Madagascar jewel (Euphorbia leuconeura). Photo: plantsam.com
You’ve never heard of the Madagascar jewel (Euphorbia leuconeura)? I’m not surprised. It’s a fairly obscure houseplant, certainly not one you see often in garden centers. However, it is making the rounds in a parallel system … as a pass-along plant. A neighbor, friend or relative gives you one, then you grow it and produce baby plants that you give to someone else. And it’s been spreading that way for years, as I can recall first seeing it about at a plant exchange about 30 years ago.
How do I know that this plant is so widely grown? People keep sending me photos with the question, “What is this plant?” Or they bring a specimen or cutting to a lecture I’m giving and ask if I know it. It’s instantly recognizable.
Oddly, I didn’t even know this plant had a common name under I decided to research this article. I’d always known it simply as Euphorbia leuconeura, which would translate as white-nerved euphorbia. The name Madagascar jewel is rather a silly one, actually. Yes, it does come from Madagascar, but I fail to anything jewellike about it. A jewellike plant would be small and kinda cute, don’t you think? But Madagascar jewel is big and rather thuggish.
E. leuconeura is a succulent shrub, even a small tree, reaching to 1.8 m (6 ft) in height. Although commonly mistaken for a cactus, it’s actually a member of the euphorbia family (Euphorbiaceae).
Young plants bear tear-shaped leaves with brilliant white nerves and a reddish petiole. The white coloration fades over time and the nerves become green. The petioles, though, retain their reddish tinge, most visible in strong light. Mature leaves are dark green and leathery, measuring up to 15 cm (6 inches) long and 6.5 cm (2 ½ in) wide. They too sometimes have a reddish tinge, especially if you grow the plant in bright light.
On young plants, the stem is tubular and green or reddish, but soon thickens and then develops 4 to 5 distinct angles with brown hairy edges. It remains green with pale brown crescent-shaped marks where old leaves were once attached. The stem grows straight up at first, only branching after several years or if pruned.
After a year or so, the plant begins producing abundant clusters of tiny insignificant white flowers without any petals at the axils of the upper leaves. They’re not attractive, but soon produce seed capsules that open explosively, shooting seeds up to 2 m (7 feet) away. The seeds germinate readily and soon baby plants begin popping up in the pots of all the houseplants nearby, even in the garden if the plant is outdoors for the summer. If you don’t want the plant to self-sow, pinch off the seed capsules.
E. leuconeura is apparently endangered in the wild, although hardly so in culture!
Growing Your Own Madagascar Jewel
This is a widely adapted plant, easy to grow indoors.
It prefers bright light to full sun, but will tolerate shade. Under low light, expect the plant to be floppy and requite staking.
Although this plant is a succulent and tolerant of dry soils, it doesn’t seem to mind regular watering either. In fact, plants grown too dry will lose more of their lower leaves (sometimes even all of their leaves) and will be less attractive than specimens grown in soil that is kept slightly moist. Just follow the golden rule of watering: water deeply, enough to moisten the entire root ball, then allow the soil to dry before watering again.
What Madagascar jewel doesn’t like are cold temperatures, below 10?C (50?F). In fact, keep it above 15?C (60?F) at all times if at all possible.
You can grow it in just about any potting mix: either a regular houseplant blend or cactus and succulent mix. You’ll probably need to repot young plants annually into larger and larger pots. Use heavy pots for big specimens, as they become top-heavy.
Fertilize your Madagascar jewel if you want, using the fertilizer of your choice, but do so lightly and during the main growing season only (spring through early fall). It will also get along fine without any fertilizer.
It’s perfectly happy with dry indoor air, so there is no need to increase the atmospheric humidity. It will, however, readily tolerate the higher humidity most other houseplants need.
As for multiplication, it usually does that on its own, seeding itself about not only in its own pot, but in those of other plants. Baby plants thus produced can then be potted up separately. You can also catch the seeds (try bagging the plant with an organza sack) and sow them, barely covering them with potting mix. They germinate in about a month at warm temperatures (22 to 25?C/72 to 77?F). You can also take cuttings if for some strange reason you need even more plants.
When pruning, wear googles and protective gloves, as the milky white sap is irritating and toxic. If you get any on your skin, simply wash it off. Keep this plant out of reach of children and pets.
Honestly, the best way of growing this plant, which gets big and ungainly over time, is to get rid of mature specimens when they take up too much space and simply replace them with one of the abundant young ones that appear everywhere.
I would not recommend growing this plant outdoors in a tropical climate (it is only hardy to USDA zones 10 and above and prefers arid to semi-arid conditions). It’s far too invasive!
Where to Find Plants
A lot of nurseries won’t grow Madagascar Jewel, considering it too weedy, but you can find plants and seeds online not only from specialist succulent nurseries, but also from such providers as eBay and Etsy.
And, of course, you can easily find specimens at plant exchanges, in flea markets or through your local garden club. Just show a photo at any plant meeting (no use comes from asking for this plant by either its common name or botanical one: few owners know either!) and hands will rise. Yes, for an obscure plant, Madagascar jewel is actually amazingly common.