Aptosimum is a genus of about 27 species of flowering plants in the family Scrophulariaceae (order Lamiales), native to the dry tropical and southern regions of Africa. The genus is centered in southern Africa, where species are characteristic of arid and semi-arid landscapes including Namaqualand, the Karoo, Bushmanland, and Namibia.
Plants are typically perennial herbs or dwarf shrublets, often forming low spreading mats or carpets. The leaves are alternate and densely crowded on shoots, ranging from linear and lanceolate to spathulate in form. The flowers are trumpet-shaped (tubular with a flared limb) and range from dark blue to violet or mauve, appearing mostly in spring and summer but capable of blooming at almost any time of year. The corolla is distinctively narrow and tubular at the base -- a "gullet flower" structure that restricts access to nectar and favors long-tongued pollinators. Pollination is primarily carried out by pollen wasps of the subfamily Masarinae (genus Celonites), with bees as secondary visitors. The fruit is a thick-walled capsule that remains attached to the plant even after the seeds have been dispersed -- a trait reflected in the genus name.
The best-known species, Aptosimum procumbens (carpet flower or Karoo violet), is valued as a drought-tolerant ground cover and has been cultivated as an ornamental since the early nineteenth century. Other species in the genus include A. indivisum, A. spinescens, A. lineare, A. glandulosum, and several others spread across southern and tropical Africa.
Etymology
The name Aptosimum derives from Greek: a- ("not") and ptosimos ("deciduous," from ptosis, "a fall"). The name refers to the genus's characteristic fruit, a capsule that is retained on the plant even after the seeds have been released -- the capsule does not fall.
Distribution
Aptosimum species are native to arid and semi-arid Africa, with the center of diversity in southern Africa. The genus ranges across Namaqualand, Bushmanland, the Great Escarpment, the Karoo (Northern, Upper, Great, and Little Karoo), the Northern Cape, and into Namibia. Species are also recorded from parts of tropical Africa. Populations commonly occur on floodplains, flats, ridges, disturbed ground, and mountain plains.
Ecology
The trumpet-shaped flowers of Aptosimum are "gullet flowers": the corolla is tubular along most of its length and very narrow at the base, protecting nectaries from all but visitors with long tongues. The primary pollinators are pollen wasps (Vespidae: Masarinae), especially species of Celonites, small blackish wasps (c. 10 mm) with red or red-and-white markings and long retractable tongues. Specific Celonites species tend to be associated with the genus in particular localities across the Karoo. Bees are secondary visitors.
Cultivation
Aptosimum species prefer full sun and are highly drought-tolerant, making them suitable for water-wise gardens in dry climates. They can be grown as ground covers, in containers, hanging baskets, or planted between paving. Propagation from cuttings is more reliable than from seed: use 10 mm tips of soft, young shoots from healthy plants, inserted into a coarse sandy medium kept moist and warm. Seed germination is possible but inconsistent.
Cultural Uses
Aptosimum has traditional medicinal use in southern Africa: plants are administered to treat krimpsiekte in sheep, an acute condition affecting joints, muscles, and the stomach. The genus has also had ornamental use -- A. procumbens was cultivated as a garden plant in England from seed supplied by explorers Burchell and Ecklon from as early as 1815 to around 1828.
