Plant Lighting

By Jeff Rugg

February 19, 2020 5 min read

Last week, I mentioned the recent OnePoll that found millennials want to grow houseplants, but are often apprehensive about taking care of them. In fact, 20% would rather have a root canal than take care of a plant because of the pressure of keeping it alive.

Before buying a plant, it is important to take a look at the environmental conditions in your house. The condition that confuses people most is how much light to give your houseplant. There are many ways to measure light, but we don't have light measurement tools like we do for temperature and humidity.

Let's keep it simple. In low light, you will just barely see a shadow of your hand. If you can see a shadow with fingers, it is medium light, and if the shadow is sharp and contrasts with the light, it is a bright light.

If you have a camera with manual settings, adjust the ISO speed to 100 and the shutter speed to 125 and then look at what the camera chooses for the aperture number. If it is less than 4, the light is low. If it is between 4 and 8, the light is medium. If it is above 8, the light is bright. There are light meter apps for phones that can measure foot-candles of light. In general, less than 300 foot-candles is low light, between 300 and1,000 is medium and over 1,000 is bright.

What kind of light can you expect indoors? If there are no outside obstructions like trees or nearby buildings on a typically sized residential window, a south-facing window will have direct sun all day long. On the opposite side of the house, the north-facing window will see no direct light at all. The east side windows will get morning light, and the western windows will get afternoon direct sunlight. Within 3 feet of a directly sunlit window, there will be bright light. Then there will be medium light for another 3 feet and finally low light to about 10 feet away from the window.

Of course, shade from trees and buildings can block a lot of sunlight, making an otherwise bright window into a low-light window. Large, atrium-style windows can allow much more light into a room than a normal window.

Plants can even shade themselves. A plant that is leaning to the light or is one-sided is indicating that it needs more light. That plant needs to be rotated on a regular basis so that it gets enough light on all sides.

Many people don't realize that tropical plants are affected by daily and seasonal temperature changes. The flowering and fruiting seasons may be signaled by temperature changes and changes in rainfall. Many houses are controlled by thermostats that keep the temperature the same 24 hours a day. It is beneficial to plants to allow the nighttime temperatures to drop — and it may benefit your utility bills.

Many new gardeners want to water their plants on a schedule. Plants in nature are not on a schedule. They may get daily rain in the wet season and then no rain for weeks during the dry season. Plants can be divided by their soil moisture needs. They may need wet, damp or dry soil, which may change seasonally. Touch the soil at the top of the pot. If it is cool to the touch, it is damp and probably doesn't need to be watered yet.

The proper humidity for growing tropical plants is important for plant health, but it is often neglected. A tropical jungle plant may need humidity levels over 70% to thrive. The humidity level in a home in the summertime may be 40% to 50%, but in the winter, it may drop to below 20%. Plants needing more humidity will often have leaf tips that turn brown, leaf edges that turn yellow and leaves and flower buds that fall off.

You may not need to raise the humidity in the whole house to benefit a few plants. A room humidifier may be useful. They may be helped with a regular misting or by placing a tray of water under the plant. The water will evaporate and raise the humidity in the area around the plant. Too much water in the saucer under the plant may drown the plant roots. Placing some stones in the saucer to raise the plant pot will keep the roots healthy and allow the water in the saucer to increase the humidity.

Next week, we will cover some easy-to-grow houseplants and how to move them outdoors for the summer. Check out the A Greener View website for a video on houseplants and their lighting needs.

Email questions to Jeff Rugg at [email protected] To find out more about Jeff Rugg and read features by other Creators Syndicate writers and cartoonists, visit the Creators Syndicate website at

Photo credit: leoleobobeo at Pixabay

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