Euphorbia lactea 'Cristata'
Euphorbia lactea 'Cristata is the fan- or coral-shaped crested form of Euphorbia lactea, one of the most instantly recognisable oddities in the succulent world. Instead of growing as an upright, candelabra-branched shrub like the parent, its growing point has fasciated into a wavy, brain-like crest, and it is almost always sold grafted onto a straight green rootstock — usually Euphorbia neriifolia — under the trade name coral cactus. Despite that name it is not a cactus at all but a member of the spurge family, Euphorbiaceae.
As a cultivar its care follows that of the parent species; see Euphorbia lactea for the general requirements, with the extra notes below for grafted crests.
Description
The crest arises through fasciation, in which the normal single growing tip is replaced by a growing line, so the stem widens and folds into a rippling, fan-like ridge rather than a cylinder. The result is a flattened, undulating body with a texture often compared to coral or a folded ribbon, edged with the small paired spines and tiny leaves typical of E. lactea. Crests may be plain grey-green or, in the popular variegated selections, marbled with cream, pink, yellow or deep purple.
Because the tissue is so heavily fasciated, the crest tends to grow slowly and unevenly, and it rarely flowers in the way an ordinary stem would. Over time a healthy crest thickens and lengthens along its wavy margin, sometimes throwing out normal cylindrical shoots that revert to the uncrested form.
Cultivation
Cultivation is broadly as for the parent species — see Euphorbia lactea — but a grafted coral cactus has a few particular needs:
- It is usually grafted. Most plants sold are a crest of E. lactea grafted onto a taller E. neriifolia stem. The graft union is the plant's weak point: keep it dry and never let water sit in the crevices of the crest. See Grafting for how these unions are made and maintained.
- Light. Bright light keeps the crest compact and, in variegated forms, brings out the colour; too little light causes weak, stretched, greener growth. Highly variegated crests carry little chlorophyll, so give them good light but shade them from scorching midday sun, which can bleach or burn the pale tissue.
- Water. Water sparingly and only once the mix has dried, using a fast-draining, mostly mineral mix. Rot at the graft or in the folds of the crest, brought on by overwatering or trapped moisture, is the usual cause of death. See Watering and Repotting.
- Warmth. Keep it frost-free and on the warm side; the E. neriifolia rootstock in particular dislikes cold, damp conditions.
Like all Euphorbia, the plant bleeds a milky white latex when cut or bruised. This sap is an irritant to skin and eyes and is toxic if ingested, so handle with care and keep it away from pets and children.
Propagation
Crested euphorbias are not grown from seed — seedlings would revert to the normal form — so they are propagated vegetatively. A piece of the crest is either rooted as a cutting (slow and prone to rot) or, far more commonly, grafted onto a vigorous rootstock, which is why nearly all coral cactus plants reach you already grafted. Any normal, cylindrical shoots that appear can be removed and, if desired, rooted as ordinary cuttings; leaving them on will gradually cost the crest its shape.
See also
- Euphorbia lactea — the parent species
- Euphorbia — the genus overview
- Euphorbia neriifolia — the usual grafting rootstock
- Grafting · Soil and potting mix · Watering · Propagation — cuttings