House plant care for the winter months

By By Steve Strong / area horticulture extension agent
Nov. 19, 2003
Thanksgiving is almost here and still no frost in sight, but now is still the time to bring tender plants indoors for winter protection.
The indoor environment differs dramatically from the outside climate, requiring several changes in cultural practices to keep your favorite plants healthy through the cooler days ahead.
The first thing that plants must adapt to is temperature change. Transferring plants from a humid climate where heat and cold varies daily to one where room temperature stays constant causes changes in plant functions. While most plants respond favorably to the even warmth provided indoors, it is important to remember that heating vents can dry them out faster, causing leaves and blooms to drop.
In contrast lower light levels reduce plant metabolism and slow down growth, meaning that the plants usually require less watering. The biggest challenge for house plant growers is figuring out how provide the right balance of light and temperature without over-watering or over-drying the plants.
Most species are happiest with bright light provided from an indirect source, like placement near a sunny window without direct sun exposure.
Windows actually magnify the sun's light and heat, and can cause leaf burn or root drying, and other problems may also arise from close contact with indoor space heaters.
Watering is the most difficult thing to do correctly, whether the plants are indoors or out.
Mature plants with pot-bound root systems dry out faster, leading to the temptation to place large saucers underneath the containers to hold reserve water. The result is usually some degree of root rot, as the roots are depleted of oxygen from being placed in standing water for long periods of time.
Poinsettias wrapped in watertight aluminum foil are a prime example, often the victims of root suffocation long before Christmas arrives. If foil or water-collecting saucers are to be left under the plants for extended periods, then be sure to pour off excess water a few minutes after irrigating.
Since plants grow slower in lower indoor light, fertilizer needs are reduced along with water. Most house plant growers tend to fertilize with some type of liquid formula, normally mixed at a rate of one teaspoon per gallon during the active growing season.
During the winter months, reduce the concentration to one-half or even one-fourth of the regular amount, and only feed the plants once every month or two.
Several house plant species such as floral hibiscus are vigorous growers, shooting up several feet in a single season, and they may outgrow their designated indoor space. Severe pruning can be performed on most woody tropicals with no harm done, and root systems may also be pruned at the same time to slow overall growth and allow for transplant into smaller indoor containers.
Pest problems like mealybugs and scale insects are always a potential threat, and they seem to pop up almost overnight when plants are crowded together in close quarters.
Several spray formulas are available to growers, but the easiest and most effective way to combat insect attack is with a "systemic" bug killer, usually found in a granular form that can be applied to the potting soil and transferred by the roots throughout the plants.
Products to combat disease pathogens are also available to homeowners, although its better to prevent disease problems with the proper cultural practices rather than curing them with chemicals.
For more information on house plant care, contact your county Extension office or visit the university Web site at www.msucares.com.