Grow Lights: Great for Growing Indoors!

Pumpkin seedlings thrive under grow lights. Photo: Amy Gaertner/FlickrYou might have heard people talking about grow lights lately -- including us, with our recent grow light bookshelf tutorial -- but do you know what they are? How do they work? Do you need one? What kind should you get? We've assembled a grow light guide for you so you can make the best choices for your indoor seedlings, winter herbs, and more, and allow your Boston garden will thrive.

Why plants need light

In order to explain grow lights, we're going to remind you that plants grow, and stay healthy, through photosynthesis, a pretty amazing chemical process. As long as they've got chlorophyll (that stuff that makes them green) and a light source, along with water and nutrition, they're sitting pretty. Here's the problem: indoors, there's not necessarily a lot of light, especially in the winter or in dark areas of your home.

Uses for grow lights

That's why some people choose to supplement with a grow light, a lamp that mimics daylight so plants get more time in the sun, so to speak. Grow lights can be used for timing and forcing seedlings, commercial hydroponic crop production, growing plants in the winter in dark locales, and a whole lot more.

Do you need a grow light?

Do you need one? Well, that depends on what you're growing and when you'd like to grow it, as well as your house. If your house is dim or you want to grow plants in spots like the bathroom and the basement, you must have a grow light to provide the light they'll require to thrive. If you want to grow in the winter months, you need a light to make up for the lost daylight hours. If you'd like to try your hand at forcing plants to grow out of season or raising plants which are native to regions with longer days, a grow light can be a good idea.

Types of lights you can use

You can use basically any light as a grow light, but incandescents (mostly phased out, so good luck finding one) usually run too hot to be safe, as do many halogen bulbs. CFLs and LED bulbs, on the other hand, run cool, provide a broad spectrum of light, and, critically, offer a lot of light with low energy use. Since your goal is very bright light, this is a big bonus!

Full spectrum light bulbs

You do need to pay attention to the spectrum of light emitted by the bulb. Plants like lots of light on blue and red wavelengths. They don't want a red party bulb, but they'd appreciate a full spectrum light bulb to help them grow, and develop even, bushy forms rather than more leggy ones. Full spectrum bulbs can be a little more expensive, but they're worth it!

The great thing about using these basic commercial bulbs is that they fit into ordinary light fixtures. You can go CIA interrogation-style on your plants with a gooseneck lamp and a single LED bulb angled to bathe them in lots of light -- except that unlike an interrogation subject, your plants will love the attention. This is a fantastically cheap, minimally disruptive way to use a grow light around the house.

High-end grow lights

High-end grow lights specifically designed for this purpose are available, including both bulbs and fixtures. They tend to be bulky, because they are designed for people and nurseries growing large numbers of plants. They're very bright, but they're also very expensive, and they tend to be huge energy suckers. In fact, you usually need a specialized electrical system with an enhanced load drop and dedicated breaker box to supply their energy needs. Unless you're planning on filling the guest room with tomatoes (and if you are, can some for me, will you?), you probably don't need one of these.


In both cases, your grow lights should be off for at least eight hours a night unless a plant has special needs. You can turn them off on your own, but most people use a timer. Timers are extremely inexpensive and easy to program, and they'll provide you with total control (and relief: no "honey, did you leave the grow light on?" at the opera!).


Make sure to experiment with distancing, because if the lamp is too close, it can be too intense for your plants. Keep it away from flammable furnishings in case there's an accident, and remember: that intense light can be unpleasant when you're watching movies, going to bed, or entertaining guests, so consider the placement of your grow light carefully.

Katie Marks writes for

Updated May 3, 2018.

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