The mother-in-law’s seat or mother-in-law’s cushion cactus (Echinocactus grusonii) received its common name as a kind of wry joke, although who first came up with it is unknown. The idea is that if you don’t want your mother-in-law to hang around and make your life miserable, then this short, round cactus with sharp spines is the perfect seat for her. If she has to sit on the cactus seat, she'll make her visit short. The plant's main common name is golden barrel cactus.
The heavily ribbed mother-in-law's seat cactus grows slowly into a barrel shape that can be more than 3 feet tall and 3 feet wide. Its barrel-like stem is pale green, but the plant received the "golden" part of its "golden barrel" name for its numerous yellow spines that light up in sunlight. A mature specimen grown in full sun yields vivid-yellow flowers in a circle on its top. The flowers are from 3 1/3 to 4 1/3 inches wide and close at night, and they may be covered by the cream-colored wool on the cactus' top. The cactus is considered to gain beauty as it ages.
Mother-in-law's seat cactus is native to the Rio Moctezuma Valley in central Mexico. Although it is becoming endangered in the wild, it is one of the most widely cultivated cactus species. It is hardy outdoors in U.S. Department of Agriculture plant hardiness zones 9 through 12.
Indoor and Outdoor Culture
If you grow a mother-in-law's seat cactus in a pot, fill the bottom one-fourth of the pot with gravel or broken crockery to promote drainage. Fill the rest of the pot with lava grit, clay or pumice combined with leaf mold or peat. The cactus should be repotted annually to give it fresh soil, but you don’t have to increase its pot size. When grown outside, it can be in partial shade, full sun or other bright exposure. If you grow it in shade, let it adjust slowly to light before moving it into full sun. If you grow it indoors, give it bright light and some direct sunlight. A mother-in-law's seat cactus needs plenty of water during its summer growth cycle, but don’t overwater it or let water sit over its roots. The soil should be allowed to dry between watering sessions. The cactus' fat stem can burn or become susceptible to fungal infections if gets wet when it’s in sunlight.
While still small, a mother-in-law's seat cactus is available at many plant nurseries, but you can grow one or more of them from seed. The plant yields ripe seedpods several months after its flowers die. Scrape the tiny, mahogany or reddish amber seeds with a knife, soak them in water overnight and place them in a germination tray containing peat moss, vermiculite and coarse sand. Cover the tray with glass, keep the soil moist and the seeds should germinate in two to six weeks.
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