Euphorbia trigona ‘Rubra’

This plant likes a nice warm spot.

Columnar euphorbias can get surprisingly large, so be sure to note the size, and place your plant accordingly.

They respond well to pruning. They will look scarred for a while, but then will push new growth wherever they are pruned, often giving you several new growth points. Take care when pruning, as euphorbias have toxic sap that can cause a skin rash or damage to the eyes (make sure to rinse repeatedly with water if sap gets on your skin or in your eyes).

They like a warm sunny exposure but do surprisingly well in shady areas as long as they aren't given extra water during winter.

As columnar euphorbias grow they will transition from colorful and smooth new growth to dull, brown and rough older growth. This is called corking, and it is totally natural. Think of this like an oak tree where the new shoots are shiny and green, but then eventually you get a trunk covered in rough dull bark.

Soft dark brown spots on Euphorbia are usually a sign of rot. Carve these spots out with a sterile knife immediately (carve all the way back to healthy-looking tissue). Rot usually results from overwatering, but it can also be caused by drastic under-watering. Occasionally this will start at the base of the plant, which means the roots have rotted. If you'd like to save the plant you'll need to remove the top above the rotten base, let the top sit for two weeks in a shady spot, and then replant in very sharp-draining soil. Place the cutting in a warm spot to re-root, preferably not in harsh sun.

In the movie 'The Gods Must be Crazy,' a villain hides under a columnar euphorbia, only to be outwitted when his pursuer shoots the plant, pouring down toxic sap all over him. Clearly the screenwriter knew their plants!

These plants are often confused with columnar cactus because, through convergent evolution, they have adapted into a similar form. However, euphorbias are not closely related to cactus. In fact they're more closely related to the holiday poinsettia. Some notable differences are euphorbia's latex sap, insignificant flowers, tiny little leaves when in growth, and thorns instead of spines to protect themselves.