Apocynaceae


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

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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

This plant is found in Africa and can take a lot of drought. It is an ideal plant for the living room; it can be grown in the full sun, so a windowsill is no problem and it can take the dry heat of the central heating. It is very easy to grow from seed, but the seed needs to be fresh. It can germinate within one or two days. The more sun it gets, the quicker it will flower, possibly within six months.
Wild Adeniums are usually various shade of red, but occasionally white ones do appear. In Thailand, a lot of breeding has taken place and because of the inherent colour variation in the wild plants, a whole range of colours are now available in cultivation, ranging from white to very dark red and all shades in between. Efforts are now made to produce a true yellow one.

Adenium obesum pink


Adenium obesum alba

Have a look at the post on Pachypodium bispinosum for more information on the germination of the seed.