Thelocactus is a succulent member of the cactus family. It originates from the arid lands of Central, and North Mexico.
Thelocactus is globe-shaped, short and cylindrical. It is a small cactus, although there are one or two species which, while only about 15 cm high, can be 25 cm in diameter; for example, T. nidulans. Thelocactus species are generally solitary, but some varieties will cluster in groups.
The ribs on Thelocacti are very clearly marked and are sometimes twisted in a spiral. There can be from 8 to 20 ribs, are rather low and normally marked with raised, angular or hexagonal tubercles. These tubercles can sometimes be difficult to distinguish. Areoles sit in a furrow directly above where the spines grow and there can be up to twenty radial/radiating spines. They are often needle-like, spread out and can be from 1.3 – 1.5 cm long. The central spines are mostly coarser, number up to six, stand vertically out from the plant and can be 2.5 – 7.5 cm long. Colours of all of the spines vary and include white, gray, golden-yellow and red-brown.
Flowers grow from the new areoles at the very top of the plant. They are funnel-shaped, have a diameter of 2.5 – 7.5 cm and their colours vary from white to shades of yellow, red or purple. They are diurnal. Fruits are small, globe-shaped and plain. They are dehiscent through the large basal pore, green to brownish purple [to magenta], spherical to short cylindrical, 5 - 18 x 6 - 17 mm, not juicy, drying immediately after ripening, scaly, spineless, hairless and with floral remnant persistent.
Thelocactus hexaedrophorus is the type species.
Thelocactus grows in the wild in central and North Mexico but also on the other (northern) side of the Rio Grande, in Texas. Species can be distinguished by where they grow, whether in mountainous stony/rocky places or grassy territory with clay soil.
Thelocactus is generally easy to cultivate, even if many species fail to flower until they are five years old. Soils should be composed of equal proportions of sand and humus. Water normally from Spring to Autumn. In Winter, keep most species at a minimum temperature of 8°C. They can survive at lower temperatures but the roots then must be kept dry. The dark brown or black seeds can be relatively large for the size of cactus and they germinate readily.
Reproduction is nearly always from seed, since the plant rarely produces plantlets. The seed should be put in a sand and compost mixture, kept moist, maintained at a temperature of 21°C and placed in a shady position.
The following genera have been brought to synonymy with Thelocactus:
* Hamatocactus Britton & Rose
This genus contained 8 species and was known from the Southwest United States and in northern Mexico. The name Hamatocactus means "hooked cactus" in Latin.
* Thelomastus Fric (nom. inval.)
Source: Wikispecies, Wikipedia: All text is available under the terms of the GNU Free Documentation License