Sometimes referred to as F. orcuttii , this  barrel cactus blooms when still of relatively small size.
 

Description:  Solitary, sometimes wider than tall.
Stems: Pale green Erect, oblate to spheric (to short cylindric), usually 10-30(-45)cm tall × 10-20(-35) cm in diameter;
Ribs: 13-21[-34], 2 cm tall shallowly notched immediately above each areole.
Areoles: Oval 10x 15mm with brownish tomentum.
Spines: 10-19 per areole, central spines and larger radial spines pink or yellowish, turning gray as they age, smallest spines per areole slender, sometimes bristlelike, less than 1 mm diam. (rarely absent); central spines 4 per areole, the lower one stronger, straight or slightly curved, annulate, thin and flattened, narrowly elliptic in cross section, principal central spine 30-50 × 2-3(-5) mm. As younger plant does have colourful spines.
Flowers: Infundibuliform 2.5-5 × 3-6 cm, color similar inside and out; inner tepals greenish yellow, sometimes with reddish brown midstripes; stigma lobes yellow.
Fruits: Dehiscent through basal pore, bright yellow (very rarely reddish), 20-35 × 15-25 mm, leathery or fleshy
Blooming season: pring-early summer.
 

The 'viridescens' variety has 13-25 tuberculate ribs and 15-25 spines per areole.
The 'littoralis' variety has 21-34 ribs that aren't tuberculate. It has 21-34 spines per areole. It is indigenous only along the west coast of Baja california down to Mission Santo Domingo.

Taxonomic notes: Ferocactus viridescens var. viridescens stems are much shorter than those of F. cylindraceus but the taxonomic distinctions between the two species are muddled. In California, Ferocactus viridescens and F. cylindraceus are allopatric. In the absence of geographic data, the largest plants of F. viridescens might not always be distinguishable from straight-spined mature plants of F. cylindraceus. Immature plants of F. cylindraceus have mostly or entirely hooked spines but gradually switch to producing straighter spines in old age.

Scientific name: Ferocactus viridiscesns (Torrey & A. Gray) Britton & Rose var. viridescens
 

• Echinocactus viridiscens
• Echinocactus orcutti Britton et Rose 1913
• Ferocactus orcuttii
• Ferocactus viridescens var. orcuttii

Origin:  USA, (Southern California in the Coastal San Diego County), Mexico (northern Baja California)

Habitat:  It can be found in rocky coastal bluffs, coastal chaparral; shrub hillsides 0-200 m; often at the crest of slopes and growing in cobbles. It occasionally is found on the periphery of vernal pools, sometimes in considerable numbers. This presumably more mesic habitat is unlike the very xeric situations where it is typically found. This barrel cactus utilizes a number of other soil types such as rocky silt loams and Redding gravelly loams.

Conservation status: Listed in CITES appendix 2.

Flower is usually yellow or yellowish-greenish and is 4cm in diameter.

Cultivation: Prefers full sun,  Will take some frost.

Propagation: Seeds are the only way of reproducing.