Euphorbia ammak
| Light | Bright light to full sun; part shade in the fiercest summer heat |
|---|---|
| Water | Sparingly; let the soil dry fully between waterings, keep nearly dry in winter |
| Soil | Fast-draining mineral mix (see Soil and potting mix) |
| Temperature | Keep above about 10 °C; frost-tender, USDA zones 10–11 |
| Propagation | Stem cuttings (see Propagation — cuttings); seed |
| Toxicity | Toxic — milky latex is a skin and eye irritant; harmful if ingested |
Euphorbia ammak is a tall, tree-like spurge from the southwestern Arabian Peninsula (Saudi Arabia and Yemen), prized as an architectural specimen for its upright, candelabra-like habit. Its blue-green branches are sharply four- (sometimes five-) angled with thin, wavy wings edged by paired short spines, and in cultivation it is best known through its cream-marbled variegated form, sometimes sold as African candelabra or Euphorbia ammak variegata. As a member of the genus Euphorbia, it is a succulent Old World counterpart to the columnar cacti it superficially resembles.
Description
Euphorbia ammak grows into a stout, branching tree that can reach several metres tall over many years, forming a short main trunk from which erect, candelabra-like branches rise. The stems are made up of thin, winged ribs — usually four-angled, occasionally five — giving each branch a strongly sculptural, fluted profile. Along the horny margins of each rib sit paired short spines and, in season, small cyathia (the reduced flower clusters typical of the genus).
The body colour is a soft blue-green, often with a paler, marbled banding between the angles. The widely grown variegated form replaces much of the green with irregular cream, ivory and pale-yellow marbling, so that whole branches can appear ghostly; because these variegated tissues carry less chlorophyll, they grow more slowly and burn more easily than the plain green plant. As with all euphorbias, every part exudes a milky white latex when cut or damaged.
Note that E. ammak is frequently confused in the trade with the similar Euphorbia ingens and other tree spurges; the thin, wavy-edged wings and blue-green cast help distinguish it.
Distribution and habitat
The species is native to the southwestern Arabian Peninsula (Saudi Arabia and Yemen), where it grows on rocky slopes and in dry scrub under a hot, arid climate with seasonal rainfall. In these habitats it forms a substantial tree, rooting in sharply drained stony ground and enduring long dry periods followed by brief wet spells.
Cultivation
Euphorbia ammak is a robust, fast-growing plant by succulent standards and makes a striking container or landscape specimen in frost-free regions. Grow it in a very free-draining, mostly mineral mix in a heavy pot that can counterbalance its top-weight, and give it bright light — full sun for the green form, with the variegated form appreciating a little shade from the most intense afternoon sun to prevent scorching of its pale tissue.
Water thoroughly once the soil has dried out completely during the growing season, then allow it to dry again; reduce watering sharply in winter and keep the plant nearly dry and above roughly 10 °C, as it is frost-tender and prone to rot in cold, damp conditions. Tall stems may need staking or a sheltered position, since the winged branches can be brittle. See Watering and Repotting for general technique.
A caution on the latex: the milky sap of E. ammak is caustic and can cause painful skin rashes and serious eye injury; always wear gloves and eye protection when cutting or repotting, keep the sap away from your face, and wash any splashes off promptly. Keep the plant out of reach of children and pets.
Propagation
The usual method is stem cuttings taken in warm weather. Cut a branch cleanly, rinse or blot away the oozing latex (wearing gloves and eye protection), then let the cutting callus in a dry, airy spot for a week or more before setting it in a gritty, barely moist mix to root. Variegated plants are maintained this way, since the trait is not reliably passed on by seed. The green form can also be raised from seed where available. See Propagation — cuttings for a full walkthrough.
Common problems
- Rot — the most common killer, almost always from overwatering, a slow-draining mix, or cold damp winters; stems soften and discolour, often from the base.
- Sunburn — pale variegated tissue scorches easily; introduce strong sun gradually and give light afternoon shade in the hottest months.
- Etiolation — too little light makes growth thin, weak and abnormally green, spoiling the plant's form.
- Pests — mealybugs (white fluff in the crevices and roots) and scale are the usual offenders; watch also for spider mites in hot, dry air. See Pests and diseases.
See also
- Euphorbia — the genus overview
- Euphorbia ingens — a similar, often-confused tree spurge
- Propagation — cuttings · Soil and potting mix · Watering · Repotting · Pests and diseases