Questions on: Crown of Thorns

Ron Smith, Horticulturist, NDSU Extension Service


Q: I am looking for a crown of thorns like I once had. It had actual flowers (red) with five or so petals, not just bracts like all the plants I find under this name. It had longer branches, covered with smaller oval leaves and not as shrubby shaped as those I see now. I am wondering if what I had was a related plant or a variation. (E-mail reference)

A: I am afraid that you must be thinking of something other than a crown of thorns (Euphorbia milii). Itís possible the one you had was misnamed either accidentally or intentionally. I'm sorry I can't help you more.


Q: I have a crown of thorns that is about 30 years old but has never bloomed. The plant is about 10 feet tall with very tight branches and lots of little branches growing with leaves. It's in a sunny southern window and also gets indirect light from the west. I live at about 7,000 feet so we get cold winters and hot summers. We do not heat our house during the day while we're at work (we use a set-back thermometer and it comes on at about 55 degrees to provide some heat if needed). I water it about once a month and fertilize every few months. As far as I can see, it's been in a continual growth stage for the last 20 years. I think I overwatered it so now itís droopy. The major branches are not as bright green and the littler branches are droopy. Is there anything I can do to save it? Should I cut back the droopy branches and hope it survives? I haven't watered it in over a month but I don't see any progress. (E-mail reference)

A: A 30-year-old plant has got to be close to a record! You probably have been overwatering it. Since itís a euphorbia, it should go through a wet/dry cycle. The drooping leaves are attempting to tell you that so allow them to defoliate. Water only sparingly during the remaining winter months. Pick up on the watering around late March or early-April and you should see some blooms next year.


Q: I was given two crown of thorn plants in 2001. They haven't bloomed since. I re potted them this summer and got plenty of leaf growth but no blooms. Can you suggest how I can get these plants to bloom? (E-mail reference)

A: Patience, along with good direct sunlight and warm temperatures, should work. Don't overwater or over fertilize and certainly don't mist. It will flower when it is good and ready.


Q: I have a crown of thorns that was passed down to me from my parents. It is 27 years old and very large. I have never done much to it other than water it and take it outside during the summer. It blooms all year long but now after bringing it inside this year, some branches are turning spongy and the leaves are turning yellow and falling off on some branches. I do not see any mites or fungus. I used an insect soap spray but that is not helping. (E-mail reference)

A: Back off on the watering and allow the soil to dry between watering cycles. Also make sure it is gets bright, but indirect, light.


Q: I have two different crown-of-thorn plants. One bloomed but now seems to be in a rest period. Should I use any fertilizer made for cactus plants? How often should I use it? The other crown of thorns has many stems that are about the thickness of a pencil. It appears to be very healthy and is constantly producing new leaves. It has been forming tiny buds but they dry up and fall off before they can fully develop. I have these plants in a south window where they get plenty of light. I am not sure of the watering requirements so I wonder if they are getting the right amount of water. Iím using a light soil that is recommended for cactus plants. (White Bear Lake, Minn.)

A: A crown of thorns (Euphorbia milii) will require as much light as the south exposure can give. Only fertilize during an active growth phase. Fertilize at half strength every two to three weeks after that. Flowers will be produced on new growth. Wet the entire root mass during active growth but allow the top inch to dry between waterings. After flowering, allow the top third of the soil mass to dry before watering. If the soil dries completely, the leaves will drop prematurely. A crown of thorns is a fickle plant to grow.


Q: I have owned a crown of thorns plant for about four years. It seems to be doing very well. However, it is very tall and I wonder if I should be cutting it back? (E-mail reference)

A: Cut it back to an acceptable lateral branch, then spray the cut end with cold water to arrest the flow of the latex sap. You might take the top three to four inches of the cut stem and try rooting it, after allowing the ends to dry for a day before placing them in a 50/50 mix of peat/sand.


Q: Until now I had two beautiful crown of thorns. I left them out during our first frost. The tops of the plants look wilted but not completely dead. The bottoms still have a pretty green color. Iím wondering what I can do to save these plants? Should I bring them indoors and see what happens or should I go ahead and prune them back? Any fertilizer? (E-mail reference)

A: I think you are going to get away with this plant surviving. I would do nothing at this point, as you might have shocked the plant into a dormant or rest period. No fertilizer until new growth is evident over the next 6-8 weeks.


Q: I've never really been a plant person, but, about two years ago, I received an approximately two-inch tall-crown of thorns. I've grown quite attached to it. It is now about a foot tall with one main branch and one smaller side branch. From pictures I've seen, the plant should have leaves along the stem, and should flower year-round. My plant only has leaves at the very top of its main stem, and at the top of its branch. It has never flowered. Is this normal? What can I do to get it to flower? Should I be feeding it anything in particular? (E-mail reference)

A: Basically, the crown of thorns can take as much direct winter sunlight as is available. Place it in a south window if possible, with a west window being the second choice. Allow the soil to dry between watering and only fertilize monthly when active growth is taking place during the spring and summer months. If it is going to flower, it will do so in the dead of winter. Repot every other year.


Q: How do you propagate a crown of thorns? (E-mail reference)

A: New plants can be raised from short tip cuttings taken in spring and early summer. Use a sharp knife or razor blade to cut off growing tips about 3 or 4 inches long, and stop the latex flowing by spraying the mother plant with water and dipping the cuttings in water. Allow the cuttings to dry out for a day before setting them in a slightly moist, equal parts mixture of peat moss and sand or perlite. Do not let the mixture to become more than slightly moist; if too wet, the cuttings will rot without producing roots. Place the pots where they can get good bright light, but not direct sunlight, keeping the mix just barely moist, allowing the top two-thirds to dry before re-wetting. Rooting should take place in about six to eight weeks. Be careful in handling!


Q: I am writing in regards to the person asking about the crown of thorns blooming. I don't think myour advice about throwing it away answered their question. My advice is to place it in cool temperatures, 55 F to 60 F, for two to three weeks and shorten the daylight, which is achieved easily by placing a paper bag over it each at 6 p.m. and uncovering each morning. (Cando, N.D.)

A: Thanks for your good advice on the crown of thorns! You are right to reprimand me for my answer--I deserved it--and I'm sure the reader's will appreciate your sound advice.


Q: I have a Crown of Thorns plant that bloomed for a long time, but now it hasn't bloomed for quite a while. It is kind of an ugly plant with many thorns on it, and I am wondering what to do to get it to bloom again. (Mahnomen, Minn.)

A: A very prickly plant indeed! It might help to prune some branches back to their connecting branches to get it to bloom again; otherwise, if you are not too attached to it, I would get rid of it. I consider it a hazard to people!


Q. I so enjoy your column in the Fargo Forum.

Hope you can help me with my problem. I bought a "Crown of Thorns" plant about two months ago. It had nice pink flowers on it. Since they fell off, I never get any more blossoms. It grows taller, but no flowers. None of my friends have heard about this "Crown of Thorns."

Please advise. (Mahnomen, Minn.)

A. Thank you for the nice words about the column.

"Crown of Thorns" is Euphorbia splendens prostrata. It, along with other flowering houseplants, requires ample light before it will reflower.

It should be located in a sunny location to produce flowers. You also need a little patience. Every flowering houseplant needs a period of rest after flowering. It is kind of like you or me running a mile at full bore--exhausting.


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