Names and synonyms

Rosenia oppositifolia (DC.) Bremer
=Polychaetia oppositifolia DC.
=Nestlera prostrata Harv.
=Rosenia angustifolia Compton
=Nestlera levynsae Hutchinson

Type

Drege, J.F. 2160, Savanierspoort, 1829-09-19 (S, LD, P, G, HBG)

Common names

Hartebeeskaroo, Bekkerbos, Blouperdekaroo, Perdekaroo, Springbokkaroo

Derivation of names

Rosenia = after E. Rosen (1714-1796), Swedish physician, botanist and professor of practical medicine.
oppositifolia = with opposite leaves

Diagnostic characters

Leaves narrow, ericoid, glandular, with pitted glands
Capitula relatively small (few-flowered)
Numerous capitula borne in a string; on short brachyblasts along the flowering stems

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Description

Multi-branched, erect or sometimes prostrate shrublets, often with a greyish appearance, up to 0.6 m tall. Leaves linear, triangular in cross section, with midrib projecting below, 1.5-10(-12) x 0.4-0.8(-1) mm, somewhat hairy on both sides, dark greyish green. Capitula about 10 mm diameter, florets yellow. Involucre narrowly cup- to bell-shaped, 2-6 mm wide. Involucral bracts 12-45, outer elliptic, inner gradually longer and narrower, to narrowly obovate, 5-7 x 1-2 mm, apically spreading with membranous margins. Receptacle epaleate with short scales. Ray florets 3-8, lamina 3-4.5 mm long. Disc florets 5-15, corolla 4-5.3 mm long. Pappus a crown of scales up to 1.3 mm long, often also with 1-2 barbellate bristles, up to 4 mm long. Cypsela somewhat three-sided, oblong, 2-3.3 x 0.4-0.7 mm, glabrous or pilose apically.

Flowering time

Mainly from September to October.

Distribution

Rather common south of and in the Roggeveld and Nieuwveld mountain ranges, as well as in the Sneeuwbergen area between Murraysburg and Middelburg. It is widespread and known from the Great Escarpment, Upper and Great Karoo, southwestern and eastern Cape and the southern Free State.
Known from more than 65 specimens.

Habitat

On flats, outcrops and ridges, often on clayey soils and in shaly, sandy or stony karoo veld.

Notes

The name oppositifolia is somewhat misleading as all the Rosenia species have opposite leaves.
Plants are rarely browsed by stock and game and can become abundant in overgrazed veld. This species is often regarded as undesirable for grazing and should be eradicated when it becomes dominant in the veld.

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References

BREMER, K. 1976. The genus Rosenia (Compositae). Botaniska Notiser 129: 97-111.
GLEN, H.F. 2004. SAPPI, What's in a Name? The Meanings of the Botanical Names of Trees. Jacana.
POWRIE, L. 2004.Common names of Karoo Plants. Strelitzia 16. National Botanical Institute.
SHEARING, D. 1994. Karoo. South African Wild Flower Guide 6. Botanical Society of South Africa.
VLOK, J. & SCHUTTE-VLOK, A L. 2010. Plants of the Klein Karoo. Umdaus Press