Pediocactus knowltonii
| Light | Bright light; some protection from intense midday sun in cultivation |
|---|---|
| Water | Very sparingly in growth; completely dry, cold rest in winter |
| Soil | Extremely fast-draining, gritty mineral mix (see Soil and potting mix) |
| Temperature | Cold-hardy but demands dry winters; USDA zones roughly 5–8 |
| Propagation | Seed; occasionally offsets (see Propagation — offsets) |
| Toxicity | Not considered toxic to cats and dogs |
Pediocactus knowltonii is a minute, cushion-forming cactus native to a tiny area of northern New Mexico and, historically, adjacent Colorado. Barely reaching the size of a thimble, it is among the smallest and rarest cacti in the United States and is federally listed as endangered. Named for its discoverer, it is commonly called Knowlton's cactus. Like the rest of its genus, it is a challenging, cold-growing plant prized by specialist collectors and almost never seen outside dedicated collections.
Description
Pediocactus knowltonii is a diminutive, usually solitary or slowly clustering cactus whose spherical to slightly flattened stems are often only a couple of centimetres across — one of the smallest body sizes of any cactus in North America. The stems are covered in small, low tubercles, each bearing an areole with numerous tiny, comb-like (pectinate) spines that are short, whitish and pressed close to the body, giving the plant a soft, felted appearance.
Flowers appear very early in the growing season, typically in early spring as the snow retreats. They are relatively large for so small a plant, funnel-shaped and pink to rose in colour, opening near the crown. Because the plant is so easily overlooked among gravel and low vegetation, wild individuals are notoriously difficult to spot except when in bloom.
Distribution and habitat
The species is confined to a very small range in the vicinity of the San Juan River in northern New Mexico, historically extending just into southern Colorado. It grows on gravelly hills and slopes derived from ancient river deposits, in sparse piñon–juniper and sagebrush country, rooted in loose, well-drained substrate among stones and scattered grasses.
Its natural range is exceptionally restricted — one of the smallest of any US cactus — which makes the entire wild population vulnerable to collection, trampling and habitat disturbance. This tiny distribution is a central reason for its protected legal status (see Legal status below).
Cultivation
Knowlton's cactus is regarded as difficult and is grown almost exclusively by experienced enthusiasts, ideally from legitimately propagated, nursery-raised stock. Like other members of Pediocactus, it is adapted to cold winters and dry conditions, and resents the warm, moist treatment that suits tropical cacti.
Grow it in an extremely gritty, mostly mineral mix in a deep pot that allows the taproot room, in bright light with a little shade from the harshest midday sun. Water carefully during the short spring growing period, then keep the plant essentially bone dry through summer dormancy and a cold winter rest. Excess moisture — especially combined with warmth — is the fastest route to rot. Many growers keep it in an unheated frame or alpine house and rely on grafting onto a hardier rootstock to keep plants alive and growing. See Watering and Repotting for general technique.
Propagation
Seed is the usual method, though germination can be slow and erratic; seed often benefits from a cold, moist period before it will sprout, mimicking the natural winter. Plants occasionally produce offsets that can be removed and rooted (see Propagation — offsets), but this is uncommon. Grafting of seedlings is widely used to improve survival and speed of growth. For a general overview of raising cacti from seed, see Propagation — seed.
Common problems
- Rot — by far the biggest killer, almost always from watering while dormant, a slow-draining mix, or warmth combined with moisture.
- Summer dormancy losses — plants that are pushed to grow through the hot months instead of being rested often decline.
- Pests — root mealybugs and, less often, red spider mites can trouble plants; inspect the roots at Repotting time. See Pests and diseases.
Legal status
Pediocactus knowltonii is listed as an endangered species under the U.S. Endangered Species Act, and collection of wild plants is prohibited.[1] It is also individually listed on CITES Appendix I — the strictest level of international trade control — so trade in wild-collected plants is effectively banned. Nursery-propagated specimens raised from legitimate stock may be grown and traded where permitted, but plants or seed must never be taken from the wild.
Despite its inclusion among legally restricted cacti, Pediocactus knowltonii is not a recognised psychoactive or mescaline-containing species. Its notability and its legal protection rest entirely on its extreme rarity and conservation status, not on any drug content. A few U.S. states, such as California, regulate certain mescaline-containing cacti beyond federal law, but those rules concern unrelated genera and reflect no property of this plant. This article is a horticultural and conservation reference only.
See also
- Pediocactus — the genus overview
- CITES · Grafting · Soil and potting mix · Watering · Propagation — seed · Propagation — offsets
References
- ↑ U.S. Fish and Wildlife Service, endangered species listing for Pediocactus knowltonii.