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full sun (6 or more hours of sun hitting the leaves per day. South-facing window, no obstructions. Under grow lights, keep them 4-8 inches away for 12-14 hours) preferred, with at least 4-8 hours of direct light daily. In lower light, growth slows and the plant can lose its compact, upright form. A south- or west-facing window is ideal indoors.Light
Water weekly in summer, allowing the soil to dry between waterings. Cut back to once a month or less in winter. The plant goes dormant in cold months and needs very little moisture during that period.Water
Tolerates average household humidity without issues. Prefers dry conditions; avoid placing in humid rooms.Humidity
Thrives in warm temperatures (70-85F / 21-29C); suited to USDA Zones 9a-11b outdoors. Bring indoors before frost. Tolerates heat well.Temperature
easyDifficulty
Euphorbia mammillaris plant

Corncob Cactus

Euphorbia mammillaris

Easy

Euphorbia mammillaris is a column-forming succulent with thick, chalky gray-green stems covered in dense rows of hexagonal, knobby tubercles that really do look startlingly like a cob of corn, right down to the arrangement of the 'kernels' in neat vertical rows. Your plant is not a true cactus despite the common name, but it is drought-tolerant and just as easy to kill with overwatering as any cactus. In late winter through early summer it produces small yellow flowers clustered at the tips of each stem, which are easy to miss but add a nice seasonal touch.

Euphorbia mammillaris plant
Rudolphous, CC BY-SA 4.0, via Wikimedia Commons
Euphorbia mammillaris plant
Rudolphous, CC BY-SA 4.0, via Wikimedia Commons
Care Guide

How to grow Corncob Cactus

Light

full sun (6 or more

Water

Water weekly in summer, allowing

Humidity

Tolerates average household humidity without

Temperature

Thrives in warm temperatures (70-85F

Soil

Well-draining cactus or succulent soil

Propagation

Stem cuttings in spring or summer.

Common Problems

Mealybugs and spider mites.

Did You Know

Fun Facts

Despite the common name, Euphorbia mammillaris is not a cactus at all; it is a member of the Euphorbiaceae family, which also includes poinsettias, rubber trees, and cassava. The cactus-like appearance is a case of convergent evolution — two entirely different plant families arriving at the same spiny, succulent body plan as a response to the same dry, sunny conditions.

Pet Safety

Toxic to pets

Toxic. The milky latex sap contains diterpene esters that cause skin irritation, eye damage on contact, and oral and gastrointestinal blistering if ingested. The NCSU Extension rates the severity as low for typical contact but warns of potential corneal damage from eye exposure. Keep away from children and pets; always wear gloves when handling.

Sources

  1. Euphorbia Mammillaris (Indian Corn Cob) - Succulent City (opens in new tab)Reference
  2. Euphorbia Mammillaris (Indian Corn Cob) - Succulent City (opens in new tab)Reference
  3. Euphorbia mammillaris - Wikipedia (opens in new tab)Reference
  4. Euphorbia mammillaris - Wikipedia (opens in new tab)Reference
  5. How to Care for Corn Cob Cactus - Succulents Box (opens in new tab)Reference
  6. How to Care for Corn Cob Cactus - Succulents Box (opens in new tab)Reference
  7. Euphorbia mammillaris - NC State Extension Gardener Plant Toolbox (opens in new tab)University Extension
  8. Euphorbia mammillaris - NC State Extension Gardener Plant Toolbox (opens in new tab)University Extension
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