Echinocereus poselgeri aka Dahlia Apple Cactus

Echinocereus poselgeri is a slender, shrubby cactus in the Cactaceae family. Its native range runs from southern Texas into northeastern Mexico. Mexican records include Coahuila, Nuevo León, and Tamaulipas. It also goes by the name Wilcoxia poselgeri. English names include pencil cactus and dahlia hedgehog cactus. Spanish names include Zocoxochitl and Sacasil. It grows in dry scrub on hills and in valleys. Wild plants occur from low ground to about 3,773 feet [1,150 metres].

The plant makes few branches and starts with upright stems. As stems lengthen, they spread out or climb through shrubs. Nearby woody plants give the thin stems support. Stems can reach about 3.9 feet [1.2 metres] long. They measure about 0.066 feet [0.02 metres] across. These are stem measurements, rather than a stated garden height. Their dark surface has six to ten ribs. Tan to grey-white spines grow along these ribs. Each cluster has one central spine and eight to fifteen radial spines. Most radial spines lie close against the stem. Those near the growing tip stand out more.

Below ground, the plant forms as many as eight tubers. Each measures about 0.20–0.33 feet [0.06–0.10 metres] long. Young tubers are pale brown and darken with age. Their shape recalls the tubers of a dahlia. These storage organs cannot make fresh shoots on their own. New shoots arise only from the main cut stem. This distinction matters when considering the plant's underground growth.

Flowers appear from late spring into early summer. Their shades range from rose pink to mauve and magenta. The bright blooms contrast with the dark, narrow stems. The fruit has an oval shape and white flesh. Its outer colour ranges from dark green to brownish. Fruit reaches about 0.066 feet [0.02 metres] in length. The seeds are black and small. The supplied sources do not establish whether the fruit is edible.

Its wild sites include sandy ground and soils laid down by water. In cultivation, LLIFLE warns against giving it too much water. It calls for a cool, dry winter rest between −5 and 10°C. The species remains widespread and abundant despite local use. The evidence does not explain those uses in detail. It provides no species-level guidance on pests, diseases, or toxicity.