Willem is a wildlife artist based in South Africa. He says "My aim is simply to express the beauty and wonder that is in Nature, and to heighten people's appreciation of plants, animals and the wilderness. Not everything I paint is African! Though I've never been there, I'm also fascinated by Asia and I've done paintings of Asian rhinos and birds as well. I may in future do some of European, Australian and American species too. I'm fascinated by wild things from all over the world! I mainly paint in watercolours. . . but actually many media including 'digital' paintings with the computer!"

Today I would like to sing the praises of a much-underappreciated plant species, the Milky Rope, Cynanchum viminale (previously known as Sarcostemma viminale). A lot of people don't know what it is at all, in spite of it being a common and widespread species. It's one of the plants I most often point out on nature outings. Some people who do have an acquaintance with it, think it's a parasite, because of the way it rampantly grows over and often overburdens neighbouring plants. Finally, even some people who do have some knowledge of it, tend to confuse it with other species, most notably the Rubber Hedge Euphorbia, Euphorbia tirucallii, and the Sjambok Bush, Kleinia longiflora. The milky rope should rightfully be extremely well-known. It is amazingly widespread: it grows in much of South Africa, the drier parts of tropical Africa, and from there into South and South-East Asia and Australia. It also grows on remote islands in the Indian Ocean, like Mauritius and the Seychelles. Over this vast range it is known by many names, including Caustic Creeper, Sacred Soma, and Rapunzel Plant. It grows in a wide range of habitats, from semi-desert to riverine forest.

So basically now, what is a milky rope? The rope part refers to the long, thin, leafless, succulent stems that make up the above-ground parts of the plant. If it grows out in the open, the stems will trail along the ground or form a tangled mound. The stems freely root wherever they touch the ground. But if shrubs or trees are nearby, the stems will quickly scramble into them, winding themselves around trunks and branches. This may make it look like it's 'strangling' these plants. It is not actively intent on killing its support plants, but can grow so wild and heavy that it weighs them down and cuts out a significant amount of sunlight reaching them. But it is not a parasite in that it doesn't steal food from them; its greenish stems contain chlorophyll and it makes its own food.

MALIGNANT, YET MEDICINAL MILK

The 'milky' part comes from the white sap which copiously exudes from the stems at the barest damage. I usually demonstrate this by making a tiny nick with a fingernail in a stem; it immediately produces a white drop of sap. This species is a member of the Milkweed Family, the Asclepiadaceae (sometimes included in the larger family Apocynaceae) where many members have such a milky sap. This sap is what can lead to confusion with Euphorbias. These, too, have milky sap, but theirs is very poisonous, potentially causing blindness if it gets into human eyes. The milky rope's 'milk' is not quite as poisonous. At least, it isn't here in South Africa, where the plant's stems are sometimes browsed by game and stock and eaten, raw or cooked, by humans. But the toxicity varies, and in some places the milky rope's sap can even burn the skin on contact. At any rate, it does contain toxic substances which affect the nerves. But butterflies make use of these! This species, and many others of the milkweed family, are popular food plants for the caterpillars of some butterflies. The caterpillars ingest the poisons without suffering harm. Indeed, now these poisons become part of the caterpillar, concentrated in its tissues, and make it unpalatable or poisonous for birds and other predators, thus protecting it! Funnily enough the birds don't seem to learn the same trick – at least not in South Africa. There are birds in New Guinea who actually eat toxic beetles and then become toxic themselves.

But this very same 'toxic' milk also has numerous medicinal uses. This again demonstrates a general principle that 'poison' is a matter of dose. Here in South Africa, this species is given to nursing mothers, to increase their ability to produce milk. Over its range, it is also used for treating wounds and sores, eye infections, diarrhoea and skin problems. Stems as well as roots are eaten or drunk as decoctions, the sap may be applied to affected bodyparts, the plant may be burnt and the patient exposed to the smoke. Sometimes the stems are made into a bed on which the patient lies! But of course, all treatments need to be applied with great care because of the potential toxicity of the sap.

In addition to helping butterfly caterpillars be more odious, milky ropes also feed the adults, and indeed many other insects. Here you see honey bees, a Painted Lady butterfly, Vanessa cardui, and a little yellow butterfly I can't ID, taking advantage of them. The yellow flowers are small but quite pretty, emerging as more or less globular inflorescences from the bare stems. Similar to many species in the milkweed group, they are fairly complex, with a structure called a 'corona' in the centre of the flower, dispensing pollen packets onto the visiting insects. In this pollinating mechanism, they are similar to their relatives the carrion flowers. They don't stink, though, being more typical flowers that reward their pollinators with nectar. Successfully pollinated flowers are followed by the long, pointed seed pods, which when ripe burst open to release the seeds, which have 'plumes' of white down that allow them to be blown far and wide by the wind.

Growing Milky Ropes

This species deserves to be grown for its weirdness and the insects and other wildlife it will attract into the garden. But please note that it is a species for a BIG garden, unless you want to keep it in a pot and constantly prune it back. It will thrive in a climate that is warm and not too wet. Do not plant it next to a small tree or shrub, unless you're willing to sacrifice that tree or shrub. If you have a large and vigorously-growing tree, the milky rope will climb into it without damaging it significantly. It can also be grown as a feature plant in a rock garden. Give it two or three metres/yards on each side for spreading. Now as to growing it, that is a matter of great ease. Just snip a small section off a plant, let it dry in a shady place for a few days, and then plant it with the bottom 1 cm/half an inch or so in a sandy, well-draining soil mixture. It should root readily and soon grow into a new plant. The species can also easily be grown from seeds. In a garden in its natural area of distribution, you may indeed find small plants germinating naturally from fallen seeds. It might not be a good idea, actually, to grow this plant in warm regions outside of its natural range, such as the southern USA, because it has potential for becoming an invasive species.

Willem

30.03.20 Front Page

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