Cactus and succulents Pruning

When a Crown of Thorns Refuses to Branch

Photo: Rachel Bernier

Question: I bought this plant about 2 years ago (it was much smaller then!), but it just keeps growing upward. How do I get it to branch out instead of producing a single central trunk?

Rachel Bernier

Answer: Your plant is a crown of thorns (Euphorbia milii), also called Christ thorn. There are many cultivars with flowers in all kinds of colors and also varieties that branch a lot while others, like yours, rarely seem to branch at all. In my experience, thin-stemmed, small-leafed varieties tend to branch more readily than large-leaved, thick-stemmed varieties like yours.

To force your plant to produce branches, cut off the top. That eliminates “apical dominance” (when the main central stem is dominant over side stems) and forces the redistribution of growth hormones that will hopefully stimulate a few dormant buds further down on the stem to start to grow.

You can simply “pinch” your plant (using pruning shears: this plant is too thorny to pinch with only your thumb and forefinger!), that is, simply prune off the growing point, or you could cut the plant back severely, to maybe 4 inches (10 cm) from its base. That will force your crown of thorns to produce at least one branch and probably several.

Wear gloves when pruning a crown of thorns: not only is the plant very spiny, but its sap irritates the skin and is even poisonous if swallowed. And after pruning, spray the wound with cold water to cause its white sap to coagulate and stop flowing.

If ever your plant produces only one branch (and yes, that can happen), let the new stem grow for 6 months or so, then cut off the tip again. You sometimes need to prune more than once to force certain recalcitrant plants to grow multiple branches.

The other possibility would be to root the top of the plant when you cut it off (again, spray the wound with water to stop its sap from “bleeding”) and plant the rooted cutting in the same pot as the mother plant. If you do this 2 or 3 times, that will give you a dense cluster of branches that will look good even if your plant really isn’t doing much branching.

Try It On Other Plants

And removing the top of most other plants with an upright growth habit will have the same effect. Cut back the top growth of any plant capable of forming branches (palms don’t for example) and the plant will soon produce new shoots lower down.

Larry Hodgson is one of Canada’s best-known garden communicators. He has notably been editor-in-chief of HousePlant Magazine, Fleurs, Plantes et Jardins, À Fleur de Pot and Houseplant Forum magazines and is currently the garden correspondent for Le Soleil and radio garden commentator for CKIA-FM Radio. He has written for many garden publications in both the United States and Canada, including Canadian Gardening, Harrowsmith, Horticulture, Fine Gardening and Organic Gardening. He also speaks frequently to horticultural groups throughout Canada and the U.S. His book credits include The Garden Lover’s Guide to Canada, Complete Guide to Houseplants, Making the Most of Shade, Perennials for Every Purpose, Annuals for Every Purpose, and Houseplants for Dummies, as well as nearly 60 other titles in English and French. He is a past president of the Garden Writers Association (now Garden Communicators International) and the winner of the prestigious 2006 Garden Media Promoter Award offered by the Perennial Plant Association. He resides in Quebec City, Quebec, Canada.

1 comment on “When a Crown of Thorns Refuses to Branch

  1. Of all the plumerias, the one that I want to branch the most won’t cooperate! I must prune the others because they branch so much. When I do, I cut the tips off the one that does not branch much at all. Some limbs make two branches. Some make only one. Oh well. It is still my favorite.

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