Raphionacme (2018)

By Bob Williams (May 2018)

Raphionacme flanaganii is one of the plants I selected for my long-range study of overpotting or underpotting to get the best caudex. Raphionacme was the HSCSS Plant of the Month in March 2005. However, the article was a reprint of one first published in a 1978 Digest. After 40 years, an update seems in order.

Raphionacme was first described by William Harvey in 1842. Like many plants we follow, Raphionacme has more recently been “moved” – from Asclepidaceae to the Apocynaceae tribe Periplocoideae. This tribe comprises just over 30 genera and approximately 190 species found in Africa, Madagascar, Asia and Australia.

With 36 species and two subspecies, Raphionacme is the largest genus in Periplocoideae, followed by Cryptolepis (30 species), Pentopetia (23), Periploca (13), Camptocarpus (nine) and Streptocaulon (nine). Of the 36 Raphionacme species, 35 are found in Africa. The lone outcast is found in the country of Oman on the Arabian Peninsula.

Raphionacme can be found over the greater part of Africa, from the Sahara Desert in the north to South Africa in the south. However, they are not plentiful in the wild. Many species are thought to be extinct.

Outside areas of Africa that receive winter rainfall, Raphionacme plants can be found in any other type of environment. Some species can be found at elevations up to 6,000 feet. They grow in arid regions; moist, tropical forest regions; moist to dry savanna; thicket bushland; and swampy to arid grasslands.

All Raphionacme species grow large, underground tubers. Most of the tubers are large and bulblike. Only a few of the species produce fingerlike tubers, which often become twisted around each other. The tubers have been used as a source of food in some areas and may also have medicinal properties.

Being a tuberous plant, only a small portion of a Raphionacme plant is found above ground. These plants produce vines that grow from the top of the caudex. The vines can be 3 to 6 feet long. Depending on where they grow, they may be on the ground or climb trees or shrubs. The flowers are small.

In the fall, raphionacme lose their leaves and go into dormancy. This may be why they do not grow in winter-rainfall climates. The vines die back and can be trimmed within just a few inches of the tuber. New vines will emerge in the spring. Propagation can be by seeds or tuber offshoots.

The plant I am growing for my potting experiment is R. flanaganii. This is the fastest-growing and one of the hardier species of this genus. It is found in Kenya, Mozambique and several provinces in South Africa.

As far as habitat is concerned, it is found in the coastal flats, as well as inland valleys, plateaus and mountains on soils that vary from black clay to grayish sands at altitudes up to 3,000 feet. R. flanaganii produces long, finger-type tubers that will become twisted over time.

Like most succulents, they should be planted in loose and well-draining soil. One website said these plants prefer a more neutral soil pH, ranging from 6.6 to 7.3.

In late September to early October, my R. flanaganii will go into dormancy. Watering will be cut back to a small amount once every three weeks or so. In the winter, they should be in an area where temperatures do not fall below 45 degrees. The one thing they do not like is watering when the temperature falls below 60 degrees. This is an invitation to rot.

There is not a large amount of information about Raphionacme on the Internet, and very few of the 36 species can be found for sale. The most comprehensive information I found was in an article published in the April 2009 South African Journal of Botany, available on the ScienceDirect website at https://www.sciencedirect.com/science/article/pii /S0254629909001768.

Sources:
Bihrmann’s Caudiciforms – http://www.bihrmann.com/caudiciforms/
National Gardening Association Plants Database – https://garden.org/plants/view/120314/Raphionacme- Raphionacme-flanaganii
Kew Science Plants of the World – http://powo.science.kew.org/taxon/urn:lsid:ipni.org:names: 3644-1