Xerophyte

Habit

It is a usually unbranched cactus (but sometime forms small cluster) with dense spines covering the stem.

Seeds

black, 2 mm long 2(-3) mm broad, shiny, much more larger at the upper end than at the lower. Testa with rounded papillae hylum large, lateral on the lower half of the seed.

Description

Sclerocactus whipplei is one of the more distinctive species, characterized by yellow flowers and flattened, somewhat daggerlike central spine directed toward the stem apex. Similar species are Sclerocactus sileri, and the yellow-flowered populations of Sclerocactus parviflorus, often referred to as subspecies Sclerocactus terrae-canyonae. However, Sclerocactus sileri and Sclerocactus parviflorus lacks the daggerlike adaxial central spines. Two subspecies are recognized, the nominate form and subsp. heilii Castetter, P.Pierce & K.H.Schwer. Following Hunt et al. (2006) subspecies heilii includes Sclerocactus cloverae K.D.Heil & J.M.Porter as a synonym. Other authors treat this as a good species, with subsp. heilii as a synonym.

Roots

The root systems are fibrous and shallow unless deep water.

Flowers

3 to 5 cm long, from near the the centre of the plant, often abundant, showy; funnelform to campanulate usually yellowish (or sometime - var. roseus ?- light purple or pinkish). Outer perianth segments with greenish or reddish midstripes and yellow margins, oblanceolate, to 24 mm long and 5 mm broad. Inner perianth segments yellow, oblanceolate, to 30 mm long and 6 mm broad

Blooming Season

Spring (in habitat late April to June)

Spines

On seedlings all radials, but on old plants both radials and centrals.

Ribs

(8-)13 to 15 often spiralled, prominent, tubercles usually evident on ribs.

Stem

5 to 35 cm tall or more, depressed-globose, or spheric to elongate-cylindric.

Radial Spines

Stouter the the radials, (5-)7-12 per areole, somewhat fattened, spreading or slightly recurved, white except for abaxial 2 that are usually purplish pink to black, (6-)12-25 mm long.

Fruits

Large dry or fleshy many-seeded berry, green to tan, almost naked, often reddish at maturity, ovoid, 10-25 long, 6-15 mm in diameter, scales few, yaline, scarious, margined, minutely toothed, membranous-fringed, each bearing in its axil a small tuft of hairs. Seeds release from splits in the base of the fruit.