Xerophyte

Central Spines

0 to 4, longer and stouter somewhat angular in cross-section, the main one often flattened, up to 7.5 cm long; usually yellowish or whitish, but sometimes reddish or blackish.

Description

Echinocereus roemeri is a densely caespitose cactus specie, often growing in large colonies up to 1 m in diameter, containing sometimes 200 or more simple stems. Echinocereus roemeri is a cactus with both hermaphroditic (bisexual) and dioecious (male and female) forms of flowers on different plants. Male flower shows pollen-filled anthers surrounding the base of the stigma lobes, while functional female flowers from different plants show reduced filaments and empty anther sacs held below the stigma lobes.

Flowers

Borne below the stems apex, oftem unisexual (plants dioecious) broad Infundibuliform, orange-red, crimson or (rarely) pinkish, 3-10 cm long, up to 8 cm in diameter, perianth-segment obtuse or retuse, stigma with 7 or 8 lobes, usually greenish, areoles on flower, and ovary felted, bearing short white bristly spines.

Blooming Season

Spring. The blooming period of large plants can extend over a period of weeks, with each bloom remaining open for several days and nights. The flowers appear specialized for hummingbirds, but are also pollinated by bees. They are huge and highly rewarding, and daily nectar production averaged 30 mg sugar/flower. This set of traits represents a syndrome rare among hummingbird flowers, in which the flower fits the head rather than just the bill, and birds are well rewarded for a risky or inconvenient visit.

Spines

Acicular, mostly undifferentiated between radials and centrals;

Ribs

8 to 11 somewhat tuberculed.

Stem

Dark green, ovoid to cylindrical, 20-40 cm tall, 3 to 5 in diameter .

Radial Spines

(5-)8-12(-20) round in cross-section, 1-2 cm long, usually whitish.

Fruits

Globose, becoming red, with spines falling away.