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Winter Care for Your Cacti
submitted by Don Janssen, UNL Extension Educator
Getting cacti through the winter is less a matter of tender loving care than intelligent neglect.
Cacti native to North America are essentially dormant during the winter. Because they aren't growing, they need very little water and no fertilizer, and they thrive on cool temperatures.
Though cacti are adapted to withstand dry conditions, they absorb moisture rapidly when they're growing actively -- during the spring and summer. During that time, people often underwater them by letting the soil get bone-dry between waterings. Growth is best, however, if the soil dries only partially between waterings. This may mean watering indoor plants every two or three days when they're actively growing. Plants put outdoors for the summer may need daily watering.
In the winter, when growth spots, plants need only a light watering every few weeks to dampen the roots slightly and keep the plants from shriveling. During this time, even once-a-week watering may be too much. Overwatered plants may rot.
How you water plants -- from the top or the bottom -- depends on whether they're actively growing, what type of growing medium they're potted in and how thoroughly they fill their pots.
Watering from the top -- pouring the water on top of the soil and letting it trickle down through -- often works very well -- unless the plant is a barrel-type cactus that fills the top of the pot from side to side. It's a good idea to keep water off the body of a cactus -- it might contribute to rot problems.
Watering from the top also doesn't work very well if the plant is potted in peat that has been allowed to dry. Water poured on the top will simply run down between the medium and the sides of the pot. The soil beneath the plant and around the roots will remain bone dry.
With bottom watering, water enters through the pot's drainage hole and is gradually wicked up through the growing medium. Whether you submerge the pot up to its rim in water or fill and refill the saucer until the medium takes up no more water, it's important to empty excess water from the saucer so the soil doesn't remain saturated for a long time.
Even when they're actively growing, cacti generally need less fertilizer than other houseplants. During the winter dormant period, they need none at all.
When they're growing, cacti need a fertilizer low in nitrogen with a relatively high phosphorus content. Fertilizers with analyses such as 5-10-5, 10-20-10 or 5-10-10, which are often promoted for use with flowering houseplants such as African violets, are fine for cacti.
Though cacti may thrive for years grown at room temperature all year round, cooler temperatures are recommended for dormant plants. An unheated bedroom or porch where temperatures range from 45 to 55 degrees F is ideal. Growing plants on a windowsill is an alternative. Temperatures near a window are often 5 to 10 degrees cooler than elsewhere in the room.
The cool temperatures, combined with occasional watering and bright light, 'harden' the plants, making them stronger and healthier. Some cacti also form flowerbuds under these conditions, so your efforts to avoid killing your plants with kindness may get you a bonus in the form of cacti flowers in the spring.
University of Nebraska-Lincoln Extension in Lancaster County is your on-line yard and garden educational resource. The information on this Web site is valid for residents of southeastern Nebraska. It may or may not apply in your area. If you live outside southeastern Nebraska, visit your local Extension office
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