Concertina plant  (Crassula rupestris)

Subspecies Crassula rupestris commutata is classified as Vulnerable (VU) in Namibia on the Southern African Plant Red Data Lists (3). Subspecies C. r. commutata and Crassula rupestris marnierana are both classified as Least Concern (LC) globally, but Rare in South Africa, on the Interim Red Data List of South African Plant Taxa (4).

The concertina plant is a spreading shrub that, during certain months of the year, becomes ablaze with colour due to the dense heads of pink flowers that form at the ends of the branches (5). The leaves of the concertina plant are lance-shaped to rounded, and are arranged opposite each other along the many branches (6). Most of the year the leaves are greyish in colour (6), but during the summer months the leaf margins turn a brilliant red or yellow (7).

Occurs in southern Namibia and in the Northern Cape, Western Cape and Eastern Cape provinces of South Africa (2) (6). The subspecies C. r. commutata is restricted to a small area on both sides of the lower Orange River, while C. r. marnieriana has been recorded from the southern slopes of the Swartberg and Anysberg Mountains in the Western Cape province (5).

The concertina plant grows on dry, stony slopes (2). The subspecies C. r. marnieriana has very specific habitat requirements and grows only on Witteberg quartzite, usually on cliffs (5).

The concertina plant flowers from June until October (2). The pretty flowers attract bees, bumble bees, and sometimes even moths, which pollinate the plant. Tiny seeds develop following pollination, and their light weight allows them to be carried away from the parent plant by the wind. The dust-like seeds are blown into rock crevices or under bushes where, once sufficient moisture is available, germination will occur. Like many plants, while thousands of seeds may germinate, only a small percentage of this will survive to be mature, adult plants. Concertina plants may live for over 60 years (7).

The concertina plant species is not yet believed to be threatened. However, the subspecies C. r. commutata is threatened in Namibia by mining, which presumably degrades its habitat, and collection (3). Within South Africa, the subspecies C. r. commutata and C. r. marnierana are not yet threatened, but their limited distribution range in South Africa places them at risk of an unexpected event causing a critical decline, and thus they are classified as Rare on the Interim Red Data List of South African Plant Taxa (4).

The concertina plant occurs within the Cape Floral Kingdom, a ‘hot-spot’ of plant diversity in South Africa in which there are a number of protected areas (8). There are no known conservation measures in place for the threatened subspecies C. r. commutata within Namibia.

For further information on the Cape Floral Kingdom and its conservation see:

• Wild Cape Nature Trust:
  www.wildcape.org