Research and Conservation in Southern Sonora, Mexico

Ferocactus emoryi ssp. emoryi (Emory barrel cactus, biznaga)

The southern members of this species are massive, barrel-shaped plants to well over six feet tall and two feet in diameter. This species has only stout spines and none of the bristles common to most other Ferocactus species. These spines are short, slightly curved, and yellowish. The pure yellow flowers are borne in July.

This form occurs from about Guaymas south to *********************** in Central Gulf Coast Sonoran Desert and Coastal Thornscrub.

Ferocactus emoryi near the coast south of Guaymas, Sonora. Note the 16-inch butcher knife. Photo: Mark Dimmitt

Ferocactus emoryi flowers

Ferocactus emoryi ssp. covillei (Britton & Rose) Hunt & Dimmitt
(Coville barrel cactus, biznaga)
syn. F. covillei

From about Guaymas north to southern Arizona, the plants originally described as F. covillei are very different from the more southerly F. emoryi. Juvenile plants are strongly tuberculate rather than ribbed. Mature plants are usually less than six feet tall and are more slender, cylindrical instead of barrel-shaped. The spines are heavier, longer, reddish in color, and the central is strongly curved at the tip. Lastly, the flowers are pure red. Flowers in July unless the summer rains are late. The range of this subspecies barely reaches southern Sonora.

Ferocactus emoryi ssp. covillei from Ajo, AZ. The flower on the right is being visited by a cactus bee. Photos: Mark Dimmitt

Obvious intermediates between the two subspecies are common only along a narrow zone of contact. Near highway Mex 15 this zone is north of Guaymas, in the Sierra Libre at Cerro Las Avispas. Here most plants are more like the F. covillei form in size and shape, the spines are intermediate in size and shape, and the flowers range from yellow through shades of orange to red.

Ferocacus emoryi-covillei intermediate on Cerro Las Avispas, Sierra Libre, Sonora. This plant is fairly stout like the southern form, the spines are intermediate, and the flowers are orange. Photos: Mark Dimmitt
This remarkable plant was found flowering in July on Cerro Las Avispas. At first one might assume that the flowers open one color and age to the other (the flowers last two to three days). But the two red flowers on the left side of the plant are young (upper) and old; the same is true of the two yellow flowers (older one is upper). Perhaps this plant is a somatic chimera with the right half of the plant in the image always producing yellow flowers and the left producing red. Photos: Mark Dimmitt

Reference: Hunt, David, & Mark Dimmitt. Entry 14356, Ferocactus emoryi ssp. covillei (Britton & Rose) Hunt & Dimmitt. in Hunt, David. 2005. Cactaceae Systematics Initiatives: Bulletin of the International Cactaceae Systematics Group 20:16. Edited & Published by David Hunt.Sherborne, England. [Basionym omitted in this publication; error corrected in issue 21:11.]

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