The Distance Between LED Lights And Plants In Each Growth Stage
It is important to understand that there is no universal rule for how far to place LED lights from plants in each phase of growth. Different manufacturers construct their LED lights in different ways. There are multiple details to take into consideration, such as the power and angle of individual LEDs within a fixture and the use of lenses to reflect light downwards. The best way to get that perfect distance between the light and your canopy is to consult with the manufacturer.
The second thing to keep in mind is that the correct LED light placement changes for each stage of growth. If your LED is dimmable, you can use dimming to adjust the intensity of the light on the plant surface. If your LED is not dimmable, your only option is to change the hanging height. These examples aren’t hard-and-fast rules, so don’t follow them without the blessing of your light’s manufacturer. But just to give you a ballpark sense of what LED light placement generally looks like throughout the growth cycle:
LED Light Placement For Seedling Stage
Seedlings need the least intensity and most distance between the canopy and the lights. You may have the instinct to blast these little guys with a high-intensity light to promote fast growth. The truth is, they’re young, vulnerable, and likelier to thrive with a gentler approach.
In the vegetative stage, you want to get your LED lights closer to your plants. In general, plants in veg only need about half the light that they need in bloom. It follows that you could have up to twice the hanging height that you use in bloom.
It’s in the flowering stage that you really need the highest intensity. It is important to build in a “hardening off” phase as you move from veg to bloom. Slowly increase the intensity or lower the hanging height until you reach the manufacturer's recommended height in bloom.
Again, these are general guidelines. Discuss the ideal distances with your manufacturer and keep an eye on your plants for signs that you’re overloading them. If your plants are getting too much light intensity, they’ll let you know.
Here’s How to Recognize Light Burn On Your Plants?
Because LED lights give off so little heat, you don’t run much risk of causing heat damage by placing your fixture too close to the canopy. What you do risk is light burn. Unfortunately, the light burn is easily mistaken for nitrogen deficiency, and many growers wind up misdiagnosing they grow and addressing the wrong problem.
If your plants have light damage, you’ll see symptoms such as:
- Leaves point upwards.
- Bleaching, which takes the form of white or yellow discoloration, typically on the leaves closest to the light.
- Veins remain green even as the rest of the leaves turn yellow.
- A nitrogen deficiency has similar characteristics, but there are a few notable differences.
A plant with a nitrogen deficiency also develops yellow patches, but the damage starts from the bottom of the plant and works its way up, while light burn begins at the top, closest to the lights.
In the case of a nitrogen deficiency, leaves wilt. In the case of a light burn, leaves turn upward and sometimes even become brittle.
The leaves of a nitrogen deficient plant fall off on their own. This does not happen to plants suffering from a light burn.
If it sounds like your plant has a light burn, it’s time to reevaluate the placement of your LED lights.
Light Distance for Growing With LED Lighting
LEDs produce less heat and use less power overall. This can reduce energy bills massively, and a lot of growers are moving from the HID lighting to LED, as it is cheaper to run, and a more environmentally friendly option of grow lighting.
The problem here is that there are a lot of makes and models of LEDs, and each one will have a specific height it will be optimal at. Most of the time, this height will be found in the owner’s manual.
LED lights produce less heat, so it can be hard to tell if the plant is too close by using the back of the hand test. You can get LED lighting very close to the plants, but because the light is so strong, you can still damage your plants and cause “light bleaching”.
LED Grow Light (COB Lighting)
COBs are the most popular form of LED grow lights, but they are made with far fewer diodes (lights). Because the COBs lights are small, you should not underestimate how powerful they are. They should be no closer than 12 inches from the top of the plants.
One of the best examples of LED grow light I would recommend is the ViparSpectra XS 1500. It is an excellent 2’ x 2’ grow light. And XS series grow lights are well-built with brightness dimmer, easy to use, generates an excellent distribution of light, and have elite efficiency. It is a great choice for 2’ x 2’ and 2.5’ x 2.5’ grow spaces. Also, the hanging height of XS1500 is available to adjust from 12” to 24” according to different growing stages of plants.
Similarly, I tested the P2000 a couple of months ago and I liked the dimmer and the size of it, so I kept it for use with seedlings. I just ran my first set of seedlings through with it and both the plants and I loved it.
All in all, the distance you need to keep lights from your plants will differ from the model and maker. You should check the instruction manual for the best light distance for growing plants.