Growing plants indoors starts with proper lighting

Beyond common houseplants predestined for a life indoors, lots of folks bring their outdoor plants inside over the winter months. All kinds of delicate perennials, tropicals, citrus and even herbs and salad greens, not to mention countless new seed starts, can wait out the cold indoors if they have the right conditions. The most important is light.

By understanding how plants use light, and the many lighting options available today, you can put together a lighting system that’s right for the plants you want to grow — or at least sustain — indoors until they are able to venture outside again.

Three of the most important considerations for lighting are:

n Intensity. All plants need light to thrive, but some plants can get by on lower intensities than others. Native tropicals, shade-loving forest plants and houseplants like ivy or philodendron don’t need as much light as Mediterranean succulents or desert cacti. Flowering plants of all kinds, such as orchids and gardenias, generally need brighter light to flower and produce fruit.

n Color. Bright sunshine contains the full spectrum of light wavelengths from red through yellow and green to blue and violet. Plants use all of these wavelengths for photosynthesis, but red and blue are two of the most important. The blue spectrum promotes vegetative growth — young plants build robust, full foliage. The red wavelengths promote flowers and fruits.

n Duration. No matter how much light they use to grow, plants need a rest now and then to accomplish their other metabolic functions. Plants’ preferences for light to dark are divided into short-day, long-day and day-neutral. Short-day plants thrive on less than 12 hours of light in a 24-hour period. Most will also need to have a stretch of even shorter days to signal them to set buds and flower.

Azaleas, chrysanthemums, poinsettias and Christmas cactuses are short-day plants. Long-day plants need 14 to 18 hours of light per day. Vegetables and most garden plants are long-day, and they get pale and stretched when they don’t get enough light. Day-neutral plants like geraniums, coleus and foliage plants are happy with eight to 12 hours of light throughout the year.

TYPES OF GROW LIGHTS

There are many kinds of artificial lights that will support plants indoors, from ordinary bulbs and tubes to superefficient light-emitting-diode lights. Most are available in multiple color spectrums.

Fluorescent tubes put out three to four times the light of incandescents for the same energy. Their color frequencies run from reds to blues so you can mix and match to suit your preferences. Full-spectrum or sunlight fluorescents are great for all plants and for starting plants from seeds. They’re often even marketed as grow lights.

Industry standard, T4 tubes fit in ordinary shop lights and household fluorescent fixtures. New, smaller T8 and T5 tubes need fixtures with special ballasts but use less power and last significantly longer.

Cool white and warm white fluorescent bulbs can be mixed in a two-bulb fixture to get a good balance of red and blue light. Metal halide lamps and mercury vapor lamps have a strong blue spectrum, high-intensity light good for developing dense, stocky foliage.

High-pressure sodium bulbs emit yellow-orange light that’s better for the flowering and fruiting phase of a plant’s lifecycle. All produce a great deal of waste heat.

The newest technology for grow lights uses light-emitting diodes. LEDs are extremely energy-efficient; they average 50,000 hours of useful operation and generate very little heat, making them safe for plants and people. You’ll spend a good bit more upfront but you can expect to save 40 to 75 percent on energy costs.

Keep the plants far enough away to prevent potential burning yet close enough to maximize the exposure these supplemental light sources provide. And regardless of which kind of lighting system you use, rotate your plants one or more times weekly to balance the amount of light each plant receives.