Mammillaria longimamma aka Pineapple Cactus

Mammillaria longimamma is a small cactus in the Cactaceae family. Its common names include finger cactus and nipple cactus. Kew places its native range in northeastern Mexico, reaching Veracruz. LLIFLE records it in Guanajuato, Hidalgo, and Querétaro. It grows in desert and dry shrubland habitats. Older names include Cactus longimamma and Dolichothele longimamma. These names refer to the same species, not separate plants.

Young plants start with one stem but soon form clumps. These reach about 0.5 feet [0.15 metres] across or more. A clump has 10–30 branches, though some reach 50. The green stems are round and lack latex. Each grows to about 0.33 feet [0.10 metres] tall. Most measure 0.10–0.20 feet [0.03–0.06 metres] across. Larger stems can reach 0.39 feet [0.12 metres] across. Thick taproots swell near their upper ends, beneath the stems.

Long, soft tubercles give the plant its finger-like look. These fleshy bumps reach 0.04–0.08 feet [0.012–0.025 metres] long. Their bases have a little wool but no bristles. Each bears about eight to ten radial spines. These range from pale yellow-white to brown. Most measure 0.04–0.07 feet [0.012–0.020 metres] long. A single central spine is usual for this species. It stays straight, rather than curving into a hook. It can reach about 0.08 feet [0.025 metres] long.

Bright yellow flowers open from May through July. They are large for a cactus of this genus. Each measures 0.13–0.20 feet [0.04–0.06 metres] in length. Their width reaches 0.15–0.20 feet [0.045–0.06 metres]. The stigmas are yellow, matching the petals. The fruits range from yellowish shades to green. Its flowers and clustered form give it ornamental value. The supplied species accounts do not establish food or medicinal uses. They also give no firm evidence about toxicity.

In the wild, this cactus grows beneath low shrubs. It also occurs among sparse plants on limestone and volcanic soils. LLIFLE records elevations of 3,281–7,874 feet [1,000–2,400 metres]. Its wild populations are scattered and rare across that account's range. Illegal collecting for ornamental use harms plants in some places. Cattle also trample plants in parts of its habitat. The species-level evidence gives no firm cultivation or frost limits. It also provides no species-level account of pests or diseases.