Indoor plants grace the house all year. Occasionally they are moved but more often that are stationary, which should mean that their climate is consistent. Wrong!
The change in light and temperature signals seasonal change to indoor plants. As the days grow shorter, plants are less likely to put out new growth and become dormant. If the plant is not actively growing, less moisture and fertilizer is needed. If watering is not adjusted, problems occur.
The two most common problems from overwatering are fungus gnats or a dead plant. Fungus gnats look the same as fruit flies and are in any organic soil. They, like all insects, need ideal conditions to hatch and reproduce. Warm, continuously wet soil that contains fungus is ideal. If left unchecked, it takes about five weeks for the eggs to hatch, become larva and then adults. Each adult can lay up to 200 eggs. Disturb any part of the life cycle and the insects will be gone.
The easiest method is to wait to water the plants until the top inch or two (two to five cm) of the soil is dry. Have patience as the larva will sill hatch into small flies until the soil is dry.
Another method is to sprinkle cinnamon on top of the soil. It kills the fungus that the larva feed on. Without food, the insects starve. Do not mix the cinnamon throughout the soil as the fungus helps break down organic matter to supply nutrients to plant roots.
Covering the top of the soil is also effective as it stops the new gnats from leaving the soil and the old ones coming back to lay eggs. The following method is once again gaining popularity: place approximately a half inch (one cm) of dry, clean sand on the surface of the soil. Sand dries out fast and contains little organic matter, making it a poor place for gnats to live and reproduce.
Soil is made up of particles, moisture and air pockets. When soil is overwatered, there is less air and more moisture in the mixture. Plant roots take in moisture by osmosis, a process that needs air. When air is not available, the process stops and the plants wilt due to lack of ability to take up moisture. More plants die from too much moisture than not enough. Always test the soil with a finger or water meter before watering. If in doubt, do not water.
Insects come into the house by flying, as eggs, by catching a ride on other plants or on clothing. Regardless of how careful one is, insect infestations on plants happen.
Taking a close look at the indoor plants when they are being watered is a good start as problems can be found before they are unmanageable. Given the correct conditions, insects populations expand rapidly.
When insects that feed on the plants are found, isolate the plants that have insect infestations. Spraying plants with an insecticidal soap will coat the plant and insects. It won’t hurt the plant but should stop the insect from flying and breathing. As soap rarely has any effect on eggs, the solution must be sprayed daily until the problem is solved.
In extreme cases, remove all the top growth from a plant and the plant material from the top of the pot. Insects are removed with the top growth and new foliage will appear insect free. This method works best on plants that are vines. The plant must have the ability to send up new growth from its roots and look attractive.
Indoor plants are part of our indoor environment. Give them a little — but not a lot — of attention and they will thrive.
Linda Tomlinson is a horticulturalist who lives near Rocky Mountain House. She can be reached at www.igardencanada.com or firstname.lastname@example.org.