Echinocactus horizonthalonius
| Light | Bright light; full sun once established, some shelter from fierce afternoon sun on young plants |
|---|---|
| Water | Very sparingly; allow to dry completely between waterings, keep dry through winter |
| Soil | Gritty, sharply draining mineral mix, ideally with added limestone (see Soil and potting mix) |
| Temperature | Tolerant of heat and light frost when dry; keep above freezing in cultivation, USDA zones 9–11 |
| Propagation | Seed (primary); often grown grafted to speed the slow seedlings |
| Toxicity | Non-toxic to cats and dogs |
Echinocactus horizonthalonius is a small, slow-growing barrel cactus of the deserts of the southwestern United States and northern Mexico, prized by collectors for its handsome blue-grey body and curved, flattened spines. Its solitary, ribbed stem is topped with pink to magenta flowers in summer, and its distinctive form has earned it common names such as Turk's head cactus, devil's head, blue barrel and eagle claw cactus. A notoriously touchy grower on its own roots, it is one of the species most often kept grafted in collections.
Description
Echinocactus horizonthalonius forms a solitary, roughly spherical to short-cylindrical stem, typically 10–25 cm tall and somewhat less across, though old wild plants can be larger. The body is a striking blue-grey to glaucous green — the colour that gives it the "blue barrel" name — and is divided into (usually) about eight broad, rounded ribs.
The areoles sit at intervals along the rib crests and bear stout, curved spines that are flattened and often banded, ranging from grey to reddish-brown; their hooked, claw-like sweep is the source of the "eagle claw" name. Flowers appear from the woolly crown in summer, pink to rose-magenta and cup-shaped, opening over several days. They are followed by dry, woolly fruit.
Distribution and habitat
The species is native to the Chihuahuan Desert region, ranging across parts of Texas, New Mexico and Arizona in the United States and south into the Mexican states of Chihuahua, Coahuila and beyond. It is strongly associated with limestone — growing on rocky desert hills, gravelly flats and calcareous outcrops, often wedged among stones in very lean, alkaline soils.
Plants endure baking heat, intense sun and long drought in habitat, contracting and hardening through dry spells. As with the whole cactus family, wild plants are listed under CITES Appendix II, and populations of some localised forms are vulnerable to collection; in the United States the Arizona variety var. nicholii (Nichol's Turk's head cactus) is federally listed as endangered. Nursery-propagated plants are the responsible choice for growers.
Cultivation
Echinocactus horizonthalonius has a reputation as a challenging species on its own roots, unforgiving of excess moisture and prone to rot at the base. Success rests on a very lean, sharply draining, mostly mineral mix — many growers add crushed limestone or dolomite to echo its native alkaline soils — in a snug pot with generous ventilation and strong light.
Water thoroughly only when the soil has dried out completely during the warm growing season, then allow it to dry again; keep the plant completely dry and cool through winter to prevent rot and encourage flowering. Because seedlings are painfully slow and sensitive, many collectors grow this species grafted onto a vigorous rootstock, which greatly speeds growth and sidesteps the root-rot problem. See Watering and Repotting for general technique.
Propagation
Seed is the standard and usually the only practical method, as the species is almost always solitary and rarely offsets. Sow onto a warm, gritty, mineral surface kept lightly humid; germination is reasonable but the seedlings grow slowly and resent overwatering. Grafting young seedlings onto a robust stock (see Grafting) is a common way to bring them on faster and more reliably. See Propagation — seed for a full walkthrough.
Common problems
- Rot — by far the commonest cause of loss, almost always from overwatering, a slow-draining mix, or moisture lingering around the base; the plant softens and browns from the bottom or crown.
- Etiolation — too little light dulls the handsome blue-grey colour and makes the body grow soft and elongated, losing its neat symmetry.
- Pests — mealybugs (white fluff in the areoles and around the roots) and red spider mites (fine webbing, bronzed skin) are the usual offenders; see Pests and diseases.
See also
- Echinocactus — the genus overview
- Grafting · Soil and potting mix · Watering · Propagation — seed · Repotting