Stress Relief for Indoor Plants

By Ellen Barredo

(This article first appeared in The Gateway Gardener January/February 2008 issue.)

a picture of houseplants growing under grow lights

Growing houseplants under lights

We all know what happened to your houseplants in December. As decorating and celebrating the holidays took place, plants were shoved into dark, dry corners, and erratic watering schedules were followed; as a result, they’re showing their displeasure with symptoms of stress, like wilting, leaf spots, dropped foliage, yellow foliage, dirty foliage, or browning tips.

Luckily, you’re reading this article! Make it a New Year’s resolution to change your ways. Modify your care routine and maintain the proper growing environment and your stressed out plants usually can be cured of their ailments.

Light is an important and challenging factor when placing plants indoors. Light changes with the time of day, time of year and, in the case of artificial light, with distance from the source.

Maintenance light levels allow the plant to survive or maintain itself with little to no growth. In this case you will want to purchase a plant the size you need it to be, and  control the fertilizer in order to not encourage growth. Many tropical plants that enjoy high light can be wintered with maintenance light levels and slowly acclimatized to higher light levels when moving back outdoors in spring.

High light levels to allow plants to grow and produce new leaves, stems, roots and flowers indoors can be difficult to provide naturally in winter, but can be achieved when supplemented by artificial light.  You can measure the light a plant is receiving with a light meter,  available at some retailers or for purchase online.  Most important here is know your plant’s light needs! Also, keep foliage dusted. Dust greatly reduces light getting to a plant. Try the Swifterâ duster to clean plant foliage.

Let your water sit out for 24 hours in milk jugs with the lid off so chlorine and fluorine can escape. Your plants will thank you. If you have a soft water system in your home,  the systems usually treat hot water only, so use cold water to fill your jugs. For special needs plant collection like orchids, many people find they get better results with water purified by reverse osmosis, available for purchase at water stations such as a some Schnuck’s stores.

A proper balance between water and air is ideal for strong, continuous plant growth. When soil pores are filled with water, the soil is considered saturated, and if saturation persists for a long period of time, root damage or death may occur due to lack of oxygen. Make sure your plants are in pots with drain holes and monitor the water applied to the plants to see if the pot is draining freely. Most importantly, don’t water by the calendar. Use a moisture meter, or stick your finger in the soil and feel how wet it is.

Where does it come from? Fertilizers! Salts can accumulate in the growing medium over time, causing browning of leaf tips or edges and can reach levels that are stressful or even toxic to roots. Follow the dosing directions on the fertilizer package. Periodic flushing of the soil with water can help remove excess salt. Don’t forget to remove the excess water in the tray!

Maintain a proper pH range to ensure nutrient availability.  Interiorscape specialists suggest 5.5 to 6.3 for soilless mixes and 6.5 to 7 for soil-based growing mediums. Simple PH tester can be found in garden centers. Be sure to clean the probe after use to ensure accurate readings in the future.

Rule of thumb: if you are comfortable indoors, the plant is comfortable.  Ideal indoor temperatures for plants are 65 to 75 degrees. There is always a lack of uniformity in temperatures within the home environment. Excessive heat or cold can damage plants. Drafts near doors or windows, heating and cooling vents blowing dry air, extreme temperatures inside garden windows, and leaves touching window glass are all commonly reported indoor problems. Cold damage symptoms may show up as brown, wet leaf margins, brown or black leaf spots and defoliation.

High temperature problems in plants display themselves by producing weak leaves and stems. We call this stretched growth. (It can also be caused by low light levels.) Defoliation and tan leaf spotting can occur if plants have been allowed to remain too dry too long. High temperatures also create a great environment for spider mites to develop.

Many houseplants come from a growing environment where the humidity is 80 percent or more, much higher than the relative humidity found in most homes. A humidifier that is in sync with the heating system can help achieve around 60% humidity, a level that is comfortable for people and to which most plants can adapt. Plants with special requirements can be group together in a room or window and be maintained with specialized care if needed. See your independent garden center for help with these techniques.

Pollutants in the home, office, or workspace can sometimes be found to cause foliage disorders in interior plants.

Kerosene heaters used to provide heat for sun porches and garage  plant storage areas may be a source of different gases that can cause problems for plants. Ventilate by opening and closing doors. Painting this winter?  The chemical additives found in many paints have been shown to cause leaf drop in some plants such as ficus trees. Good ventilation during the painting process will help avoid these problems. Hair salons often find their interior plants suffer with the negative effects of hair spray. Monitor plants in bathrooms and use ventilation when spraying hairspray and deodorants. Frequent cleaning of foliage is helpful in maintaining a healthy plant.

I hope this information will help you provide an environment that will keep your plants healthy for 2008!

Ellen Barredo studied horticulture at the St. Louis Community College at Meramec, and is a Missouri Certified Nursery Professional with more than 27 years in professional horticulture. She works at Bowood Farms and can be reached at (314) 454-6868.