Glasshouse plants

Echinocactus grusonii
Golden barrel cactus

This plant originates from Mexico.

Its body is green, globose and usually solitary, but sometimes producing offsetts with maturity, or after damage to the growing point. It grows up to 80cm (32in) in diameter. It is covered in concertina-like ribs, about five on young plants, up to 40 or more on mature plants. The ribs are covered by groups of about 12 golden yellow spines that are up to 5cm (2in) long, each group coming from a tuft of wool (areole). Yellow flowers are produced from the tops of the bodies, but only on very mature plants. It is therefore grown for its body form rather than its flowering potential.

There are a few cultivars; forms with white spines and also almost-spineless forms are available, but the original wild form is arguably the most attractive.

Like most succulent plants and cacti, this should be grown in conditions of bright light and a dry atmosphere. It should be watered from March through to early October, but kept dry during winter when growth ceases; allow the compost to almost dry between watering. A high-potassium liquid feed can be applied at about every third watering.

The winter temperature should be greater than 5ºC (41ºF) to prevent the stem becoming marked, but lower temperatures are tolerated if the humidity is kept very low.

Pot on into a larger pot in spring when the stem diameter equals that of the original pot. Carefully remove some of the old soil and then fill pot with a 2:1 mixture of John Innes Compost No 2 or 3 and coarse grit. Young plants will need to be repotted every year, older plants less frequently. Growth will be quicker if plants can be grown in a greenhouse bed. Propagation is exclusively from seed which is readily available and should be sown in spring at a temperature of 20-25ºC (68-77ºF).

The genus Echinocactus, as presently recognised, contains only six species of which E. grusonii is undoubtedly the most popular and most easily grown. There are hundreds of thousands of plants in gardens, houses and greenhouses around the world, nearly all of which have been raised from seed produced in cultivation. It is actually considered to be a very rare plant in the wild in Mexico and its best-known site has been decimated in the last few years by a dam project. Fortunately, recent explorations have revealed a disjunct colony growing 500km away from the original inundated one.

Terry Smale

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