Most gardeners think of diascias as low-growing bedding plants suited to a summer container or the front of a sunny border.
However Diascia personata breaks the mould and produces stiff stems that grow 3ft tall. The substantial bright green foliage supports dusky pink flowers and these appear in profusion from early May to November.
Handsome, upright and show-stopping, it first came to my attention when Fergus Garrett of Great Dixter in East Sussex brought it to a Perennial Plant Day at RHS Wisley in June last year.
Having never seen it before I then spotted it two days later on a Hopleys' stand (see details below) and snapped it up.
Although the form I acquired was labelled 'Hopleys', it is the same plant grown at Great Dixter.
Diascias are found on the eastern side of southern Africa. There are 70 species in all and most are annual, but there are a few perennials.
They are members of the Scrophularia or figwort family, together with verbascum and buddleia, although the whole tribe has recently been reclassified.
The common name of diascia is "twinspur" and this refers to two spurs found at the back of the flower. The closely related genera Alonsoa and Nemesia look similar, but have more spurs - often these are longer.
Although diascias flower for months in Britain they have a much shorter flowering season in their native land because they are pollinated by a different species of bee: Bees from the genus Rediviva (native to southern Africa) have extra long forelegs, and this allows them to reach the spurs of the flowers in order to collect a fatty oil produced by the glands.
The legs of the bee soak up the oil, rather like a sponge, and pollen is transferred to the body of the bee during this process. The flowers are then pollinated and fade. Our native bees have shorter legs and so fail to pollinate the flowers.
In the wild, different species of diascia growing together evolve and produce stamens of varying lengths, or in varying positions, so that any pollen deposited sticks to different parts of the bee's body.
This system prevents cross-pollination. But if the necessary species of bee is absent, the flowers are not pollinated, so flower longer.
The late plant breeder and hobbyist, Hector Harrison, of Appleby, in South Humberside, found out about diascia's pollination needs and began hand-pollinating three species about 1978. His first hybrids flowered in the mid-Eighties and he generously gave them to nurseries and enthusiasts.
Harrison hybrids include 'Appleby Apricot', 'Iceberg', 'Salmon Supreme' and 'Lilac Belle'. White, lilac, various pinks and apricot diascias are all available.
Some of these hybrids may be sterile even if they encounter the long-legged bees required for pollination: sterility often occurs when two closely related species hybridise.
Harrison was, however, unaware of the first British-raised diascia. The late John Kelly, once curator at Abbotsbury Subtropical Gardens, applied the pollen from D. cordata to D. barberae. He grew nine seeds and named the best red-pink 'Ruby Field' after a lady who sometimes worked on the nursery.
It is now listed under D. barberae in the RHS Plant Finder so may not even be a hybrid. The diascia gene pool was further expanded when new species were collected in the Seventies for the Edinburgh Botanic Gardens.
Diascia personata is a perennial from the Eastern Cape and hardier than the annual forms. It will survive most winters given a sunny position and well-drained soil.
Its hardiness equates roughly to the dahlia in my opinion and "insurance" cuttings should be taken in early summer, in case of a hard winter.
Sometimes another plant, the similarly upright D. rigescens, is mistaken for D. personata and the flowers are a similar colour.
They are, however, significantly different: D. rigescens is shorter, between 1-2ft and the foliage a duller blue-green. It has less stature. I have successfully over wintered both of these, but last winter saw them off.
GROWING TIPS
Diascias are sun-loving plants, but enjoy fertile rather than dry, poor soil. The cushion-forming types can get straggly so cut them back in late April and late August to keep them compact.
Hardiness can be a problem, but many will survive winter in well-drained soil.
Cuttings can be taken between May and September. However, if you want to keep cuttings through the winter take them in the first half of summer so that a good root system is developed.
Look for new growth that has started to harden slightly, preferably without flower buds. Cut off just below the node (the bumpy part where leaves are attached) so that your cutting measures roughly 4in long. Trim the cutting just below the bumpy node and strip any lower leaves.
Plunge into a suitable rooting matter. This could be a mixture of compost and horticultural sand. I prefill small seed trays with damp horticultural sand and plunge cuttings in as I take them. No rooting compost or special equipment is needed.
You can containerise Diascia personata, but it has to be a substantial pot to balance the height of the plant. The ruby-pink flowers are excellent with dark blue agapanthus, purple dahlias or fluffy pennisetums.
At Great Dixter they use D. personata with the green and cream vertically striped grass, Miscanthus sinensis var. condensatus 'Cosmopolitan' to great effect. Graham Gough, of Marchants Plants, also uses it in his grass-led garden and he describes it as "remarkable and lofty".
WHERE TO BUY
Hopleys, High Street, Much Hadham, Herts (01279 842509)
Great Dixter nursery, Northiam, Rye, E. Sussex (01797 253 107)
Marchants Hardy Plants, Mill Lane, Laughton, E. Sussex (01323 811737)
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