Yard and Garden: Take Care of Indoor Plants during Winter

With cold weather and snow outside, it's a good time to focus on indoor plants. Iowa State University Extension and Outreach horticulturists offer tips for keeping indoor plants healthy during winter months. For answers to additional questions, contact the ISU Hortline at 515-294-3108 or hortline@iastate.edu.

Why does my fig tree lose some of its leaves during the winter?

Environmental conditions indoors during the winter months are often rather poor. Low light levels, cold drafts, low relative humidities and other environmental factors are stressful to plants. The stressful conditions may cause figs and other houseplants to shed a few leaves in winter. Good, consistent care during the winter months should keep leaf drop to a minimum.  

Fig trees prefer brightly lit sites near windows. Sites near east and west windows often are best. Make sure the plant is kept away from cold drafts or heat sources. When watering a fig tree, continue to apply water until it begins to flow out the bottom of the pot. Discard the excess water. Allow the soil surface to dry to the touch before watering the fig tree again. Figs, like most houseplants, don’t need to be fertilized during the winter months.

My African violets aren’t blooming well. Why?

The African violets may not be receiving adequate light. The proper amount of light is essential for good bloom. Generally, windows with north or east exposures are best for African violets. However, if these exposures are not possible, the plants also perform well under fluorescent lights. Suspend fluorescent lights 8 to 10 inches above plants. The lights should be lit for 12 to 16 hours per day.  

Excessive fertilization also could be responsible for the poor bloom. African violets need to be fertilized to promote bloom. However, excessive fertilization leads to vigorous vegetative growth and poor flowering. Using a complete, water soluble fertilizer, apply a dilute fertilizer solution once every two weeks in spring, summer and fall.  Fertilization usually isn’t necessary during the winter months.

The leaves on my houseplant are covered with a sticky sap. There also are small “bumps” on the stems. What is the problem?

It’s likely the houseplant is infested with scale insects. These small, inconspicuous insects have shell-like coverings. They attach themselves to stems or leaves and suck sap from plants. As they feed, the scale insects excrete a sweet, sticky substance called honeydew. The honeydew accumulates on the plant’s lower foliage, furniture, carpeting or other objects beneath the infested plant.  

The life cycle of scale insects consists of the egg, nymph and adult stages. Eggs are laid below the scale coverings of the adult females. When the eggs hatch, the nymphs crawl from underneath their mother’s scale and move a short distance to their own feeding site. The newly emerged nymphs are also called crawlers. At their new locations, the nymphs insert their slender stylets (mouthparts) into the plant and begin sucking sap. The covering or shell develops soon after feeding begins.  Scale insects remain at these feeding sites the rest of their lives.  

A small scale infestation causes little harm to healthy houseplants. However, a heavy scale infestation may result in poor, stunted growth. In severe cases, death of infested plants is possible.

Scale insects are difficult to control. Systemic insecticides are generally ineffective. The shell-like covering protects the scale from contact insecticides. The only time scale insects are vulnerable to contact insecticides is during the crawler stage. Since scale insects on houseplants don’t reproduce at a specific time, scale-infested plants will need to be sprayed with insecticidal soap or other houseplant insecticide every seven to 10 days until the infestation is eliminated.

Small infestations can be controlled by individually scraping off the scales or by dabbing each scale with an alcohol-soaked cotton swab. It’s often best to discard houseplants that are heavily infested with scale as control is nearly impossible and the insects could spread to other houseplants.