Echinocereus
Echinocereus is a genus of small, mostly clustering cacti native to the southern United States and Mexico, prized among growers for producing some of the most brilliantly coloured flowers in the whole cactus family. Their spiny, cylindrical or globular stems are usually low-growing and offset freely into cushions, and their common names — hedgehog cactus and rainbow cactus — nod respectively to their bristly appearance and to the banded spine colours of certain species. They are widely grown as cold-hardy, floriferous collector plants.
Description
Members of Echinocereus are generally small cacti with soft-fleshed, ribbed stems that are cylindrical, club-shaped or almost globular. Most species branch and offset from the base to form clumps or dense mats, though a few remain solitary. The ribs carry areoles bearing spines that range from short and comb-like (pectinate) to long and needle-like, and in some species the spines are arranged in coloured bands that give the "rainbow" effect.
The great attraction of the genus is the flower. Blooms are large relative to the plant, funnel-shaped and often vividly coloured — magenta, pink, scarlet, orange, purple, yellow or white depending on species — and unusually long-lasting for cacti, frequently staying open for several days. A distinctive feature shared across the genus is that the flower buds burst through the stem skin rather than emerging from the areole, and the flowers commonly have green stigma lobes. Fleshy, often edible fruits follow, which in some species are covered in deciduous spines.
Distribution and habitat
Echinocereus ranges from the southwestern United States — Texas, New Mexico, Arizona, California and neighbouring states — south through much of northern and central Mexico. Species occupy a wide spread of habitats, from hot Chihuahuan and Sonoran desert flats to rocky hillsides, grasslands and cooler mountain slopes. Those from higher elevations and more northern latitudes are notably cold-tolerant, which has made the genus popular with growers in temperate climates.
Notable species
- Echinocereus rigidissimus — the classic rainbow cactus, with tight pectinate spines banded in pink and white.
- Echinocereus triglochidiatus — the claret cup, forming large mounds topped with scarlet, hummingbird-pollinated flowers; among the most cold-hardy of all cacti.
- Echinocereus pectinatus — a handsome comb-spined species with large pink to magenta blooms.
- Echinocereus reichenbachii — the lace cactus, a variable, hardy species with fine lacy spination.
- Echinocereus coccineus — another red-flowered hedgehog, closely allied to E. triglochidiatus.
- Echinocereus viridiflorus — an unusual small species with green to yellow-green, sometimes lemon-scented flowers.
Cultivation
Most Echinocereus are rewarding and undemanding given the two things they insist on: sharp drainage and strong light. Grow them in a gritty, mostly mineral potting mix and give them the brightest position you can, which brings out spine colour and encourages the free flowering the genus is grown for. Water generously through the warm growing season once the mix has dried, then keep them dry and cool over winter — see Watering for the seasonal rhythm.
A cold, dry winter rest is not just tolerated but usually required to set flower buds, and many of the North American species are hardy enough to grow outdoors in temperate gardens if kept dry in winter. Watch for rot at the base in plants that are kept too wet or in stagnant, airless conditions. See Repotting for general technique.
Propagation
Because most species clump readily, the easiest method is to detach rooted or unrooted offsets in the warm months, let any cut surface callus, and pot them into a dry mineral mix until roots form. Species are also easily raised from seed, which is the usual route for solitary types and for maintaining wild-type variability. See Propagation — cuttings for handling of detached stems.
Cultivars and hobby notes
Echinocereus is grown more for its wild species and natural forms than for a large body of named cultivars, and much of the interest among collectors lies in the geographic variation within widespread species such as E. reichenbachii and E. triglochidiatus. Occasional cristate (crested) and variegated forms appear and are propagated vegetatively; as with most such novelties these are less vigorous than normal plants, may be grafted to keep them growing, and often need a little extra care. The fruits of several species are edible and were traditionally eaten, which lies behind the old regional name "strawberry cactus".
Common problems
- Rot — the main killer, almost always from overwatering, a poorly draining mix or cold-and-wet winter conditions.
- Failure to flower — usually caused by too little light or the lack of a proper cool, dry winter rest.
- Pests — red spider mites and mealybugs are the usual offenders; see Pests and diseases.
See also
- Cactaceae — the cactus family
- Echinocereus rigidissimus · Echinocereus triglochidiatus · Echinocereus pectinatus
- Soil and potting mix · Watering · Propagation — offsets · Propagation — seed