Jatropha cathartica
| Light | Bright light to full sun; tolerates some afternoon shade |
|---|---|
| Water | Regularly while in leaf; keep dry during winter dormancy |
| Soil | Very free-draining mineral mix (see Soil and potting mix) |
| Temperature | Keep above freezing; USDA zones 9b–11 |
| Propagation | Seed (primary); cuttings and tuber division less common |
| Toxicity | Toxic if ingested; sap and seeds contain irritant compounds |
Jatropha cathartica is a small, caudiciform member of the spurge family from northeastern Mexico and southern Texas, grown for the swollen, rounded tuber (caudex) it forms at its base. In habitat the caudex sits underground, but collectors almost always grow the plant lifted, with the fat grey-green caudex raised above the soil as an ornamental feature. It is prized for combining a bonsai-like woody base with delicate, deeply lobed leaves and clusters of pink to coral flowers, and is widely sold in the succulent trade under the synonym Jatropha berlandieri, a name commemorating the naturalist Jean-Louis Berlandier.
Description
Jatropha cathartica develops a solitary, more-or-less spherical tuber that can reach the size of a grapefruit or larger with age, its surface smooth and pale grey to greenish-brown. From the top of the caudex the plant sends up slender, semi-succulent stems bearing long-stalked leaves that are palmately and deeply divided into narrow lobes, giving a fine, almost feathery silhouette. The foliage is bright green and is shed as the plant enters dormancy, leaving the bare caudex on display.
Small flowers appear in warm weather in loose clusters held above the leaves, ranging from soft pink to reddish-coral. Like most Jatropha, the plant is monoecious, carrying separate male and female flowers in the same inflorescence. Pollinated flowers give way to small capsules that split to release the seeds.
Distribution and habitat
The species is native to Tamaulipan thornscrub and dry grassland in the Mexican state of Tamaulipas and neighbouring areas, extending north into the Rio Grande valley of southern Texas. It grows in gritty, sharply drained soils among low shrubs, where the caudex sits buried and insulated below the surface and the plant drops its leaves to pass the cool, dry winter dormant.
Cultivation
Jatropha cathartica is a rewarding caudiciform for a bright windowsill or greenhouse and is more forgiving than many tuberous plants, provided its dormancy is respected. Grow it in a very free-draining, mostly mineral mix in a pot that leaves room for the caudex to expand. Give it bright light to full sun to keep the stems compact and encourage flowering.
Water regularly while the plant is in active growth and leaf, letting the mix approach dryness between waterings, then taper off sharply as the leaves yellow and drop in autumn. Keep the plant nearly dry and frost-free through winter dormancy; wet, cold roots are the quickest route to losing the caudex to rot. Many growers gradually lift the caudex higher at each repotting to expose more of it, a purely aesthetic choice that also lets the base be inspected for firmness. See Watering for general technique.
Note that all parts of the plant contain irritant, purgative compounds typical of the genus — the epithet cathartica refers to this — so handle cut stems and seeds with care and keep them away from children and pets.
Propagation
Seed is the usual and most satisfying method, producing plants that build a naturally swollen caudex from the outset; sow onto a warm, gritty surface kept lightly moist and germination is generally quick. Cuttings will root but tend to produce a thinner, less characterful base, and division of an established tuber is possible but risky. See Propagation — seed and Propagation — cuttings for full walkthroughs.
Common problems
- Rot — the main danger, almost always from watering during dormancy or a mix that holds moisture; the caudex softens and discolours.
- Etiolation — too little light stretches the stems and spoils the compact, bonsai-like look.
- Pests — mealybugs can hide in the leaf axils and around the caudex crown, and spider mites may appear on the foliage in hot, dry conditions. See Pests and diseases.
See also
- Jatropha — the genus overview
- Repotting · Soil and potting mix · Watering · Propagation — seed · Propagation — cuttings