Sometimes referred to as F. pottsii var. alamosanus, this rare and distinctive barrel cactus has relatively delicate spines for a Ferocactus, and is very hard to find a good size plant like this in cultivation.

Family: Cactaceae (Cactus Family)

Scientific name: Ferocactus alamosanus (Britton et Rose) Britton et Rose 1922

Origin:  Known only from a restricted area in the mountains at East of Alamos, Sonora, Mexico. Said to be heading for endangered species list.

Conservation status: Listed in CITES appendix 2.

Synonyms:

• Echinocactus alamosanus Britton et Rose 1913
• Ferocactus alamosanus var. platygonus G.E.Lindsay 1942
• Ferocactus alamosanus ssp. reppenhagenii (G. Unger) N.P. Taylor
  Pubblished in: Cactaceae Consensus Initiatives 6: 15, 1998
• Ferocactus reppenhagenii G. Unger,
  Pubblished in: Kakt. And. Sukk., 25 (3): 50., 1974
• Ferocactus alamosanusvarp. reppenhagenii
• Ferocactus pottsii var. alamosanus.
• Parrycactus alamosanus ssp. reppenhagenii,
  

(This Taxon belong to a group of six closely allied species. The group is: F. alamosanus, F. pottsii, F. schwarzii, F. reppenhagenii, F. glaucescens, & F. echidne)

Sometimes referred to as F. pottsii var. alamosanus, this rare and distinctive barrel cactus has relatively delicate spines for a Ferocactus, and is very hard to find a good size plant like this in cultivation.

Taxonomy note: The differences with Ferocactus pottsii are in reality very small, the ribs in F. alamosanus are more numerous and the central ribs is more long,  The subspecies 'alamosanus' has usually about 20 acute ribs, heavy spination, and only grows to 25 cm high. The subspecies 'reppenhagenii' has 12-18 rounder ribs and connecting areoles and will grow up to about 70-100 cm.).

Cultivation: They are summer-growing and pretty easy plants thought slow to start. They are suited for any rich, well drained soil  such us clay, pumice, lava grit, and only a little peat or leaf-mould. If potted, repot them preferably in the spring, if their roots become cramped.  Generally, they should be repotted every other year in order to provide fresh soil. However, this doesn't necessarily mean they'll need larger containers. Fill about a quarter of the pot with broken crocks, gravel, etc. to promote good drainage. After repotting, do not water for a week or more. Water regularly during the aestival growth cycle (this plant need plenty of water, but do not overwater and let their soil dry out between waterings), and also needs to be avoided wetting the body of this plant while it is in sunlight. A wet cactus in the sun light can cause sun burning which can lead to scares or even fungal infections and death, keep rather dry in winter. No water should ever be allowed to stand around the roots. Feed with a high potassium fertilizer in summer.
Exposure: Outside they need a bright exposure, full sun or half shade in summer if the location is exceedingly hot or bright, inside needs bright light, and some direct sun. It can tolerate moderate shade, and a plant that has been growing in shade should be slowly hardened off before placing it in full sun as the plant will be severely scorched if moved too suddenly from shade into sun.
Frost Tolerance: Light frost protection required for safe cultivation, but can tolerate sporadic light frost. This plants need a period of cool rest in winter to produce flowers abundantly.
Diseases and pests: Watch for infestations of mealybug, scale insects and spider mite.
Plant in good conditions will start to  bloom when reach the diameter of only 15-18 cm.

Propagation: Seeds are the only way of reproducing.