Origin and Habitat: Republic of South Africa (Eastern Cape, Northern Cape, Western Cape).
Habitat and ecology: Mainly Succulent Karoo. Crassula columnarisSN|26654]]SN|26654]] is found widely on gravel flats in Namaqualand and on the quartz fields of the knersvlakte. Plants are variously coloured to blend in with the harsh, dry and rocky habitat in which they grow. The typical subspecies is found in the Little Karoo, western Great Karoo and towards Vanrhynsdorp. it flowers mid-winter to early spring (May to August). The plant, being monocarpic, dies after flowering, but this single act must be any successful because the plants are quite common[4]. C. columnaris has a resting period in summer.

• Crassula columnaris Thunb.
• Tetraphyle columnaris (Thunb.) P.V.Heath

• Crassula columnaris Thunb.
• Tetraphyle columnaris (Thunb.) P.V.Heath
• Crassula mitrata Friedrich
• Tetraphyle columnaris var. mitrata (Friedrich) P.V.Heath

• Crassula columnaris subs. prolifera Friedrich
• Tetraphyle columnaris var. prolifera (Friedrich) P.V.Heath
• Crassula columnaris var. elongata E.Mey. ex Drège
• Crassula semiorbicularis Eckl. & Zeyh.

Description: Crassula columnarisSN|26577]]SN|26654]] (Stonecrop family) is a dwarf, compact, perennials or biennials succulent with with single short erect stems 1,5-6 cm high in which the grey-green to brownish leaves are rounded, fleshy, broader than long, arranged in 4 closed ranks; the leaves are incurved and so closely packed over each other as completely to hide the stem. The plant takes five to ten years to reach maturity, at which time, and if rain falls, the round body opens and a dense 'shaving brush' of cream to orange-yellow sweet-scented flowers appears 26654]SN|26577]]. Mature specimens of the latter are invariably branched, while C. columnaris plants remain unbranched or have short axillary branches at the base.
Roots: Fibrous.
Branches: Short, erect, simple, (3-)15-60(-70) mm high, 3-4 mm in diameter, rarely with short axillary branches at base, completely hidden by the 8-10 leaf-pairs throughout. As Marloth aptly states, the specific name is unsuitable, as the typical plants in nature are often sunken and globular, only becoming columnar in cultivation [4].
Leaves:Sessile, connate at the base, 4-ranked, broader than long, 10-15 mm long, 10-23 mm wide, becoming shorter upwards and forming a short tapering columnar, brownish-green, imbricate, tightly clasping and patelliform, rounded, fleshy, concave on the inner or adaxial surface and convex outwardly, lower face not keeled, tip rounded, rarely mucronate, often with membranous margins with grey-green to brown inflexed (slightly recurved) cilia.
Inflorescences: Flowers are borne in a sessile, capitulum (head) directly on top of the plant (often partly hidden among the upper leaves) 10 mm tall and to 22 mm in diameter, rarely a rounded thyrse more or less hidden by leaves below, densely many flowered.
Flowers: White, creamy-yellow or or tinged with red, sweetly scented. Calyx-lobes (sepals) linear to elliptic-oblong, (1.5)3-4(-5) mm long, obtuse, green to brown translucent, tips green. Corolla slender ampulliform, fused basally for 7-13 mm, white, pale yellow and often tinged red. Petals connate below, narrowly elliptic-oblong, 7-13 mm long, tapering above into a blunt, yellowish, beak 1 mm long. Stigma subsessile. Stamens with yellow to brown anthers. Filaments 1.2 - 2 mm. Anthers yellow or brown. Nectar-glands reddish.

Bibliography: Major references and further lectures
1) Urs Eggli “Illustrated Handbook of Succulent Plants: Crassulaceae” Springer Berlin Heidelberg, 05/Nov/2012
2) J.P. Roux “Flora of South Africa”, 2003
3) W. H. Harvey “Flora Capensis”, Vol 2, 1894
4) Doreen Court “Succulent Flora of Southern Africa” CRC Press, 01/June/2000
5) Gideon Smith, Ben-Erik Van Wyk “The Garden Succulents Primer” Timber Press, 2008
6) Joan Compton “Knowledge through Color; House Plants” McGill-Queen's Press – MQUP
7) Peter Joyce “Flower Watching in the Cape: Scenic Routes Throughout the Year”
Struik, 2004
8) Foden, W. & Potter, L. 2005. Crassula columnaris Thunb. subsp. columnaris. National Assessment: Red List of South African Plants version 2017.1. Accessed on 2017/08/06
9) Vera Higgins “Succulent Plants Illustrated” Blandford Press, 1949
10) Hermann Jacobsen “A Handbook of Succulent Plants: Descriptions, Synonyms, and Cultural Details for Succulents Other Than Cactaceae”, Volume 1 Blandford Press, 1960
11) “The Illustrated London News”, Volume 223, 2nd Edition, Illustrated London News & Sketch Limited, 1953