Pair indoor plants, including transplants and flowering houseplants, with the right light for strong, healthy growth and maybe a generous harvest, too, if you’re growing vegetables or herbs inside.

By Megan Hughes
Updated April 06, 2020
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Snipping fresh basil from the plant on your countertop is a reality with the help of many affordable, efficient, and easy-to-use growing lights on the market. Plants need light to trigger photosynthesis which turns energy into the sugars plants need to grow, but different species can vary widely in how much light they need to thrive. Low-light houseplants rarely need supplemental lighting unless you're trying to get them to flower. But seedlings and produce grown indoors demand lots of bright light to grow and fruit. Depending on what you're growing, make sure you choose the best lights for your home and your plants.

indoor green cart lighted with potted plants seedlings and metal watering can
Credit: Peter Krumhardt

Plant Grow Lights Used by the Pros

The brightest plant grow lights are high-intensity discharge (HID) lights. While these can be installed anywhere in your house, garage, or basement, they need special fixtures. There are two categories of HID lamps: Metal halide (MH) and high-pressure sodium (HPS). MH bulbs produce light at the blue end of the spectrum which encourages compact, leafy growth. HPS bulbs emit light at the red end of the spectrum. Red light waves cause plants to flower and fruit more rapidly.

An entry-level HID lighting kit starts around $400 and the price goes up rapidly. Because home gardeners usually only need grow lights for a few weeks or months a year, HID lights can be a little too pricey for using at home.

Should You Choose LED or Fluorescent Lights?

LED and fluorescent bulbs both produce full-spectrum light that plants need to grow. There are many plant light kits on the market that include LED or fluorescent bulbs, but LED systems offer several advantages that make them the better choice. For starters, although LED bulbs cost more than fluorescents at purchase time, they use half of the electricity fluorescents require and last five times longer than the average fluorescent bulb. They also give off less heat and mercury-free LED tubes don't shatter like glass fluorescent tubes, leading to fewer safety hazards and LED tubes in landfills.

Lighting Plan for Transplants

Newly emerged seedlings and young plants grow well with the aid of full-spectrum light, both blue wavelengths and red wavelengths. Special LED and fluorescent “grow lights” will work, but so will less expensive fluorescent tube bulbs. Be sure the light source is within 6 inches of the plant foliage for the best results. For easy movement, suspend the fixture on chains or elevate your plants on a table or tray. To keep your lights working efficiently, gently wipe down the light tubes to remove dust and grime before using them each year.

Lighting Plan for Flowering Plants

Red light waves are essential for spurring plants to flower and fruit indoors. Shop for LED bulbs and fixtures that are specifically designed for growing plants. They're usually labeled “grow lights” because they're created to produce a high number of red light waves.

Some electric brands produce plant-friendly LED bulbs called “High-output LEDs.” High-output LEDs are generally twice as bright as standard LED grow lights. These ultra-bright lights are excellent for growing plants that are native to full sun, dry climates such as cactus, citrus, rosemary, and geranium. Plan to light flowering and fruiting plants for 16 to 18 hours a day. Place the light source 12 inches or so away from plant foliage.

How Much Light Do You Need?

Once you’ve decided which kind of plant grow light you want, it’s time to decide how big a bulb you need for the space you have. First, determine how much space you need to illuminate. As a rule, you want 20 to 40 watts per square foot. Divide the wattage of your bulb by 20 (such as 1,000 divided 20 = 50), then divide the wattage of your bulb by 40 (1,000 divided by 40 = 25).

The answer gives you the extremes of your light intensity range. With one 1,000-watt system, you can light between 25 and 50 square feet of interior landscape. Also, be sure to match the wattage of your bulbs with what your fixture is designed to handle. For example, a 400-watt bulb should not be used in a 250-watt system. Adjust your setup as you observe how well your plants grow. Increase or decrease the intensity of the light by shifting the placement of your plants or light fixture so the plants are closer or farther from the light source.


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