This attractive, dainty South African perennial will do well in
temperate gardens around the world. Easy to grow and long-flowering
this is an ideal plant for the front of a mixed border, a rocky
bank or a container.
The name Diascia (pronounced Dye-ass-ee-a or Dye-ass-kee-a)
is derived from the Greek di (two) and askos (a sac),
referring to two pouches/sacs found on the flowers of D. bergiana,
the species first named in this genus. There are more than 50 species
of Diascia, widespread throughout South Africa and many have
horticultural potential. The genus may be divided roughly into annual
species which tend to occur in the western, winter rainfall parts
of the country and perennial species from the summer rainfall, eastern
areas. These plants thrive in Highveld gardens provided they are
given enough water. They also do well in the mediterranean climate
of the Western Cape, provided they receive adequate water in summer.
They are hardy enough to grow out of doors in milder areas of Britain
too, where several hybrids have been bred. Diascias are some of
South Africa's most attractive soft perennials and annuals. Diascia
interregima is another species frequently cultivated in
The natural distribution of Diascia rigescens extends from
KwaZulu-Natal - especially in the Harding and Mount Ayliff districts
to the coastal regions of the Eastern Cape - especially in the Keiskammahoek,
Stutterheim and Hogsback districts. In these areas it is usually
found in damp places on grassy mountain slopes, often among rocks
or in full sun at forest margins. It is also found in Lesotho and
the Free State. D. rigescens shows some variation in form
in its various localities. The most robust plants occur in the Mount
Kemp and Stutterheim districts.
D. rigescens is a showy perennial herb that grows up to
600 mm tall. Several stiff stems that are four-angled grow from
the crown. The specific name "rigescens" is Latin for
'rather stiff' and refers to the stem. This plant may also sprawl
down banks or over rocks. The upright stems are less branched than
those that are sprawling. The leaves are simple, sessile, thick-textured,
heart-shaped, opposite and have sharp little serrations along the
margins. The leaves are mostly crowded at the base of the plant,
becoming more sparse towards the top.
are carried in loose clusters and vary from pink to rose with a
deep rose throat. They are especially adapted to attract oil-collecting
bees. The main flowering time is summer, however, flowers may appear
throughout the year. The flowers last well in a vase, but become
pale if they open indoors. The fruit is a dry capsule, which contains
many small, brown seeds, which are approximately 1,5 mm long.
Diascias have a fascinating co-evolutionary relationship
with oil-collecting bees which pollinate their flowers. The flowers
of most of the species in the Racemosae section of Diascia (to which
D. rigescens belongs) have translucent "windows"
at the base of the upper corolla lip. These attract the bees which
are seeking the oil secreted in the two corolla spurs. Modified
hairs on the bee absorb the oil while the flower deposits pollen
on the feeding bee who then flies away to visit another flower carrying
a load of pollen.
Growing Diascia rigescens
The twinspur can be propagated by seed. Although seed may not set
in cultivation, if it is available it may be collected when ripe
and sown on a fine seedling mix. Cover seeds lightly to ensure that
they do not dry out. This plant also grows easily from cuttings.
In spring you can root the softwood cuttings; while in summer, semi
hardwood cuttings will do better.
The mature plant prefers full sun and will grow well in fertile,
moist but well-drained soil. This plant grows out of doors in mild
areas in Europe. Established plants can be clipped back if they
get straggly during the season. Pruning will promote new growth
and a fresh crop of flowers.
The twinspur's sprawling habit, heart shaped leaves and dense flowering
makes you sit up and take notice of this beautiful shrubby perennial.
It looks great trailing down a rock wall or in the sunny spot of
the Highveld garden.
- Batten A., 1986, Flowers of Southern Africa, Sandton: Frandsen
- Benham S. 1987. Diascia - A survey of the species in cultivation.
The Plantsman 9(1)1-17.
- Garbutt S. 1994.The up-and-coming Diascia. The Garden: Journal
of the Royal Horticultural Society. 119:18-21.
- Grey-Wilson C. 1986. Diascia rigescens. Kew Magazine
- Steiner Kim E. 1990. The Diascia (Scrophulariaceae) window:
an orientation cue for oil-collecting bees. Botanical Journal
of the Linnean Society 102:175-195.
- Van Jaarsveld, E., 2000, Wonderful Waterwise Gardening, Cape
Town: Tafelberg Publishers.
Mhlonishwa D. Dlamini & Alice Aubrey
Walter Sisulu National Botanical Gardens
with additions by Yvonne Reynolds