The Best Light for the Job
Casey Jones Fraser shares some tips on how to find the right grow lights for the right uses.
With so many different types of grow lights on the market, choosing a system for your garden can be confusing. If you have high performance in mind, there is no cheating the system. You will need professional grow lights to get professional results from your garden. So, which grow light is the best light for the job?
Best Type of Lights for Seedlings and Cuttings
Seedlings and cuttings don’t require as much light as mature plants. In fact, too much light can overwork them and dry out the growing medium. Fluorescent lights are perfect for tiny young plants. I don’t recommend T12 lights, but they will get the job done.
T8 fluorescent tubes are better, but T5 fluorescent lights are the clear winner in their category. T5s deliver more light, and they are available in the ideal daylight spectrums for your plants. A 4-ft. T5 fixture with four tubes can cover up to five propagation trays. Standard propagation trays are 20-in. by 10-in., so a couple of 2-ft. T5 tubes will cover a single tray.
You could also use a couple of 26-W compact fluorescent lights over a prop tray, but they tend to produce concentrated light footprints. Basically, you get bigger plants directly under each bulb and small plants on the perimeter. Fluorescent tubes spread light over the surface of the growing area, and therefore promote even growth.
Once you are out of the seedling or cloning stage, you will want the best lights for producing leaf growth. T5s and metal-halide lights are the first two choices for top-notch vegetative plants. When choosing a T5 fixture, pick the units in accordance to the size of your garden. If you are growing in more than a 2-ft. by 4-ft. area, get a 4.ft. T5 with eight tubes. In other words, get a 2-ft. by 4-ft. T5 light to cover a 2-ft. by 4-ft. area. Here are the coverage areas for the most common T5 fixtures.
- 4-lamp, 2-ft. T5 = 1-ft. x 2-ft. vegetative garden
- 4-lamp, 4-ft. T5 = 1-ft. x 4-ft. vegetative garden
- 8-lamp, 2-ft. T5 = 2-ft. x 2-ft. vegetative garden
- 8-lamp, 4-ft. T5 = 2-ft. x 4 -ft. vegetative garden
When choosing a metal halide light, you can expect the following coverage:
- 250-W metal halide = 2-ft. by 2-ft. vegetative garden
- 400-W metal halide = 3-ft. by 3-ft. vegetative garden
- 600-W metal halide = 4-ft. by 4-ft. vegetative garden
- 1,000-W metal halide + light mover = 4-ft. by 8-ft. vegetative garden
With these lighting recommendations, you can expect up to 18 in. of leaf and stem growth. If you are trying to grow taller vegetative plants, go with a 1,000-W light over a 4-ft. by 4-ft. garden. With that kind of intensity, you could produce 5-ft.-tall tomato plants and get a jump start on the outdoor garden season. Fruiting and flowering (the reproductive phase) is the goal for many indoor gardeners. For plants to achieve the same kind of growth made possible by the sun, some serious intensity during the fruiting and flowering stages will be required.
High-Pressure Sodium Lights (HPS)
HPS lights continue to produce excellent results for those seeking both quality and yield. When operating a large flowering room with multiple lights, some growers prefer a mix of metal-halide and high-pressure sodium lamps for a mixed spectrum. Metal-halide lamps will grow healthy flowering plants, but the yield is slightly reduced compared to HPS. When using HPS light for flowering indoors, go with the following guidelines for matching the right light to your garden:
- 400-W HPS = 2-ft. by 2-ft. flowering garden
- 600-W HPS = 3-ft. by 3-ft. flowering garden
- 1,000-W HPS = 4-ft. by 4-ft. flowering garden
While HPS lights can produce healthy plants over larger areas than suggested here, the plants themselves will be reduced in size. Spreading the light over a larger area tends to get a similar yield with lower quality and smaller individual fruit size. By keeping the lighting at maximum intensity, you will get the highest yield for the amount of space you are using.
Light-Emitting Diodes (LEDs)
LED lights have become common for gardeners these days. Unfortunately, many failures in the growroom have been attributed to low-quality LEDs sought by bargain hunters. High-quality LED grow lights do exist from a few companies.
LED technology offers benefits including reduced heat, reduced electrical usage and no bulbs to replace. For growers who are used to the performance of a 1,000-W HPS over a 4-ft. by 4-ft. garden, you will need to spend $2,000 to $4,000 to get the same results with LEDs.
That 1,000-W HPS light would cost more like $300 to $600. In the long term, LED lights could be the better choice, as long as you can afford top-of-the-line units. The electrical savings, especially during hot summer months, will add up over a few years. If you plan on gardening for a long time, your LED lights could eventually pay for themselves with the savings on your power bills.
Induction lights are another technology that promises savings on your power bill. The costs of induction lights and power savings are similar to those seen with LED lights. Another similarity is long lamp life. Induction lights will continue to operate for years with healthy plant growth. Unlike an incandescent lamp or conventional fluorescent lamps, there is no electrical connection going inside the glass bulb; the energy is transferred through the glass envelope solely by electromagnetic induction.
High-Wattage Compact Fluorescent Bulbs
High-wattage compact fluorescents are used by some growers for vegetative and flowering growth. These lamps range from 125 W to 300 W, and require a mogul base fixture. While they can produce quality vegetative growth, they are not the ideal choice for flowering plants. Yield and quality will be significantly reduced compared to HPS or MH lights.
The best way to use compact fluorescents in flowering is by hanging them next to plants for supplemental side lighting. Using HPS lights overhead and compact fluorescents on the side will give you healthy tops and healthy lower growth.
While some growers hang HPS and MH lights between plants, compact fluorescents are a safer option. If you bump into them, you won’t get burned skin or melted clothes.
A Final Note
New lighting companies often make claims that are hard to believe. If a light really works, it will become popular in the marketplace.
Thousands of growrooms exist all over the world and professional indoor growers dump plenty of capital into experimenting with different lighting technologies.
Currently, these large-scale growers have continued to find the best flowering results from 600-W and 1,000-W HPS lights, or some pricier LEDs. So, kick your garden into high gear with some high-output grow lights and run your garden like a professional.
Read Next: How to Tell When Your Lights Need Replacing