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Growing in the Desert Column

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Adeniums for Winter Color

by Mark Dimmitt

Photos by Mark Dimmitt unless noted

(This article may only be reprinted with the author's permission.)

Most people who grow adeniums in cool-winter climates let them go dormant for the winter (Figure 1). If they can’t be kept at least in the 80s F during the day and above 50 at night, this is the safest way to prevent rot. They are often stored in a poorly lit location and given little or no water. Some will flower sparingly under these conditions. But if you have a hot, sunny location, many adeniums will flower profusely throughout the cold months (Figures 2, 3). They are a great way to provide color during a time of year when few succulents are in bloom.

If kept hot and bright all year, the majority of commonly sold adeniums begin flowering when summer heat breaks (about late September in Tucson), and flower well into winter or all the way into May (Figure 4). All adeniums produce most of their annual vegetative growth in summer, and bear fewer or no flowers during this season. (Plants forced into dormancy tend to shift their flowering season to summer.)

The simplest suitable location is a south-facing windowsill; an east or west exposure may also be adequate. If it’s uncomfortably hot to hold your hand on the sunny windowsill, adeniums and other plants are likely to burn. Light shade such as from a window screen or a leafless tree outside the window may be necessary. Increasing air circulation with a small fan may be sufficient to avoid burning. Smaller cultivars such as 'Happy Princess' (Figure 5) or dwarf strains of A. arabicum (Figure 6) are well suited to windowsill storage.

For more plants, a simple lean-to greenhouse can be built on the south side of the house, consisting of a PVC or conduit frame covered with clear plastic. Build it over a window, and leave the window open at night to provide heat. Of course, nothing beats a greenhouse once you get hooked.

As already stated, the majority of adeniums in cultivation are potentially evergreen and winter-flowering if kept under tropical conditions and watered regularly. Those plants that are in leaf should be watered every couple of weeks, just enough to keep the caudex firm. The deciduous species should be given much less water, even if they are in full bloom. Larger plants with substantial caudexes may not need any for months at a time. This group includes all the pure species except Adenium obesum. (Adenium arabicum and A. socotranum may retain most of their leaves all winter, but they still need very little water when not growing.) Some adeniums flower only during winter. These are rarely found for sale. Nurseries tend not to carry them because few customers buy adeniums in winter. Adenium multiflorum (Figure 7) sheds its leaves when the weather turns cold, and flowers profusely from January to March. The plant can grow quite large, but as with most succulents, size can be controlled by keeping it underpotted and fertilizing sparingly. One of this species’ few hybrids, ‘Winter Remedy’ (A. multiflorum X A. swazicum, Figure 8), has the same habit, but some flowers continue into early summer.

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