This guide is for who?
If the seedlings you’re starting are located on a windowsill with sun exposure and you have a genuine desire for gardening, you should instead get yourself a grow light. Immediately you’ll notice a difference in your seedlings growth and color before they’re put outdoors come springtime. They’ll be stockier and greener, with stems that are stronger, and they’ll take less time to grow than if they were exposed to filtered, limited light from your window.
If you’re currently with a setup of T12 or T8 traditional fluorescent light bulbs (their diameter being around 2.5-4 cm/1-1.5 in.), you’ll probably want to look into upgrading.
Spanning five years, you can expect to spend $30 up to $60 more if you were to use T5 bulbs versus using two T8 bulbs, and this is dependent on what your electricity will cost. But it has its benefits: You’ll get more green color from your seedlings and they’ll be more quick in growth because more photons will be delivered from the T5s to their leaves (who dearly love light) than the T8s. You’ll even see additional benefit with crops requiring long periods of indoor growth before they’re moved outdoors (sluggish offspring, cardoons, artichokes, eggplant, peppers, tomatoes…).
Tested and picked, how?
What grow light is going to be best? Well, what is it you want grown? The best grow light will grow that. Enough photons are produced in the right 400-700 nm spectrum so the plants are given the needed energy for growth and have adequate light at both “blue” and “red” wavelengths to get your plants to grow thick stems and green, dark leaves. The light that’s best won’t give you more light than is needed, but just enough (since electricity is something you don’t want wasted), and heat won’t be produced in excess. For gardeners, unfortunately, it’s not that easy to get solid info on plant lights.
The measurements given out by lighting companies aren’t relevant, and the internet gets stuffed up by typists who seem to only care for growing orchids, salt-water corals, or yes, those “naughty greens”.
Most growers that are in it for the hobby- from petunias to pot- unfortunately don’t capitalize by publishing any scientific (rigorous) research into the methods they use for growing plants. The guys known for aquarium lighting actually have their setups tested, but there’s a bit of difference in their criteria for what makes a well-rounded light from that of a typical grower of tomatoes (same for the orchid peeps).
So, after consulting five experts (Bruce Bugbee, Neil Mattson, Ph.D., Peter Wardenburg, Ed Harwood, Ph.D, and Gene Giacomelli, Ph.D.), here’s what was found for a grow light to be a good one that will be needed by most gardeners:
In a nutshell, if your plants are going to be grown indoors, your choices are metal halide, compact fluorescent, fluorescent, and LED bulbs or HPS (high pressure sodium) lamps. The size of these bulbs will vary, along with how much light they emit, and what light wavelengths they put out.
Drawing from the analysis of plant lighting from the experts listed above, greater emphasis was put on lights which would give the required output of photons for regular tabletop lettuces, herbs, and seedlings.
After the estimation on performance, the calculations were done on what it would cost to use the fixture over five years, which considers the cost of bulb replacement and the purchase itself, along with how much electricity will be needed so plants are given enough DLI (daily light integral).
For Most- The Hydrofarm Envirogro FLT24 is the Best Grow Light
The Envirogro FLT24 (about $90) is low-maintenance and economical, it’s cool when running in small, limited space, and it allows stout plants to be provided with bright light. We’d put our dollar on this grow light.
The research results and expert input left no doubt. If you envision your seedlings should be given a start that’s worthy of a greenhouse performance, commute to wherever it is that has a T5 fixture (four-bulb) with T5 24-watt HO (High Output) bulbs (T5 plain bulbs with lengths at 2 feet only supply 14 watts and light produced isn’t as much.)
There are few T5 four-bulb 2-foot fixtures available- and the reviews on T5 setups are even less- but the favorite among reviewers on Amazon overwhelmingly goes to the Hydrofarm FLT24 4-Tube/2-Ft T5 System. They praise how even the light illuminates over all of a seedling flat, how bright it gets, and the stocky, fat seedlings that are raised.
➡ Complaints from some of the reviewers pointed a finger at customer service for broken bulbs being replaced from shipment. Hydrofarm president, Peter Warburg, gave the go-ahead to T5s versus other kinds of different lights for gardeners. He suggests you won’t find a system that’s more cost-effective for starting seeds, and that they’re affordable and practical.
Horticulture professor of Cornell University, Neil Mattson, takes tissue cultures from which plants in his lab are raised (also using T5 lights). He pointed out that for him it works well. And, the growth you get with a shelf (2 feet wide) beneath four lights is far superior to just two. However, there is a bit of heat put out by this light. The temperature of one orchid grower’s terrarium, as noted here, was raised with this light fixture by 3-5ºC (5-7ºF). Then again, you won’t find many seed-starters position their flats in a glass box, but rather out in the open. In a case like that, there should be a minimal increase in temperature.
The light temperature of the Hydrofarm T5 is “daylight” rated, or 6500 K, meaning the light will slightly appear bluish on white.
With the Hydrofarm T5 sitting above your plants, their colors (as you look at them) are almost no different than if you were to take them out under noon sunshine.
If your preference is for a rustic, woodsy shade of brown for the housing of your plant light, rather than white (yes, dazzling), the Hydrofarm T5 4 Tube 2Ft Designer Fixture (almost $110 most places) is just about indistinguishable from the above FLT24. What makes it different from the FLT24, other than its bronze-mottled distinguished exterior, is that a 3-prong outlet is featured at one of the light’s corners.
It allows growers to have their lights “daisy-chained” together and a single timer used for controlling a set of lights, which is a big clue to why the white version costs $16 less. Also, if you have $10 you could just get a timer (w/ two outlets) when it comes to the point you need a second light plugged in, but you won’t get the thrill of spotting a block of mud-colored gleaming metal above hovering your precious seedlings. It’s your choice.
Electricity will cost how much??
The answer to that will be dependent on your electricity cost. It could be anywhere between $33 up to $100 for the lights to run half a decade and the photons that reach your seedlings will be plenty- a daily light integral of 6 spanning a 16 hour period in a day- to get the most of their potential.
Now, if you want their seedling potential to be around average, have your lights run only 11 hours per day to get a daily light integral of 4 and the cost of your electricity will be a third less. With the life of your bulb expected to go 20,000 hours, you can expect to enjoy 22 years of starting seedlings.
Flaws, but Forgivable
As earlier mentioned, the Envirogro T5 4-Tube fixture won’t fully bring out the potential of your tabletop greens. If this light is kept on all hours of a day, you’ll only still be getting a daily light integral of 9- far less than the daily light integral of 12 that greenhouse users think of as a necessity for producing spinach, herbs, lettuce, and other popular green varieties.