Astrophytum capricorne
| Light | Bright light; a little shade from the fiercest afternoon sun |
|---|---|
| Water | Sparingly; let the mix dry fully between soakings, and keep dry over winter |
| Soil | Fast-draining mineral mix (see Soil and potting mix) |
| Temperature | Keep above freezing; roughly USDA zones 9b–11 |
| Propagation | Seed (primary method) |
| Toxicity | Non-toxic to cats and dogs |
Astrophytum capricorne, the goat's horn cactus, is a globular to shortly cylindrical species from northern Mexico, easily recognised by its long, flattened, twisting papery spines that curl and tangle across a body flecked with white woolly scales. In late spring and summer it produces satiny yellow flowers with a striking red throat.
Description
Astrophytum capricorne forms a solitary, mostly spherical body that lengthens a little with age, typically carrying seven or eight prominent ribs. Like the rest of the genus, the epidermis is dusted with small tufts of white woolly scales (trichomes), giving the plant a speckled, marbled appearance that ranges from lightly flecked to almost silver depending on the individual.
Its signature feature is the spines: long, flattened, flexible and papery, they emerge dark and twist and curl over the crown and down the sides, often interlacing across the ribs — the resemblance to a goat's or ram's horns gives the plant its common name. Flowers appear from the areoles near the top of the plant, opening a glossy yellow with a deep red or orange centre, and are followed by small scaly fruit.
Distribution and habitat
The goat's horn cactus is native to the Chihuahuan Desert of northern Mexico, where it grows on limestone hills and in open, gravelly desert scrub. In habitat it endures a wide daily temperature swing, strong sun and a long dry season broken by seasonal rains — conditions worth keeping in mind when setting up its care at home.
Cultivation
Astrophytum capricorne is a rewarding and generally undemanding plant for a sunny windowsill or greenhouse. Give it as much bright light as you can; a touch of shade during the most intense summer afternoons helps prevent scorching, but too little light produces weak, distorted growth.
Plant it in a fast-draining, largely mineral mix (see Soil and potting mix) and choose a pot only a little larger than the plant. Water thoroughly during the growing season, then allow the mix to dry out completely before watering again (see Watering). Through the winter keep it cool and completely dry — this dry rest not only prevents rot but also encourages a good display of flowers the following season. Feed lightly with a dilute low-nitrogen fertiliser during active growth.
Propagation
Because the species is normally solitary and rarely offsets, propagation is almost always from seed (see Propagation — seed). Seedlings germinate readily in warm, humid conditions and grow at a moderate pace. Named forms and choice selections are sometimes grafted onto a vigorous rootstock to speed them along, though seed-grown plants on their own roots make handsome, long-lived specimens.
Common problems
- Rot — the most common cause of loss, almost always from overwatering, a poorly draining mix, or watering while cold. Keep it dry in winter and let the soil dry fully between waterings.
- Etiolation — insufficient light causes the body to elongate and pale, and the spines to grow thin and weak. Move it to a brighter spot.
- Pests — watch for mealybugs (including root mealybugs) and red spider mites, especially on plants kept warm and dry indoors.
See also
- Astrophytum — the genus overview
- Astrophytum asterias · Astrophytum myriostigma · Astrophytum ornatum
- Grafting · Soil and potting mix · Watering · Propagation — seed