Columnar Euphorbia Care
Columnar Euphorbia make excellent houseplants when grown in a fast draining cactus mix. Here’s how to care for them in your home:
Euphorbia are plants that want warmth; south- or west-facing windows are the best place for them inside (four or more hours of direct sun shining on the plant), though they can also be grown in very bright indirect light. Since their skin is more delicate than cactus, they may burn if placed within 18 inches of a window. Arranging them at an angle to the window will help prevent this. If you are growing them in bright indirect light, make sure the plant has excellent drainage and is kept as warm as possible.
Since these plants grow during the summer, water should be gradually increased through late spring into summer, when they can go dry without being bone dry. This means that the soil throughout the pot doesn't feel wet, but also doesn't feel crackly and chalky. Don't let them sit around bone dry during this time; shriveling is a sign they’ve been under-watered. While fertilizer is usually unnecessary, you can apply an all-purpose fertilizer at 1/4 strength during the summer months.
Water should be gradually decreased during the fall. In nature euphorbia get very little winter rainfall. During the winter they should become bone dry between watering. It is often hard to reconstitute water into a bone dry plant (as it is like a dry sponge, where water will just run off) so make sure you let your euphorbia stand in a saucer of water until it has completely sucked up the water. Continue adding water and letting the plant suck it out of the saucer until there is standing water in the saucer that isn't absorbed. You can then either dump out the saucer or put a rag / sponge / turkey baster in the saucer to absorb the extra water and remove it. Don't ever let columnar euphorbia stand in water more than 12 hours.
The most common issue with these columnar euphorbia presents as brown spots. If they are light brown and hard like a scab, this is likely corking, which is the natural progression of the plant becoming older. Think of corking as the smooth green bark of a tree becoming woody over time. This is totally normal, don't worry.
However, if the brown spots are darker and squishy, this is a sign of rot. Rot needs to be surgically removed, as it will spread and kill the plant. The sooner you catch rot, the more likely you'll be able to save your plant. There are three possible scenarios here:
- For just a little spot of rot, dig back to healthy vibrant tissue and let the plant scab and recover.
- For rot that's circled the column midway up, you'll need to remove the top, clean the rot from both top and bottom back to healthy vibrant tissue and re-root the top. Do this by letting it scab over for 2-3 weeks and then replanting the top in very fast-draining soil (1/2 pumice or lava rock and 1/2 cactus mix) and place it in a warm bright spot out of direct sun. Rooting hormone is also useful for this, if you have it. Cement or tile floors are great for re-rooting as they transfer that heat to the plant, but you can also use a heat mat set at 72F if you have one. In this scenario you'll get a new plant from the top, and the bottom will sprout a new head and continue growing. (This is also how you would propagate the plant, usually done in late spring when the plant is actively growing.)
- If rot happens at the base, circling the column, you'll need to propagate the top, but the bottom is done for and should be discarded.
Euphoriba have toxic sap so always wear gloves and eye protection when pruning!!
Other common problems with indoor-grown euphorbia usually arise from plants cultivated in cold rooms without enough sun. We see issues when plants are drastically under-watered during summer; however, even a little overwatering in winter can be disastrous. Watering without reaching full saturation is another common mistake