Cactuses not Blooming

Q: Over the last few years, I’ve collected a number of cacti and succulents. When I look them up online, it shows that they have gorgeous flowers. Mine never bloom. I have them in various windowsills and on tables near the window. Do they have to be older to flower? Do they need a certain kind of fertilizer?

A: I’m amazed how popular cacti and succulents have become. I see them for sale in most nurseries, grocery stores, and big box stores. I even often see them in my drug store. The species I see are easy for the production nursery to grow (Echevaria, Sedum, Mammillaria, Crassula, etc.) but are not necessarily the best for windowsill culture. These also are not known for their beautiful flowers.

Now most of the cacti that we grow indoors come from Central America. They may be from desert or mountainous areas but most species live in regions that are hot during the day and quite chilly at night. This temperature fluctuation is often necessary for stimulating cacti to produce flowers. Think about it; most homes stay at a similar temperature day and night. To stimulate flowers, look for a cooler room (like a guest bedroom) to keep the plants in (at least during the winter months). Shut off the heat register and give them as much light as possible. Temperatures between 45°F and 55°F will stimulate flowers in most species. If you don’t have such a room, there’s an alternative plan. Move your cacti and succulents outdoors in early June and leave them outside until light frosts begin in September or October. The natural temperatures in our region can fluctuate 20-30°F from day to night. This will certainly help with the flowering process.

Very little fertilizer is needed for cacti but it can be helpful in their overall health. Find a fertilizer that is particularly designed for cacti. These often contain calcium nitrate. Or use fertilizers from the sea such as kelp or fish emulsion with more natural calcium. Apply fertilizers only while the plants are in their active growth phase which is usually from March through September. Less is more. In general, let cacti and succulents dry thoroughly between waterings. Also, water much less while they are cool in the winter months.

Written by Kelly Grummons, who writes our Q & A column, is co-owner of the mail order nursery businesses, coldhardycactus.com and dogtuffgrass.com