Echinocactus grusonii
| Light | Bright light to full sun; more colour and denser spines the sunnier it grows |
|---|---|
| Water | Moderately in the growing season; keep dry and cool in winter |
| Soil | Gritty, fast-draining mineral mix (see Soil and potting mix) |
| Temperature | Keep above freezing; hardy to roughly USDA zones 9b–11 |
| Propagation | Seed (primary); offsets from clustered plants |
| Toxicity | Non-toxic to cats and dogs |
Echinocactus grusonii, the golden barrel, is a globe-shaped cactus from central Mexico prized for its rings of brilliant golden-yellow spines and its woolly, felted crown. Sometimes sold as golden ball or, jokingly, mother-in-law's cushion, it is one of the most widely grown ornamental cacti in the world and a fixture of dry gardens and collections alike. It belongs to the genus Echinocactus, the true barrel cacti.
Description
Echinocactus grusonii forms a solid, spherical to broadly barrel-shaped body that becomes more elongated with age, eventually reaching a substantial size in old, well-grown plants. The body is bright green and divided into numerous sharp, regular ribs. Along each rib sit closely spaced areoles bearing stout, straight to slightly curved spines in shades of gold to honey-yellow, with the areoles and the growing crown clothed in soft yellowish wool.
Flowers appear only on mature plants, emerging in a ring around the woolly apex in summer. They are relatively small and yellow, partly hidden in the crown wool, and open in bright sun. Plants may remain solitary for many years, though some eventually cluster to form impressive multi-headed clumps.
Distribution and habitat
The golden barrel is native to a limited area of east-central Mexico, where it grows on rocky volcanic slopes and in ravines. In habitat it is a genuinely rare and threatened plant, its wild range much reduced by collection and by habitat loss, including flooding of parts of its range for a reservoir.
There is a sharp contrast between its status in the wild and in cultivation: like all cacti it is listed under CITES, and wild populations are protected, yet nursery-grown golden barrels are produced in enormous numbers, inexpensive, and entirely legal to own and trade. Garden plants should always be nursery propagated rather than wild collected.
Cultivation
Echinocactus grusonii is an easy and forgiving cactus, which is a large part of its popularity. Grow it in a gritty, very free-draining mix and give it as much sun as you can — strong light keeps the body compact and brings out the golden spine colour, while too little light causes pale, drawn growth. Water moderately through the warm growing season once the soil has dried, then keep the plant dry and cool over winter to prevent rot and to help it toward eventual flowering.
The species tolerates heat well and, once established in the ground in a suitably mild, dry climate, is a striking landscape plant. In pots it is slow but steady; see Watering and Repotting for general technique, and take care when handling, as the spines are stiff and sharp.
Propagation
Seed is the main method of propagation, and the vast majority of plants in the trade are seed grown. The seed germinates readily on a warm, mineral surface kept humid, though seedlings grow slowly and take years to reach a good size. Plants that have formed clusters can also be divided, with offsets removed and rooted; solitary specimens seldom offer this option. See Propagation — seed and Propagation — offsets for full walkthroughs.
Cultivars
Several forms are grown by collectors, including short-spined and near-spineless selections, plants with paler or whiter spines, and variegated forms with irregular yellow or cream patches. Because variegates lack full chlorophyll they are weaker and are often grafted onto a vigorous rootstock and given careful light.
Common problems
- Rot — the usual cause of loss, almost always from overwatering, a slow-draining mix, or cold wet winters; the body softens and discolours from the base.
- Etiolation — too little light makes the plant grow pale, narrow and elongated, spoiling the tight globular shape and dulling the spine colour.
- Pests — mealybugs (white fluff in the crown wool and among the spines) and red spider mites are the most common; the dense wool can hide infestations, so inspect the crown regularly. See Pests and diseases.
See also
- Echinocactus — the genus overview
- Grafting · Soil and potting mix · Watering · Repotting · Propagation — seed · Propagation — offsets