How do I encourage my indoor cactus plant to bloom? It was blooming when I bought it, but it hasn’t bloomed since. –Barbara
Proper maintenance will vary depending on the type of cacti you are growing. There are two main types of cacti: desert and jungle/forest cacti. The difference between the two is relatively simple: Desert types originate in desert regions, and jungle/forest cacti are native to tropical areas. Here are general growing requirements for each type, though various species may need additional care.
Your label may tell you what kind it is; otherwise you should try the desert cacti tips first, and if it is not showing progress, try the jungle/forest tips.
Desert cacti (the spiny kind) are a challenge to get to bloom indoors, simply because we can’t provide as much light as a sun-drenched desert. In addition to light, two other important factors for blooming are: Age: Some plants take as many as 50 years to mature. The best way to check this is to buy one that’s already blooming. Dormancy: Many desert cacti bloom in response to a cool, dry, dormant period. During the winter, you should reduce watering to only about once a month—just enough to keep the plant from shriveling up—and move your cactus to a cool spot, around 50 degrees, which has plenty of sunlight.
Desert cacti are successful when planted in a well-drained potting mix specifically used for growing cacti. If you do not have access to cacti potting mix, make sure to use soil that has ingredients such as perlite, sand and Supersoil mixed into it. Apply a cacti-specific fertilizer only during the growing season. Make sure not to keep feeding fertilizer once the season is over, because the cacti need to begin preparing for dormancy. The dormant period—usually during the cold, dry months of winter—is essential to healthy, flourishing plants.
Desert cacti thrive when grown in very sunny locations. They need strong, constant light to prosper. Make sure to place them in a south or west-facing window, supplementing with fluorescent lights when necessary. Keep them in a location with consistent temperatures between 55 and 80˚F. During their winter dormancy, make sure to keep them in a cooler (yet still bright) area—50 to 55˚F if possible.
Jungle/forest: Most jungle/forest cacti will successfully grow in average well-drained potting soil. For better chances of success, you can add perlite to the soil for faster drainage. You can use a general fertilizer during the growing season; however, make sure not to feed the cacti during the dormant period. Typically water jungle/forest cacti once per week. During winter/dormant months, water only when soil is dry to the touch. If the plant begins to shrivel, you may be watering too little or too often. Test soil by touching it to see what adjustment is needed.
Jungle/forest cacti do not need as much sun as desert varieties and need some periods of shade to flourish. Keep them in a bright location, but make sure they have some time each day when the sun’s rays aren’t striking them.
All indoor cacti do best in a sunroom or south-facing windowsill. They’ll receive the most sunlight, and the air around windows is generally cooler in winter than the interior of a room. Cacti need strong, constant light to do well. Keep all cacti in a location with consistent temperatures between 55 and 80 degrees.
During the growing season (spring and summer), your cactus needs maximum light and heat. Put your plant in direct sunlight, and turn it occasionally for even light exposure.
One of the most common mistakes cacti growers make is overwatering. Cactus will also need more water during the growing season. Allow the top 2 inches of soil to dry out before watering the plant thoroughly until it runs out the bottom (empty the drainage tray). Imagine a sudden desert rainstorm that soon dries in the sun, so never leave your plant in soggy soil. Only water when the soil is dry to the touch. Once a month is plenty during the dormant season, which is normally in the winter.
Fertilize cacti only in the spring and early summer, using a cactus-specific fertilizer or a highly diluted fertilizer lower in nitrogen and higher in phosphorus and potassium. Overfeeding will not make your cactus bloom!
Repot your cactus using a potting mix designed for cacti and succulents. This fertilizer or a highly diluted fertilizer lower in nitrogen and higher in type of soil is available at nurseries and other retailers that sell plant supplies. Don’t water your cactus for a week after repotting.
With these tips you should be able to keep your cactus in tip-top shape. They are easy plants which can thrive on neglect. Just keep an eye on them and set them out in the summer and you will love growing cactus.
Garden question? Send it to me at firstname.lastname@example.org.