Indigofera is a large genus with wide distribution
throughout the Far East, particularly in China and the Himalaya areas, while
some species are native to Australia. The genus includes about three hundred
species of evergreen or deciduous shrubs and herbaceous perennials. The
best-known is Indigofera tinctoria, not as a decorative garden plant, but
valued and cultivated since ancient times for the dye, indigo, which the plant
provides. This use was first recorded by Marco Polo. Indigofera tinctoria is
indigenous to southern India, where it is widely cultivated.
It is mainly the shrubby species that are of garden value.
These are hardy deciduous shrubs with small attractive freely produced pea-
like flowers, and much-divided elegant foliage. They are plants with few
demands, asking only for a fertile not-too-heavy soil, good drainage, and
either sun or partial shade. Indigoferas can be propagated from seed sown in
coldframes or in an unheated greenhouse in spring; by means of soft cuttings
taken in late spring or early summer and inserted in sand in a warm greenhouse;
or by means of semi-woody cuttings taken in July—August and inserted in a
sandand-peat soil in frames.
Indigofera amblyantha
Craib.
Native to China. A deciduous shrub up with pinnate leaves
generally composed of ten leaflets. The flowering period is particularly long,
from June to October, with an abundance of small pink blooms borne in erect
racemes The plants require a light
pruning in spring.
Indigofera decora
Lindl.
Native to China. A dwarf deciduous shrub with pinnate leaves
and inflorescences in the form of erect 6-in.-high racemes, each bearing some
rather large pinkish-white pendulous flowers. An elegant, attractive little
plant that remains in bloom until the end of summer. Although the above-ground
part of the plant is not resistant to very severe cold, it will, like
Indigofera gerardiana, re-grow from the roots if the upper part is
frost-killed.
Indigofera gerardiana
Baker
Native to the Himalayas. The best-known species in general
cultivation in gardens. Although normally hardy, the above-ground part of the
plant may be killed by very severe frost. As in the case of Indigofera decora,
new growths are invariably produced from the base in spring. If the current
season's growth is not killed back by frost, severe pruning is necessary in
spring (leaving only buds at the base of
the growths), as the current season's flowers are produced on the new growths.
A deciduous shrub of modest proportions, much-branched and with a luxuriant
mass of foliage. The leaves are pinnate and composed of leaflets, each leaf
about long, and the individual leaflets I in. long; light green in colour and
graceful in appearance. Inflorescence a raceme long, axillary, and bearing
some individual pea-shaped purple-pink
flowers. Blooming is very prolific, from mid-summer until autumn.
Indigofera pendula
Franch.
Native to China. One of the tallest species normally
cultivated in gardens. Habit wide-spreading and expansive. Leaves pinnate.
Distinguished from other species by the pendulous inflorescences, long, freely
produced from late summer until autumn. The individual blooms resemble those of
broom (Cytisus) and are very numerous, opening from the base of the raceme
upwards. They have a most pleasing reddish-purple colour.
Indigofera potaninii
Craib.
Native to the Kansu province of China. Discovered in 1885 by
the Russian botanical explorer Potanin, but not introduced into Western gardens
until 1912. A wide-spreading deciduous shrub with pinnate foliage long and
consisting of up to seven pairs of leaflets. Pink flowers are borne in axillary
racemes long. Particularly free-flowering from June onwards.
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