University of Vermont
Department of Plant and Soil Science
Winter News ArticleGROWING CACTI INDOORS
Dr. Leonard Perry, Horticulture Professor Emeritus
University of Vermont
Want to exercise your green thumb this winter? Try growing cacti as
houseplants. Desert cacti are well-suited to most indoor settings,
where the relative humidity is rather low (20 to 30 percent) during
True cacti, a type of succulent, are native to the Americas. Many
types may be grown as houseplants, each different in size, color,
shape, and flowering habit. Among the most popular types are the
star cactus, golden barrel, old man, bishop's cap, bunny ears,
rat-tail, pincushion, Turk's cap, and ball cactus.
Most cacti purchased at plant shops, garden stores, florists, and
grocery and discount stores prefer a growing space with plenty of
sunlight. Cacti grown on windowsills facing south usually flourish.
The next best exposure is light from an east or west window, since
it can provide direct sun for part of the day.
Many gardeners think there is too little light in our area during
the winter, but this is often not the case. With snow cover, more
light is reflected during the winter than penetrates through shade
trees around the home in summer.
If you just donít have enough light, you can supplement it with
artificial lighting. Be careful of the spot-type plant lights, as
they may get too hot and burn the plants if closer than 6 inches or
so. Many use tube plant lights, or simply daylight or natural light
fluorescent tubes, hung 6 inches or so over plant tops. Use plant
lighting, on timers, for 12 to 16 hours a day.
You can place the plants outdoors in summer, just donít move them
from lower light indoors into direct full sun outdoors, and donít
let them get watersoaked during rainy weather.
Perhaps the main trick to growing cacti is proper watering, and this
varies with time of year or rather if the plant is actively growing.
Many cacti have been killed from overwatering during the winter,
including mine. If the weather is cloudy, or even predicted to be
cloudy, don't water. If in doubt whether the soil is dry, don't
When watering actively growing plants (usually spring and summer),
water well, allowing excess water to drain. If pots are in a
saucer, empty the water out. In the winter when plants generally
take a rest, water very littleóperhaps once every couple weeks or
even once a month. Then, apply only a small amount to moisten the
soil area around the roots.
Maintain the temperature during the growth period (usually spring
and summer) at 60 degrees (F) at night and 10 to 15 degrees warmer
during the day. During the dormant period (usually fall and winter),
reduce the temperature to 45 to 55 degrees. If most of your rooms
are warmer than this, then place your cacti near a window (but not
touching it) where the temperature may be five to 10 degrees cooler
than in the middle of the room.
Fertilize the cacti several times during the growth period with a
liquid fertilizer. Use a complete balanced fertilizer, or look for a
fertilizer labelled for cacti and succulents. For a general
houseplant fertilizer, use only one-quarter of the label amount,
every other watering.
When repotting, use a soil mix prepared and sold for cacti. Or make
your own from one part coarse builder's sand, one part loam soil,
and one part peat moss. After repotting, donít water for a couple
weeks to avoid any rots on roots damaged during repotting.
Finally, if you brush against your cactus and get a few spines stuck
in your fingers, use heavy duty tape (sticky side to the spines) to
pull them out.
Return to Perry's Perennial