Xerophyte

Central Spines

3-7 per areole, 13-30 mm long, 1 mm wide at base, brownish black at least above, the bases sometimes white when young, ageing to pale grey or white, stout, rigid, not flattened, nearly straight or slightly curved.

Seeds

Grey to nearly black, 3.5-5 long, 3-3.5 mm thick, papillate and rugose.

Description

Pediocactus sileri is an exceptionally rare plant long cherished as a Utahia sileriSN|18237]]SN|18237]] and found to be rather difficult in cultivation, but nevertheless much sought after. It is a solitary or, less commonly, few-branched cactus measuring up to to 25 cm tall and nearly 12 cm in diameter, making it one of the larger plants in the genus. It is similar to Pediocactus simsonii, but all of the spines have thick bases. 3 central, erect spines are brown or blackish, but lighten to a white colour with age, while the 8-15 radial spines are similar to the central ones but white or pale grey and about half as long straight or slightly curved. Although numerous, the spines only hide about half of the blue-green stem. During the spring, bright greenish yellow flowers about 2.5 centimeters in diameter will bloom and produce greenish yellow fruit. This plant does not shrink significantly in summer or winter as so many other plants in this group do.

Note

Sileri is named for Andrew Lafayette Siler, a 19th-century rancher and plant collector.

Flowers

Greenish yellow about 1.8-2.2 long, 2-3 cm across, and the spines do not allow them to fully open. Scales on hypanthium long fringed. Outer perianth segments brown, with white margins, and conspicuously fringed 9-15 mm long, 3-4.5 mm wide. Inner perianth segments yellow or yellowish, with purple or maroon veins, 15-20 mm long, 4.5-6 mm wide.

Blooming Season

Spring (April and May).

Distinguishing Characters

In this species the scales of tube and outer perianth-segments are conspicuously ciliate.

Stem

It usually does not cluster. Depressed-hemispheric or at times elongate-cylindric, 5-15(rarely to 25) tall, 6-12 cm broad with pronounced tubercles. Tubercles 9-15 mm long, 6-11 mm wide.

Radial Spines

11-16 per areole and white, 11-21 mm long. Spines around the base of the cactus may help to anchor it to the soil.

Fruits

Dry, greenish yellow, cylindrical, short cylindric, 12-15 mm long, 6-9 mm broad, the scales finally deciduous.

Areoles

Large, circular to pyriform, persistently white-felty.