Mammillaria spinosissima f. rubrispina - Red Headed Irishman cactus

Mammillaria spinosissima f. rubrispina, commonly sold under the name “Red Headed Irishman”, is a form of Mexican cactus with red prickles, highly sought after for its neat silhouette and regular flowering. This plant suits cactus enthusiasts who appreciate plants with a strong identity, but are quite easy to care for if light is sufficient. Indoors, it will be happy with a very bright window in a room with low humidity and good ventilation.

This variety belongs to the Cactaceae family. The reference species, Mammillaria spinosissima, is native to Mexico. Its natural distribution ranges from Durango to Morelos and Guerrero, where it grows in arid or semi-arid habitats, on rocky slopes, among dry scrub and on well-drained soils. The name rubrispina corresponds to a horticultural form with red thorns, widely spread in cultivation; in the trade, it is very often known by the nickname “Red Headed Irishman”.
The plant is initially globose, then becomes cylindrical to columnar; usually solitary, it may branch slightly with age. Its growth is slow to moderate. In a pot, it reaches 15 to 30 cm in height and 5 to 10 cm in diameter. The dark green stem is entirely covered with conical tubercles arranged in a spiral. The areoles bear numerous fine, white to yellowish radial thorns, and dense, longer central thorns, reddish-brown to copper. In spring, sometimes until early summer, depending on conditions, small funnel-shaped, deep pink to carmine flowers appear, about 1.5 cm in length and diameter, arranged in a crown near the stem tip. They can be followed by small, elongated, bright red fruits when the plant goes outside for the summer. 
The name “Mammillaria” comes from the Latin “mamilla”, meaning “little breast”, referring to the mammillate tubercles characteristic of the genus.

Indoors, this cactus requires very bright light, even a sunny position, a dry to moderately dry atmosphere, around 30 to 50% humidity, and temperatures between 18 and 30°C during the growing season. A winter rest in a room between 10 and 14°C will encourage flowering in spring. Its cultivation is possible for a beginner, careful about excess water and lack of light. It is best placed on a windowsill facing south or west, in a bright conservatory, an office, or any other very bright and low-humidity room.

This cactus greatly benefits from time outdoors as long as temperatures allow, and it dislikes rooms that are too heated in winter. It should be brought indoors before the first frosts and placed in a cool, dry, frost-free location, protected from winter moisture.

In a collection of succulents, Mammillaria spinosissima f. rubrispina mixes well with other species with varied forms and colours. It can be associated with Kalanchoe beharensis var. subnuda, Peperomia ferreyrae ‘Nevada’, Cotyledon orbiculata 'Silver Dollar' and Tradescantia sillamontana. The contrast between tubular leaves, broad triangular leaves, thick rosettes, and woolly stems further enhances the dense texture of the red prickles of the Mammillaria than a selection of cacti that are too visually similar. Placed on a cactus tray or in a nice terracotta pot, it adds a desert touch to your living room or office.