The dark days of winter are upon us, but that doesn’t mean you have to give up on gardening until the spring. Grow lamps are becoming increasingly popular in gardening circles these days. And new breeds of low-power lights make them affordable options for those looking to keep a kitchen stocked with green herbs through the winter months, or those just looking to jumpstart their seedlings for next spring.
Before going any further, we need a quick scientific crash course. Plants need fairly intense light to grow, and the intensity of light in measured in a factor called lumens. The higher the lumen value of a bulb, the stronger the light and the better your plants will grow. For noticeable growth, you’ll want a bulb that puts out at least 4,000 lumens, and some bulbs can produce upwards of 40,000 lumens.
But a light’s intensity isn’t the only thing you have to look for; the temperature of the light is also important, a value measured in kelvins. Temperature in this case refers to the color of the light: the bluer, or colder the light, the higher the kelvin value. The warmer, or redder the light, the lower the value.
High-noon daylight is fairly blue, around 5,600K, and it’s important to get a light source in this range to ensure strong plant growth. However, most plants also require light in the red and yellow ranges — somewhere around 2,400K — to flower, produce seeds or bear fruit, so it is good to have a mix of both in any good grow-lamp setup.
The final thing you want to check for is a light’s wattage. Keep in mind, watts measure energy usage, not how much light a bulb produces. So when looking for an efficient light source, you want something that will produce a lot of lumens per watt.
Just about any type of bulb can add a little extra something to your garden’s growth, but many won’t do this very well. So let’s consider the options.
Want to fry your plants and bankrupt yourself with huge energy bills? Great! Grab an incandescent bulb! These heat-producing energy-hogs should be avoided at all costs. Sure, the bulbs are dirt cheap. But with the high cost required to run them, you might just as well buy tomatoes from the grocery store. Heck, you can even spring for the fancy organic kind.
A growing favorite with the greenhouse DIY set, fluorescent lights used to be too weak to produce full, flowering plants. However, with the introduction of compact fluorescent lights — those curly soft-serve creations we’ve been told to switch to for the last few years — fluorescents have become a viable option and are especially well-suited for beginners.
Because of their compact construction, these bulbs can pump out a good amount of light in a small space. And since they run cool to the touch, you can place them a couple of inches from your sprouts and seedlings, maximizing efficiency.
Compact lights can work great as spotlights on a few plants, but if you’re looking to plant rows of seedlings, you might want to consider a few T5 bulbs, which look like skinnier versions of fluorescent tube bulbs. Despite their trimmer profile, these bulbs actually produce a lot more light than their traditional counterparts.
Both kinds of fluorescents come in a range of color temperatures, so you can mix both cooler and warmer lights, depending on whether you are looking for growth or flowering. But before you run to the closet to grab a couple of compact fluorescents, take note: to get really effective results, you are going need a bigger light source, something in the 125 watt range, which costs about $30, and produces about 7,000 lumens. Though not as powerful as some light options, this will be more than enough to start seedlings or buck up a few potted plants.
The reigning favorite amongst gardening enthusiasts, HID lights — short for high intensity discharge — come in two types: metal halides and high pressure sodium. Metal halides come closest in reproducing the glowing tones of true sunlight and are amongst the most efficient, producing about 39,000 lumens with a 400 watt bulb, enough to produce things like peppers and tomatoes. On the downside, these lights pump out a lot of heat. So if you’re not careful, you can reduce your garden to potpourri. Because of the high heat, halides need to be kept three or four feet away from plants, which means the lights are going to illuminate a far larger space than fluorescents, making them a better option for larger indoor gardens.
High pressure sodium lights emit a much redder light, so they aren’t very useful if you are looking to coax a few sprouts from the soil. But they are great in the later stages of a plant’s life when trying to get it to produce fruit or flowers. Like their halide siblings, these lights run very hot, so they can be a little tricky for novice growers.
LED systems are the latest craze to hit the shelves. They can cut power use in half, produce almost no heat and last around 10 years, but a lot of greenhouse aficionados say they just don’t have the growing power of other light sources. The lights are also pretty costly, and bathe your plants in an otherworldly purple glow more akin to an imminent alien abduction than the sun’s golden rays. That said, as costs for these units come down and the technology improves, they promise a low-powered alternative for those undeterred by the sci-fi sheen they cast.
Once you have decided on a bulb type, setting up a grow rig is as easy as slapping the bulb into the appropriate light fixture and setting up a reflector so that as much light as possible is directed at the plant. If you’re looking to make one yourself, your local hardware store likely carries all equipment you need. And if you’d like an easier approach, readymade units are available as well.
Finally while you might be tempted to keep your lights running 24/7 in a quest to grow veggie behemoths, remember, plants need their sleep just like you do. In general, giving plants at least 8 hours of darkness each day will help them flower and produce better fruit.