Indoor Grow Light FAQs
Growing outdoors might be the easy and cheap option, but to get the best quality, growing indoors is much more effective.
Growing outdoors has a lot of benefits. You save on lights, you can save on water when it rains, and you can grow some pretty massive plants if you know what you're doing.
But due to the nature of growing outdoors (get it?), a lot of growers have moved indoors to avoid bad weather, bugs and other problems outdoor growers face. And while it is more challenging and expensive to grow indoors, most growers who make the transition don't look back.
However like we said earlier, outdoor growers get the benefit of free light in the form of the sun, while indoor growers must supplement. For growers new to indoor growing, this usually brings up some questions.
Here's some of the common questions we get asked about growing indoors, and the best answers to those questions!
1. How big of an area will my light cover?
The size of the garden area will determine the wattage you need. If we assume that the plants will get no sunlight, a 1000 watt light will cover about 7 x 7 feet of growing area. A 600 watt will cover 6 x 6 feet, a 400 watt will cover 4 x 4 feet, and a 250 watt will cover 3 x 3 feet. These sized areas would be considered the “Primary Growing” areas.
These lights will light-up larger areas, but plants placed outside of the Primary Growing area, will stretch and bend toward the light; a phenomenon called phototropism. Keep these areas of coverage in mind when using multiple fixtures. The best results occur when the areas of coverage overlap.
2. How high do I need to hang my lights above my plants?
The higher the wattage the further away you want the light to be from your plants due to the amount of heat. HID lighting will be further away than a fluorescent fixture because of this. When mounting your lighting fixture take into account the type of plant and how tall the plant will grow.
You want to keep the light as close as you can, but not so close to burn the plant. A simple rule is if it is comfortable for the back of your hand, it will be a safe distance for your plants.
3. How often do I need to change my light bulb?
Most lamp manufacturers rate their lamps by “Average Life Hours” and usually claim 10,000 to 24,000 hours. These ratings are based on when the lamp will completely fail to come on. They do not factor in loss of intensity or loss of color. HID lamps lose intensity and color through normal use.
This is OK if you are lighting a warehouse, but when it comes to plant growth, these losses can mean wasted electricity and poor plant performance. Serious horticulturalists recommend that you replace your lamps after 6000 hours of use.
4. How long should I run my lights?
This depends on the type of plants and whether you have natural sunlight available to your garden. As a general rule, when you are in a vegetative stage of plant growth and you have no natural sunlight, run your lights 14-18 hours a day. If you have natural sunlight like in a light deprivation greenhouse, it will vary because the sunlight may or may not be direct.
It will take a little experimenting to find the best length of time to run your lights. If you are in the flower stage, the rule is to run your lights 12 hours a day if you have no natural light.
5. What is the difference between MH and HPS
Metal Halide (MH) lamps provide more of the blue/green spectrum, which is ideal for plants that are in a vegetative stage. MH lamps provide a more natural appearance in color and are typically the choice for plants that have little to no natural light available.
HPS lamps provide more yellow/orange/red spectrum, which is ideal for most plants that are flowering. In addition, HPS lighting is the choice for growers looking to supplement natural sunlight. Ideally, you want to use MH to grow your plants and HPS to flower your plants.
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Get some more answers to grow light specific questions from Hawthorne Garden Company, one of Cultivate's biggest distributors.