Origin and Habitat: USA, (Southern California in the Coastal San Diego County), Mexico (northern Baja California)
Altitude: From sea level to 200 metres.
Habitat: It can be found on sand and gravel in arid hills near rocky coastal bluffs, coastal chaparral, shrub hillsides, 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. Ferocactus viridescensSN|21503]]SN|13617]] has a much less pubescence and protective spine cover of the apex than Ferocactus acanthodesSN|10113]]SN|10113]], Ferorocactus wislizenii, and Ferocactus covilleiSN|13617]]SN|21503]] is and less tolerant to low temperatures.

• Ferocactus viridescens (Torr. & A.Gray) Britton & Rose
• Echinocactus viridescens Torr. & A.Gray
• Melocactus viridescens (Torr. & A.Gray) Nutt. ex Teschem.

• Ferocactus viridescens (Torr. & A.Gray) Britton & Rose
• Echinocactus viridescens Torr. & A.Gray
• Melocactus viridescens (Torr. & A.Gray) Nutt. ex Teschem.
• Ferocactus viridescens subs. orcuttii (Engelm. ex Orcutt) F.Wolf & R.Wolf
• Echinocactus orcuttii Engelm. ex Orcutt
• Ferocactus orcuttii Britton & Rose
• Ferocactus viridescens var. orcuttii (Engelm. ex Orcutt) G.Unger

• Ferocactus viridescens subs. littoralis (G.E.Linds.) F.Wolf & R.Wolf
• Ferocactus viridescens var. littoralis G.E.Linds.

Description: Ferocactus viridescensSN|13617]]SN|13617]] is a solitary barrel cactus, sometimes wider than tall.
Stems: Pale to deep green, somewhat glossy, erect, mostly depressed-globose or globose (to short cylindric), with little apical pubescence, usually 10-30(-45)cm tall and 10-20(-35) cm in diameter.
Roots: Fibrous root system.
Ribs:: 13-21, 1-2 cm tall somewhat rounded, obtuse, undulate shallowly notched immediately above each areole.
Areoles: Narrow elliptic to oval 10-20 mm long with brownish tomentum, spine-bearing in the lower part, felted in upper part, flower-bearing and also with several reddish glands, these becoming elongated and spinescent in age.
Spines: 10-19 per areole, central spines and larger radial spines pink or yellowish, becoming duller by age or turning yellow or horn-coloured, smallest spines per areole slender, sometimes bristle-like, less than 1 mm diam. (rarely absent).
Central spines: 4 per areole forming a cross, spreading at about 45° angles, the lower one stronger and more flattened, narrowly elliptic in cross section, straight or slightly curved, conspicuously annulate, principal central spine 30-50 cm long and 2-3(-5) mm broad. As younger plant does have colourful spines.
Radial spines: 10-20 per areole, similar to the centrals but smaller 1-2 cm long, spreading irregularly, stiff and straight.
Flowers: Infundibuliform 2,5-5 long 3-6 cm on diameter, colour similar inside and out. Perianth-segments oblong, obtuse, sometimes apiculate, more or less serrulate on the margins, greenish yellow or greenish with some pink, sometimes with reddish brown midstripes; flower-tube bearing stamens almost to the top of the ovary; scales on the ovary orbicular, imbricate. Stigma lobes yellow.
Fruits: Barrel-like, bright yellow (very rarely reddish) with a pleasant acid taste, 20-35 long and 15-25 mm across, fleshy, skin leathery with about 30 fimbriate-denticulate scales. Dehiscent through basal pore.
Blooming season: Spring-early summer.
Seeds: Conspicuously bur minutely reticulate, elongate-obovoid 1,6-1,8 mm long, hylum basal but oblique.

Notes: Ferocactus viridescensSN|10102]]SN|13617]]: stems are much shorter than those of Ferocactus cylindraceus but the taxonomic distinctions between the two species are muddled. In California, Ferocactus viridescensSN|10102]]SN|13617]] and Ferocactus cylindraceusSN|13617]]SN|10102]] are allopatric. In the absence of geographic data, the largest plants of Ferocactus viridescens might not always be distinguishable from straight-spined mature plants of Ferocactus cylindraceusSN|13617]]SN|10102]]. Immature plants of Ferocacactus cylindraceus have mostly or entirely hooked spines but gradually switch to producing straighter spines in old age.

Bibliography: Major references and further lectures
1) Edward Anderson “The Cactus family” Timber Press, Incorporated, 2001
2) James Cullen, Sabina G. Knees, H. Suzanne Cubey "The European Garden Flora Flowering Plants: A Manual for the Identification of Plants Cultivated in Europe, Both Out-of-Doors and Under Glass" Cambridge University Press, 11/Aug/2011
3) David R Hunt; Nigel P Taylor; Graham Charles; International Cactaceae Systematics Group. "The New Cactus Lexicon" dh books, 2006
4) Park S. Nobel "Environmental Biology of Agaves and Cacti" Cambridge University Press, 16/ott/2003
5) Lyman D. Benson "The Native Cacti of California" Stanford University Press, 01/set/1988
6) Nathaniel Lord Britton, Joseph Nelson Rose “The Cactaceae: Descriptions and Illustrations of Plants of the Cactus Family” Volume 3, 1922

Cultivation and Propagation: Ferocactus viridescensSN|13617]]SN|13617]] are winter-growing plant, but adapts well in cultivation to a cool winter resting regime, and quite easy plants thought slow to start. They are suited for any rich, well drained soil such us clay, pumice, lava grit, and only a little peat or leaf-mould. If potted, repot them preferably in the spring, if their roots become cramped. Generally, they should be repotted every other year in order to provide fresh soil. However, this doesn't necessarily mean they'll need larger containers. Fill about a quarter of the pot with broken crocks, gravel, etc. to promote good drainage. After repotting, do not water for a week or more. Water regularly during the aestival growth cycle (this plant need plenty of water, but do not overwater and let their soil dry out between waterings), and also needs to be avoided wetting the body of this plant while it is in sunlight. A wet cactus in the sun light can cause sun burning which can lead to scars or even fungal infections and death, keep rather dry in winter. No water should ever be allowed to stand around the roots. Feed with a high potassium fertilizer in summer.
Exposure: Outside they need a bright exposure, full sun or half shade in summer if the location is exceedingly hot or bright, inside needs bright light, and some direct sun. It can tolerate moderate shade, and a plant that has been growing in shade should be slowly hardened off before placing it in full sun as the plant will be severely scorched if moved too suddenly from shade into sun.
Frost Tolerance: Light frost protection required for safe cultivation, but can tolerate sporadic light frost. This plants need a period of cool rest in winter to produce flowers abundantly.
Diseases and pests: Watch for infestations of mealybug, scale insects and spider mite.
Plant in good conditions will start to bloom when reach the diameter of only 12-14 cm.
Propagation: Seeds are the only way of reproducing. Seed Collecting: Permit fruit to ripen. Fruit must be significantly overripe before harvesting seed; clean and dry seeds.