Pencil cactus  (Euphorbia tirucalli in the Euphorbiaceae family) is a common houseplant and a fast grower. Mature plants can grow up to 25 feet tall and often have a “pine tree” sort of appearance. Pruning them is fairly easy and should not harm the plant.  Here are some tips on pruning.

· Protect your eyes, skin and clothes from the white latex-like sap. This sap can cause skin and eye irritation which can sometimes be severe. It will also stain your clothes and become black when it dries. Also, because of this sap, these plants are not good for composting.

· Remove any dead, damaged or diseased branches. This will both tidy up the plant and promote new growth.

· Determine the shape and height you would like for your plant. Then use pruners or sharp, heavy scissors to shape the plant as desired by cutting off the branches above a node. When pruning, cut to the base of each branch at its point of origin. Do not leave a stub sticking out of the stem.

· If desired you can also thin the plant further by removing vertical branches that are thin and weak or too numerous. Again, cut these branches at their point of origin. Thinning also allows more air circulation through and around the plant, thus improving its overall health.

· Carefully throw out the parts of the plant you removed. Alternatively, give them away to friends who may want one of their own. Just be sure they wait a few days to let the wound dry and callus over before planting the bottom few inches of the cuttings in soil.

The best time to prune is in the spring when light and temperature have increased and the plant has started its active growing period. Be careful not to remove too many branches at one time because that could shock the plant. As a general rule, no more than 1/3 of the plant should be removed during any given pruning. Also remember that once something is cut off, you can’t stick it back on. So you may want to prune lightly and then see if that meets your needs. If not, then prune some more until you get the desired result.

For tips on a variety of gardening topics, see our guides - https://libguides.nybg.org
- Courtesy of NYBG Plant Information Service