Pachycereus schottii
| Light | Full sun to bright light; tolerates intense desert sun once established |
|---|---|
| Water | Sparingly; allow the mix to dry fully between waterings, keep dry in winter |
| Soil | Fast-draining mineral mix (see Soil and potting mix) |
| Temperature | Keep above freezing; roughly USDA zones 9–11 |
| Propagation | Seed and stem cuttings; monstrose forms from cuttings |
| Toxicity | Not a recognised serious hazard to cats or dogs, but the stems contain bitter isoquinoline alkaloids (lophocerine, pilocereine) — best kept out of reach |
Pachycereus schottii is a clustering, columnar cactus of the Sonoran Desert, instantly recognisable by the long, grey, bristly "beard" that mature stems develop near their tips. Widely known as the senita (and long grown under its older name Lophocereus schottii), it forms dense clumps of upright grey-green stems that branch mostly from the base. It is the parent of the popular totem pole cactus, a knobby spineless monstrose form beloved by collectors.
Description
Pachycereus schottii is a many-stemmed cactus that branches low down to build large clusters of erect columns, in age reaching a few metres tall. The individual stems are relatively slender, grey-green, and marked by a small number of prominent ribs — often around five to nine — bearing widely spaced areoles with short spines.
The species' most distinctive feature appears only on mature, flowering-age stems: the upper portion produces a mass of long, twisted, grey bristles (a pseudocephalium), giving the stem tips a shaggy, whiskered look and inspiring the common name "senita", from a Spanish term for old age. Small nocturnal flowers, pale pink to pinkish, open at night among these bristles in the warmer months and are followed by small reddish fruit.
Distribution and habitat
The senita is native to the Sonoran Desert, occurring across much of Sonora and the Baja California peninsula in Mexico and reaching into southern Arizona in the United States. It grows on desert flats and gently sloping ground, often in sandy or gravelly soils among other desert shrubs and cacti.
In its native range the plant is famous for an obligate pollination mutualism with the senita moth, which pollinates its night-opening flowers while laying eggs whose larvae feed on some of the developing fruit — one of the classic textbook examples of a plant–pollinator partnership.
Cultivation
Pachycereus schottii is an easy, forgiving desert cactus for a warm, sunny position. Grow it in a very free-draining, mostly mineral mix and give it as much light as you can; established plants take full sun well. Water thoroughly when the mix has dried out during the growing season, then let it dry again, and keep the plant dry and cool through winter to avoid rot. It is more cold-tolerant than many desert columnars but still resents hard frost and prolonged wet.
Because it clusters readily, it makes a striking specimen in a large pot or, in frost-free climates, in the ground. See Watering and Repotting for general technique.
Propagation
The species grows readily from seed sown on a warm, gritty surface. It is also easy from stem cuttings: a severed stem is left to callus for a week or two, then set in a dry mineral mix and watered sparingly until roots form. Cuttings are the standard route for the monstrose "totem pole" clones, which do not come true from seed.
Cultivars
The best-known form in cultivation is the totem pole cactus, a monstrose mutation with smooth, spineless, lumpy grey stems that look sculpted or braided. It is grown almost entirely for its bizarre texture and is propagated only from cuttings. Other knobby, smoother selections circulate under similar names; all follow the same easy culture as the wild species.
Common problems
- Rot — from overwatering or a slow-draining mix, especially in cool weather; stems soften and discolour from the base.
- Etiolation — too little light makes new growth thin, pale and stretched, losing the sturdy grey column form.
- Pests — mealybugs (white fluff in the areoles and among the bristles) and scale are the usual offenders; see Pests and diseases.
- Cold and wet — combined winter cold and damp is far more damaging than either alone, so keep plants dry when cold.
See also
- Pachycereus — the genus overview
- Sonoran Desert cacti
- Propagation — cuttings · Propagation — seed · Soil and potting mix · Watering · Repotting