Xerophyte

Central Spines

One to three, lowermost one up to 5 cm long.

Seeds

Dark brown to black, shining, 1.8 to 2.5 mm long.

Description

The organ pipe cactus Stenocereus thurberi is a large shrubs or treelike cactus usually without a definite trunk, that shows latitudinal variation in growth form, from a multi-stemmed shrub sending up from the base 5 to 20 branches 3 to 8 meters high in dry northern habitats to a ten metre columnar arborescent cactus in tropical deciduous forest. The habit of branching just at the base is unusual in this genus, in which most of the species have definite, though often short, trunks. The flowers, which appear from March to August, are followed by the large delicious fruit much prized by the native, who knows it as pitahaya or pitahaya dulce. Two subspecies are recognized, the nominate form and subsp. littoralis (K.Brandegee) N.P.Taylor. The latter subspecies is considered by some experts to be a separate species.

Branches

Erect or ascending, green, 1-8 m high, 15 to 20 cm in diameter, the basal ones usually simple but occasionally with lateral branches, this doubtless being caused by injuries to the growing tips.

Flowers

Funnelform, white to pale lavender 6 to 9 cm long, 6 to 7 cm in diameter, borne on the upper portion of the stem but sometimes 3 dm below the top. Night-blooming but remaining open the following day. Outer perianth-segments broad, reddish, imbricated, gradually passing into the scales on the tube. Inner perianth-segments white or light purple with nearly white margins and bases, widely spreading or even turned back at the apex, broad, obtuse. Necta chamber relatively large, its secretion copious. Filaments short, numerous, erect, white, borne all over the throat, 2 to 2.5 cm long. Lower part of flower-tube or tube proper smooth within. Pericarpel tuberculate, bearing small, ovate, acute purplish-red scales, these with white and brown hairs in their axils.

Blooming Season

Flowering occurs mostly from May to June (but recorded March-December) and bats are the main pollinator. Most plants reach reproductive age when 2-2.5 m tall (15-35 years old !).

Spines

Numerous, acicular to subulate, unequal, brownish to black, becoming grey in age

Ribs

Numerous, 12 to 17(-19), rather low but sometimes 2 cm high, rounded to acute, separated by narrow intervals forming more or less noticeable tubercles.

Radial Spines

Seven to nine 1 cm long.

Fruits

Globular, 4 to 7.5 cm in diameter, edible, very spiny, olive without, crimson within and ripens in late summer. When mature, the fruit loses its spines and shows the red pulp.

Areoles

10 to 15 or rarely 30 mm apart, large, sometimes becoming 1 cm in diameter, circular, brown-felted, more or less glandular, the whole areole becoming a wax-like mass within one or two years. The exudate producing dark red to black encrustation on the spines.