Ferocactus glaucescens
| Light | Full sun to bright light; needs strong light for tight, colourful spination |
|---|---|
| Water | Moderate in the growing season; allow to dry between waterings, dry rest in winter |
| Soil | Gritty, fast-draining mineral mix (see Soil and potting mix) |
| Temperature | Keep above freezing; hardy to roughly USDA zone 9 if kept dry |
| Propagation | Seed (primary); offsets on clustering plants |
| Toxicity | Non-toxic to cats and dogs |
Ferocactus glaucescens is a striking barrel cactus from the limestone hills of east-central Mexico, prized for its pale blue-green, waxy (glaucous) body set off by neat, golden-yellow spines. Mature plants carry clear lemon-yellow flowers in a ring around the crown, and a much sought-after spineless form (inermis) is also grown. The powdery blue skin gives it the common name blue barrel cactus.
Description
Ferocactus glaucescens forms a solid, rounded to shortly cylindrical body that is usually solitary when young but may cluster with age, sometimes building up broad mounds in old plants. The most distinctive feature is the skin colour: a chalky, pale blue-green coated in a fine glaucous bloom that can be rubbed off like the wax on a plum. The body is divided into numerous prominent ribs, and along the rib edges sit evenly spaced areoles bearing several stiff, straight to slightly curved spines. These are a warm golden yellow in good light and fade to greyish tones on plants grown too shaded.
Flowers appear in a neat circle around the woolly crown, mostly in late spring and summer. They are cup-shaped and a clear, bright yellow, opening over sunny days and followed by small whitish fruits. The overall effect — blue body, gold spines, yellow flowers — makes it one of the more colourful barrel cacti in cultivation.
Distribution and habitat
The species is native to east-central Mexico, where it is most common in the state of Hidalgo but also occurs in neighbouring Querétaro, Guanajuato and San Luis Potosí. It grows on limestone slopes and rocky outcrops in semi-arid scrub and dry forest, over a wide range of elevations. In habitat it roots into gritty, alkaline, sharply drained ground and endures strong sun, seasonal summer rain and a long dry period. As with all cacti it is listed under CITES Appendix II, but nursery-raised plants are widely available, inexpensive and entirely legal to own and trade.
Cultivation
Ferocactus glaucescens is one of the more forgiving barrel cacti and a good choice for a grower moving on from beginner species, though like all barrels it resents cold, wet roots. Grow it in a very free-draining, mostly mineral mix, ideally with some added limestone grit to suit its alkaline habitat, and give it the brightest position you can — strong light is what keeps the spines gold and the body compact.
Water thoroughly through the warm months once the soil has dried, then ease off sharply as autumn arrives and keep the plant completely dry and cool over winter. A dry winter rest both prevents rot and encourages the following season's flowers. It is slow but steady, and a well-grown plant will thicken into a handsome specimen over the years. See Watering and Repotting for general technique.
Propagation
Seed is the usual and most reliable method. The seed germinates readily on a warm, gritty surface kept humid until the seedlings establish; see Propagation — seed for a full walkthrough. Clustering plants can also be increased by removing rooted offsets — allow any cut surface to callus before potting into a dry mineral mix (see Propagation — offsets). The spineless inermis form comes largely true from seed and is propagated the same way.
Cultivars
The best-known selection is the spineless form, often sold as F. glaucescens f. inermis. It has the same blue glaucous body and yellow flowers but produces few or no spines, leaving smooth ribs and bare, felted areoles — a look many collectors covet. Occasional crested and monstrose plants also turn up in specialist collections.
Common problems
- Rot — almost always from overwatering or a slow-draining mix, especially in a cold winter; the body softens and discolours from the base.
- Dull, weak spines — too little light causes pale, sparse spination and a loss of the compact shape; move the plant to a sunnier spot.
- Marked bloom — the glaucous coating is easily rubbed off by handling, leaving fingerprints or scars that do not fully recover; handle by the pot where possible.
- Pests — mealybugs (white fluff in the areoles and around the roots) and red spider mites are the usual offenders; see Pests and diseases.
See also
- Ferocactus — the genus overview
- Soil and potting mix · Watering · Repotting · Propagation — seed · Propagation — offsets