Escobaria
Escobaria is a genus of small, globular to clustering cacti native to North America, easily recognised by the lengthwise groove running along the upper side of each tubercle. The genus is closely allied to Coryphantha, and recent taxonomic work has variously merged many of its species into Coryphantha or into Pelecyphora — so a plant sold as an Escobaria today may well carry a different name tomorrow. Despite the shifting labels, these are charming, cold-hardy little cacti that reward the patient grower.
Description
Escobaria species are small plants, ranging from solitary golf-ball-sized globes to dense mounding clumps of many heads. In place of true ribs, the body is covered in spirally arranged tubercles — finger-like projections tipped with a spiny areole. The defining feature of the genus is a narrow groove that runs along the upper surface of each mature tubercle, from the spine-bearing tip toward the growing point; the flowers arise from this groove rather than from the tubercle tip. This grooved-tubercle arrangement is what links Escobaria so closely to Coryphantha, and it separates the genus from the ungrooved Mammillaria, with which small specimens are easily confused.
Spination is typically dense, with numerous fine radial spines that often obscure the body, and sometimes stouter central spines. Flowers are small to medium, borne near the crown, and range through white, cream, pink, and purplish-magenta depending on species; they are followed by small fleshy fruits that are frequently green or reddish.
Distribution
The genus is centred on the deserts, grasslands, and montane regions of North America, spanning the southwestern and central United States and much of northern and central Mexico. A few species extend surprisingly far north — into the Great Plains and even up toward Canada — making the genus one of the more cold-tolerant groups in the cactus family. Plants typically grow in gritty, well-drained soils on rocky slopes, limestone outcrops, and open grassland, often nestled among rocks or low vegetation that offers a little shelter.
Notable species
- Escobaria vivipara — the widespread "spinystar" or "beehive cactus", ranging across a huge swath of North America and among the hardiest of all cacti.
- Escobaria sneedii — a small, densely white-spined clustering species from the Chihuahuan Desert borderlands, of conservation concern in the wild.
- Escobaria missouriensis — the "Missouri foxtail cactus", a low, cold-hardy plant of the Great Plains.
- Escobaria orcuttii — a clustering species from the southwestern deserts.
- Escobaria tuberculosa — the "cob cactus", named for the corky, cob-like appearance of its old lower stem.
Cultivation
As a group, Escobaria are undemanding but intolerant of wet, stagnant conditions. Grow them in a very free-draining, mostly mineral mix in a snug pot, in bright light — most species relish full sun, which keeps the plants compact and encourages flowering. Water thoroughly when the mix has dried out during the growing season, then let it dry again; keep plants cool and completely dry through winter.
That dry winter rest is especially important because many Escobaria are genuinely cold-hardy and, when kept bone-dry, will tolerate hard frost — some of the northern species survive outdoors in continental climates. The enemy is almost always moisture around the roots and lower stem in cold weather rather than cold itself. See Watering and Repotting for general technique.
Propagation
Clustering species are readily increased by removing rooted offsets from the clump. Solitary and slow-clumping species, and any effort to raise plants in quantity, are best grown from seed, which germinates well on a warm mineral surface. See also Propagation — cuttings for general vegetative technique.
Taxonomy and hobby notes
Escobaria has long been a taxonomically unsettled genus. It sits within the broader Coryphantha alliance, and different authorities have treated its species as belonging to Escobaria, to Coryphantha, or — in recent molecular treatments — to an enlarged Pelecyphora. Several segregate names now treated as synonyms, including Neobesseya and Cochiseia, reflect earlier attempts to split the group. For the collector this mostly means that the same plant may appear under several names on labels and in seed lists; the grooved-tubercle plants themselves are consistent even when the names are not.
Escobarias are prized by growers of small, hardy cacti and by rock-garden and alpine-house enthusiasts, who value the cold tolerance of the northern species. A number of species are rare or restricted in the wild and are protected; as with all cacti, plants should be nursery-propagated rather than wild-collected.
See also
- Coryphantha — the closely related grooved-tubercle genus
- Pelecyphora · Mammillaria
- Soil and potting mix · Watering · Propagation — seed · Propagation — offsets