Arun Kumar Paul sent me an email from Kolkata, India, to say that he loved plants like his own life. "I have a few adenium plants," he added, "but I have little knowledge of their culture. Could you give me some ideas?"
From Malaysia, Rosli Abdulhalim wrote to say that he bought his first adenium a few weeks ago. It did well during the first two weeks, then the upper leaves turned yellow and the flower buds turned brown.
"The planting medium I use is a mixture of compost, charcoal and stone," he said, adding that he watered his plant daily and fertilised it with NPK 5-7-5. "Can you explain to me what happened to my adenium?" he asked.
I would have to examine Mr Rosli's plant to be able to say exactly what is wrong with it. There are many factors to consider. Is the plant getting enough sun? Is the soil soggy all the time because of the daily watering? However, stone does not absorb water, and the opposite could be the case. Perhaps the plant is not getting enough moisture from the planting medium? How much fertiliser was applied? Where was it applied? Did he water the plant after applying the fertiliser? Applying it on the roots and not watering could cause root burn, making the leaves turn yellow and fall off.
If I could grow only one kind of flowering plant, I would choose adenium, commonly known as the desert rose (chuan chom in Thai), as hybridisers have developed so many cultivars that I could have 50 plants with no two alike. Their attractive flowers, some of which resemble roses, come with single or double and even triple petals in many different colours and colour combinations. Adeniums are inexpensive and, more importantly, are prolific bloomers and much easier to grow than roses.
EXPERT: Veteran grower Manit Suksamer has been selling adeniums at Chatuchak plant market for many years. Photos: Normita Thongtham
I could not grow as many adeniums as I would like as they need full sun and my yard is mostly shaded. However, the dozen or so that I have are enough for me to know how to grow them properly. And just to make sure, for the sake of Arun Kumar Paul and Rosli Abdulhalim, I went to Chatuchak plant market to compare notes with a veteran grower, Manit Suksamer, who has been selling adeniums at the market for many years.
Apart from full sun, or at least five hours a day, preferably in the afternoon, adeniums need a porous, well-aerated soil with good drainage. For his plants, Mr Manit uses a combination of finely chopped coconut husk and decomposed rain tree, or monkeypod, leaves (Albizia saman, or kambhu in Thai). Loamy soil, coarse sand and rice husk are also good planting material and may be used at a ratio of two parts soil or coarse sand to one part each of rice husk and finely chopped coconut husk. For large specimens in big containers, chunks of crushed brick may be added.
Adenium is native to southern Africa and Arabia and, as the name desert rose implies, it prefers desert conditions. Watering can be done daily or every few days, preferably in the morning, but water just enough to keep the soil from completely drying out. Do not water the whole plant, only the base, as wetting the flower buds makes them susceptible to fungal disease that causes them to turn brown and dry up before they even open.
Another cause of flower buds turning brown is insects that enter and suck the life out of the buds. These insects are so tiny they could hardly be seen by the naked eye.
Leaves turning brown can be due to too much or too little water, mealy bugs sucking the sap of the roots, or fungal disease in the roots. All this can be avoided by watering your plants just enough to keep the soil minimally moist. What's more, your plants will bloom more diligently if the soil is not always soggy.
For general health, give your plants slow-release fertiliser every three months. The amount applied depends on the size of the plants; a pinch should be enough for small ones, and two or three for big plants. Too much, and you will have plants with healthy green leaves but no flowers. Apply around the edge of the pot, where the feeder roots are located, and water accordingly.
A light feeding with 12-24-12 fertiliser will help your plants to develop flowers. Dissolve a teaspoon or two of the fertiliser in water and use this to water your plants every two weeks. It will also help if you choose the right cultivar when buying a plant. A compact, small-leaved and heavily branched plant tends to bloom more prolifically than one with few long branches.
In plant contests, adeniums are judged not just by the beauty of their flowers but also by their caudex, the swollen stem at the base of the plant. A reservoir for nutrients, the caudex differs from species to species and from plant to plant. Plants grown from seed tend to produce a nice, rounded caudex. Plants grown from cuttings also develop caudexes over time. All the cultivation methods mentioned above contribute to the formation of a good caudex.
When applying chemical fertiliser, never apply directly at the base of the plant as this could burn the caudex and the roots around it. The caudex could soften and rot, and the leaves turn yellow and drop off. Do not feed with liquid fertiliser if the soil is dry; water slightly first to avoid root burn.
Full sun is required for the manufacture of carbohydrates that are stored in the caudex and make it swell. Repotting the plant, using fresh planting medium, every six months will also help develop the caudex. Every time you repot, raise the plant a bit from the pot so that the upper half of the caudex is exposed.
Unless you kill them by overwatering or fertiliser burn, adeniums do not die easily. I had a plant whose leaves were eaten by a caterpillar, but soon new leaves grew up again. If your plants become too tall, all you have to do is cut them down. The pruning encourages the growth of new branches that will bear flowers.
The cuttings could be rooted in moist sand in the shade to increase your collection or to give away to friends. Grown in the right conditions, new roots will sprout in five to six weeks. Wait another six weeks for the roots to mature before planting the cuttings in individual containers.
Email nthongtham@gmail.com.
GARDENERS' FAVOURITE: Adeniums are prolific bloomers and much easier to grow than roses.
