Garden Variety: Make sure your plants have proper lighting indoors

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Lighting is one of the biggest challenges to maintaining healthy plants indoors, and the shortened days of fall and winter make these seasons the toughest.

Fortunately, plant-appropriate supplemental lighting has improved in recent years and is more energy-efficient, affordable and aesthetically pleasing than ever.

Plants that are typically kept indoors include tropical species often referred to as houseplants; other plants that are not winter-hardy in Kansas but can live multiple years if kept from freezing; and seedlings produced to be transplanted into the garden in spring. Seedlings are usually not started until late January or February, depending on the crop.

In homes and offices, lighting for plants must come from a window, skylight, special supplemental lighting or a combination of factors. Standard home and office fixtures are too far away and inadequate for almost all plants. One popular exception is the increasingly available ZZ plant (Zamioculcas zamiifolia), which almost seems to grow better away from a window. For everything else, identify the species and what kind of light it needs, and get the plant into the right environment.

Tropical species can be categorized by what kind of lighting they prefer: bright light, moderate light or low light.

Bright light might mean an unshaded south or west window. Moderate and low light might be from an east window or a shaded window. The actual intensity of the light depends on how much sun reaches plants and how long it reaches them, which is affected by location, angles, UV protection on panes, window treatments and other factors.

Other plants that are sometimes overwintered indoors are things like basil and some species of begonias. Although they tolerate shade outdoors, they need bright light to survive the winter indoors. Use supplemental lighting to keep these plants healthy.

Seedlings need brighter light than what is available even in most south and west windows indoors. Use supplemental lighting to prevent plants from becoming stressed and spindly.

What to use

Lighting types and styles depend on where and how the lights will be used. For example, for tropical plants, a floor lamp or hanging fixture with LED or fluorescent bulbs will work well and is the most aesthetically pleasing for most gardeners. For racks with orchids, African violets or trays of seedlings, “shop light” fixtures often work best.

Many bulbs and fixtures are advertised as grow lights or plant lights. These bulbs are advertised as such because they produce a full spectrum of light similar to sunlight. They are the best option for plant lighting but are often the most expensive. Grow lights or plant lights are mostly available as fluorescent or LED bulbs.

In lieu of grow lights, regular LED lights are the next best selection for supplemental lighting. Look for ones that provide a full spectrum of light, or that at least produce red and blue light spectrums (they will still look white). LEDs are ideal because they are typically more energy-efficient and last longer than fluorescent bulbs.

After LED lights, fluorescent bulbs are the next best option. Use bulbs labeled as cool white or warm white for best results. For shop lights, use T5 or T8 bulbs for the best energy efficiency.

Any bulbs that are labeled simply as “white light” or “daylight intensity” are less suitable for fostering plant growth, as they are on a different spectrum than the bulbs described above. Incandescent bulbs provide the right spectrum of light but are less suitable because they produce too much heat for plants and burn out too quickly.

How to use them

Set lights up to be close to plants while giving them room to grow. There is not a hard and fast rule about light distance for tropicals, but keep it close and adjust as necessary. A floor lamp or hanging fixture can light a group of plants and should be easily adjustable. For seedlings, keep lights about 4 to 6 inches above the top leaves. For shop light fixtures, use chains to hang the lights so the height can easily be adjusted.

Use a timer with any plant lights to provide consistency in lighting. The timers sold for Christmas lights work for plant lights also and are easy to find this time of year. Plan to have lights on for about 12 hours a day for tropicals and other ornamentals. This can be adjusted down if plants are also receiving some window light. Use longer lighting periods if needed with seedling starts in the spring.

— Jennifer Smith works in regulatory horticulture and has worked as a horticulturist for various government entities. She has experience in landscape design and maintenance and as an educator.

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