Genus honouring Marcel Kroenlein (1928-1994), Monegasque, director of the famous Jardin Exotique of Monaco (1969 to 1993). See portrait above, cJean-Marie Solichon.
Monotypic genus of globular to short columnar plants up to 2 m high, flat to slightly depressed at the apex, solitary or branched from the base with age. Stems with many ribs (up to 40), apex densely covered with wool. Large areoles, generally elongated, close, joined in adult plants, without nectar glands. Spines are strong, cross-ribbed, centrals and radials same length.
Flowers diurnal, appearing in the apical wool, shortly funnel-shaped to bell-shaped, yellow, with scales with brownish thorns, pollinated by bees. Fruits elongated, fleshy with a white pulp, becoming dry when mature, indehiscent, densely covered with scales and wool. Seeds oval, smooth, shiny, brown.
The genus Kroenleinia grows among bushes and herbs, on stony soils, rather mineral than organic, usually limestone, also alluvial soils, or on rocky slopes, on the edge of ravines, from 1400 m to about 2000 m above sea level, with other cacti. Annual precipitation is usually 500-700 mm, falling between June and September, and winter is punctuated by short frosts. There is a significant disjunction in habitat, and at 550 km from plants commonly known but becoming extremely rare in their habitat, a rich population that exclusively grows on volcanic cliffs was discovered in 2005, in Zacatecas.
Mexico (Guanajuato, Hidalgo, Queretaro, San Luis Potosi, Zacatecas).
Currently only one species:
– Kroenleinia grusonii* (Hildm.) J.Lode 2014 (ex Echinocactus grusonii Hildm. 1886)