Othonna is a genus in the Sunflower Family (Asteraceae or Compositae), in the senecioid subdivision of the family. About 90 species are native to summer and winter rainfall areas of southern Africa, northward to Angola and Zimbabwe. The genus is especially diverse in the winter rainfall areas of South Africa.
Othonnas exhibit much variation in their life form or habit and may be shrubs, dwarf succulents or geophytes. Only the last group, called the "Othonna Bulbosa Group" (Magoswana 2016), is considered here. Members of this assemblage are characterized by having a tuberous root that is conical, fusiform or napiform. The foliage may be basal or cauline, with considerable variation in size, shape, color and vestiture. The mostly yellow flowers are arranged in radiate or discoid heads. The few Othonna species with purple flowers are found only in this tuberous group.
Most cultivated othonnas are in the domain of succulent collecting, and the geophytic species have been more recently introduced as an adjunct interest. The upper part of the tuber of these plants can be raised above the soil like a "caudex" with some success. In general the rootstock seems to prefer life underground, with the top of the tuber a centimeter or so below the surface. The same is true for species of Eriospermum, Brachystelma, etc.
The tuberous Othonna species are all or nearly all winter growers. They prefer bright light and cool nights in winter, followed by a dry summer rest. They are long lived in containers and can be propagated by root divisions and seed. Hand-pollination of two or more plants is required to generate seeds. A suitable soil mix for these plants is low in organic material (10-20%), and mostly consists of drainage material such as pumice or scoria, with 10-20% sand as a stabilizer. Some growers have found that the seed germinates much better if sown in spring, dry, and allowed to bake dry all summer before commencing watering in the fall.
The name is probably from the Greek word, othonne, for linen or cloth, referring to the soft leaves of some species.
Othonna auriculifolia Licht. ex Less. is a species with a deep and rather slender main root, about 1-2 cm thick, and solitary flower heads. It flowers in winter (January) in California. It appears to be quite variable in nature and this name might be a label for a group of related species. Photos by Dylan Hannon of an example from Nieuwoudtville (ex Silverhill).
Photos from Dylan Hannon who writes of photo 1: "the following two entities could be called O. cf. auriculifolia:Namibia: Halenberg.'" and of photo 2 "this plant was collected by Michael Vassar (no. 4847), without locality at this time. I've given it the provisional name O. auriculifolia 'Crispa'."
Othonna cakilifolia DC. is a bulbous plant, but not a monocot. Known as Baboon cabbage, this species was named by De Candolle, in 1838, for the resemblance of its leaves to those of the genus Cakile, commonly called sea rocket. Photos 1 and 2 by Arnold Trachtenberg, remaining photos by Dylan Hannon from Lutzville, South Africa and Steven Hammer 2082.
Othonna cakilifolia hybrids are being created by Carl Frederick. He is growing and hybridizing Othonna cakilefolia and related species. Crossing yellow and purple/pink species has resulted in many differently-colored flowers. Some are pictured below.
Othonna digitata L.f. is from the Southwest Cape. The foliage and "non-yellow" flowers are distinctive. Photos by Dylan Hannon
Othonna gymnodiscus (DC.) Sch.Bip. 's name comes from Greek "naked disc", think gymnasium and discus. Photos by Arnold Trachtenberg of what may be Othonna gymnodiscus or possibly Othonna undulosa (DC.) J.C.Manning & Goldblatt (syn. Othonna perfoliata var. undulosa (DC.) Sch.Bip.). The history of Arnold's plants is: Othonna aff. perfoliata ex Mike Vassar 7454, Simonsviel- (ex BX 353 as Othonna sp? white). These have large fleshy leaves with purple backs and small yellow florets without ray petals and do very well if occasionally watered well while in growth in fall-winter.
Othonna heterophylla L.f. is foud on sandy and clay flats and slopes in the southern Cape. It flowers May to September. Photos by Dylan Hannon of Othonna heterophylla from Elandsberg ex Silvehill Seeds. The last photo shows plants emerging from dormancy in late fall.
Othonna incisa Harv. is considered by some authorities to be a synonym for Othonna rosea Harv. Photos by Dylan Hannon who writes "This species name is sometimes regarded as a synonym of Othonna rosea. I retain its use for the material shown here, which is very robust and large compared to the circumscription of Othonna rosea given by Magoswana (2018). It was originally collected in the Kamiesberg (ex Silverhill) and grows to 100 cm tall -- double the 50 cm height figure given for Othonna rosea by Magoswana. The conspicuously toothy leaves are also distinctive. Flower color variation is within the same original gathering."
Othonna lilacina Magoswana & J.C.Manning is a species from the Northern Cape originally from Riethuis described in 2019. It was formerly confused with Othonna rosea. Photos by Dylan Hannon; the second shows young plants.
Othonna lyrata DC. is a species from the Western Cape. Photos by Dylan Hannon, from Cedarberg, ex Silverhill Seeds.
Othonna macrophylla DC. is a Western Cape species with large tubers originally from Kosies. Photos by Dylan Hannon.
Othonna ovalifolia Hutch is a species with unusual "variegated" leaves. This name has recently been cast into synonymy (Magoswana, 2018) under Othonna macrophylla. Several characters render it distinct from what is normally called Othonna macrophylla: leaves rosulate, flat on the soil, variegated; flowering stems unbranched or few-branched. Photos by Dylan Hannon
Othonna perfoilata (L.f.) Jacq. is yellow. The name "perfoliata" refers to stem-clasping leaves. Ray petals are a defining feature of O. perfoliata. Photos by Dylan Hannon of plants originating from Clanwilliam: Pakhuis Pass. Photos 1 and 2 show juvenile leaves, which are petiolate and basal. Adult plants have only aerial stems, without basal leaves. This is also true of Othonna undulosa (syn. Othonna filicaulis). The cauline leaves are sessile and amplexicaul (not perfoliate as the name suggests), while the basal leaves of juvenile plants have slender petioles. Adult and juvenile leaves are different in shape as well and either type may be purple below and mottled above.
Photos by Dylan Hannon of plants from a different unknown locality. These show the clasping cauline leaves (stem leaves) and petiolate basal/juvenile leaves, and their different respective shapes, together for comparison. There are several plants in this pot.
Othonna pinnata L.f. is a species from seasonally wet or moist areas in the Southwestern Cape. Photos by Dylan Hannon obtained under E. Specks 3131.
Othonna primulina DC. photos by Dylan Hannon who says "a tentative determination for this recently introduced, distinctive species". The tuberous root is large, about 5 cm diameter, in proportion to the rosette of primrose-like leaves. Flower heads are solitary, on long stalks.