Basic Grow Light Information for Indoor Gardening

Growco is here to help you garden where the sun doesn't shine!

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Many of us live in areas where gardening outdoors in the fall/winter months is simply not possible. But, if you love to garden, there's no reason why you shouldn't keep it up through the winter months.

Growco has been in the business of helping our customers set up indoor gardens for well over ten years now, and we've watched horticultural lighting evolve plenty in that time. It all started out with standard fluorescent tube fixtures, and now we're selling space age LED lighting!

Back in the old fluorescent days, yield was sparse because fluorescent tubes have always been lacking in "penetration" capability. But, the newest generation of fluorescent fixtures, T5's have almost twice the output of the old fluorescent tube lights.

We've found that our T5 fixtures are great for all vegetative growth. With the "cool" spectrum bulbs, they're all you'll need for small plants like leafy greens and herbs. For larger plants, T5's are the best quality light to start your vegetative growth before switching to HID lighting for fruiting/flowering. We recommend using T5's to get your plants up to 8-12" in height before switching to HID's. For other plants like orchids or bonsai trees, T5's are perfect. Use the "cool" bulbs (6500k) for vegetative growth, and the "warm" (2700k) bulbs for flowering, or mix the two spectrums for full-spectrum output. Find those types of grow lights here.

We recommend HID lighting for larger plants like vegetables and other big flowering plants, and during the fruiting/flowering stages of growth. HID lighting is superior to fluorescent lighting in that it has the ability to "penetrate" the plants canopy, and cover a larger area. This higher intensity light will get through the canopy and down to the lowest leaves on your plants. What this means to you is a healthier and seriously more productive garden. In our HID selection, we've got two types of light- metal halide (MH), and high pressure sodium (HPS). Most of the fixtures we sell will run either MH, or HPS lights as you choose just by switching bulbs.

Metal Halide (MH) lights are centered toward the "cooler" end of the spectrum (although there are exceptions), and High Pressure Sodium (HPS) lights are toward the "warm" end of the spectrum.

MH light is generally a white/blue (cool) spectrum of light, much like the bright light of spring and early summer, and will achieve much better compact vegetative growth than HPS (fatter stronger stems, and broader leaves). If you're growing large plants (over 3' tall), MH is the best choice for the rest of your vegetative growth phase after you stop using the T5's for beginning vegetative growth.

HPS lights are the closest you can get to natural outdoor summer light quality. For optimal fruiting/flowering results, you simply can't beat HPS lighting! HPS is more centered toward the yellow/orange (warm) end of the spectrum, more like the filtered light of late summer to early fall. When a plant "see's" this warm light, it triggers a flowering response in the plant, and causes a hormonal output to take place that forces the plant to produce it's fruit or flowers.

In considering the correct wattage for your area, keep in mind that although higher wattage will absolutely equate to bigger yields, it also means higher energy consumption and more heat output to deal with. First and foremost, when you're creating an indoor garden area, you've got to be able to control your atmosphere. This means maintaining a "warm summer day" at all times for the plants. Keep this in mind when you're choosing the correct wattage. The sizing chart we've provided below is also a helpful guide for deciding on the correct wattage for your garden. A state-of-the-art garden area often uses sealed up, ducted reflectors to effectively remove the light heat from the garden area. We offer a huge selection of ducted reflectors to best meet the needs of your particular garden area. You can find those here.

LED lighting is the newest form of horticultural lighting on the market. We've been experimenting with LED's since we could get our hands on the first one to hit the market. What we've found is that LED lighting is perfect for some garden areas. The growth you'll experience under LED lighting is very nice compact development, but kind of slow. The advantages to using LED's is that there is very little electrical usage, and almost no heat to deal with. If you've got a very small space that can't be ducted to remove heat, LED's may be the best answer for you. Others may find that when used as a supplementary light source in addition to fluorescent or HID lighting, LED's will improve the results from your garden without adding any heat or additional power usage. Adding supplementary LED's to the garden perimeter will cause additional flowers to develop, where there may have been none before. As either supplementary lighting, or stand-alone lighting, LED's have found their place in the indoor garden! Check out LED grow lights here.

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How large of an area can I grow under with the various grow light bulb wattages?

The yellow region shows your primary light coverage and the orange region represents supplementary light coverage.

3.5' by 3.5'

2' by 2'


5' by 5'

2' by 2'


8' by 8'

5' by 5'


10' by 10'

6.5' by 6.5'


12' by 12'

8' by 8'


Here is a brief reference list of some common plants to help you determine the footcandles of grow lights.

Plant with Recommended Footcandles:

Dr Greenthumb

Mounting Heights Chart

The above chart shows the recommended Mounting Heights for your grow lights.

Pepper (Sweet)
Sweet Pea




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