African milk tree

African milk tree: how do you recognise it?

Growth habit

Upright succulent, indoors usually up to 1.5 m tall and 50 cm wide; later it branches, with side branches growing up like a candelabrum.

Stems

Three-sided, fleshy, dark green with a light, marbled pattern. Small brown spines sit in pairs along the ribs.

Leaves

Small, oval, 3–6 cm, along the ribs near the stem tips. They drop in winter or in low light; the green stems then do the work.

Sap

All parts contain a white milky sap that runs out of every wound and is toxic.

Roots

Shallow and branched: it wants a wide, heavy pot and little compost.

Plants: March–April · Pruning: April–May

Why grow it?

• A striking, sculptural plant with three-sided stems, a real eye-catcher in a bright corner.
• Grows fast and becomes a sturdy column up to 1.5 m tall over the years.
• Very sparing with water: it tolerates drought better than too much water.
• The red form brings colour without needing flowers.
• Easy to propagate from cuttings.

African milk tree: where does it grow best?

• Plenty of light and preferably a few hours of sun a day: a south-, east- or west-facing window. Get it used to sun gradually, as it scorches after a sudden change.
• Very free-draining, lean compost: cactus and succulent compost with extra sand or pumice; neutral to slightly acid.
• Warm: 18–28 °C in summer and 12–18 °C in winter, never below 10 °C.
• Use a heavy pot, preferably terracotta, because it becomes top-heavy. Keep it out of draughts.

Light

Sunny or bright, out of direct sun

Potting soil

Cactus compost

Acidity

Neutral

Watering

Sparingly

Size

1.5 m tall, 0.5 m wide

Temperature

Minimum 10 °C

Goes well with

• Mother-in-law’s tongue (Sansevieria): Just as sparing with water and tough in a bright, dry corner.
• Aloe: A succulent with the same compost and the same sparing watering.
• Echeveria: A low rosette that contrasts nicely with the tall column.
• Cacti: The same light and dry compost for a desert corner.

African milk tree: when and how to plant it?

Plant in March–April.

1. Repot in April, every 2–3 years or when the roots fill the pot. Wear gloves: the sap is toxic.
2. Choose a heavy pot with drainage holes, one or two sizes larger, and put a layer of clay pebbles in the bottom.
3. Use cactus compost with a third of sand or pumice so that water drains away at once.
4. Set the plant at the same depth as before and firm the compost gently. Mind the spines.
5. Do not water for the first week and afterwards only sparingly; damaged roots then heal without rotting.

Care

Water

In summer, when the compost is completely dry, then let it drain right through. In winter hardly at all, at most a little every 4–6 weeks.

Feeding

From May to August, once a month, half the dose of a cactus feed. Not in winter.

Light

The more light, the more compact and sturdy the plant. In too little light it stretches and drops its leaves.

Support

A tall plant becomes top-heavy: put it in a heavy pot or give it a stake.

Cleaning

Dust it with a soft, dry brush or a damp cloth; wear gloves.

Tip: Put it in a heavy pot and get it used to the sun gradually. Water only when the compost is completely dry and wear gloves when you prune or repot it: the milky sap is toxic and irritates skin and eyes.

African milk tree: when to prune it?

Pruning months: April–May.

When: In April–May, when the plant starts growing actively.

How:

• Cut off a branch that is too tall or leaning with a clean, sharp knife.
• Let the sap run and dab it away with a cloth, or rinse it off with lukewarm water.
• Remove dead or soft stems at the base.
• The cut branch can be used as a cutting; the parent plant regrows below the cut.

Caution: Always wear gloves and safety glasses: the milky sap is toxic and irritates skin and eyes. Wash your hands and the tool afterwards.

Pruning: when and how · Pruning calendar and basic rules

Propagation

Stem cuttings

In May–July: cut a piece of 10–15 cm from a side branch, rinse off the sap, let the cut dry for 1–2 weeks and set it 3–5 cm deep in dry cactus compost. Water only after 2–4 weeks and carefully; roots form after 1–2 months.

African milk tree: how does it get through the winter?

• Not hardy: the minimum temperature is 10 °C. It must never overwinter outdoors.
• Keep it bright and cool (12–18 °C) and hardly water it: a cold, wet plant rots quickly.
• Leaf drop in winter is normal. Keep it away from radiators and draughts.
• From March gradually give a little more water and get it used to sunlight again.

Diseases and pests

• Rotting stems: A soft, brown or black stem comes from too much water or cold feet. Cut the rotten part away to healthy tissue (wearing gloves) and let the plant dry out. A cutting can sometimes save the plant.
• Leaf drop: Normal in winter. Heavy leaf loss in summer means too dark, a draught, too wet or too dry. Move it somewhere brighter and water regularly but sparingly.
• Mealybugs and spider mites: White fluffy patches or fine webbing on the stems. Wipe with a cotton bud dipped in a little alcohol or soapy water and repeat weekly.
• Stretching and toppling: Too little light gives thin, floppy growth. Move it somewhere brighter, support it and cut it back if needed.

Through the year

• January: Rest: bright and cool, hardly any water.
• February: Rest. Still hardly any water.
• March: More light. Slowly start watering again.
• April: Repot and prune (wearing gloves).
• May: Start feeding. Take cuttings; from mid-May get it used to sun outdoors.
• June: Growing season. Water when the compost is completely dry.
• July: Growing season. Take cuttings.
• August: Last feed.
• September: Less water. Stop feeding.
• October: Bring indoors before it falls below 10 °C.
• November: Rest. Hardly any water.
• December: Rest: bright, cool and dry.

Edible and useful

Not edible. Spurges grown as houseplants, such as crown of thorns and African milk tree (which looks like a cactus), contain a white, milky sap in all their parts that is poisonous and caustic: on the skin it causes redness and itching, in the eyes severe pain and possibly damage to the cornea. Cats, dogs and small children that chew them can get a burning mouth, drool and vomit. Keep the pot out of their reach, wear gloves and safety glasses when pruning, taking cuttings and repotting, and wash your hands and tools afterwards. If sap gets in your eyes, rinse them at once under running lukewarm water for at least a quarter of an hour and see a doctor. If any is swallowed, call a poison centre (in Belgium 070 245 245) or your doctor at once.

Did you know?

• It is not a cactus but a spurge (Euphorbia): the resemblance comes from both plants storing water in fleshy stems in dry regions. Cacti have areoles, spurges have white milky sap.
• The small leaves often drop; the green stems then take up the light and make the sugars.
• The poinsettia (Euphorbia pulcherrima) is a distant relative from the same genus.