The genus Rubus, (especially the blackberries, which are often loosely referred to as Rubus fruticosus agg.) presents some of the most difficult taxonomic problems. This is partly due to the frequency of polyploidy; also to the frequent occurrence of hybridization; and also due to apomixis, where minor differences between plants are preserved because seedlings are genetically identical to their parent. As a result, differences of opinion on the number of species to be recognized from a given region can vary tremendously (for example, a treatment by M. L. Fernald[
] in 1950 recognized 205 species for the northern half of the eastern United States plus parts of southeastern Canada, whilst H. A. Gleason and A. Cronquist in 1991 recognized only 25)[
]. Where possible, a relatively conservative approach is taken here[
Rubus giraldianus Focke
Rubus thibetianus auct.
Rubus cockburnianus is a vigorous deciduous shrub producing each year a cluster of sparsely-armed, arching, biennial stems from a woody rootstock; the stems can grow 150 - 300cm tall[
]. The stems only produce leaves in their first year of growth, forming flower and leaf-bearing branches in their second year and dying after fruiting. Plants can spread freely at the roots, forming large thickets of growth.
The plant is harvested from the wild for local use as a food. It is often grown as an ornamental in gardens, being valued especially for its white stems and its arching, pendulous branches, which give a remarkable fountain-like aspect to the shrub[
E. Asia - central and southern China.
Thickets on sunny slopes, dense forests in montane valleys, riversides at elevations of 900 - 4000 metres[
|Other Uses Rating
Rubus cockburnianus is hardy to at least -15°c.
Easily grown in a good well-drained loamy soil in sun or semi-shade[
Plants in this genus are notably susceptible to honey fungus[
Fruit - raw or cooked. Small and of poor quality[
]. The purplish-black fruit is up to 10mm in diameter[
This species is used in breeding programmes in England, where it is crossed with Rubus occidentalis with the aim of increasing the number of flowers and for obtaining a higher quality of fruits and resistance to viruses[
A purple to dull blue dye is obtained from the fruit[
Seed - requires stratification and is best sown in early autumn in a cold frame. Stored seed requires one month stratification at about 3°c and is best sown as early as possible in the year. Prick out the seedlings when they are large enough to handle and grow on in a cold frame. Plant them out into their permanent positions in late spring of the following year.
Cuttings of half-ripe wood, mid summer in a frame[
Tip layering in July. Plant out in autumn.
Division in early spring or just before leaf-fall in the autumn[