Adeniums are one of the easiest to grow and most rewarding of the fat plants (caudiciforms). Their adaptability to a broad range of conditions makes them forgiving of less than ideal care. This attribute enables just about anyone to grow and bloom them despite individual climate conditions.
In most areas it is best to provide the highest level of light possible. The exception are locales that experience extremely high temperatures combined with low humidity and drying winds. Under these conditions you will want to provide some shade during the seasons of most intense weather.
We recommend a good quality, bark-based, soilless potting mix amended with coarse perlite (3 parts mix to 1 part perlite is adequate under most conditions) to improve aeration and drainage. If you are unable to find a local source of such a mix try visiting a commercial greenhouse grower. Most professional growers are plant enthusiasts themselves and will gladly sell you a bag or two of their mix and you’re more than likely to get a good dose of very sound advice to go along with it.
Many sites on the internet recommend using extremely high percentages of drainage material (up to 70%) in the mix to avoid root rot. The problem with this method is that you run the risk of inadequate moisture and nutrient retention leading to a drastic slowing of growth that can actually increase the risk of rot rather than reducing it. Additionally, if you choose to grow in a mix such as this with a very high percentage of inert material, you will have to radically increase fertilization to compensate for the mixes lack of ability to retain nutrients.
When you water, you should do so thoroughly. This means applying water until the potting mix is saturated and the excess begins to run out through the drainage holes. This will greatly reduce any possibility of harmful excess soluble salts accumulating in your mix.
The amount of time between waterings will vary based on your conditions, container size, and whether your Adenium(s) are in active growth or not. Ideally, you will allow the mix to almost dry before watering again. With a little practice you should be able to determine whether it’s time to water by lifting the pot and inspecting the upper surface of the potting mix. As the mix dries, your pots will become much lighter signalling that it’s time to water your Adeniums again.
Overwatering can lead to root rot and should be avoided, but if you have used a mix with adequate drainage you should have a fair margin for error. If you know that you have a heavy hand with the watering can you should add a slightly higher percentage of perlite to your mix.
Under watering can be nearly as destructive as overwatering, so you should never allow your mix to become dust dry as this will desiccate and destroy the delicate feeder roots necessary for water and nutrient uptake.
If you intend to hand water your Adenium(s) it is best if you use a good quality water breaker on your hose or watering can. This will prevent wash out and damage to delicate roots.
Probably the simplest and most effective way of providing your Adenium(s) with proper nutrition is through the use of a good quality controlled release fertilizer. A balanced blend such as 13-13-13 or 14-14-14 will yield excellent results. These mixes are available in different release times ranging from a couple of months to nearly a year. We use and recommend the shorter release terms because they activate almost immediately, vs. up to several weeks for the longest term formulations, and will allow you to easily time the discontinuation of feed if you live in an area where your Adenium(s) will go through a period of winter dormancy.
Adeniums differ from many of the other fat plants in that they do not like to be underpotted, so it is important that you choose the appropriate size container. We think that it is best to use a container not much more than double the diameter of that of the caudex (swollen base). By keeping a watchful eye on root development you can step your plant(s) up to larger container(s) as needed. This will ensure healthy root development, keep the roots growing in fresh mix, and reduce the risk of rot associated with planting into a container which is too large initially. Our normal progression is from a 4″ standard pot to a 6″ azalea to a 6″ standard to an 8″ azalea to a 10″ standard. After the 10″ standard size we normally change from plastic to terra cotta or ceramic.
Whether you use plastic or ceramic is entirely up to personal preference but you must keep in mind that clay pots dry out much faster than plastic. An important fact to also remember is that the strong roots of Adeniums have no respect for clay or ceramic pots and, unless the container is bowl shaped, can easily break them as they grow.
Since the form of the caudex and large roots is as important as the bloom to many collectors, we feel we should mention that the formation of the caudex is controlled, to a large degree, by the depth and width of the container.
This means that if you want a wide squat caudex and root system then you will want to choose a wider, shallower container. As you can see in the photo to the right, the base of the caudex is much narrower than the widest point of the roots. This type of form could never have been achieved in a narrower pot, nor would it have been likely to produce the large girth of roots in a very deep pot.
If you are growing an Adenium somalense or similar cultivar with an upright growth habit, as in the photo to the left, you will want to select a narrower, deeper container.
Experiment. Come to your own conclusions. There are few plants that offer as many forms or are as adaptable as Adeniums are. Above all you should have fun with your plants.