About the genus
Adeniums are caudex-forming plants in the Apocynaceae, which are native to Africa and the Arabian peninsula. There is some controversy over the number of species, and it is impossible to carry out any research in most of their natural habitats to resolve this, but A. obesum, A. arabicum, A. multiflorum, A. boehmianum, A. swazicum, A. oleifolium, A. somalense, A. socotranum and A. dhofarense are all generally accepted.
Leaves vary naturally between species – A. obesum has deep green glossy leaves, A. somalense has long and quite narrow leaves with a silvery white midrib and veins, and A. arabicum leaves are often velvety/furry. In habitat flowers are almost always pink and five-petalled, with some variation between species such as pale or dark centres, spots/stripes, rounded or pointed petals. Most species have been in cultivation for decades, with A. obesum and A. arabicum being commonly available. After years of breeding it is now possible to get multi-layered flowers of many colours and a variety of caudex colours and forms, leaf shape and also plant size, with miniatures becoming quite sought after.
How to grow them
Adeniums grow well in a greenhouse, conservatory or a sunny window. They can also be grown successfully under grow lights. They will not survive being cold and wet, and are not frost hardy. An average temperature of at least 24°C during their growing period is preferred.
While they are actively growing, adeniums will appreciate regular feeding, preferably with a feed that contains micronutrients, at half- strength once a week. They need a very free-draining potting medium and grow well in pumice or a coco coir/pumice mix. Plastic pots are preferable for younger plants with fast-growing roots. Adeniums can survive being too dry, but too much water causes root rot.
Most adeniums have a dormancy period over winter and need to be kept somewhere that is at least 15°C at this time. Dormancy usually starts by early October – leaves start to turn yellow or brown and no new leaves will appear. This is the signal to decrease watering. After a few weeks adeniums will have stopped actively growing and all watering can be stopped. By this time the leaves will likely have fallen off. Some adeniums do retain a few leaves through winter, but will not show any signs of growth. By the beginning of April adeniums should show signs of waking up, which is when watering can start again, using a reverse of the dormancy watering schedule, light watering at first progressing to the weekly schedule. Any adenium that does not want to go to sleep through winter and keeps producing new leaves can be watered as normal.
Adeniums are admired for their bonsai-like appearance and can be trained in a similar way. To achieve the interesting root formations young plants are grown for several years with the roots kept under the potting medium, and then gradually raised when re-potted. Formation of branches can be encouraged by trimming, especially in A. obesum and A. arabicum, but some species, notably A. somalense, are best left to grow naturally.
It should be noted that adeniums are poisonous, so they should be kept out of the reach of children and small pets, and remember to wash your hands after re-potting or trimming.
Text and photos: Marie Iryna
No part of this article may be reproduced without permission. Copyright BCSS and the Author 2022