A Beginner’s Guide to Grow Lights
Grow lights turn the darkest room into a tropical paradise! They’re essential for seed starting, winter houseplant care, and other fun horticultural activities. Keep one in storage—you’ll never know when you may need it. Longtime plant light user Jerad Bryant shares all you need to know to get started.
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Though many homes have windows, not all have brightly lit ones. Sunshine comes at a price indoors, where reflected or filtered sunlight is the norm. With grow lights, you control the sunshine. Wherever you need plants to perform, you can brighten the space and bring lush beauty into dining rooms, living rooms, and bedrooms.
Plant lights seem complicated but they’re incredibly easy to use. The most difficult step is researching which type is best for your space, though it’s an essential part of a proper setup. The shape, frequency, and type of technology all influence how well your plants perform. Find the right kind and they’ll thrive with little care.
Though almost any type can work for seed starting, growing houseplants, crops, and succulent seedlings offers unique challenges. Certain plants require specific frequencies and temperatures depending on their season of growth. Don’t worry, we’ll cover all you need to know! Let’s start with what this technology is and how it works.
Grow Lights Explained
Rays from artificial lighting work much like sunlight. They mimic the color, intensity, and frequency of the sun on a small scale. Plants soak up the imitation sunshine and grow as they normally would on a windowsill. Though the lights aren’t the same as natural sunlight, they offer a close substitute for seedlings, houseplants, and potted trees.
They differ depending on their color and intensity. Sunlight offers a full spectrum of light colors, appearing white or golden. The best lighting setups mimic the sun’s full spectrum with strong intensity. Though plants mainly use red and blue light, they need a full spectrum to grow well for long periods.
To a degree, the frequency influences the type of plant growth. Warmer red light leads to bud formation, flowering, and fruiting, while cooler blue light leads to vegetative growth and seed germination. A combination of red and blue works well for many growing purposes, as it mimics the sunlight’s full spectrum.
Grow Light Types
Dozens of different grow lights exist, from heavy, expensive models to new, efficient LEDs. Each type has pros and cons, though LEDs tend to have the fewest cons and are the most electronically efficient. It’s best to invest upfront in a good model that’ll stand the test of time.
Light Spectrum
The light’s spectrum refers to the wavelength, or color, of the light. Light moves in waves, and how long or short they are determines what color we see the light as. Long waves are red, while short ones are purple, and the other colors range between the two, with green in the middle.
Which frequency is best depends on your growing needs. Seed starting most often relies on blue frequencies with short wavelengths; they cause rapid vegetative growth that helps seedlings mature before they grow outdoors. Red wavelengths are long and help plants transition from leaf and shoot growth to flower and fruit production.
The best types have a full spectrum, like sunshine. It’s the closest mimicry of the sun we gardeners have available. Though it’s unnecessary for seed starting, it’s ideal for growing houseplants, fruiting trees, and bonsai indoors.
Temperature
Light temperature shifts with frequency changes. How hot or cold a bulb is refers to how red or blue the light looks. While bulbs with red wavelengths have warm temperatures, those with blue wavelengths emit a cool blue hue.
Kelvin is the rating for temperature and measures the fancy term “Correlated Color Temperature,” or CCT for short. Natural light has a rating of 6500K and is ideal for growing plants. Warmer ratings with lower numbers are perfect for fruiting and flowering, while cooler ratings with high numbers are better for vegetative growth and sprouting seeds.
Technology
Not all bulbs work equally well! LEDs, or “light-emitting diodes,” are energy-efficient and low-cost in the long run. Though they’re more expensive than other lighting types, their low energy costs account for their high upfront fees.
Fluorescent types are the other popular ones for home usage. They struggle to offer a full spectrum, as they often are too warm or cool to mimic the sun’s natural frequencies. They’re less energy efficient and last less time than LEDs but are cheaper upfront.
The last two categories are less common in homes because they pose significant fire risks and are unnecessary for personal cultivation. Metal halide and high-pressure sodium bulbs are incredibly bright, blasting light over a large radius. Though intense, they emit lots of heat and last a short while. They’re better for large-scale grow operations with safeguards in place than they are for home use.
Using Grow Lights
Once you find the perfect kind for your indoor setup, you’ll want to grab a few more things to ensure it works properly. Timers, zip ties, and extension cords are useful when setting up an inside garden. Shelves are beneficial too, as they provide lots of space for potted plants to grow underneath bright bulbs.
Place Lights at the Correct Distance
How far to place your bulbs depends on the plants you’re cultivating. Here’s a quick guide:
| Plant Type | Distance from Light |
| Seedlings | 4-6” |
| Herbs and Leafy Greens | 6-12” |
| Houseplants | 12-24” |
Flowering houseplants can tolerate a shorter distance, between 6 and 12 inches. They love warm, long-wavelength light waves from reddish bulbs. After they flower, they’ll thrive with cool, blue ones.
When cultivating seedlings, move the bulbs as the plants grow to maintain a four to six-inch distance. Avoid having the leaves touch them, as they may burn or scorch the young shoots.
To hang your bulbs, use zip ties or string to tie them onto a secure surface. Drill hangers in the ceiling to hang long tubes, or attach them to existing shelves with space for young plants.
Consider Photoperiods
Photoperiod is a fancy term for how plants react to day lengths. Some species flower as the days shorten in fall, while others prefer blooming in summer when the days are long and the nights are short. Common houseplants like Christmas cacti, poinsettias, and chrysanthemums need many long nights to form flower buds.
If you desire leafy growth, you’ll want your lighting setup to stay on for more hours than it’s off. To promote flowers and fruits, switch the setup off for 12 or more hours daily. The best rule of thumb is to match the lighting setup with your region’s natural daylight cycle.
Though this rule of thumb works well for most species, it won’t for all of them. Tropical plants originate from regions where the days are consistent. The sun is out for 12 hours and away for 12 hours. When growing tropical, leafy species, grant them the same day length they’d experience in their native range. Remember to offset those that need indirect light.
Set Up a Timer
Timers are the most helpful tool for granting plants their preferred day length. There are two main types, electronic and mechanical.
Mechanical timers are classic ones that are simple to use. They work with a gear inside that ticks like a kitchen timer. Most are silent or have minimal ticking noises for your sanity! They’re cheap and commonly available at garden centers and grow stores.
Electronic timers are more expensive than mechanical ones, though they offer more customization capabilities. Some allow you to set up the lighting cycles for an entire year, while others have multiple modes you can easily switch between. Opt for whichever works better for your home—I have mechanical timers that have worked for years!
Watch for Water
As with all electronics, water is a no-no. While some lights have splash guards for safety, others have parts that spark or stop working when water touches them. Use caution when watering, and ensure you have a way to collect the water that flows out of the pots’ drainage holes.
Try saucers or trays for catching excess water. Saucers work well for individual houseplants. They come in a range of sizes for specimens of all shapes. Trays are better for holding multiple pots in one location; they’re essential for seed starting stations.
Some plants dislike sitting in standing water, so you may have to remove the saucer and dump it after watering. Other tough species, like spider plants, tolerate temporary sogginess and won’t require dumping. Using steady hands, dump the saucers and trays without spilling water onto the lightbulbs.
Repair As Necessary
When using fluorescent, metal halide, or high-pressure sodium bulbs, you may have to replace them a few times a year. Most plant lighting setups of these types have bulbs or tubes you can swap in and out after they stop working. Find replacements at hydroponic shops, online retailers, and specialty garden stores.
First, turn off the lamps before replacing them. They’re shock hazards while they’re on, and you can cause short circuits with certain setups. After fully swapping the tubes, turn the machine back on to see if it works again.
