Natural History -- December 2000

Drosera slackii -- A living Jewel from South Africa

Robert Gibson

Keywords: observations: Drosera slackii.

Received: 14 August 2000

Drosera slackii is an attractive evergreen rosetted sundew endemic to the Cape Region of South Africa. It was named in honour of the well known carnivorous plant grower, and author, Adrian Slack (Cheek, 1987).

This sundew forms a flat rosette up to 8cm across which over time forms a very short stem. There are two distinctive features of this species’ leaves: their pandurate (guitar body) shape and the few coarse appressed red hairs on their undersurfaces. The leaf shape is due to the development of two flared edges to the base of the otherwise narrowly wedge-shaped leaves. Each spring mature plants produce one scape, or rarely two, which rise to 40cm tall. The scapes have a strongly down-curved base and a dense cover of red short-stalked glands. The dark-pink petalled flowers are up to 2.5 cm across and have contrasting white stamens.

The cytology of this species has been found to be 2n=40, which is equal to that of other Drosera species from the region, namely: D. admirabilis, D. venusta, D. capensis and some forms of D. aliciae (Bennett & Cheek, 1990; Rothfels and Hermburger, 1968).

The natural habitat of this sundew is the small peaty wetlands of the Kleinriviersberg Mountains and the southern Kogelberg, between 70 and 100km south-east of Cape Town. In the Kleinriviersberge this species is known from the boggy beginnings of at least two streams, and includes the type location. In this area it grows in the company of D. admirabilis, D. aliciae, D. capensis, D. x corinthiaca (=D. aliciae x D. glabripes), Utricularia bisquamata, and the sticky-leaved Roridula gorgonias. In the southern Kogelberg this species has been collected in the Palmiet River catchment and has narrower leaves than those of populations to the east. In both areas the plants grow in locations which receive precipitation throughout the year thanks to the not infrequent summer mists. These areas also experience periodic fires, which remove the above-ground growth of this sundew, but it readily resprouts from the roots.

Drosera slackii is an easy plant in cultivation, preferring a peat-based mix, a deep pot, water year-round, and plenty of sun. Whilst not experiencing frost in its natural habitat it is mildly frost tolerant and will resprout from the roots if the rosette is damaged. It is easily propagated by leaf cuttings, root cuttings and, when available, seed.

In conclusion, Drosera slackii is a distinctive and attractive South African sundew named after one of the key figures in raising the awareness and delight in growing carnivorous plants worldwide. It is a living jewel, which is appropriately named in honour of Adrian Slack.

Acknowledgment

I wish to thank Eric Green for his hospitality during my visits to South Africa, in addition to Dr. John Rourke and the other friendly staff at the Compton Herbarium, Cape Town, for providing study access to the herbarium collection, and also to Paul Debbert for sharing information on this species.

Literature

Cheek, M. 1987. A new species of Drosera from South Africa, Kew Bulletin, 42(3): 738.

Bennett, S.T. and Cheek, M. 1990. The cytology and morphology of Drosera slackii and its relatives in South Africa, Kew Bulletin 54(2): 375-381.

Rothfels, K. and Hermburger, M. 1968. Chromosome size and DNA values in sundews (Droseraceae), Chromosoma 25(1): 96-103.

Figures

Figure 1: Drosera slackii flowering in the wild.



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