The Christ thorn is interesting, exceptionally decorative and is one of the few plants that make us happy with flowers in winter. In the following article you will find out that it is also one of the easiest to care for plants that you can invite into your living room, but is also quite dangerous.
Wanted poster of the Christ thorn
The Christ thorn bears the botanical name Euphorbia milii, it is native to the islands of the Indian Ocean. The leafy, succulent thorn bushes ended up as souvenirs in the Botanical Garden of Bordeaux and proved to be surprisingly easy to care for in our climate. The Christ thorn even survives winter here well; unlike many other plants, it is more than okay with the dry heating air in our rooms. A Christ thorn can easily withstand decades on your windowsill, where it gradually grows into a magnificent bush and can also be kept very well in hydroponics. Because it still looks so beautifully bizarre, after its introduction in Europe it quickly developed into a popular houseplant that still has many friends today.

The Christ thorn is not entirely harmless

The Christ thorn belongs to the milkweed family, the Euphorbia, an interesting family of plants, but all poisonous. It is not for nothing that the plants have the term “milkweed” in their name: They delight us harmlessly and friendly with their flowers, but if you get just a little too close to the apparently peaceful plants, they defend themselves with the “milkweed” – the one at the the smallest injury emerges from the plant with light pressure. It contains highly effective phytochemicals which, depending on the chemical compound, can easily or very severely burn and inflame our mucous membranes, irritate our skin and cause considerable pain.

The Christ thorn and other euphorbias should therefore be handled with care, if milk (latex) gets on the skin, it should be washed off immediately and thoroughly, and if the mucous membranes are burned, a doctor should be consulted. Euphorbias are generally not recommended for households with small children and pets, and if large euphorbias are pruned in greenhouses, the vapors of the latex can even spread to such an extent that they are severely irritating to the eyes and respiratory tract even at a distance of several meters.

The right location for the Christ thorn

In Madagascar it is warm, very warm, it lies in the middle of the tropical climate of the south equatorial current. The average annual temperature is 25 degrees or higher, there is no summer and winter, but rainy and dry seasons.

He never gets as much warmth and sun as the Christ thorn is used to from us, he would like to take what is possible with him from the south window. He likes full sun, but also dry air, so he gets along very well in our heated living rooms in winter.

In summer he likes to stand outside, but then please in a location without too much direct sun, e.g. B. in the shade of a tree.

Caring for the Christ thorn

Any loose soil mixture is suitable as a substrate. The Christ thorn would like to be watered regularly during the growth phase, but you don’t need to be shocked if you forget that and it drops the leaves – just put it in a slightly cooler place, let it almost dry out and wait until it settles again show new shoots, then gradually pour a little more, at some point your Christ thorn will be “complete” again.

Your Christ thorn does not want to be watered too abundantly either, and you should above all make sure that excess water can drain out of the plant pot.

The Christ thorn has its growth phase between April and September, now it would like to receive some fertilizer once a week.

You can repot the Christ thorn as needed, and when you see roots down in the drainage holes, it’s time. Younger plants usually need a new pot every year, older Christ thorns usually only need to be repotted every few years. The new pot should always be a little bigger than the last pot, otherwise splendid roots will grow, but only a little Christ thorn in the upper area.

The flowers of the Christ thorn would bloom most profusely when they experience short days, i.e. from the end of December to the end of March – but then it does best with us in the drought, the flowering should be at the very beginning. In order for your Christ thorn to set these blossoms at all, he also needs “short days” for a few weeks, i.e. days with no more than 10 hours of light, as he would experience in his home country. With us, however, if you are in doubt, you can fake it by putting a box over it after 10 hours and it will bloom whenever you want. The right time would be around the beginning of September, when it will bloom when you are just starting to “keep it shorter”.

Wintering of the Christ thorn

The plant, which is accustomed to warmth, falls into drought in its home during the dry season, with us abroad it needs this break even more urgently. Since we lack the natural signals, you have to “force” this dry calm on your Christ thorn by literally drying it out, so gradually watering less and less. In winter only enough water is poured so that the root ball does not dry out completely. The Christ thorn will now lose almost all of its leaves and will not sprout again until next spring.

If you simply continue to water the Christ thorn in the normal way over the winter, it would develop its flowers in a natural rhythm, including the short days required for flower induction in autumn. However, that doesn’t suit him very well, he then tends to become very horny, catches some diseases or just rots away. If you want to see how your Christ thorn grows, you should better rely on the program with winter drought and a slightly postponed flowering period.

Propagation and pruning

You can prune the Christ thorn where and when you want, it is even advisable from time to time to keep the plant in shape. Otherwise it will only be pruned if it gets too big, which should be done in the spring, then you can use each section as a cutting. Because of the dangerous milkweed you should only touch your Christ thorn with gloves and only work on it in a well-ventilated room.

The Christ thorn can easily be propagated by cuttings. It is best to cut these in spring (with gloves, please) and put them in a mixture of earth and sand. After cutting the cuttings, you can prevent the milky juice from escaping further by briefly dipping the interfaces in lukewarm water.

They should be placed in a room with the highest possible temperature, ideally 24 degrees, then roots should have formed after just under a month.

Diseases and pests

With its poisonous milky sap, the Christ thorn is very well armed against animal pests, you have little to fear in this regard. If the humidity is too high, powdery mildew can occur and the rest of the symptoms are almost always due to incorrect care: Too much watering, especially in winter, leads to root rot, too little water to total leaf loss, and the Christ thorn can react to sudden changes in temperature also react with leaf fall. Eliminate errors, wait a little, in most cases the Christ thorn catches itself again. You should only try to save a cutting and pull a new Christ thorn out of it if the entire root area has already rotted through.


There are several varieties of the species Euphorbia milii, here is an overview:

  • Euphorbia milii Desmoul. var. milii: Grows as a very richly branched shrub that reaches heights of up to 1.5 meters, its branches can be up to 1 cm thick. Comes from western Madagascar, has small pink to flamingo-colored pseudo-flowers.
  • Euphorbia milii var. Bevilaniensis: Comes from southern Madagascar, where it has developed a very interesting triangular leaf shape at its locations on rocks in the forest.
  • Euphorbia milii var. Hislopii: A species from central Madagascar, only grows there as a hedge plant, robust and large-leaved variety that can reach a height of 2 meters.
  • Euphorbia milii var. Imperatae: Comes from the coastal forest in eastern Madagascar, where it could only develop into a small shrub with thin branches and a maximum height of around 50 cm.
  • Euphorbia milii var. Longifolia: Also from central Madagascar, where it develops many shoots next to each other on granite rocks, popular with us as a high trunk that can be up to 1.5 meters high.
  • Euphorbia milii var. Roseana: comes from the south of Madagascar, forms fairly upright branches with narrow leaves up to 9 cm long.
  • Euphorbia milii var. Splendens: From central Madagascar, up to 2 meters high shrubs with light green leaves, very many thorns.
  • Euphorbia milii var. Tananarivae: The second hedge plant from Madagascar, up to 2 m high shrubs with thick branches.
  • Euphorbia milii var. Tenuispina: Rare species from the mountains of southern Madagascar, which stands out due to a caudex (succulent thickening at the base) and very slender thorns.
  • Euphorbia milii var. Tulearensis: Southwest Madagascar, unusually small thorns and unusually bright red inner flowers.
  • Euphorbia milii var. Vulcanii: Central to southern Madagascar, extraordinary blue-green and huge leaves on long stems.

In the normal flower shop you will mostly only find the Euphorbia milii var. Splendens of the original varieties. In specialist shops you can also find the other species, all of which can be kept as indoor plants.

Even easier to care for: hybrids of the Christ thorn

The Christ thorn is often crossed with a closely related milkweed plant, the even more undemanding and vigorous Euphorbia lophogona. The E. lophogona also grows in Madagascar, and the two are so closely related that they also cross “voluntarily” when they e.g. B. stand next to each other in collections. Since this is said to have happened for the first time in California, this pairing is also called “California hybrids”. These hybrids are sold, but are also popular starting plants for further breeding. Most of the cultivated forms that are commercially available are based on these “California hybrids”.

The so-called “Heidelberg hybrids”, which are named because a professor from Heidelberg University discovered them, were created directly in Madagascar and quite naturally. E. lophogona and E. milii also crossed here, but the new plant called Euphorbia × lomi has thinner stems and thicker leaves compared to the Californian hybrids.

Then there are Christ thorn hybrids on the market from Thailand, the origin of which is not known, but the hedge euphorbie E. milii var. Tananarivae is considered to be one of the parents. The plants, which are regarded as lucky charms in Thailand and neighboring countries, are eagerly bred there and sometimes also imported to us.

These hybrids are ideal houseplants for all of us, which are satisfied with a partially shaded place on the windowsill and sufficient watering. They even like to stand over the radiator. They often bloom almost all year round here, in white, yellow, pink or red. The hybrids are cultivated over the winter, they like to be watered in winter and usually keep their leaves for several years until natural aging causes a decline.


The Christ thorn is certainly not one of the best houseplants for a lively family with children and pets. Just as sure, however, it is really interesting and surprisingly easy to care for and can bring a lot of joy to so many curious carpenters.

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