African Milk Tree

Check your light →

Happiest where direct sunlight lands for part of the day, from a window facing east or west; that keeps its fast pace going. Bright light beyond the sun’s beam works too, set back a little from the glass.

It isn’t a desert plant. It grows in the seasonally dry tropical forests between Gabon and Malawi (Kew; Missouri Botanical Garden). Missouri rates it for full sun to part shade, and NC State suggests partial sun for plants grown outdoors.

In a Chicago winter, consider a south-facing window, where the low winter light reaches deepest into the room.

Spurges dislike surprises. NC State warns that sudden swings in light, temperature, or humidity can harm them, so if you’re moving it from a dim corner to a sunny sill, consider doing it in stages over a week or two.

Being a tropical forest native, it has no tolerance for a Midwest fall: a summer on the balcony is fine, but bring it in before nights drop below 45°F (NC State).

Give those columns some sun, and they’ll do the climbing.

In summer, a modest drink every two to three weeks; in winter, every three to five. It forgives a skipped turn easily; a pot that stays wet is what leads to root rot.

Its native forests go through a real dry season each year (Kew), and it treats a dry pot as more of the same.

Its small teardrop leaves may thin out in the dry season. Missouri Botanical Garden notes that the leaves fall seasonally. A few bare stems in winter are part of that rhythm, and the ridged columns carry on without them.

Gone for a while? A month is fine if it’s watered the day you leave; it’s built for dry spells.

A candelabra of ridged green stems, up to 6 feet tall indoors and quick to get there. Give it the floor and a heavy pot, out of walkways where spines snag sleeves; cut tips back, gloved, to cap its height.

In its native range it becomes a real tree, 6-12 feet tall and 5-10 feet wide, on a stout gray trunk (Missouri Botanical Garden). A potted one ages the same way: NC State notes that the smooth green bark turns gray to brownish as it matures.

Its branches rise close to the main stem, so it climbs more than it spreads. That suits the slim places most rooms waste: beside a window frame, behind an armchair, either side of a doorway. A matched pair reads like columns at an entrance.

Cut pieces can root on their own (NC State lists stem cuttings and air layering), but every cut weeps white milk, so put gloves on before the pruners. A red-leaved form, 'Rubra', has stems edged in red (NC State).

A chewed stem may irritate the mouth and stomach of a pet or child, sometimes bringing on vomiting. Its milky sap is the part to handle with care.

The milky sap irritates skin and can badly hurt eyes, so wear gloves when cutting it and keep the sap well away from your face.

The irritants are diterpenoid euphorbol esters, carried in that white sap (NC State). It leaks from any cut or broken stem (Missouri Botanical Garden), so pruning, repotting and a snapped branch are the moments it turns up.

For a dog or cat that chews a piece, the usual course is a sore mouth and stomach, maybe a bout of vomiting, and then it passes. If symptoms don’t settle or anything worries you, Poison Control can help with a child, and ASPCA Animal Poison Control can help with a pet (a fee may apply).

Still want one? Give it a heavy pot on a stand, or a room where kids and pets rarely play, and sweep up any fallen pieces before a curious nose finds them.

1. ASPCA: mild for dogs.
2. Pet Poison Helpline: mild for dogs.
3. ASPCA: mild for cats.
4. Pet Poison Helpline: mild for cats.
5. NC State Extension: mild for kids.

Cats and dogs: Most of the leading sources agree.

Kids: Sources disagree (NC State toxic, UC ANR mild; the majority wins, a tie goes lower).

Happiest at 65-85°F, and it shouldn’t sit below 45°F. Humidity can drop to 10% without trouble.

Temperature

65-85°F

Mealybugs are the likeliest guests, so check the stem ridges, the spine bases, and the leaf bases. Spider mites may settle on stem surfaces and new growth, and aphids on fresh growing tips.

• Mealybugs
• Spider mites
• Aphids

Few, as long as it’s sunny and dry. Mealybugs are the one to watch; aphids and spider mites turn up now and then, and rot if the soil stays wet.

Mealybugs look like tufts of white cotton in the grooves along the ridges and around the spines. Dab them with a cotton swab dipped in rubbing alcohol, then check again next week; if they keep coming back, an insecticidal soap spray is the next step.

Spider mites leave pale speckles and fine webbing; aphids cluster on new growth. Rinse the plant off with water (carefully, around the spines), and use insecticidal soap if they return.

Rot shows as an arm turning soft and dark at the base, from soil that stays wet or a plant set too deep. Let the pot dry right out; if the base is gone, save the healthy upper arms as cuttings (see Propagation).

Quarter-turn it toward the window each month so it stands straight, and feed lightly 3 times in spring and summer. Prune in early spring only to reduce size. Repot every 2 years in gloves; re-⁠stake leaners.

• Prune1× a year
• Feed3× a year
• Rotate12× a year

A clay pot with a drainage hole, filled with a mix that drains fast: half potting soil and half sand or perlite, or a bagged cactus mix. A heavy clay pot also keeps a tall one from tipping.

Repot each spring while it’s young, one pot size up, and no bigger: extra soil stays wet around the roots. Once it’s tall, repot only when it outgrows its pot. Wear gloves, and wrap the arms in a towel or folded newspaper to handle them.

Food is optional: a cactus or houseplant fertilizer at half strength three or four times between March and September is plenty. Skip high-⁠nitrogen feeds.

Three-sided green columns branch like a candelabra, edged with tiny leaves along the ridges. The green is one plain shade with a slight sheen, and the stems stand apart so soil shows between them.