December 5, 2011

Yard and Garden: Houseplants

By Richard Jauron and Willy Klein
Iowa State University Extension Scott County

Indoor plants help create a welcoming, calming, aesthetically pleasing environment in homes. In fact, more than 80 percent of homes in the United States have at least one houseplant, with a national average of 10 plants per household. Of the many plants in the world, only a few hundred lend themselves well to indoor culture. To have houseplant questions answered, contact Iowa State University Extension Hortline at (515) 294-3108 or

Should houseplants be fertilized in winter?

Fertilization is generally not necessary during the winter months, because most houseplants are growing very little or
resting. Indoor gardeners should fertilize their houseplants on a regular basis in spring and summer when the plants are actively growing.

What is the proper temperature for houseplants during the winter months?

Most houseplants grow well with daytime temperatures of 65 to 75 degrees Fahrenheit (F) and night temperatures of 60 to 65 degrees F. Temperatures below 50 degrees F or rapid temperature fluctuations may harm some plants. Keep houseplants away from cold drafts, radiators and hot air vents. Also, make sure houseplant foliage doesn’t touch cold windows.

How often should houseplants be watered in winter?

In general, houseplants require less frequent watering during the winter months than in spring and summer. Watering frequency is determined by the plant species, type of container, composition of the potting soil and environmental conditions in the home.

When watering houseplants, water thoroughly. Some water should flow through the potting soil and out the bottoms of the pots. Discard the excess water.

How can I raise the relative humidity indoors for my houseplants?

Many houseplants prefer a relative humidity of 40 to 50 percent. Unfortunately, the humidity level in many homes during the winter months may be only 10 to 20 percent. Humidifiers are an excellent way to increase the relative humidity in the home. Simple cultural practices can also increase the relative humidity around houseplants. Grouping plants together is an easy way to raise the humidity level. The water evaporating from the potting soil, plus water lost through the plant foliage, will increase the relative humidity in the vicinity of the houseplants. Another method is to place houseplants on trays (saucers) filled with pea gravel or pebbles. Add water to the trays, but keep the bottoms of the pots above the water line. The evaporation of water from the trays increases the relative humidity.

Misting houseplants is not an effective way to raise the relative humidity. Plant foliage dries quickly after misting. Misting would have to be done several times a day to be effective and is not practical for most individuals.

Several houseplants that were brought indoors in fall are dropping leaves. Why?

When plants are brought indoors in fall they often drop leaves. Environmental conditions indoors are less favorable than those outdoors. The less favorable growing conditions are stressful to plants. Plants respond to this stress by dropping leaves. It usually takes plants one to two months to adjust to the indoor environment when brought indoors in fall. Leaf drop may occur during this one to two month period.

Plants will be able to adjust to their indoor environment fairly quickly if they receive good, consistent care. Poor or inconsistent care will prolong the adjustment period.