Grow Lights Guide

A Beginner's Guide On How To Use LED Grow Lights

grow light and plant

As we all know, sunlight helps everything grow. Grow light is  is a light source that uses light instead of sunlight according to the natural law of plant growth and the principle that plants use sunlight for photosynthesis. Click here for more types of grow lights.

Three purposes of using plant lights:
(1). Provide all the light needed for plant growth;
(2). Supplement sunlight when the daylight hours are short in winter;
(3). Increase the length of the "day" to promote plants growth and flowering.

To make grow lights to work effectively on your plants, you should know how to use grow lights properly.

Set a reasonable light distance

What is a reasonable distance between grow light and plants? Grow lights allow plants to supplement proper lighting by adjusting the height of the lights suspended above the plants. Too far away from the plants will not provide the plants with enough light and heat they need; too close to the plants will cause uneven light exposure to plants, resulting in less than expected growth conditions and the possibility of burning the plants. It is important to note that it is the distance from the light to the plant canopy, not the distance from the roots to the light.
The correct LED grow light position will change as the plant grows.
For seedlings, LED grow lights should typically be installed between 24-36 inches above the plant canopy.
During the veg stage, LED grow lights should be 12-24 inches from the top of the canopy.
As plants progress through the flowering stage, their need for bright light decreases. The top leaves of the canopy should be 18-24 inches from the light source to produce blooms.

The distance will also vary based on the wattage of your light.
Low-wattage LEDs of about 200 watts should be located 12-20 inches from the top of the plant canopy.
Higher power LEDs of 1000 watts and above should be located between 36-46 inches from the top of the plants.

distance of grow light from plant canopy

Please note that PPFD (umol/m²/s) will decrease with increasing LED grow light position. Learn more about PPFD.

Adjust light brightness according to crop growth stage

For dimmable LED grow lights, in addition to changing the hanging height, dimming can also be used to adjust the intensity of the light so that the plants are properly illuminated. Different periods of the same plant have different needs for light.

Seedling stage: It is recommended to use LED lights with 50% brightness
Vegetation period: It is recommended to use LED lights with 80% brightness
Flowering period: 100% brightness of LED light is recommended

And this is just a rough suggestion, in your planting, the light can be adjusted according to your experience. Learn about the relationship between carbon dioxide and light.

adjust grow light brightness


Using the light schedule

When using a grow light, you need to determine when the light is on and off. Most plants need long hours of sunlight to bloom and bear fruit, which is why summer is the best time to grow vegetables outdoors.

It is recommended to expose plants to 12 hours of light per day, with 16-18 hours of light recommended for flowering plants. However, keep in mind that your plants also need some dark time to rest. Look for LED grow lights with handy timers to adjust the lighting.

The symptoms of too much light and too little light

Whether it is adjusting the brightness or setting the light time, the purpose is to allow the plants to get enough energy  through photosynthesis for them to thrive.

There are some symptoms when plants receive too much light or lack of light. If the following symptoms appear in your plants, you can increase or decrease light for your plants according to different situations.

Plants show a variety of signs when there is too much light.

  • The most obvious sign is burning leaves.
  • The leaves are drooping. When a plant has any health problems, its leaves are usually the first places to go wrong.
  • Plants may develop brown patches throughout their leaves, which may be caused by sun or grow light burns.
  • wilting leaves, especially young leaves.
  • The leaves will fade and eventually turn white.

Plants are not getting enough light, which can be observed by a marked change in the appearance of the plants.

  • The plants that should have grown thick have become slender, which are all signs of leggy branches and leaves.
  • If the plant does not have sunlight, the leaves will turn yellow.
  • Plants in low light may also drop leaves, especially older leaves.
  • Plants grow slowly or even stop growing.
  • The leaves are thinner and smaller than normal plants

Other precautions

1.LED grow lights are for indoor use only;
2.Regularly clean the dust on the LEDs, the dirt will not only affect the appearance but also cause corrosion on the surface of the lights;
3.Avoid looking directly at the lights of LED grow lights;
4.Follow the manufacturer's other precautions for use.

Read this article to find out if plant lights are harmful to people.

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