Adenium Cultivation

Adeniums are relatively easy to care for as long as you think of your plant as actually being two quite different plants with different requirements at different times of the year. In summer while in full growth, they should be treated as a tropical plant, watered abundantly and frequently, and fertilized rather generously. In the winter time they need a dry rest, and should be treated like a cactus, with only light occasional waterings during warm bright days.

Like most all succulents, adeniums, especially when dormant, are susceptible to root rot (which can rapidly kill the entire plant) caused by prolonged, overly wet soils. Therefore, they should be potted in a well-drained soil mix. Any light commercial mix can start as a base, but should be augmented with about 1/3 to ½ drainage material such as coarse (screened and washed) sand, clean poultry grit, gravel, or sponge rock (such as Perlite). If you use a peat-based mix, you should repot into fresh soil about every two years. Any type of pot (clay, plastic, or ceramic) is acceptable, but must have good drainage (be sure the saucer doesn’t retain water). The pot should only be a bit larger than the size of the root mass; significant overpotting can result in soil moisture retention and root rot. However, these plants are easily potbound, which restricts overall growth. So every year or two increase the pot size until the plant achieves the desired size. Another point to remember is that these plants can make MASSIVE roots. They are capable of breaking through the sides of plastic and even thin-walled ceramic pots. Many growers use a relatively shallow, bowl-like pot somewhat larger than the root system would dictate. The shallow nature of the pot allows for more rapid drying of the soil mass, while allowing room for root expansion.

Again, like most succulent plants, adeniums need bright light for normal growth and flowering. Spring growth in Wisconsin normally starts in February as soon as the days begin to lengthen. After all threat of frost, established plants thrive outdoors in the Wisconsin summer. They love our summer thunderstorms and full, day-long sunlight is ideal. If kept too shaded during the growing season, adeniums will develop unnatural, weak growth and will not bloom. All adeniums are very sensitive to frost and cool weather. As evenings begin to cool in the fall, plants should be brought back indoors and placed in a bright location where the temperature will stay above 50°F. Full sun is not necessary for dormant plants. For those folks with greenhouses, adeniums will thrive under greenhouse conditions throughout the year, but seem to enjoy at least a few good warm, soaking summer rains. But remember, these are drought-adapted plants and it’s not necessary to hire a plant-sitter to water them while you are away on your two-week summer vacation.

Provide ample water during the growing season. If your soil is well drained and the weather is warm and sunny, the roots rapidly absorb soil moisture which is lost through normal transpiration. In well drained soils during active growth in the heat of midsummer, plants can literally be watered daily. Adeniums are becoming favorite landscape plants in tropical parts of the world such as Asia and southern Florida, where rains can be heavy and almost daily through the summer; the plants thrive under these conditions.

Restrict water a bit during cooler, cloudy periods, and cut back on watering as fall approaches. Adenium obesum can be kept in leaf almost throughout the year, especially under ideal conditions such as in a warm greenhouse. In this case, light watering is acceptable, especially on warmer days, perhaps every week or two throughout the winter. But in many cases all the leaves will fall off your plant in the early winter. Some species, such as the fairly common A. multiflorum, have an obligate deciduous period for 3-4 months in winter. Be particularly careful when watering leafless plants; a monthly watering from October through February is adequate. Some adenium specialists believe that there is better flowering after a totally dry dormant period. Adeniums can be fertilized weekly during the growing season, using any good quality balanced houseplant fertilizer, but only at half the recommended label rate.

There are a few pests that attack adeniums. Spider mites and mealybugs are the worst problems but are readily treated with normal remedies. These pests are more of a problem if plants are grown indoors or in a greenhouse than if grown outdoors where natural controls (predators, rain) are so important. Mites can be particularly bad on some species and cultivars, building up very rapidly and resulting in total leaf drop. Affected plants will rapidly re-leaf once the mites are controlled. Plants grown outdoors during the summer can occasionally get colonies of large yellow aphids with black legs. This is the same aphid that commonly attacks wild and garden milkweeds. Interestingly, plant taxonomists have recently concluded that milkweeds are so closely related to the periwinkle family that they are now all classified together in one group; seems like the aphids were trying to tell us something!