Cactus e Dintorni

Habitat: California, Arizona, Nevada, Utah, New Mexico, Colorado.
Description: a genus of small plants living at high elevations with a globular or subglobular shape. The tubercles are pronounced and the oval areoles have whitish, radial spines. The flowers are diurnal and appear in the summer.
Synonyms may occur within Navajoa, Coloradoa, Echinocactus, Toumeya, Pilocanthus, Uthaia.
Soil: 25% good garden soil, 50% sand and 25% pumice (approximately 2 mm in diameter). Peat-based or humus-rich soils kill the roots in 2 or 3 years.
Location: filtered light.
Temperature: they are tolerant of very low temperatures (-7°C / 19°F) as long as they are not watered; they might as well be overwintered at a minimum of 5°C (41°F) in a dry, bright place.
Water: less than average since these plants are native to low-rainfall regions. Water sparingly during the rest period to prevent the flower buds from dropping. An abundant supply of water should be granted when the vegetative period starts again, usually in February.
Cultivation tips: they’re best grown outdoors. Plants awake early each year and produce flowers from March to May. Growth occurs in May and June followed by a period of rest during the hottest months and is resumed in the autumn until mid-November when the plants finally enter a dormant state. Grafting is advisable, especially for the American species which may be quite difficult to grow (sileri, paradinei, knowltoni), while the cultivation of the Mexican ones is not complicated. They enjoy cool nights with high diurnal temperature variations (30°C/86°F high to 8°C/46°F low) when flowering is over and lower temperatures during the formation of the flower buds. They can be treated like other species adapted to cold winters, such as  Austrocactus, Sclerocactus, Toumeya, and Echinomastus.
Main species of Pediocactus: Pediocactus simpsonii, lives on highlands of Arizona; start watering in April. Its growing period extends over part of the summer; Pediocactus bradyi, Arizona, Colorado; Pediocactus winkleri, Utah; Pediocactus despainii, from Utah, it prefers a slightly calcareous soil;
Pediocactus sileri, found on highlands of Arizona and Utah, needs porous soil improved with some leaf mould; it only grows during the spring;
Pediocactus paradinei, naturally found at 1800 metres (5900 ft) of altitude in the desert of Navajoan (USA); it grows only slightly in the summertime;
Toumeya lophophoroides, an exquisite specimen; Tediocactus papyracantha; Tediocactus schsmiedickeana; Tediocactus schwarzii.