Euphorbia mammillaris f. variegata

Euphorbia mammillaris f. variegata

Family: Euphorbiaceae
Common Name: variegated corn cob
Geographic Origin: Euphorbia mammillaris f. variegata is a nursery-created forma of E. mammillaris, which originates from the subtropical thorny bush-lands, steppe, and low-savanna within Little Karoo and the Southern Cape of South Africa.
Description: The variegated corn cob is a succulent shrublet that forms a dense cluster of club-shaped lateral branches. The thick stems are simple, ribbed, and covered in vertical rows of hexagonal tubercules, resembling an ear of corn. Although the straight species possesses dark green stems, the stem of the variegated forma will be cream-colored to greenish-white, with random sections of emerald green. Small, ephemeral leaves may be present on the extending tubercules, but the spines are scattered and do not emerge from the tubercules. Thick, blunt, and white, the extending spines are solitary sterile peduncles.
From late winter to early summer, succulents will develop a solitary yellow cyathia at the apex of each stem, possessing several bracts and yellow-green to purple nectar glands. Flowers will be followed by the obtusely lobed fruits and smooth ovoid seeds.
Interesting Features:

When exposed to cold temperatures and full winter sun, the stems of the variegated forma will become rose-colored.
The strong resemblance of E. mammillaris to cacti within the Mammillaria genus is the result of convergent evolution within similar environments. However, the “nipple-like” tubercules present in E. mammillaris and Mammillaria cacti led to the shared Latin “mammillaris”, for “having nipples”.
As with all Euphorbia species, E. mammillaris f. variegata will exude a toxic white sap from the stems when cut. Exposure to this sap can lead to skin or eye irritation – wear gloves when handling.

Uses: Although there are no known uses of the variegated forma outside of cultivation, the toxic sap of the straight species has historically been used as a poison for arrows.

Cultivation and Care:
- Watering: Moderate

Intolerant of drought, E. mammillaris f. variegata should be watered whenever the soil is dry several inches below the surface. Provide moderate irrigation from March to September, weekly watering in the summer, and keep almost completely dry in winter.
However, the species is equally intolerant of wet soil, and should never be allowed to stand in water.

     - Soil Type: E. mammillaris f. variegata can flourish indoors as well as outdoors, requiring a well-draining medium of non-organic material such as lava grit, pumice, clay, and a little peat or leaf-mold. If planting outdoors, add organic matter or fertilizer to the planting hole. Prefers small pots, but should be repotted in very late winter or early spring if necessary. Not particular about soil pH.
     - Lighting: Requires full sun, but is capable of surviving moderate shade. However, plants grown under shady conditions must be slowly hardened off before placing in full sun, to avoid severe scorching.
     - Propagation: The variegated corn cob may be propagated through offsets, cuttings, or seed. However, offsets are only rarely produced after several years, and seed may be difficult to find or germinate. As a result, the species is usually propagated by cuttings, which should be dipped in rooting hormone to ensure success.
     - Cold tolerance: 20°F, USDA hardiness zones 9a to 11b.
     - Special Accommodations: E. mammillaris f. variegata is very frost tender and should only be planted in frost-free locations. If grown in poor soil or outdoors, feed monthly with a half-strength cacti or succulent fertilizer. However, in summer, a high potassium fertilizer is required to ensure growth. When adequate heat, sun, water, and nutrients are provided, the species will show remarkable growth during the active growing season.
Sources: