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How Far Away Should Grow Lights be from Cannabis Plants?

Updated August 20, 2022

Growing cannabis is a science. When it comes to lighting, every type of lighting requires a different distance from your plants. This is a mistake that many growers, even advanced growers, make. You could really be cutting yourself short, as light is the food your plants need to produce big, solid buds that dry and cure perfectly. This quick reference guide will help you ensure proper distance between plants and their lights.

Fluorescent Light Options

Fluorescent lights aren’t very hot at all. The benefit is that you can have them mere inches from your cannabis plants and not cause harm. Do the hand test. Place your hand between the light and your cannabis plant. If you can hold your hand there for at least 30 seconds, the location of the light isn’t too close.

Continue performing the hand test until you’re at a distance where your flesh doesn’t feel like it’s burning after 30 seconds.

If fluorescent lights are your choice, make sure that you choose a method of plant training. Canopies are suggested to keep the height of your plants minimal and to ensure that the essential portion of each plant is getting an ample amount of light.

LED Lighting

LED lights are trusted by many master growers. They are, however, a little tricky. LEDs don’t have a standard distance when it comes to space between the light and your cannabis plants. When LED grow lights are used, the size of the light matters as much as the strength of the light. Some manufacturer packaging may include tips for optimal plant growth, including an appropriate distance from your plants.

When that information is not available, contact the manufacturer and ask them specifically how far away the LED light should be away from the top of your plants.

It’s confusing with LED lights because they are generally cool-running bulbs. That doesn’t mean that they can sit directly on top of your plants though, they can still get light burn. Light burn usually shows as brown spots on your leaves.

Here’s a quick reference guide for LED lights:

  • 1W bulb – one-foot from the top of plants
  • 3 – 5W bulbs – minimum of 18-inches from the top of the plants
  • 300W+ - the light should be at least 2 and a half feet from the top of the cannabis plant LED grow lights in the blue spectrum are ideal for the final weeks of growing.

HID Grow Lights

Like LED lights, the size and strength of an HID light does matter. HID lights are most commonly used during the vegetative stage of growth. You are, however, likely to get bigger yields from using HID lighting. They are not the most economical option, but often produce the best results.

Quick HID light distance guide:

150W – minimum of 8-inches from plant tops250W – minimum of 10-inches from plant tops400W – at least 1-foot from the tops of plants600W – minimum of 14-inches from plant tops1000W – at least 16-inches from plant tops

If you are using higher wattages than those shown here, contact the manufacturer for proper distance suggestions.

Closing Thoughts

Lighting is one of the most important elements to successfully growing cannabis plants indoors. You have the best opportunity to control the environment and provide the best light source possible. While some grow light options may not be super economical, they make up for it by helping produce bigger yields and more potent cannabis.

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