Echinomastus erectocentrus
Small cylindrical cacti, usually less than a foot tall, with long, dense, reddish or purple spines.
Found in light-colored gravel (felsic volcanics, granite, or limestone) on south-facing desert slopes.
Small white areoles are borne on narrow tubercles that have a central fissure on the upper side.
One or more thicker, darker central spines are surrounded by horizontal radial spines that are white at the base.
TWO VARIETIES have been described, similar in general appearance
but differing in range, elevation, flower color, and in the size, number and arrangement of the central spines on each areole.
Both of these cacti are rare, choosy of habitat, and have very restricted ranges in Arizona.  Also found in Mexico.
E. e. var. acunensis:  Acuna cactus
Bajadas or moderate to steep south-facing slopes in Sonoran desert scrub.
Four known populations in Pinal, Maricopa, and western Pima County.
Each areole has multiple central spines to one inch long.
E. e. var. erectocentrus:  Needlespine Cactus
Flats or gentle south or east facing slopes in Chihuahuan desert upland or semi-desert grassland,
Pima and Cochise County, south and east of Tucson.
Each areole has a single central spine, .5 - .75 inch long.

Federal Threatened and Endangered Species status:
E. e. var. acunensis:  candidate for listing as endangered.
E. e. var. erectocentrus:  USFS Sensitive Species.

HUMAN THREATS:  Development, mining, ORV use, grazing and trampling, possibly collection.
NATURAL THREATS:  Drought (especially var. acunensis), freezing (var. erectocentrus), parasites.

Southern Arizona Botany HOME

Var. erectocentrus

 
 FLOWERS bloom in March and April.  An individual plant blooms over a period of about a week, though each flower only lasts a day.
Var. erectocentrus (LEFT & CENTER) has pale pink or lilac flowers with green centers.
Var. acunensis (RIGHT) has salmon pink flowers with brownish centers (not shown).

 
VERY YOUNG PLANTS have a single inconspicuous ascending central spine.
LEFT:  var. erectocentrus  RIGHT:  var. acunensis

 
VEGETATIVE BUDS are occasionally found on older plants.  Basal buds may grow as large as the main stem,
resulting in a multi-headed plant.  Smaller, round buds grow from the side of the main stem.

 
Var. erectocentrus

 
Var. acunensis growing with the Fire Barrel, Ferocactus cylindraceous (center). BARREL CACTUS PHOTOS

 
RADIAL SPINES grow in a flat circle around the edge of the areole.
CENTRAL SPINES grow from the areole center.  Thicker, longer than radial spines.
TOP  var. erectocentrus:  Radial spines spread below and to the sides of the
central spine.  Single central spine, strongly vertical.  Spines shorter than those of
var. acunensis. Tubercles are separate and distinct, not usually forming ribs.
BOTTOM  var. acunensis:  Radial spines spread below and to the sides of the
central spines, and one or more radial spines may be vertical.
Multiple central spines (usually three) spreading at angles up to 45 degrees
from the radial spines, with the top two nearly vertical.  Spines are half again as long
as those of var. erectocentrus. Tubercles are located on the crests of
moderately distinct ribs, as shown in the photo above.

 
HABITAT:  var. erectocentrus
Here the cactus grows on gentle to moderate east-facing slopes in altered felsic volcanic gravel.
Associated plants include ocotillo, banana yucca, soaptree yucca, Arizona barrel, fairy duster,
Engelmann's prickly pear, desert zinnia, fluffgrass, and whitethorn acacia.

 
HABITAT:  var. acunensis
Here the cactus grows on moderate to steep south-facing slopes between small fractured outcrops.
Associated plants include saguaro, fire barrel, yellow palo verde, ironwood, bursage,
brittlebush, several chollas, and the occasional ocotillo.

 
SIMILAR SPECIES  Drawings show the arrangement of spines on a single areole.
Echinocereus species (Hedgehog Cacti) are taller, usually clustered.
Echinomastus erectocentrus
var. erectocentrus
Needle-Spined Cactus
Rounded cone-shaped,
prickly top, spines pink or purple.
Single vertical central spine.
Flowers white or very pale
pinkish purple, green at base.
Echinocereus pectinatus
Rainbow Cactus
Cylindrical, rounded top,
spines in pink and white bands
around stem.  No central spine.
Flowers bright pink with
 white and yellow center.
Coryphantha vivipara
Beehive Cactus
Round and often multi-headed.
White spines are sparse to dense.
Central spine horizontal, thicker
than the others, brown-tipped.
Flowers pink or lilac.