Berberis
is a genus of over 450 species of evergreen, semi-evergreen and
deciduous shrubs from all over the world, preferring rocky soils
in mountainous areas. Barberrys are commonly recognised for their
sharp spiny stems.
Though Berberis are not recognised as a classic bonsai subject,
there are many species that have small leaves that back bud easily,
numerous small, showy flowers in a variety of colours and on mature
trees can display beautiful bark markings.
Species suitable for bonsai include:
Berberis
thunbergii varieties / Barberrys
Dense, rounded, deciduous shrub with ovate leaves to 3cm long,
fresh green above and bluish-green underneath. Racemes of 2-5
yellow flowers are produced in Spring followed by glossy-red fruit
to 8mm long in Autumn. Reaches heights of 1metre in its native
Japan.
There are a number of varieties of B.thunbergii of which the red-leaved
varieties are preferred, Berberis thunbergii Atropurpurea has
dark purple-red foliage and vertically-striped bark. Variegated
red-leaved varietes are generally far weaker and more susceptible
to mildews than the plain red varieties.
Berberis darwinii / Barberry
Vigorous, evergreen Barberry reaching heights of upto 3metres
in its native Chile and Argentina. Dark green leaves upto 3cm
long are kept on the tree year round, while dark-orange flowers
appear in Spring followed by glaucous-blue/black fruit appear
in Autumn.

Berberis buxifolia / Barberry
Evergreen/ semi-evergreen Barberry that loses leaves only when
exposed to low temperatures in Winter. Has leathery, dark-green
leaves up to 2 cm long, dark orange-yellow flowers in Spring and
dark purple fruit in Autumn.
Bonsai
cultivation notes
Position Full sun or partial shade, protect from frosts
below -5°C to avoid twig die-back.
Feeding Every two weeks
Repotting Every two years before bud break in Spring, use
standard soil mix.
Pruning Trim back after flowering unless fruits are required.
For trees that require stronger growth, remove dead flowers to
avoid wasting energy on fruit production. When pruned, Barberrys
display unusual yellow inner stem, root and trunk colour.
Propagation Sow seed outside in early-Spring, root softwood
cuttings of deciduous species in Summer, take semi-ripe cuttings
of deciduous and evergreen species in Summer. Air-layer or ground
layer in Autumn or Spring.
Pests and Diseases Powdery mildew can occasionally be a problem,
aphids.
Styles Informal forms in single or multiple trunk groups.
In small to medium sizes. Try to avoid stiff, angular trunk forms.