Opuntia santarita
| Light | Full sun; the more light and stress, the deeper the purple |
|---|---|
| Water | Sparingly; allow to dry fully between waterings, dry rest in winter |
| Soil | Fast-draining gritty mineral mix (see Soil and potting mix) |
| Temperature | Hardy for a prickly pear; roughly USDA zones 8–11 (to about −7 °C/19 °F, colder if kept very dry); brief frost tolerated |
| Propagation | Pad cuttings (easiest); also seed |
| Toxicity | Non-toxic, though glochids and spines cause mechanical injury |
Opuntia santarita is a shrubby, pad-forming prickly pear of the southwestern United States and northern Mexico, prized by collectors for its rounded, blue-grey pads that flush a striking deep purple to violet when the plant is stressed by cold, drought or strong sun. Widely known as the Santa Rita prickly pear, it is often treated in the literature as a variety of Opuntia gosseliniana (var. santa-rita), of O. chlorotica, or of O. violacea, and it is one of the most ornamental of the hardy landscape opuntias.
Description
Opuntia santarita builds up into a low, spreading shrub of stacked, jointed pads (cladodes). The pads are broad and nearly circular, thin, and covered in a waxy bloom that gives them a chalky blue-grey to blue-green colour in comfortable conditions. Under stress — winter cold, drought, or intense sun — much of the pad surface turns a rich purple, lavender or wine-violet, most saturated around the areoles and pad margins; the colour softens back toward blue-grey when the plant is well watered and mild.
The pads are largely spineless over most of their surface but carry conspicuous tufts of yellowish-brown glochids (fine, barbed bristles), ageing browner, in the areoles, and older or margin areoles may bear a few slender spines. Flowers appear in spring and summer, broad and cup-shaped in clear yellow, often with a red base, followed by fleshy reddish-purple fruit (tunas).
Distribution and habitat
The Santa Rita prickly pear grows in the desert and semi-desert grassland of southern Arizona, New Mexico and western Texas, and south into northern Mexico (chiefly northern Sonora). It is at home on rocky slopes and open flats in gritty, fast-draining soils, exposed to full sun and a wide daily and seasonal temperature swing — exactly the conditions that bring out its purple colouring.
Cultivation
This is one of the more forgiving collector opuntias and an excellent choice for a hot, sunny spot or a xeric landscape bed. Grow it in a very free-draining, mostly mineral mix and give it as much sun as you can — colour intensity is driven directly by light, cold and drought, so a coddled, shaded plant will stay plain blue-grey. Water thoroughly when the soil has dried out completely during the growing season, then let it dry again; keep it dry and cool through winter, which both prevents rot and deepens the purple.
The species is notably cold-hardy for a prickly pear and tolerates brief frost once established and kept dry, making it usable in the ground in milder temperate gardens as well as in pots. Handle with care: the glochids detach at the lightest touch and are far more of a nuisance than the sparse spines — use folded paper, tongs or thick gloves when repotting or taking cuttings. See Watering for general technique.
Propagation
The easiest method is by pad cuttings. Detach a healthy pad at the joint, let the cut surface callus over for several days to a week in a dry, shaded spot, then set the base in dry, gritty mix; withhold water until roots form, then water sparingly. Plants can also be raised from seed, though this is slower and less common in the hobby. See Propagation — cuttings and Propagation — seed for full walkthroughs.
Common problems
- Rot — the usual cause of loss, from overwatering, poor drainage, or cold and wet combined; pads soften, discolour and collapse at the joint.
- Loss of colour — plants grown in shade or kept lush and well fed stay blue-grey; the purple is a stress response and needs sun, cold or a dry spell to develop.
- Glochids — not a plant problem so much as a grower one; the barbed bristles work into skin easily, so always handle with protection.
- Pests — cochineal scale (white cottony patches that crush to deep red), mealybugs and, under glass, spider mites. See Pests and diseases.
See also
- Opuntia — the genus overview
- Propagation — cuttings · Soil and potting mix · Watering · Repotting · Pests and diseases