The cathedral cactus is one of my favorite houseplants. It is extremely easy to grow and can become quite large, making for quite a specimen in your home. It is also not a cactus.
The cathedral cactus (Euphorbia trigona) belongs to a large genus of plants – Euphorbia – also known as spurges. Most of these can trace their origins to Africa, and the cathedral cactus is from tropical West Africa. It gets its common name from how its stalks grow upward, looking like the spires of a Gothic cathedral. It is also sometimes called the African milk tree. This name comes from the milky substance that is produced when the stalks are cut or broken. This substance contains latex and can cause skin irritations; therefore, you should always wash your hands anytime you come in contact with this substance.
I started my first cathedral cactus from a piece given me by a friend. In fact, to start a cathedral cactus, all you need to do is cut off a stalk of the plant. Stick this in some potting soil, water, and sit it in bright light. Some gardening books may tell you to mix up some kind of special potting mix for your cathedral cactus; however, I have never found this necessary. I have always planted mine in standard potting soil. [For more information about different kinds of potting soils, see my article Making Your Own Potting Mixes for Your Houseplants.] You do want to make sure that your cathedral cactus does have good drainage, though.
The cathedral cactus requires regular watering during the growing period in the spring and summer. You do not want the soil to be soggy, though. Water well and then allow the soil to dry out between waterings. Apply a balanced fertilizer every 2-4 weeks during this period, too. As your cathedral cactus grows, it will produce numerous bracts that look like leaves. These are actually the plant’s blooms, which will start dying and dropping off as the cathedral cactus begins to go into its dormant stage. During this period – in the late fall and through the winter – you can virtually ignore the plant. I throw some water on mine whenever I happen to think about it – about once every two weeks.
Cathedral cacti have rather shallow roots and generally do not require frequent transplanting. However, as they grow taller – I had one that was easily 7-8-feet-tall and at least 4-feet around – you will probably want to plant it in a much larger container to keep the plant from tipping over. (They do tend to get a bit top-heavy.) Be careful when transplanting, though. There is a reason this Euphorbia has been mistaken for a cactus – it has thorns. Wear heavy-duty gloves. I have even wrapped my larger cathedral cactus is a blanket in order to move it from one pot to another.
Cathedral cacti like bright light. [See my article Houseplants: Determining Light Levels in Your House.] You might also consider moving your cathedral cactus outside during the spring and summer. I have noticed, however, that they do not like the hot afternoon sun we have in the South and will scorch. You will, therefore, want to give them some protection. Also, the cathedral cactus does not like even a little frost. You should, therefore, not move it outdoors until all danger of frost has passed and bring it back indoors well before the first frost in the fall. (Note: If you live in zones 10-12, you can grow the cathedral cactus outdoors in the ground.)
Dena is a freelance writer and publishes extensively online with articles appearing periodically in local print publications. As a gardener for over 40 years and a TN Master Gardener, she enjoys sharing gar… View profile