How to Prune a Crown of Thorns
Crown of thorns, Euphorbia milii, is a semi-succulent shrub capable of year-round blooming. Since flowering is solely dependent upon the amount of light the plant receives, pruning won’t interfere with its bloom production. This plant benefits from and responds well to judicious pruning. Young specimens usually don’t require any pruning until their second or third years. Euphorbia is a slow grower that typically only needs to be pruned lightly every two or three years thereafter. Wait for cool, dry spring weather to minimize the possibility of disease entering open wounds.
Remove any dead, damaged or diseased stems with pruning shears.
Cut out stems that are--or threaten to become--excessively tangled or intertwined.
Prune stems wherever you think the plant could use branching. Shorten any that have become too long or unattractive. Trim back any growth that doesn’t appeal to you.
Cut particularly leggy Euphorbias back by half to promote branching of larger main stems. You can safely remove from 1/3 to 2/3 of this plant at a time. New growth with emerge from just below the cuts, resulting in a fuller plant.
Spritz the plant’s cut stems with water to staunch the copious flow of sap secretions.
Wash your hands thoroughly after handling this plant.
Prune Crown Of Thorns?
Most crown of thorns don't require pruning until their second or third year, if at all, due to their slow growth rate. When pruning is required, the University of Florida IFAS Extension recommends pruning this plant during cool, dry weather to help prevent or lessen the risk of stem diseases. Hard prune every two to three years in late spring. Pruning crown of thorns is similar to pruning many other types of woody shrub. Cut any pruned branch back to an axillary branch. This will allow for increased branching and healthier, more prolific blooms from your plant. Remove any broken, diseased or misshapen branches whenever you see them. Crown of thorns will damage your favorite shears in a heartbeat. Just because you're not using your best pruning shears doesn't mean you should use unsterilized blades. Spray the pruning blade with disinfectant spray and wipe it before you use it to cut your crown of thorns.
Pull on sturdy gloves to prune your crown of thorns. Not only is it heavily armed with stiff spikes, the thick, sticky, milky-looking sap can irritate the skin of sensitive individuals. The secretion also contains diterpene esters, or tumor-promoting substances. Keep your hands away from your face when handling this plant. Provide crown of thorns all the bright light possible following pruning. This will ensure that the new growth remains compact, rather than becoming rangy from reaching for elusive light.
- University of Florida: Crown of Thorns--Euphorbia milii
- Weekend Gardener: Pruning Crown of Thorns
- Guide to Houseplants: Crown of Thorns
- Missouri Botanical Garden: Euphorbia Milii
- University of Florida Cooperative Extension Service: Crown-of-Thorns
- Wisconsin Master Gardener Program: Crown of Thorns
- Tropica Nursery: Euphorbia Milii Cultivation