A good plant for cactus collectors, because in the winter it can take low temperatures (even a bit of frost) if kept dry. It comes from the Eastern Cape in South Africa and the tuber can grow to a height of 25-30 cm. The branches that grow on top of the tuber can, if they get too large, be cut back. The flowers develop all over the branches, so you do not lose them if you cut the top bits of the branches off. The flowers are similar in shape to those of Adenium obesum, but smaller. The pollinator is probably a moth as the depth of the flower excludes other pollinating insects. When pollinated successfully, twin seed horns will appear which grow to a length of about 5 cm, containing up to 30-40 seeds. The seed has a parachute on the end enabling it to be carried away to a new area to grow. You can tell the difference between an Adenium seed and a Pachypodium seed, because the latter has just one parachute, while Adeniums have two. It is important to remember that the seed from both these species must be sown fairly quickly after collection, because they have a short ‘shelf-life’. It can be kept for a maximum of one year, but the germination will only be about 10%, if you’re lucky. The fresher the seed, the better the germination, possibly up to 100% if sown the first few days after collection.
Pachypodium bispinosum is virtually identical to Pachypodium succulentum when not in flower. To tell them apart, you need to see the flowers; the ones from the succulentum are flatter. In the wild, their localities overlap a little bit, but there is hardly any cross-pollination, probably because the pollination needs different insects.

Pachypodium bispinosum caudex

Pachypodium bispinosum caudex


Pachypodium bispinosum flower

Pachypodium bispinosum flower

This rare species comes from South-Africa, to be more precise, from the mouth of St. John’s River in Natal. It is a tuberous-rooted species and produces annual growth. It can take some frost as long as it is covered over in winter. It can also be grown in a cool greenhouse, but will get straggly if it gets too hot. The risk of spider mite will also be greater if the temperatures gets too high. It will flower from July onwards, no matter where it is grown. The colour of the flower varies from pinkish-white to pink; the most common colour in circulation is the one you see in my picture below.
The plant is propagated either by seed or cuttings; the latter being the most common means of reproduction as there is little seed available, because you need two clones to get seed. The cuttings of this species will produce a tuber unlike, for instance, impatiens tuberosa which does not. The plants grow to about 50-100 cm high in pots and topping will force it to produce side shoots for a nice bushy plant. In the wild, it can grow to 2 metres high.

 

Impatiens flanaganae

Impatiens flanaganae

This plant is also known as Stultitia conjuncta, but in 1978 it was moved to Orbeanthus. Recently, Peter Bruyns, one of the top Stapelia people, has placed it in Orbea, but there is a lot of movement in the naming of Stapelias, so it is entirely possible that it will be moved back to Orbeanthus. This genus contains only two species; the other one being Orbeanthus hardyi.
It is not a common plant in cultivation, but is very suitable for a hanging pot; the stems can grow up to 50 cm in length and are greyish green mottled with darker green. The flowers are cup-shaped and look similar to those of Hoya archboldiana, the colour being white with a red centre. The flowers are produced singly or in pairs, mainly in the summer.
It requires a well-drained soil, preferably mixed with grit. Propagation is by seed or cuttings. Cuttings need to dry for a couple of days before being put in the soil to avoid rot, as is the case with most succulents. Bottom-heat is preferred to speed up rooting. The plants can be grown either in full sun or shade, but you will get more mottling on the stem if they are kept in the sun.

Orbeanthus conjunctus

Orbeanthus conjunctus

Because so may people liked the picture I put on my Facebook wall, I thought I’d write a bit more about Strophanthus speciosus. This plant belongs to the Apocynaceae, the same family the Adenium obesum (see previous post) belongs to. Most of the species in this family come from Africa, mainly from the tropical part, but one or two come from India, the Philippines or China. The S. speciosus comes from South-Africa. The name Strophanthus means twisted cord flower. Strophanthuses can be either climbers or shrubs.
The plants in cultivation are mainly grown from seed which will germinate in a couple of weeks in a temperature of about 20°C, but only if the seed is fresh, which you can achieve by hand-pollination. S. gerardii produces a tuber when grown from seed which I had not expected, as there is very little information in the literature about caudex Strophantuses. As far as I know that is the only caudex species, S. speciosus certainly does not have one.
They do not seem to be fussy about the soil type, but are not quick growers. They can be grown in either warm or cool conditions and are sometimes grown as container plants for moving outdoors in the summer. I have not tried it, but I doubt they can take frost. They do, however, have to grow to a fairly large size before they will flower.

Strophanthus speciosus

Plectranthus is a member of the Coleus family; a few have a caudex, such as Plectranthus ernstii which comes from South-Africa and was discovered in 1982 by Ernst van Jaarsveld. There are about 350 species of Plectranthus coming from Madagacar, South-Africa, Indonesia and India, so roughly the countries around the Indian Ocean. They are very easy plants to grow and can take a wide varieties of temperatures; some are even hardy. The ernestii, however, is not, but can take low temperatures as long as they do not drop below 0°C.
The ernestii is very easy to propagate by cuttings. It does produces seed, one seed per flower, but as it is so easy to propagate by cuttings, I have not tried to sow them. Cuttings will always produce a tuber which will, with age, thicken up. Depending on the conditions the plant is grown in, the leaves will either be large or small. Cooler temperatures will result in a more compact plant with smaller leaves. It can be grown in full sun or shade.

Plectranthus ernstii

Plectranthus ernstii

This is a very easy species to grow, just as easy as Ceropegia woodii. It is a trailing variety which will sometimes climb; it will grow very long, but do not be tempted to cut it back or you will lose the flowers. The flowers will appears when the plant has reached a length of about 1.50 metre. The flowers are about 2cm long and do not stand out. The leaves are long and thin, hence the name linearis. If you grow a stem horizontally, for instance on a potting table, the nodes will send out roots if they touch the soil. This is an easy way of propagating the plant, which is useful as linearis seed is rarely produced.

It is a tuberous-rooted species and the tubers will form from cuttings, as is true of all tuberous-rooted ceropegias. It will grow in most soils and requires only a little bit of heat (5-10°C) in the winter. In the summer, it prefers to be grown in a shady place, but temperatures can be quite high without any problem.

Ceropegia linearis

Ceropegia linearis

Ceropegia ampliata is one of the easiest South African species to grow in a greenhouse. It has thick fleshy roots, succulent stems and tiny leaves. The large flowers always appear in the autumn. In the winter it should be kept dry and it can take temperatures down to 8°C. If grown in good conditions, it can grow a number of metres in a year.
It is very easy to propagate from cuttings as they root very well. It does not readily produce seed in cultivation, so you will not often see seed on offer. Hybrids from this species are not available, unlike those from Ceropegia sandersonii and Ceropegia stapeliiformis which are quite common. The pollination mechanism in Ceropegias is so complicated and small that it is virtually impossible to do by hand; you must leave this delicate work to insects. It does not matter much what species of insect attempts to pollinate the flowers, it is the size of the insect that is important.

 

Ceropegia ampliata

Ceropegia ampliata