Many of us gave our houseplants a vacation all summer long to recharge and recover from being indoors. Yet here we are again dealing with them for the dark days of winter.
It is absolutely true that they need to be watered and maybe even fed occasionally, but the most important piece to keep them going until spring is light. Unless you have that sunroom with windows all around, keeping up on the light requirement can be hard to do for every kind of houseplant we have.
You know something is up when the houseplants begin to have small leaves and long thin stems reaching for more light. Older leaves may begin to yellow and drop, and in general, your plants may be looking weak.
Light levels
Different houseplants require different light levels, which means the location in your home makes a difference. Low light levels (sometimes referred to as 75 foot-candles) come from not getting any direct light, such as a north window or being 8 feet or more away from any other light source. Windows that face east or west give us a medium level of light (or about 150 foot-candles), which is like being about 5 feet away from a southern window. The winner of the foot-candle race is a south-facing window, giving bright light at about 300 foot-candles. Natural light is the best, even if one-sided and coming in from the window. To prevent one-sided growth, rotate the plants to keep growth even.
More light factors
Besides the need for light, there are three other conditions to consider: duration, quality and intensity.
- Duration is how long the plants receive light.
- Quality is about the wavelengths in the light.
- Intensity is the strength of light the plants receive.
Houseplants need the correct amount of each in order to bloom. Foliage plants can be acclimated to lower levels of each and still look good.
Sources of supplemental light
If you want to supplement your light or use non-natural light, fluorescent was the best option for many years, but now we have a new player on the block, LED.
Fluorescent tubes can have improved quality of light as “grow bulbs” or “grow lights,” and fit the standard 48-inch fixture. Cool white and warm white bulbs add to both the duration and intensity by how long the fixture is on and how close the foliage and the tubes are. Fluorescent fixtures do generate heat so that can be a concern.
LEDs can be found with light that satisfies the quality and intensity issue without the heat factor. LEDs designed for plant growth will give us an interesting “glow” and the plants and any flowers will not look “natural” with the lights on, yet they will be a lot healthier.
• Richard Hentschel is a Horticulture Extension educator with University of Illinois Extension, serving DuPage, Kane and Kendall counties. This column originates on his blog at go.illinois.edu/overthegardenfence. To get more tips from Hentschel, watch his “This Week in the Garden” videos on Facebook and YouTube.