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Euphorbia

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  • Indoor Plants
Euphorbia x lomii 'Gaby'
Photo: Jardin botanique de Montréal (Gilles Murray)

Onglets

Botany

Origin and description

Euphorbia milii, a species better known as Crown of Thorns, is native to Madagascar, where it grows in cracks in granite. This succulent shrub of the same family as the poinsettia has strong thorny stems, branched at the ends, which grow small tufts of green elliptical leaves. This plant grows to over a meter high in its natural habitat. The leaves last for several months before falling to expose the thorny stems. New leaves appear only on new growth, which is why only the tip of the stem is leafy. Crown of Thorns produces tiny, unspectacular white flowers surrounded by colorful bracts, usually red. There are many cultivars of this species, with white, cream, red, pink or yellow bracts.

Species, cultivars and related plants

Euphorbia milii ‘Antananarivo’ produces yellow bracts. Euphorbia hislopii has thorny stems 6 cm thick and pink or red bracts. Euphorbia milii var. Splendens can reach 1.8 meters tall, with 2 cm thick stems and bright red bracts.

Toxicity

Warning! This plant contains latex that is irritating to the skin and can be toxic. In addition, the thorns on the stems can cause physical injury. Place it out of the reach of children and animals.

Common name

Euphorbia / Crown of thorns / Christ thorn

Latin name (genus)

Euphorbia milii

French common name

Botanical family

  • Euphorbiaceae
Horticulture

Growing conditions

Crown of Thorns requires a lot of light and sun to bloom. Place it near a window, preferably facing south or west. It adapts to normal temperatures indoors (18 to 21°C). In winter it enjoys a slightly cooler temperature, so do not place it too close to a heat source. The temperature should never fall below 13°C. It tolerates dry air. It can also go outside in the summer in direct sunlight after a period of acclimatization.

Easy to grow?

Crown of Thorns adapts to varied growing conditions. Cultivation is easy as long as you do not overwater it. It is not uncommon to see the blooming period extended if you continue regular watering, maintain a temperature of 18°C, and if the lighting is excellent.

Watering and fertilizer

During the growing season (March to October), water to wet the entire root ball, then let the soil surface dry between waterings. Never leave water in the saucer, as this plant does not tolerate excess water. Reduce watering frequency after the flowering period, especially if the temperature is cooler. Although this plant tolerates periods without water, it is best to never let the soil dry out completely because the leaves may age prematurely and drop off. Fertilize this species every two months during the growing season with a balanced fertilizer for houseplants or an all-purpose fertilizer such as 20-20-20. Stop fertilizing in the winter.

Pruning and maintenance

Prune the plant in the spring before the growing season to stimulate branching. Spray the pruned branches with water at room temperature to decrease the flow of latex.

Repotting

Crown of Thorns is a plant that grows slowly and likes to be tightly bound in its pot. Re-pot if necessary in the spring. Use a soil that drains well and contains a little more organic matter – cactus mix, for example, or a mixture of two-thirds all-purpose potting soil and one-third coarse sand or perlite. Place gravel in the bottom of the pot to ensure good drainage. It is preferable to use stoneware pots.

Propagation

Pests and diseases
Physiological disorders

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