giving a greenish-white overall appearance.

Terminal racemes of saucer-shaped rose-purple flowers, 1cm (0.5in) across are borne in summer, followed by inedible spherical black fruit, 1.5cm (0.7in) across.

This species makes an attractive, impenetrable hedge.

AGM

The RHS Floral Committee B awarded Rubus cockburnianus 'Goldenvale' an Award of Garden Merit and described it as follows: This yellow-leaved cultivar of a well-known species from North and Central China was introduced into cultivation in 1990. The pinnate leaves to 20 x 8cm have 7 to 9 sharply toothed leaflets, the terminal leaflet ovate deeply lobed at the base to 7 x 4cm and the lateral leaflets ovate with acute apex, to 5 x 3cm. The young leaves are golden yellow (yellow group 13B to 6B to 8C) becoming greener as they age (green-yellow group 1A-D). The young stems and petioles are light green covered with a bloom and with pale greenish yellow thorns but the older arching branches are purple to brown and covered with a white bloom, giving a striking effect in winter. The small rose-pink flowers borne in a terminal inflorescence in early summer are not conspicuous amongst the foliage.

Cultivation

Grow in well-drained, moderately fertile soil in full sun or partial shade.

Pruning, if needed, should be done annually, after flowering, by cutting back flowered shoots to strong buds or young lower or basal growth.

On established plants, cut back a quarter to a fifth of old shoots to encourage replacement growth.

Grey mould (Botrytis) may be a problem.

Propagation

Root greenwood cuttings in summer, or hardwood cuttings in early winter.