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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: P. simpsonii, lives on highlands of Arizona;
start watering in April. Its growing period extends over part of the summer;
P. bradyi, Arizona, Colorado; P. winkleri, Utah; P.
despainii, from Utah, it prefers a slightly calcareous soil;
P. sileri, found on highlands of Arizona and Utah, needs porous soil
improved with some leaf mould; it only grows during the spring;
P. 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; T. papyracantha; T.
schsmiedickeana; T. schwarzii.
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