This is the tiniest Echinocereus species (only 1 to 2 cm wide!)  plants are extremely diminutive and mostly  subterranean (geophytes),  usually do not  offset. Blooms very early in March. The flowers are greenish and diffuse a pleasant lemony scent.

Family: Cactaceae (Cactus Family)

Scientific Name: Echinocereus davisii A.D. Houghton 1931
Published in: Cact. & Succ. J (U.S.) 2: 466(1931)

Distribution:  The single known population occurs in west Texas, (Brewster Co., Marathon)

Habitat: Grows in flat hills on a specific substrate (rich in quartz sand) in a semi-desert grassland at an elevation of 1,200 m Sometimes plants in drought periods shrink well below ground level.

 Synonyms:  

• Echinocereus viridiflorus var. davisii (A. D. Houghton) W. T. Marshall in Marshall & Bock. Cactaceae: 119 (1941); a
• E. viridiflorus fa. davisii (A. D. Houghton) Krainz,
  In:  Kat. ZSS, 2^a ed.: 51 (1967); b
• E. chloranthus var. davisii (A. D. Houghton) Cullmann
  In Kakteen: 156, fig. 154 (1984) nomen invalidum (CINB, art. 33.2); c
• E. viridiflorus ssp. davisii (A. D. Houghton) N. P. Taylor
  In Hunt. Cact.Cons. Init. 3: 10 (1997).

E. davisii SB 426 Locality: Brewster County, Texas, USA
Blooms very early in March. The flowers are greenish and diffuse a pleasant lemony scent.

Description: This is the tiniest Echinocereus species, plants are extremely diminutive and mostly subterranean (geophytes),  usually do not offset.
Stem: Spherical stems  with 6-9 ribs, dark green epidermis up to 1-2cm in high and1-3 cm in diameter (but cultivated specimens can grow bigger).
Spines: The areoles contain 8-14 spines, usually radial, white whit a dark contrasting tip. 10-20 mm long.
Roots: Fibrous in young plant became tuberous in age.
Flower: Yellow-green whit a green stigma and yellow pollen, up to 2 cm across, (buds acute, reddish and yellow-greenish).
Phenology: Blossoming and fruiting occur on 3 to 4 year-old plants. Blooming period in cultivation is March-April.

New spines

it starts flowering when less than 1 cm in diamete

Cultivation: In culture E. davisii is without problems but very slow growing and regularly shows its small green flowers if we provide an adequate winter rest period. It is sensitive to overwatering (rot prone) needs good drainage, Keep drier and cool in winter. Need full sun; Very cold resistant hardy to -18° C or less for short periods of time.

Propagation: Seeds.

It is the tiniest of all the echinocereus

A seven years old specimen

NOTE: E. davisii is part of the E. viridiflorus compless that comprises a large number of infraspecific taxa, differing in various combinations of flower color, spine color, number and thickness of central spines, and other characters, including floral scent. Wherever such taxa are sympatric they intergrade; all are freely interfertile in the greenhouse. Among them:

• E. viridiflorus var. viridiflorus: (Typical form)With small stems and relatively pure yellow flowers, extends from central New Mexico and the Texas Panhandle to South Dakota.
• E. viridiflorus var. chloranthus (E. chloranthus) with the most numerous central spines (five or more per areole), giving the plants a bristly appearance, are often considered a separate species.
• E. viridiflorus var. russanthus (E. russanthus) : Plants with a bristly appearance usually with reddish or russet flowers. Yellow-spined plants may occur at high altitudes.
• E. viridiflorus var. cylindricus (E. chloranthus var. Cylindricus) : The common morphotype at middle altitudes in Texas and southeastern New Mexico has 0-2(-3) central spines.
• E. viridiflorus var. correllii  (E. chloranthus var. Cylindricus "corellii") A poorly defined, yellow-spined population near Marathon, Texas.
• E. viridiflorus var. neocapillus (E. chloranthus var. neocapillus): Remarkable for its softly hairy, not sharply spiny, seedlings.
• E. chloranthus subsp. rhyolithensis Bristly red-spined plants from New Mexico.

E. viridiflorus in the broad sense may prove paraphyletic with respect to E. davisii, but they are phenologically isolated, with E. davisii flowering earlier and thus appearing reproductively isolated in the wild. Controversy among botanists as to whether davisii is a species or variety of E. viridiflorus.