Obregonia denegrii Frič
Ariocarpus denegrii, Strombocactus denegrii
Obregonia denegrii is a cactus with a solitary squashed globular stem with triangular, spirally arranged tubercles, resembling an inverted pine cone with a woolly apex. It is related to Ariocarpus and is the only representative of its monospecific genus. The stem is grayish-green to dark green and grows up to 6 inches (15 cm) in diameter. Flowers appear from the center of the dense fuzzy wool at the apex in summer. They are diurnal, white, funnel-shaped, and up to 1 inch (2.5 cm) in diameter. The fleshy edible fruits are white, pear-shaped, and hidden in the wool.
USDA hardiness zones 9a to 11b: from 20 °F (−6.7 °C) to 50 °F (+10 °C).
How to Grow and Care
This slow-growing cactus isn't always the easiest species to cultivate but can enlarge relatively fast when well grown. It is often seen as a grafted plant but grows very well on its roots too.
It needs very well-drained soil with little organic material (peat, humus). Requires full sun to develop good compact growth, and watering should be rather infrequent to keep the plant flat shaped and not become excessively elongated and unnatural in appearance. Use water sparingly from spring to fall and keep perfectly dry in winter or at night temperatures below 50 °F (10 °C). It is hardy to 20 °F (-6.7 °C) for a short period; in the rest period, no high atmospheric humidity. Ensure good ventilation.
It is propagated almost exclusively by seeds. But the seedlings are tiny and very slow-growing. At first, they take one or two years to reach the diameter of 0.2 inches (0.5 cm).
This species is native to Mexico. It occurs at an altitude of about 1,000 meters above sea level.
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