Obregonia denegrii Description: Obregonia is among the most famous of all cacti for is unique artichoke-shaped stem. It is the only representative of its monospecific genus and is related to Ariocarpus. It grows almost always as a solitary plant levelled with the ground, with the sunk and woolly apex. It is considered an intermediate form between Ariocarpus and Lophophora.
Stem: Solitary, globular-squashed resembling an inverted pine cone with a woolly centre, it grows up to 15 (or more) cm in diameter and is greyish green to dark green.
Tubercles: Arising in a rosette, not imbricate, arranged in a spiral, deeply cut like an artichoke, triangular, prominent, leaf like, flat above, keeled below and with a basal ridge.
Areoles: Small at the tips of the tubercles, with wool when young.
Spines: 2 to 4 whitish to brown about 5 to 15 mm long in the young tubercles, ± soft flexible, slightly curved and often rapidly shedding.
Roots: Thick taproot.
Flowers: The flowers grow between the wool of the apex, in the centre of the stem on young tubercles, they are funnel-shaped white diurnal, up to 2.5 cm in diameter, 2.5-3 cm long. External perianth segments greyish, pericarpel naked or with few scales. Filaments reddish purple or pink, anthers yellow, style white and stigma lobes white.
Blooming season: Summer.
Fruits: Hidden in the wool, pear-shaped, white naked, fleshy and edible that dry when mature. The withered flowers remaining attached.
Seeds: Large and black 1 to 1.4 mm long.
Cultivation and Propagation: This slow growing plant 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 own roots too. Needs a very well drained mineral substratum with little organic matter (peat, humus). Requires light sun sun to develop good compact growth and waterings should be rather infrequent, to keep the plant flat shaped and not become excessively elongated and unnatural in appearance. Use Water sparingly from March till October and keep perfectly dry in winter, or when night temperatures remain below 10° C (but some people give this plant a light monthly watering to prevent the drying and shedding of the lower tubercles.) It is hardy to -4°C (or less) for a short period. In the rest period no high atmospheric humidity!! Ensure a good ventilation.