Mammillaria elongata 'Cristata'
Mammillaria elongata 'Cristata — widely sold as the brain cactus — is a crested (fasciated) form of the ladyfinger cactus, Mammillaria elongata. Instead of the tidy, finger-like stems of the parent species, its single growing point stretches into a line, and the stem builds up as a meandering, ridged mass that folds back on itself in undulating, brain-like or coral-like convolutions.
Description
The crest arises from a growth aberration called fasciation, in which the normal single growing point of a stem elongates into a line. Rather than adding stem length in one direction, the plant grows along an expanding front, and the result is a dense, wavy fan of tissue packed with the small spiralled tubercles typical of Mammillaria. In this cultivar those tubercles carry the same soft, comb-like radial spines as M. elongata — usually golden to pale yellow, sometimes tan or reddish — laid neatly along every ridge so the whole plant takes on a woven, textured look.
Over time a single crest widens and heaps up into a mounded cushion, and the folded ridges deepen into the characteristic "brain" surface. Small cream to pale-yellow flowers can appear along the crest in spring, though the cultivar is grown far more for its sculptural form than for bloom. Fasciated plants are not fully stable: a crest will sometimes throw a normal, finger-like stem, which many growers remove to keep the crested habit dominant.
Cultivation
Care follows the parent species — see Mammillaria elongata for the full picture. In brief, grow it in a fast-draining, mostly mineral mix, water thoroughly only once the soil has dried out, and keep it dry and cool through winter. It is an easy, forgiving plant and a good choice for beginners.
A few points are specific to the crested form:
- Light. Bright light keeps the crest compact and the spination dense; in too little light the ridges grow soft, stretched and pale. A little shade from the fiercest afternoon sun helps prevent scorching on the exposed crest tissue.
- Watering and rot. The heaped, convoluted surface traps moisture and dries slowly, so the crest is more prone to rot than an ordinary stem. Water at the base rather than over the top, give it good air movement, and err on the dry side. See Watering.
- Shape. Remove any reverted, normal-growth stems promptly if you want to preserve the crested form.
Unlike variegated or chlorophyll-poor crests, this one grows on its own roots perfectly well and is only occasionally grafted — usually just to speed up a small piece or rescue a rotting crest.
Propagation
Crested plants are propagated vegetatively so the fasciated trait carries over; seed does not reliably reproduce it. A section of the crest can be cut, the wound left to callus, and the piece rooted much like any cutting or offset. Grafting a fragment onto a vigorous rootstock is another route where quick recovery matters. See also Grafting and Propagation — offsets.
See also
- Mammillaria elongata — the parent species
- Mammillaria — the genus overview
- Grafting · Soil and potting mix · Watering · Propagation — cuttings