It’s one of the questions growers most ask, we get asked it daily, sometimes more than once!
So let’s settle the evergreen question of “How close to put grow lights to my plants?”
Firstly let me start by saying it depends on a few factors such as;
- Type of light you use (HPS, CFL or LED)
- Wattage/power of the light you use
- The temperature just above the canopy of your plants
- The type of plants you’re growing
- Amount of vertical space you have available
A good rule of thumb to follow if you’re in doubt is 1-2ft away from the canopy of your plants. Some plants can react strangely to having the light to close whilst others thrive with the light right on top.
It’s too hot to get my light close enough to my plants
Some growers report problems with higher wattage HPS lighting systems as they cannot get the light source close enough to the plants. To solve this there are several solutions:
- Point a clip on fan at the light, this will cool it down and push the hot air away
- Upgrade to a cool tube or air cooled lighting system
- Use a lower wattage HPS light, CFL lights or LED lights
- Get a higher power extractor fan to suck the hot air out
How close can I put my 400w or 600w HPS system to my plants?
Taking all of the above into account you should place your HPS system between 12 & 18 inches away from your plant, this is the ideal position. You want to to be close up during the early stages of your plants life to avoid stretching and as they get bigger you can risk having the HPS light a little further away.
What distance should my LED grow light be from my plants?
LED grow lights don’t produce anywhere near as much heat as HPS systems so you can theoretically get them much closer to your plants without running the risk of damaging them. LED lights are more penetrating than HPS lights however different brands of bulbs / kits have different qualities, view angles & coverage areas.
In general you want to place your LED grow light 6-12 inches above your canopy although different manufacturers have different guidance depending on how they are built.
A good rule of thumb to follow when figuring out the distance to put your LED light from your plants is to get them as close as possible without compromising the coverage area and leaving plenty of room for them to grow into.
How far away should I put my CFL grow light from my plants?
CFLs are like LEDs but they are nowhere near as penetrating as HPS or LED lights. This is one of the biggest drawbacks of CFL grow lights and one of the reasons why growers decide to use multiple CFL lights.
Another problem with CFL lights is that they can, will and do burn your plants if they are too close. With this in mind you want to get your grow light as close as possible to penetrate and far enough away so that they don’t burn.
Depending on wattage you should be able to get your CFL: grow light 2-5 inches away from your plants.
What happens if my grow light is too far away from my plants?
If you put your grow light too far away from your plants you can cause much damage. The biggest problem of all is stretching, this is when your plant puts extra effort into growing taller so that it can be nearer the light source.
Because they put all their energy into getting closer to the light they don’t put as much energy into producing fruit, this will lower your yields by as much as 30%, let me repeat, you could be getting 30% less fruit simply because you positioned your grow light to far away!
What happens if my grow light is to close to my plants?
On the flip side you can also cause problems to your plants if the grow light is to close. The obvious problems occur with CFL and HPS lights because of the heat they emit they can easily burn the tops of your plants.
Many growers also report strange or stunted growth when the light source is placed to close to plant.