Stetsonia coryne
| Light | Full sun to bright light; acclimatise gradually to avoid scorch |
|---|---|
| Water | Moderate in warm growth; allow to dry between waterings, keep dry in winter |
| Soil | Fast-draining mineral mix (see Soil and potting mix) |
| Temperature | Keep above freezing; USDA zones 9b–11, tolerates brief light frost when dry |
| Propagation | Seed (primary); cuttings of branches also strike |
| Toxicity | Non-toxic to cats and dogs; the spines are the only real hazard |
Stetsonia coryne, the toothpick cactus, is a large, tree-forming columnar cactus from the arid lowlands of Argentina, Bolivia and Paraguay, and the only species in the genus Stetsonia. Mature plants develop a short woody trunk crowned by many blue-green branches, each armed with long, needle-like spines whose dark black tips give the plant its common name.
Description
Stetsonia coryne is one of the giants of the cactus world, eventually reaching the size of a small tree — often 5–8 m tall in habitat, with an open, candelabra-like crown of ascending branches rising from a distinct woody trunk. The stems are handsome and glaucous, a waxy blue-green that stands out among the more grassy greens of neighbouring cacti, and are divided into a modest number of broad, rounded ribs.
The areoles carry clusters of stout, straight spines that are pale at the base and abruptly tipped in black, resembling scattered toothpicks — the feature behind the common name. The specific epithet coryne derives from the Greek for "club". Large white, funnel-shaped flowers open at night near the branch tips on established plants, followed by a fleshy rounded fruit. As a slow-maturing, night-blooming species, flowering is uncommon on young or pot-grown specimens.
Distribution and habitat
The toothpick cactus is native to the Gran Chaco, the vast dry lowland plain spanning northern Argentina, southern Bolivia and western Paraguay. There it grows in hot, semi-arid thornscrub on flat or gently sloping terrain, frequently forming a conspicuous part of the woody vegetation alongside mesquite and other drought-adapted shrubs and trees.
Conditions in habitat are marked by intense sun, a pronounced dry season and occasional light winter frost, all of which the plant tolerates well when its roots are dry. Like the whole cactus family it is listed under CITES Appendix II, but it is neither rare nor threatened, and nursery-grown plants are freely and legally traded.
Cultivation
Stetsonia coryne is a robust and forgiving grower for a large cactus, asking mainly for strong light, warmth and sharp drainage. Plant it in a very free-draining, mostly mineral mix and give it as much sun as you can, introducing full sun gradually so the waxy skin does not scorch. Water moderately through the warm months once the soil has dried, then keep the plant dry and cool over winter, which improves cold tolerance and prevents rot.
It will take brief, light frost if kept bone dry, though in cooler climates it is safest grown in a container that can be moved under cover. Because it ultimately becomes very large, plan for periodic repotting into a stable, heavy pot, and mind the fierce spines when handling. See Watering for general technique.
Propagation
Seed is the usual and most rewarding method: sown on a warm, mineral surface and kept humid until they germinate and establish. Branches removed from established plants will also root as cuttings — allow the cut end to callus for a week or more in a dry, shaded spot before setting it on barely moist mineral mix. See Propagation — seed and Propagation — cuttings for full walkthroughs.
Common problems
- Rot — the main killer, almost always from overwatering, a slow-draining mix, or water left standing over winter; stems soften and discolour from the base.
- Scorch — a sudden move into full sun can bleach or blemish the blue-green skin; acclimatise gradually.
- Etiolation — too little light produces thin, pale, weakly ribbed growth that never develops the sturdy branching form.
- Pests — mealybugs (white fluff in the areoles) and, in dry indoor air, red spider mites are the usual offenders; see Pests and diseases.
See also
- Stetsonia — the genus overview
- Soil and potting mix · Watering · Propagation — seed · Propagation — cuttings · Repotting