While desert cacti are almost impossible to kill, possibl because they have evolved to survive the harshest conditions.
Ultimately if you care for indoor cacti as you do other houseplants, your cacti are doomed to failure, however, once you understand their needs, your indoor cacti will thrive under your care.
How Do I Grow Indoor Cactus?
Cactus do well indoors. You should try to place indoor cacti in a window facing south, if possible. Choose an east- or west-facing window otherwise.
Supplement with additional bright light for a total of 12 to 18 hours a day during the cacti’s growing season to encourage flowering.
Maintain a relative humidity of 10 percent to 30 percent and a temperature between 65 and 90 degrees Fahrenheit.
The Less Light = Less Water
Move cacti to a location where the temperature ranges from 45 to 55 so they can go dormant for the winter.
During Winter, water cactus sparingly and from the bottom, just often enough to keep the plants from shriveling.
Even watering once a week may be excessive, depending on the plant and growing medium. Stop feeding cacti during their dormant period.
Is It Time To Repot Your Cactus?
Things You Will Need
Peat moss (optional)
Garden soil (optional)
Cactus potting mix (optional)
Hygrometer and Thermometer
Pot a desert cactus in a mix of 1 part peat moss, 1 part garden soil and 1 part sand, or a prepackaged mix designed specifically for cacti.
Transplant in the spring after the cactus has grown within 1/4 inch of the sides of the pot, but don’t allow it too much extra space.
Plant the cactus in the next pot size up. Do not fertilize immediately after transplanting.
Do All Cactus Bloom?
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, another important factor for blooming is age. Some plants take years to mature.
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.
Water just enough to keep the plant from shriveling up and move your cactus to a bright, sunny, cool spot, around 50° F.
When water uptake increases and buds are developing, the plant is no longer dormant and will need to be provided with care during the growing season.
Tip: Watch for flower buds to form and monitor the moisture level.
Warning… Do not allow water to stand or pool on the flesh of any cacti, especially barrel cacti. This practice can lead to a variety of rots and problems.
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!
Old-hand gardeners know for best success indoor cactus and succulent plants require a certain amount of neglect.