Gardening Under Artificial Light: What You Need to Know
Are your indoor plants hungry for more light? While your house may look well-lit, it's quite possible your plants are actually starving for more light.
Growing plants in the home comes with its share of challenges and, among them, insufficient light is usually the most serious. It is hard to believe that most homes are too dark for plants -– they seem so well lit -– but some growers just starting out fail to distinguish between light adequate for human needs as opposed to plant needs.
Plants require lots of light and might actually starve to death for lack of light in a house with perfect lighting for common activities such as reading. This is because plants see and use light differently than humans do.
Maximum Light Produces Best Growth And Flowers
An outdoor garden may receive more than 10,000 foot candles of light during bright summer days, and experience has taught us that some plants produce the best growth and flowering rates only where they receive the maximum amount of sunlight. However, other plants grow better in somewhat shadier locations.
The greenhouse grower has better control over the light condition and distribution for their plants. They can provide maximum lighting at all times for commonly indoor-grown plants like roses, carnations, and chrysanthemums, while shade lovers, such as African violets, gloxinias, orchids, and foliage plants, need no more than 1,000 foot candles of light.
To convert foot candles to Photosynthetic Photon Flux (PPF), which is a measure of Photosynthetically Active Radiation (PAR) – the range of lighting plants require, check out this calculator here. Here’s a sample conversion of 10,000 foot candles:
Good Light May Not Be Plant Light
In the home, it is unusual to find more than 40 foot candles of light except for maybe near a window free from obstructions. Typically, the sunlight entering through the window is hindered by trees, nearby buildings, eave overhangs, blinds, shades, curtains, or drapes. This results in a window considered to provide good light for humans to be a well-shaded window as far as plants are concerned.
In spite of these vast differences in light values between outdoor and indoor areas, plants can be grown successfully in the home. In general, plants that flourish in shaded areas outdoors will do best indoors, provided temperature and moisture conditions are suitable. Only a few plants will thrive in dark areas (Aspidistra or Mother-in-Law’s Tongue, for example), such as on inside walls, while most plants grow better near a window or in other well-lighted areas.
Growing Under Lights With Excellent Results
We often assume growing plants under lights as something new, but it’s not. More than 50 years ago, research at Ohio State University and the Ohio Agricultural Experiment Station showed excellent results in growing plants indoors under fluorescent lights, without any sunlight whatsoever.
Nowadays, fluorescents, LEDs, and other types of lighting systems such as HID systems designed specifically to create lighting in the PAR spectrum ensure plants can be grown without sunlight. The practical applications for growing indoors in the home are many.
Plant Lighting In Our Homes
In our homes, the lighting in the living area should be ornamental as well as functional. Very often the light must be attached somewhat high above the plants, resulting in insufficient light to produce active growth, but enough to maintain them in good condition. Since it is often more desirable to keep foliage plants in constant, slow growth, additional artificial grow lights are advisable even though the source is some distance from the plants.
If you can devote a particular area like a basement or spare room for growing plants, an ideal indoor garden can be established using fluorescent lamps as the sole source of light. Provide a uniform temperature of 65 to 70° F and a convenient method for watering the plants and you are ready to grow.
The size of the area you want to light and the types of plants you plan to grow will determine the kind of lighting installation. You will need to light the area for about 18 hours each day, and for African violets and foliage plants you will need 500 foot candles of light.
Simple Set-up To Get Started
To accomplish this, suspend two 40-watt industrial type fluorescent fixtures a foot above the tops of the plants. That provides uniform lighting to an area about 3 x 4 feet. You can economically light a larger area using a single strip fluorescent fixture mounted on plywood, painted with white enamel to increase light reflection. Plants such as gloxinias and orchids grow better with more light. To provide it, place the single strip fixtures closer together on the board and lower the lamps to within six inches of the leaves.
Many growers use their indoor garden to start annuals and veggies for their outdoor gardens or growing indoor plants year-round. Garden plants require high light intensities, and about 1200 foot candles of light can be furnished using single strip fluorescent fixtures placed about two inches apart on the reflector board, with the lamps kept within six inches above the leaves. Several qualities of fluorescent lamps are available, but the most satisfactory in the Ohio tests was the cool white fluorescent lamp. I've used cool white fluorescent tubes for years.
If plant growth is slow, weak, or spindly, it may indicate insufficient light, either not enough intensity or a lighting period which is too short. Just like a soil test provides details about the soil makeup and gives you a starting point to make improvements, a light reading will give you an idea of the amount of light being developed in your grow room, allowing you to make adjustments to your lighting periods and the distance the lights are placed above the plants.
TIP: Ask a photographer friend to help you get a proper light reading of your installation. They are always checking light levels!
When you establish an indoor garden using the lighting of your choice in a spare room or the basement, the plants can be displayed periodically throughout the home and returned to the growing area later for rejuvenation. In a well-lit indoor garden, you can expect startling results.
Written by Gary Antosh
Gary Antosh runs Plant Care Today, where he shares his 30+ years of commercial growing experience to help others learn to grow.