Mammillaria longimamma
| Light | Bright light with some protection from the harshest afternoon sun |
|---|---|
| Water | Moderate in the growing season; keep dry and cool in winter |
| Soil | Fast-draining mineral mix (see Soil and potting mix) |
| Temperature | Keep above freezing; roughly USDA zones 9b–11 |
| Propagation | Seed; occasional offsets; detached tubercles can sometimes be rooted |
| Toxicity | Non-toxic to cats and dogs |
Mammillaria longimamma is a small clumping cactus from central Mexico, easily recognised by its unusually long, soft, finger-like tubercles and its large, bright-yellow flowers. Because those elongated tubercles set it apart from most of its relatives, the species was long placed in the segregate genus Dolichothele before being folded back into the broad genus Mammillaria.
Description
Mammillaria longimamma forms a low, rounded plant that slowly offsets into a small cluster. Its most distinctive feature is the tubercles — soft, cylindrical and finger-like, far longer than those of a typical Mammillaria, giving the plant a loose, knobbly outline rather than a tightly packed one. Each tubercle is tipped with an areole bearing a few slender, radiating spines and, usually, one longer central spine; the spination is sparse and does not obscure the green body.
The flowers are large for the size of the plant — bright, glossy yellow and funnel-shaped, opening near the growing tips in late spring and summer. They are among the showiest in the genus relative to plant size, which is a large part of the species' popularity. Small clubbed fruits and seed may follow flowering.
Distribution and habitat
The species is native to central Mexico, where it grows in rocky and grassy ground, often nestled among stones or low vegetation that give it partial shade. As with many small Mexican cacti it tends to grow in gritty, sharply drained substrates and pulls back into the soil during prolonged drought.
Cultivation
Mammillaria longimamma is an accommodating and rewarding plant, well suited to beginners. Grow it in a very free-draining, mostly mineral mix in bright light, with a little shade from the fiercest afternoon sun to keep the tubercles firm and green. It is a touch thirstier than many desert cacti during active growth, thanks to its soft, water-storing tubercles, so water thoroughly once the soil has dried and then allow it to dry again. Reduce watering sharply in autumn and keep the plant dry and cool through winter — this rest both prevents rot and encourages the following season's flowers. See Watering and Repotting for general technique.
The main risk is overwatering, especially in a heavy mix or during cold weather, which causes the fleshy tubercles to soften and rot.
Propagation
Seed is a reliable method and gives large numbers of plants; sow on a warm, mineral surface kept humid until germination, then grow on. The plant also offsets, so clumps can be divided and the pups rooted as offsets once any cut surface has callused. Growers sometimes detach a plump tubercle and root it much like a cutting, though this is less dependable than seed or offsets. See Propagation — seed and Propagation — cuttings for detail.
Common problems
- Rot — the usual cause of loss, from overwatering, a slow-draining mix, or moisture during the cold winter rest; tubercles soften and discolour from the base.
- Shrivelled, floppy tubercles — often just underwatering during growth, but check the roots, as the same look can follow root loss from rot.
- Etiolation — too little light stretches the plant and makes the tubercles pale, weak and elongated even by this species' standards.
- Pests — mealybugs (white fluff in the areoles and among the tubercles) and red spider mites are the usual offenders; see Pests and diseases.
See also
- Mammillaria — the genus overview
- Soil and potting mix · Watering · Propagation — seed · Propagation — offsets · Repotting