Common Name: diascia
Type: Herbaceous perennial
Family: Scrophulariaceae
Zone: 5 to 9
Height: 1.00 to 1.50 feet
Spread: 1.50 to 2.00 feet
Bloom Time: July to October
Bloom Description: Rose-pink
Sun: Full sun to part shade
Water: Medium
Maintenance: Medium
Suggested Use: Annual
Flower: Showy
Culture
Easily grown in deep, moderately fertile, well-drained loams with consistent and regular moisture in full sun to part shade. Full sun is best in cool summer climates and part shade is best in hot summer climates. Avoid wet soils. Deadhead spent flower stems to prolong flowering. Cut back flower stems after flowering is completed. Most species in the genus Diascia are winter hardy to USDA Zones 7 or 8 and are grown in St. Louis as annuals. The within species is an exception to this general rule. It is native to the Drakensberg Mountains in South Africa and is considered to be winter hardy to USDA Zone 5. Regardless of winter hardiness, however, some experts maintain that this plant should always be grown as an annual because the best ornamental flower display each spring to fall will occur on plants that are propagated and replanted each spring rather than from plants that return in spring as perennials. Whether grown as a perennial or as an annual, plants will often struggle with hot and humid summer conditions to the point where they may just stop blooming in mid-summer.
Noteworthy Characteristics
Diascia integerrima, commonly known as twinspur, is a short-lived, stoloniferous, clump-forming tender perennial that is often grown as an annual. It is a tough, floriferous species that is native to cliffs, gravelly areas and streamsides in mountainous areas of South Africa typically found growing between 7000-9500’ in elevation in eastern parts of Free State, Lesotho, the Drakensberg mountains and Eastern Cape Province. Upright, wiry but rigid stems rising to 18” tall are clad with narrow leaves primarily near the base of the stems. Stems are topped with terminal racemes of four-petaled rose-pink flowers (3/4” across). Each flower has two prominent recurved spurs, hence the common name of twinspur. Spurs contain oils which are craved by several species of bees. Each flower has a drooping lower lip and four smaller curly petals at the top. Flowers open along the raceme from bottom to top with the tip continuing to produce new buds as the lower flowers are opening up, resulting in a long, continuous, often abundant bloom of showy flowers from July to frost. Ovate toothed leaves (to 1” long) are glossy green.
Genus name comes from the Greek words di meaning two and kaskos meaning sac or pouch in reference to the two spurs.
Specific epithet comes from the Latin words integer meaning entire and –rimus which is a superlative ending in reference to the entire leaf margins.
‘Coral Canyon’ was discovered in the Drakensberg Mountains. It is noted for having excellent winter hardiness (broadens winter hardiness range of the genus), perhaps to USDA Zone 5. Soft coral pink oval flowers. Typically grows to 12-18” tall and as wide.
Problems
No serious insect or disease problems. Watch for snails and slugs.
Uses
Mass in border fronts, rock gardens, pots/containers, hanging baskets. Foliage trails attractively from containers and window boxes.