Xerophyte

Central Spines

(1-)2-3(-4), reddish brown, stout, rigid, 4-30 mm long.

Seeds

About 1.2 mm dull black.

Description

Arrojadoa penicillataSN|4866]]SN|4866]] is a shrubby, much branched cactus, to 2 m high often supported by the surrounding vegetation or semi-scandent to decumbent (especially when growing in sand-dunes). The bright crimson flowers are produced at the growing tip of stems from the cephalium (a structure of wool and bristles at terminal ends of joints forming a thick ring around the stem), they measure 4 cm in length. The slender stems rarely exceed 10 mm in diameter except near the cephalium. There are about 10 low ribs with closely set areoles bearing short spreading spines. It is not easy to maintain, but very interesting to cultivate.

Roots

Rootstock fibrous, not tuberous or rhizomatous.

Note

Latin penicillatus = shaped like a brush.

Cephalium

Apical produced following each season's vegetative growth, producing 3 or 4 ring-like clusters on the same axis of abundant white wool and long red to brown bristles to 20-30 mm long. Once flowering begins the flower buds will form from the cephalium.

Flowers

In clusters of 6-12, opening during the day, bird pollinated, pinkish magenta or reddish pink, to 3 cm long and 2 cm in diameter. Pericarpel 7-8 mm long. Tube to 12 mm long and 4-7 mm across, cylindric, with fleshy bract-scales only at apex. Perianth-segments bright pink with a very fine darker line around the margin, outer segments to 7 mm long triangular to lanceolate, well-expanded, innermost segments remaining erect and forming a tube which encloses the stamens, its opening 3-4 mm in diameter. Stamens included within the perianth-segments. The filaments below the anthers are thin, like threads, while the lower stamens form a nectar chamber. Style 10 mm long, stigma-lobes 6-8, included.

Ribs

10–12, low.

Stem

Segmented, not very fleshy, olive-green, very slender, to 2(-4) m long, 1-1.8 cm in diameter, expanded to 2.5(-3.0) cm in diameter below the cephalia. Vascular cylinder very woody.

Radial Spines

(6-)8-10(-12), short (± 3-5 mm long), very fine, flattened against the surface.

Fruits

Globose to obovate, sometimes laterally compressed, smooth, greenish to dull red, olive-brownish or whitish,12-25 cm long and about 12 mm in diameter.

Areoles

Small (± 2 mm in diameter), close set, long hairs present but soon falling.