The Homeowners Column

The Homeowners Column

Diagnosing Houseplant Problems

Photo of Sandra Mason

Sandra Mason
Extension Educator, Horticulture
slmason@illinois.edu

Is there a film on your philodendron? Does your fern look fried? As the dull dreary days of winter roll in, our houseplants can look as forlorn as a gardener after the first hard frost. The dry air of our homes in winter along with the lower light levels can send our houseplants into a downhill spiral.

Some plants are more tolerant to these environmental changes than others. Philodendrons and pothos take all kinds of abuse before they show symptoms of decline. Other plants such as rosemary, ferns and gardenias are not as forgiving and may not survive even one episode of extremes in watering, temperature, and light. Therefore it's important to do some homework to discover the proper methods for caring for your particular houseplants.

The lower humidity of our homes in winter is also a problem for plants. To raise the humidity around plants use a humidifier, group plants together or use pebble trays. Plants can be kept on a tray of wet pebbles or sand. As the water evaporates, it will increase the humidity around the plants. Misting plants does little to increase humidity unless done continually throughout the day.

Lower light levels can also be a problem. Supplemental lighting with fluorescent lights can help especially if they are within 8 to 10 inches from the plants. Even the addition of an incandescent light will help plants to make it through the winter in better health. With all due respect to Mr. Edison, incandescent lights are an inefficient light source with most of the energy given off as heat so leaves can be burned if placed too close to the light.

If you like to keep your house really warm during the winter, some plants will suffer. Rosemary and Christmas cactus prefer a cooler environment between 50 and 65°F. However others such as African violets tend not to bloom at low air temperatures.

If your houseplants are looking like they are on their way to the compost pile in the sky, you may have to play detective to come up with the cause. Is your spouse emptying coffee into the coleus? Here are a few symptoms and the possible causes of unhappy houseplants. To really confuse us, notice over-watering and under-watering can show similar symptoms and a variety of symptoms

Leaves fall off quickly
  • extreme temperature changes
  • extreme changes in light
  • root loss after transplanting
  • over-watering
  • under-watering
  • exposure to your son's new hairdo
Gradual leaf drop
  • not enough light (common with weeping figs that vacationed outdoors over the summer)
  • insufficient fertilizer
  • over-watering
  • under-watering
Wilting of entire plant
  • exposure to cold
  • excess fertilizer
  • over-watering
  • under-watering
  • exposure to cold thoughts, cold hearts and cold deeds
Spotted leaves
  • sunburn (distinct light tan spots)
  • cold water on leaves (especially fuzzy leafed plants such as African violets)
  • leaves touching cold windows
  • bacterial or fungal disease (spots may have concentric rings or brown border)
  • air pollution
  • over-watering
  • mite damage (looks like tiny yellow speckles)
Leaf tips turn brown
  • low humidity
  • soil pH not correct
  • air pollution
  • water quality (some plants such as spider plants and dracaenas are sensitive to fluoride)
  • not enough fertilizer
  • too much fertilizer
  • over-watering
  • under-watering
Dark bumps on leaves or stems
  • scale insects
Sticky spots on leaves and sometimes even on the floor around the plant
  • aphids
  • scale insects

Houseplants may seem like a bother at times. However keep in mind studies have shown the calming effects plants can have on us in our environment, indoors or outdoors. Hugging a silk plant just doesn't have the same effect.

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