Euphorbia ritchiei aka Medusa's Head Cactus

Euphorbia ritchiei is a succulent subshrub native to Kenya. It belongs to the spurge family, Euphorbiaceae. An older name is Monadenium ritchiei. Its native range lies in eastern Africa's dry country. Kew places it in desert or dry shrubland. LLIFLE records it near Isiolo in Kenya's Meru District. There, it grows on steep slopes strewn with stones. Its habitat receives some summer water but none in winter.

This perennial has an upright shape in garden records. It spreads through underground shoots and forms clumps over time. A broad pot gives those shoots room to grow. Growing it under conditions close to its habitat helps maintain compact growth. Its leaves can drop when the light level changes. Dry conditions can also cause it to shed leaves. This leaf loss alone need not mean something is wrong. Chicago Botanic Garden lists it as a specimen plant. It records pink flowers from September through October.

Light shade suits this species, though it can also take sun. Chicago Botanic Garden lists partial shade as its preferred exposure. Plants grown in shade need a slow move into sun. An abrupt change can badly scorch them. Use a loose potting mix that lets water drain freely. LLIFLE recommends mostly mineral material, with little organic matter. Suggested ingredients include pumice, lava grit, and clay. The species accepts a range of soils, but drainage remains essential.

Water sparingly from March through September, according to LLIFLE. Keep the plant almost dry during the winter months. Do not leave water standing around its roots. Long wet spells can cause rot, most of all in winter. Good watering and airflow help reduce this risk. The plant cannot withstand freezing temperatures. LLIFLE reports that it can cope with about 45°F (7°C). Chicago Botanic Garden lists USDA hardiness zones 10–11.

Seeds and cuttings both offer ways to raise new plants. Let a removed offset dry for several days before planting. This gives the cut surface time to heal. Planting fresh cuts too soon can lead to rot. Set the stem end partly into the growing mix. Keep the cutting upright as roots begin to grow. LLIFLE advises repotting every two years, in late winter or early spring.