You’re just not into Easter? The idea of filling your home with perfumed flowers to celebrate a Christian version of an old pagan festival just doesn’t appeal to you? You’re deep into religious denial? Perhaps you can express your utter distaste with a plant that is all Easter, yet not so soft and cuddly as a lily or a daffodil, a sort of gothic Easter plant, if you like: the crown of thorns (Euphorbia milii). It’s much like keeping a rat as a sign of your reject of society … only easier to keep and less likely to escape.
The plant bears the name crown of thorns well: it is truly nasty! Seriously spiky thorns cover its branches and you’d be more tempted to handle it with a bottle holder than with your bare hands. Yet, subversively, it bears stunning blooms that certainly catch the eye.
The common name refers, of course, to the woven crown of thorns placed on the head of Jesus before his crucifixion (thus strongly linking the plant to Easter). No one knows which thorny plant was actually used for this purpose, but many plants (Paliurus spina-christi, Gundelia tournefortii, Koeberlinia spinosa, etc.) have picked up the common name crown of thorns as a result.
The best known crown of thorns plant is the one discussed here: Euphorbia milii, a popular succulent houseplant in colder climates (hardiness zones 1–8) and a common outdoor shrub in arid tropical climates (zones 9–12). You may also know it as Christ plant or Christ thorn.
In spite of these names, it was probably not the plant actually used to make Jesus’s crown of thorns, as it comes from Madagascar, not Israel, although there is some historical evidence suggesting in may have been introduced to the Middle East at just about the right time.
The crown of thorn’s botanical name Euphorbia honors Euphorbus, Greek doctor to the King of Mauretania around the time of Christ. The epithet milii honors Baron Milius, who is said to have introduced this species to cultivation in France in 1821.
The crown of thorns is a branching shrub up to 1.8 m (6 ft) tall (usually much smaller when grown as a houseplant) with extremely spiny gray stems. The broad oval fleshy leaves are mostly carried on new growth, leaving the lower stems bare. It’s usually grown for its attractive blooms, composed of two (sometimes more) colorful petal-like bracts that can last for months. The actual flowers in the center of the inflorescence are small and inconspicuous. The bracts are typically red or, more rarely, yellow in the wild, but there are all sorts of cultivars in a wide range of colors in culture—white, cream, pink, orange, bicolor, etc.—as well as dwarf varieties and cultivars with variegated foliage.
There is also a common hybrid species with much larger flowers and leaves and a considerably thicker stem: E. x lomi (E. milii x E. lophogona). It’s sometimes called giant crown of thorns. Its blooms are particularly striking and come in an equally wide range of colors. The Somona hybrids are a group of cultivars from California with especially nice blooms while there is a horde of Thai hybrids often called Poysean hybrids, Poysean being the Thai word for I. milii. It’s generally less branching than the straight species and a bit of pruning may be needed to encourage it to produce more than one stem.
When a crown of thorns is given good conditions, it can bloom at any time of year, although mostly in spring or summer. Some of the better cultivars will, if given top care, flower non-stop all year long. Under harsh conditions, notably extreme dryness, the crown of thorns may actually go dormant and not only stop flowering, but lose all of its leaves. When watered again, though, it will slowly come “back to life.” (Yes, a truly verifiable case of resurrection!)
The sticky sap of the crown of thorns is a toxic white latex. Don’t eat it and keep it out of your eyes and off your skin. Obviously, when working with this plant, it’s best to wear safety goggles and gloves. And keep this plant away from kids and pets!
Growing Crown of Thorns
It’s a very adaptable plant, but prefers full sun and well-drained soil. In hot climates, some protection from the midday sun is best. Although highly drought tolerant, it will nonetheless bloom best when kept moderately moist by regular watering. It will grow in just about any soil, from standard potting mixes indoors to poor rocky or sandy soils outdoors. It seems to get along fine with very little fertilizer, but you can apply some lightly during its main growing season, usually from early spring to early fall.
In dry tropical climates, it’s sometimes grown as a defensive hedge or to keep cattle out of fields. Certainly, cows won’t eat it, nor will deer or rabbits.
One thing the crown of thorns will not tolerate is cold. Even temperatures approaching freezing (35˚F/2˚C) can kill it. It’s best not to expose it to temperatures lower than 50 °F (10 °C).
The More the Nastier
You want to multiply your crown of thorns? You can theoretically grow it from seed, but that’s a slow and difficult process and germination is often poor. Plus, seedlings will likely not be like the mother plant. And good seed is hard to find! Be especially wary of web sites selling you multicolor crown of thorn seeds: they’re almost certainly scams.
However, you can readily grow crown of thorns from stem cuttings, best taken in spring or, failing that, summer. Water the plant a few days ahead so its stems are well hydrated.
Euphorbias of all kinds, including this one, tend to “bleed” white sap for a while after you cut them. This is not only alarming, but it weakens the cutting. To staunch the wound, spray it with cold water: this causes the sap to coagulate.
Next, apply rooting hormone to the wound (as the name suggests, it helps promote rooting) and insert it into a pot of barely moist soil. In fact, for a fuller final appearance, place three or more cuttings in each pot.
Place the cuttings in a warm spot. They’ll need only moderate light and very little watering at first. When you see new growth appear, give them full sun and water more thoroughly to bring them into bloom.
Finding a Specimen
I don’t think you’ll have any trouble finding standard red crown of thorns plants: they’re widely available and sold in most garden centers. If you’re looking for special cultivars in a wider range of colors, though, you may need to find an on-line succulent nursery in your country.
Crown of thorns: possibly the most irreverent Easter plant of all! And yet, behind those nastily spiny stems, it’s a charmer and certainly one of the easiest houseplants to get to bloom!