Plants need water, soil and sunlight to thrive. But sometimes, your home can’t provide quite enough light to keep your favorite houseplant or a tray of vegetable seedlings happy and healthy. That’s where grow lights come in.
“If you’re noticing that your plant looks pretty healthy but has stagnant growth, it could benefit from a little bit more light,” says Anna Ohler, co-owner of Bright Lane Gardens in Lake Ann, Michigan.
Grow lights are a great way to ensure that light-thirsty plants and seedlings can successfully grow indoors. You can also use them to provide a little supplemental light to your plants. Here’s what you need to know about choosing, using and buying grow lights to keep your indoor plants looking lush.
What are grow lights?
Grow lights are light bulbs or fixtures for indoor plants that are designed to mimic the natural light plants receive from the sun when they’re grown outdoors. Plants convert light into food through photosynthesis, so giving them more light means you’re fueling more healthy growth.
Grow lights can be as simple as old-school incandescent light bulbs, though their light is weaker and they give off a great deal of heat. Fluorescent bulbs can also be used as grow lights, but most grow lights use LEDs. They’re brighter, more efficient and emit less heat than the other options.
Why use grow lights?
If you love plants, but your home or apartment doesn’t get much natural light, keeping indoor plants may be a challenge. There are plenty of low-light plants like pothos, spider plants and Zamioculcas (ZZ) plants that can handle lower light conditions. But if you want to grow houseplants that require more light, you’ll need some help.
Some plants that require lots of very bright, direct light to thrive, like some succulents and cacti, dwarf citrus trees and flowering plants, need a supplemental grow light even in the brightest indoor spaces to grow properly. If you plan to start seedlings indoors for your vegetable garden, even the brightest, sunniest window won’t give those baby plants the bright light they need.
A sign that your for flowering or fruiting plants might not be getting enough light is that they aren’t reaching appropriate stages of development. Another sign that plants need more light is that they’re etiolated, or leggy. This means that the stem is growing tall, with lots of space between sets of leaves, in an effort to get more light.
Houseplants and seedlings may also lean or reach toward a light source if they’re not getting enough. Variegated plants may revert back to green, and colorful plants like crotons can’t maintain their coloration without sufficient light.
How to choose the right grow light
Plants can use different parts of the light spectrum for different purposes. Blue light supports vegetative growth, while red light helps with fruiting and flowering. There are also white spectrum grow lights, which shine white light (a combination of all light colors), and full spectrum grow lights, which give off white light at a temperature that more closely mimics natural light.
When choosing grow lights to buy, where that particular light falls on the light spectrum plays a role, but the intensity of that light is a more important factor, according to Justin Hancock, a horticulturist with houseplant nursery Costa Farms.
“What I learned in horticulture school is that your plants, in general, care far more about getting enough light than the wavelength,” said Hancock.
That light intensity is measured in foot-candles, which describe the amount of light falling on a surface. The wattage, which you’re probably used to equating with brightness on regular household light bulbs, measures how much electricity the bulb uses.
When you’re shopping for basic grow lights, you’ll see different measurements listed in the specs. Foot-candles are the most important measurement to consider.
“Your average grow light bulbs are probably going to meet your needs for the average houseplant—anything from 50 to 200 foot-candles, which is a pretty wide range,” Ohler said.
If measuring foot-candles is a little too complicated, you can choose grow light bulbs for houseplants based on wattage instead. Ohler recommends providing 10 to 20 watts of light per square foot for a standard houseplant.
Grow lights for houseplants
Your houseplants may benefit from grow lights even if you keep them in a very bright room that receives sunlight throughout the day.
“People underestimate how much light is needed for certain types of plants. If you get a lot of sunlight through your windows, it’s natural to assume you’re good to go,” Ohler said. “But that window is only allowing light to come in from one angle, and once the sun gets past that angle, the direct light is cut off.”
Ohler recommends basic white spectrum LED lights for your average houseplants. Start by placing the grow light two feet away from your houseplant. Based on how the plant responds over time, you can adjust how close the plant is to the light or experiment with a stronger light.
Grow lights for seed starting
You may be able to help a houseplant thrive with a single bulb, but using grow lights to start seeds indoors will require stronger light.
“Seedlings are a lot needier,” Hancock said. “A good, strong light is going to be really beneficial for them. Otherwise, you’re going to end up with leggy seedlings.”
You’ll want to use panels of full spectrum LEDs that can cover the surface of a seed tray to ensure your seedlings don’t end up weak and leggy. Fluorescent shop lights are another popular, lower-cost option if you have them on hand. However, they’re not as energy efficient as LEDs and they run hotter, which means that you’ve got to be careful with how close they get to your seedlings’ delicate leaves.
Start with light panels about two inches above the soil line when you see the first green growth, then gradually increase the height as plants grow. Many models come with hardware like chains that can allow you to attach them to a wire rack, shelf or ballast above the plants so you can adjust the height of the light as plants grow taller.
Where to buy grow lights
There are plenty of high-end grow lights on the market, but both experts recommend against shelling out for something fancy when more basic, affordable bulbs will probably do the job just as well. However, Ohler recommends steering clear of many of the bargain-priced grow lights available on Amazon.
Instead, she recommends starting with an LED grow light bulb from your local hardware store that’s probably more reliable than some online brands. Depending on where you shop, you can find bulbs specifically labeled as grow lights from established brands like Phillips and Sylvania.
Ohler does recommend one brand on Amazon. Vivosun sells a variety of LED grow light panels, seed starting mats, ballasts for hanging grow lights and other gear for indoor gardening.
“Don’t overthink it too much, but also don’t, don’t pick the cheapest option on Amazon,” Ohler said. “Somewhere in between will usually do just fine for anything you’re doing inside the house.”
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