All About Grow Lights

Seedlings under a purple grow light
Seedlings under a grow light

text-box-multiplePart 1 in our Seed Starting Series link

All the info you need to start your seeds indoors!

Starting veggie seedlings indoors is a great way to get a head start on the gardening season and relieve that “gardening itch” that many of us get in the winter. One of the most important things a seedling needs is the right amount of light. However, chances are your average house window isn’t bright enough and you’ll need to supplement the light with a grow light. But if you’ve shopped for grow lights recently, you may have been overwhelmed by all the different options. We’re going to break down the best options for home gardeners that will best suit your seed-starting needs.

Tomato and pepper plants.
My seed starting station in 2022. Also, my workbench 🛠!

Grow Light Types

There are two primary technologies for grow lights: LEDs and fluorescent lights. For a long time, fluorescent lights were the go-to bulb for gardeners, but LEDs have quickly become the standard.

Fluorescent grow lights come in a variety of shapes and sizes, including the traditional tube and the “compact” swirl style. They’re available in a wide range of color spectrums and intensities. They are also typically less expensive up-front than LEDs, but less energy-efficient.

LED grow lights, on the other hand, are more energy-efficient and come in even more shapes, sizes, intensities, and spectrums. Some even come in tubes like fluorescent lights.

There are a few other lighting technologies that are typically used in commercial applications, such as metal halide lights and sodium vapor lights, but we won’t be focusing on those.

Okay, time for some science!

Grow Light Color, AKA “Spectrum”

The electromagnetic spectrum is the entire range  of  wavelengths of electromagnetic radiation. A longer wavelength is associated with lower energy and a shorter wavelength is associated with higher energy. The types of radiation on the spectrum, from longest wavelength to shortest, are: radio, microwave, infrared, visible, ultraviolet, X-ray, and gamma ray. Visible light is composed of different colors, each having a different wavelength and energy level.  The colors, from longest wavelength to shortest, are: red, orange, yellow, green, blue, indigo, and violet.
The electromagnetic spectrum and the portion that is visible light. Image modified from Electromagnetic spectrum, by Inductiveload (CC BY-SA 3.0), and EM spectrum, by Philip Ronan (CC BY-SA 3.0). The modified image is licensed under a CC BY-SA 3.0 license

More important than the type of grow light is the color and intensity of the light that it produces. Plants use light in the photosynthetically active spectrum between 400 (violet) and 700 (red) nanometers. However, not all of that spectrum is used equally. Typically, plants use more blue-green light when they are seedlings and more red light later, when they begin to flower and produce fruit or seeds. Because of this, plants appear green/yellow because they reflect light in those wavelengths. Hence, many grow lights on the market try to mimic these wavelengths and are a mixture of blue and red, often appearing purple when combined.

Optimal absorption of light occurs at different wavelengths for different pigments. Image modified from [The light-dependent reactions of photosynthesis: Figure 4](, by OpenStax College, Biology ([CC BY 3.0](
Optimal absorption of light occurs at different wavelengths for different pigments. Image modified from The light-dependent reactions of photosynthesis: Figure 4, by OpenStax College, Biology (CC BY 3.0)

For fluorescents and some LEDs, spectrum is often labeled as the color temperature or K (Kelvin). A higher color temperature, such as 6500K, is best for starting seeds. Many LED fixtures include a variety of colors, so instead of a Kelvin number you may see a spectrum graph, similar to the one above.

When deciding between the “purple” and “full spectrum” grow lights, one important factor to consider is where your seed-starting station is. If you’re starting your seeds in the basement or some other less-used space, go ahead and get the purple grow lights. On the contrary, if you’re starting them on the kitchen counter or some other common space, consider going for the full spectrum grow lights. The reason is, the purple grow lights aren’t very pleasant to be around for long periods of time. I start my seeds in the basement, so I don’t mind the purple hue and can deal with it in exchange for a bit more energy efficiency.

Grow Light Intensity

Lightbulbs hanging on wires with one swinging

When buying grow lights, in general, more light intensity is better. Every light on the market has a watt measurement, which is the amount of energy that the unit uses.

Some grow lights will also include more helpful intensity units including:

  • Lumens - When shopping for lighting fixtures, including grow lights, you may come across the term lumens. Lumens are a measure of the visible light emitted by the light source. In general, the brighter a light source appears, the higher its lumen output will be. While lumens can be a useful tool in determining the appropriate lighting for a room, they are not relevant to the needs of your plants. Lumens do not provide information about how well plants will respond to visible light.
  • PPFD - Photosynthetic Photon Flux Density (PPFD) is a crucial measurement for your plants. Unlike lumens, which only measure the brightness of a light source, PPFD measures how much of the necessary light within the photosynthetic spectrum (400-700 nm) is reaching your plant.
  • Foot-candles - A measure of how much light a square foot receives at a distance of 1 foot.

Grow Light Height

A good rule of thumb is to position your lights 6-24” away from your plants. Don’t just set it and forget it though! Pay attention to your seedlings, and if you notice them becoming “leggy”, they’re not receiving enough light, so you should lower your lights. On the contrary, if your lights are too close, plants can get damaged by the heat of the light. Try adjusting your lights to find the sweet spot, and periodically raising them as the plants grow.

Our Recommendations

There are so many grow light options out there, it can get overwhelming. So we’ve done the research and read the reviews for you. Here are our recommendations:

Disclosure: This post contains affiliate links and we receive a commission if you visit a link and buy something. Purchasing via an affiliate link doesn’t cost you any extra, and we only recommend products and services we trust.

Barrina Grow Lights

Available in full spectrum, pink, or red/blue, these LED grow lights comes in both 2ft and 4ft lengths. Both lengths come in a 6 pack, perfect for gardeners who want to start a lot of seeds or are looking to start an indoor garden.

Barrina’s grow lights are highly rated, so if these options don’t work for you, check out their other options such as their 4 pack.

iGrowtek Seed Starter Kit

This kit contains everything you need to start seeds, minus the soil and the actual seeds. The light is full-spectrum.

iPower Stand and Grow Light

Perfect if you don’t need the seed starting tray but still want a stand.

Kullsinss LED Grow Light Strips

If you’re starting your seeds on the kitchen counter, this might be the grow light for you. You can stick these light strips to the underside of a cabinet or shelf, perfect for spaces where hanging a reflector wouldn’t work.

Adjustable Gooseneck Grow Lights

For the ultimate in adjustability, these grow lights are mounted on goosenecks. They are available in 4 different color options and are perfectly suited for lighting large houseplants as well as veggie seedlings!

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