rotting euphorbia ?


Hello – we have a very tall but sickly looking euphorbia (I think it’s one). Can it be saved? Should the rotten top be cut down? It’s covered with it’s prickles so I’m not sure how it can be re-potted. The current pot is about 18 inches across. There are 3 plants, all about 5 foot high. The plant is in a small company and I think they have been overwatering it for years but am not sure. Pls help as it’s been with the company so long and we want to revive it. thx


Thank you for contacting the Toronto Master Gardeners concerning your much loved Euphorbia  trigona (African Milk Tree)

Cactus are low maintenance plants that thrive with benevolent neglect.  All cacti prefer to be slightly pot-bound, and although the temptation might be to put a tall cactus into a much larger pot, it is often better to leave them in their smaller containers, and if they are top-heavy, place this container into a larger pot and anchor this pot with heavy stones or other decorative materials.  Repotting a columnar cactus isn’t necessary until it is evident that the roots are protruding from the bottom of the pot.

The following information on the proper technique for repotting a cactus comes from a compilation of a number of our archived posts:

It is important to repot in a new container that is only one size larger, rather than moving the cactus into a much larger container. Large containers retain more moisture than smaller pots, and cactus roots, which are tender and easily damaged, are susceptible to excessive moisture. Over-watering is one of the most frequent reasons cacti fail to thrive. Ideally, a clay pot should be used. Use soil that is specifically for cacti which can be found in most nurseries & garden centres.

Repotting a cactus this size can be a tricky undertaking as you not only have to protect yourself from the spikes but from the white sap that is produced by all Euphorbias. This  sticky white sap can be irritating to the skin, eyes and mouth. As a result, the use of tough leather gloves and safety glasses is recommended.

Once you have assembled your soil, new pot, and protective gear, turn the pot upside down. Place one hand around the plant to guide it from the pot while you tap the bottom of the pot with your other hand.  If the cactus does not come easily out of the pot break the pot.  This will prevent root damage. Once you have the cactus out of its old pot, inspect the roots to make sure it is not severely pot bound, diseased or infested with mealybugs. Loosen roots if necessary.

Add new soil to the bottom of the new pot and then sit the cactus on top, checking that the base of the cactus comes to the lip of the pot – it is important that the cactus is not planted any lower that it was originally — so no new soil on top. This is also a good time to straighten or re-position the plant. When the cactus is positioned correctly, fill in around the plant using a chopstick or bamboo skewer to poke the soil around the outside. A few gentle taps of the pot on the counter in an up-down motion will also help settle the new soil around the roots.”

Ideally, your plant should be repotted every two to three years. Once repotted, placing this plant in a south facing window is ideal, however an east or west facing window will also work as long as they receive at least 4 hours of bright indirect light each day. Make sure that your plant dries out between watering. Place your finger 1” into the soil, if its dry, it’s time to water.

Looking at your photo it appears to have a few healthy arms coming off the top and side. These can easily be removed with a serrated knife or saw . The following links give step by step instructions as how to go ahead and propagate your Euphorbia from these cuttings: How to Propagate African Milk Tree, How to grow and Care for African Milk Tree

Here’s to many years of enjoyment of your beloved Euphorbia cactus.