By Larry Hodgson
The cacti family is a large one, comprising more than 1,700 species, most of them from extremely arid climates. And it’s precisely the desert cacti that we find most often offered as houseplants in garden centers, row upon row of very spiny plants of various forms—globular, columnar, branching, single, etc.—and often very hairy as well. And several produce beautiful flowers.
And there’s the complication. You’ll want your houseplant cactus to bloom, obviously. But what you need to do to get it to flower in the home? Many gardeners have had desert cacti for a decade or more without ever seeing a single flower. What can the average home gardener do to get their desert cacti to bloom?
Here are 3 secrets that cactophiles know … and now you will too!
1. Choose the Right Cactus!
The most important secret to getting a cactus to bloom is … to buy one that is in bloom!
Now, that may seem like cheating, but, above all else, you do need to make sure the cactus is old enough to bloom. So, if it is in bloom (or bearing fruit) at the time of purchase, at least it’s clearly mature enough. Some cacti take 50 years or more before they reach the flowering stage, and others almost never bloom indoors, yet some cacti flower in their second year. Unless you’re incredibly patient, you’ll want plants from the latter category!
Also, make sure the flowers are real. Many stores sell cacti with glued-on dried flowers often dyed in brilliantly artificial colors! If the flower is soft and silky and, underneath, it’s attached directly to a stem (yes, you have to look really closely), it’s a real cactus flower. If it is papery in texture and clings to the plant through a drop of hardened glue, it’s a fake. (You can learn more about fake cactus flowers here.)
2. Benign Neglect
The other mistake many gardeners make is treating their cacti too well.
True enough, cactus love the sun and it’s nearly impossible to give them too much, so a position in front of a south- or west-facing window would be ideal, but don’t water and fertilize them abundantly like other plants.
In the wild, desert cacti live under really tough conditions: little rain, extreme heat, often horrible soil. Watering them and fertilizing them abundantly stimulates an exaggerated and pale growth, but discourages blooming. In spring and summer, therefore, water only when the soil feels dry to the touch. In fall and winter, let the soil really dry out even more: a month or more without water is fine!
As for fertilizer (and “cactus fertilizers” do exist, although a standard all purpose one will do just as well), it’s best to give them only sparingly, at 1/10 of the recommended dose, and only in spring and summer.
3. Cool to Cold Winters
Finally, one last tip. The majority of desert cacti come not from tropical lowlands where temperatures remain much the same throughout the year, but from high altitudes where winters are cool or even cold. To stimulate flowering, therefore, place your cacti near a cold window, down to 40?F (4?C), during winter. And remember, water very, very little.
Do not be too discouraged if this treatment doesn’t seem to work immediately, because, while the treatment needs to be given in the winter, the plant won’t be blooming until the following spring or summer. That’s blooming season for most desert species. Also, if your plant was treated too generously in the summer, it may need to take a year or so to get back into blooming condition.
Still, you’ll be surprised at how many cacti will bloom yearly when they are 1) mature, 2) given benign sunny neglect in the summer and 3) grown cold and dry in the winter.
Ha! Years ago, I grew a tub of about three canes of cereus cactus that made the trip between Los Gatos and Los Angeles a few times, without ever blooming in my garden. I liked it just for the striking form, but would have liked to have been able to brag about it blooming in my garden. I brought it home from Los Angeles in about 1990. It was happy for a few years, but did not bloom. My colleague took it back to Los Angeles, where it bloomed almost immediately. I know that bloom was initiated in my garden, but did not happen until the cactus was back in Los Angeles. Nonetheless, I had nothing to brag about. Anyway, I brought it back to get it to bloom in my garden. It never did. Of course, my colleague brought it back to Los Angeles, where it promptly bloomed. Seriously! It did that a few times, and is now much too large to bring back here.
Good advice. I have a couple who bloom reliably in the early winter. They spend the summer outdoors but then go into an unheated greenhouse until it gets really cold. The cooler temps than warmer seem to trigger bud formation. Alas you have to watch the plants carefully as the blooms are very short lived
Great tips! I didn’t know about the cooler temperatures helping to stimulate bloom. I’ll give it a try this winter.