If your indoor garden is supposed to mimic a plant’s environment, then the grow light is the sun from which everything grows- only you have control over what type of light and how much of it your plant receives. That’s partially why growers say more light=better yields. But does that mean you should get more lights and hang them as close to your plants as possible without touching them?

Of course not. It means making sure they receive enough energy to grow quickly without overpowering them. But to assure that your plants are getting exactly what they need- no more, no less- you’ll want to check the type of light you’re giving your plants: LED, HID, or Fluorescent. Some lights offer more heat energy, and others offer better spectrums, and each need to be hung in a different distance from your canopy. LED’s, for example, need to be hung farther away from your plants than HID’s to avoid bleaching your canopy from strong spectrums. Fluorescent lights need to be hung closer to plants than HID’s in order to have an effect on them because while their spectrums are okay, the energy coming from the light isn’t enough to get plants growing when hung from a distance.

You’ve got lights, plants, nutrients, and everything you need to grow. You set up your grow tent, set your plants in place, and start hanging your lights. But before you switch those lights on, are you sure you know how high you need to hang them above your plants?
Hanging your lights too low can burn them, but hanging them too high can leave them stretched and weak. Some lights need to be far away from plants so you don’t burn them, but some lights are too weak to hang more than 10 inches away- so what do you do?
The trick is to hang your lights right in that sweet spot of effectiveness and safety. The distance of your lights to your plants is all about getting your plants the power they need to turn nutrients in to food for growth. So before we start talking numbers, let’s talk about the idea behind hanging your grow lights:

Fluorescent Grow Lights
Fluorescent grow lights are a nice, easy blend of energy and spectrum output. They’re low in both, but still effective enough to grow nearly any plant. But to do so, you’ll need to hang them pretty close.

What makes hanging fluorescent lights so tricky is that not all of them are the same. For instance, 35w CFL bulbs can generate some decent heat over an extended period of time because of their compact size, whereas a longer 54w 2ft T5 grow light won’t generate lots of heat because it can dissipate it along its tube. Not only that, but the more bulbs you use the more heat you’ll generate, which is dangerous if it’s hung too close to the plants.

Fluorescents aren’t known for kicking off lots of heat, but they will generate some so you’ll need to watch your plants carefully for signs of burning or bleaching. Depending on the wattage and size of the light, as well as how many bulbs are in the light, you’ll want to start off hanging them around an inch away from your plants. If your canopy feels hot move the light up another inch, and further if the canopy is still too hot.

LED Grow Lights
So is the heat these lights give off the reason they can’t be hung so close? Yes and no. Yes, because they’ll burn your plants with intense heat. No, because even if you eliminate heat you still need to worry about light temperature.

Simply put, what makes a light a “cool” blue light, or a “warm” red light, is the temperature of the light’s spectrum(s). HID’s give off good light temps, but LED’s are much more focused on spectrum output than energy generation, so you actually need to hang them higher above your plants than HID’s to avoid light bleaching. Light bleaching can be just as bad for your plants as over heating and will result in an underwhelming crop.

LED’s don’t generate lots of heat, but you’d be surprised by how high you have to hang them above you plants. For LED lights used to grow little patches of wheat grass, herbs, and spices (15w-90w) you’ll want to go at least 15″ away from your plants. For higher wattage lights it’s even further.

(240-400w) 16-30” away from plants
(450-550w) 20-30” away from plants
(600-850w) 24-26 away from plants
(900w+) 26-42” away from plants

HID Grow Lights
If you’re using HID grow lights you know that they generate a lot of heat, so hanging them close to your plants isn’t an option. On the opposite end, your plants will be flimsy and can even start to stretch too much if they’re looking for good light. Your plants spend more time trying to grow branches and not leaves and flowering sites when lights are far away.

That’s why when it comes to HID lighting, it’s best to keep them at least 12″ (30cm) away from your plants at all times. The stronger the light, the further you’ll need to hang it, so if you have a 1000w you may want to hang it at least 15″ (38cm) away. Depending on the strength of your light, you won’t want to go higher than 30 inches (76cm) above your plants. Smaller sized lights like 400w’s can only be around 20″ (~51cm) away from the plants, and medium sized 600w’s can be around 25″ (64cm) above the plants without losing vitality.

HID’s need to be hung above your plants at a good height because of the heat they generate, so if you’re using HID’s it’s important to have a tall growing space:

(400w) 12″-19″ away from plants
(600w) 14″-25″ away from plants
(1000w) 16-31″ away from plants

LED Grow Lights was best grow light for indoor growing plants.