Repotting guide

When & how to repot Euphorbia horrida (Euphorbia horrida)

Also called African milk barrel, horrid euphorbia.

More about euphorbia horrida

About Euphorbia horrida

Euphorbia horrida · also called African milk barrel, horrid euphorbia · houseplant

A robust, cactus-like succulent spurge from South Africa's Eastern Cape, forming a heavily ribbed grey-green to blue-green column armed with stout spine-like persistent peduncles. Often mistaken for a true cactus, it clusters into impressive colonies with age. Easy and architectural, it exudes toxic milky latex when damaged, so handle carefully and keep from pets.

Mature size: Typically 20-30 cm tall, eventually forming clumps up to around 1 m wide in ideal conditions.

Watch for — Etiolation and fading: In low light the stem stretches and loses its blue-grey colour. Move to full sun or the brightest possible window to keep growth compact and well-coloured.

How to tell euphorbia horrida needs repotting

Repotting on a calendar is less reliable than reading the plant. For euphorbia horrida, watch for these signs:

Roots growing out of the drainage holes, or the rootball lifting the plant proud of the rim.
Soil that has shrunk away from the pot sides and no longer holds water.
The pot is unstable because the plant has grown top-heavy.
Old, compacted, broken-down mix that stays wet too long — for a succulent that is a rot risk, so refresh it even if the pot size is fine.

For the underlying biology of a pot-bound root system and why it stalls a plant, see our guide to spotting and fixing a root-bound plant.

How often to repot euphorbia horrida

Every 2–3 years, into bone-dry mix. Euphorbia horrida's growth habit — upright, columnar, deeply ribbed succulent that branches and clusters from the base into dense colonies with age; armed with persistent woody spine-like flower stalks. — sets the pace. A robust, cactus-like succulent spurge from South Africa's Eastern Cape, forming a heavily ribbed grey-green to blue-green column armed with stout spine-like persistent peduncles. Often mistaken for a true cactus, it clusters into impressive colonies with age. Easy and architectural, it exudes toxic milky latex when damaged, so handle carefully and keep from pets.

What size pot to step euphorbia horrida up to

Use a pot only one size up — or even the same pot with fresh gritty mix if the roots have room. Euphorbia horrida stores water and rots in a large pot of slow-drying soil. A tight terracotta pot that dries fast is far safer than a generous plastic one. Never up-pot a succulent by several sizes.

Not sure of the exact diameter? Our pot size calculator takes the current pot and root spread and tells you the right next size — it deliberately recommends a single step up, never a big jump.

The best time of year to repot euphorbia horrida

Spring or summer, while euphorbia horrida is in active growth and warm, is best — roots recover fastest then, and the plant is not sitting in cool damp soil. Avoid repotting a succulent in winter dormancy.

Step-by-step: repotting euphorbia horrida

Repot dry. Do not water euphorbia horrida for several days first. Working with dry roots and dry mix dramatically lowers the rot risk for a succulent.
Pick a snug, fast-draining pot. Choose terracotta one size up at most, with a drainage hole. Have gritty gritty, mineral cactus and succulent mix ready.
Tip it out and clean the roots. Slide the plant out, crumble off the old soil, and trim any black, mushy or dead roots with clean snips.
Pot into dry mix. Set euphorbia horrida at its original depth in dry gritty mix, firming gently. Do not bury the stem deeper than it was.
Wait a week before watering. Leave it completely dry and out of harsh sun for about 7 days so any damaged roots callus. Only then water lightly.

Aftercare

Keep euphorbia horrida completely dry and out of fierce sun for about a week so any nicked roots callus before they meet moisture; watering a freshly repotted succulent is the classic way to rot it. Then resume the normal lean, dry rhythm. Do not fertilise for about 3 weeks — fresh mix already carries nutrients and feeding freshly disturbed roots scorches them.

The right soil mix for euphorbia horrida

Euphorbia horrida wants gritty, mineral cactus and succulent mix. A sharply draining blend of cactus compost with coarse sand, grit or pumice. Fast drainage and an open, airy structure protect the swollen stem base from rot. Always use fresh mix when you repot — reusing old, broken-down soil reintroduces the compaction and poor drainage you are repotting to fix.

Repotting euphorbia horrida — frequently asked questions

How often should you repot euphorbia horrida?

Every 2–3 years, into bone-dry mix for euphorbia horrida. Repot euphorbia horrida every 2–3 years into a snug pot of gritty, mineral cactus and succulent mix, ideally in spring or summer. Let it sit in dry soil and do not water for about a week afterwards so any nicked roots can callus. Over-potting and watering straight away is what rots succulents.

What size pot does euphorbia horrida need?

When is the best time of year to repot euphorbia horrida?

Should you water euphorbia horrida after repotting?

No — not straight away. Repot euphorbia horrida into dry mix and wait about a week before the first watering so any damaged roots callus over. Watering a freshly repotted succulent is the single most common way to rot one.

Should you fertilise euphorbia horrida after repotting?

Not immediately. Wait about 3 weeks after repotting euphorbia horrida. Fresh mix already contains nutrients, and feeding freshly cut or disturbed roots burns them. Resume your normal feeding routine once you see new growth.