How to Set The Perfect Height For Your Cannabis Grow Lights

An in-depth guide on how to find the best grow light height for your indoor weed garden.

How to Set The Perfect Height For Your Cannabis Grow Lights Cover PhotoOnce you’ve installed your grow lights and adjusted the lighting schedule with a timer — it’s time to set the stage for success by finding the perfect height for your cannabis grow light system.

From increased bud production to maximized space efficiency, setting your grow light system’s height works wonders for cannabis cultivators.

Read along to learn how to set the perfect height for your grow lights in a few easy-to-follow steps. You’ll discover how close or far a grow light can be for optimized cannabis yields and star-studded growth.

Ready to put your grow lights to work? Let’s go!

Why You Need to Adjust the Height of Your Grow Light System When Growing Marijuana

When discussing lighting issues with indoor cannabis growers, the number one question is always: What is the best height between grow light and plant canopy?

As you know or will come to find out, cannabis plants are continually growing. From the seedling stage to the explosive growth of the pre-flowering phase — there’s never a fixed grow light height that cultivators can rely on.

Instead, cannabis cultivators must stay on-guard to adjust the height of their grow lights when necessary. In other words, cannabis growers must continuously find the perfect balance between grow lights and the plant canopy for healthy results.

If your grow lights are too far or close to the plant canopy, several problems may occur, such as:

  • Reduced vigor
  • Burned or bleached leaves
  • Low yield
  • Long internodes
  • Fluffy buds
  • Bleached buds

Alternatively, the right grow light height is known to:

  • Increase bud and resin production
  • Speed up the overall flowering process
  • Stimulate healthy and rapid growth
  • Produce dense flowers and short internodes
  • Produce thick stems and branches

As you can, there are several reasons why the height of your indoor grow lights matters.

Aside from cannabis-related problems, inadequate height will also throw your cannabis garden into disarray, primarily by:

  • Reduced space efficiency
  • Wasted wattage/lumens
  • Increased electricity bill

On the flip side — finding the perfect height for your grow lights will:

  • Enhance and maximize space efficiency
  • Increase gram per watt
  • Distribute light evenly

Now that you understand the negative and positive implications of the grow light’s height — let’s move on and discuss how to find the best height for your indoor marijuana garden.

How to Find The Best Height For Grow Light Systems in Three Easy Steps

Although LED systems are growing in popularity, HID systems, such as HPS or MH, are still preferred by cannabis cultivators worldwide. However, this doesn’t mean one grow light is better than another.

Instead, HIDs, LEDs, and CFL-based grow lights play a crucial role within indoor cannabis gardens worldwide. Depending on the grow light, there will be a difference in the overall height, such as HIDs and CFLs.

Remember, HID means high-intensity discharge. In other words, HID systems pack a massive punch of lumens that are powerful at a distance. Alternatively, CFLs are low-watt and ideal for small grow rooms. As you can imagine, each of these grow light systems will have optimal, yet different, heights in the grow room.

With this in mind — here are three steps to quickly find the ideal grow light height without an expensive light meter.

Step One

First, assess the current grow light height in relationship to the weed canopy.

As a rule of thumb, your grow light system should not be closer than 12-inches (30.5cm) to the cannabis canopy. On the other hand, grow lights should not be further than 50-inches from the cannabis canopy.

Now ask yourself — are you below or above a generalized height of 12-inches? Regardless of your answer — you will adjust the grow light to the 12-18-inch baseline to ensure generalized light efficiency and bud production.

However, move to step two to hone the light position and height for maximum efficiency.

Cannabis Grow Light Distance

Step Two

Next, observe the light’s footprint.

Does the light’s footprint encompass your marijuana plants, or does it begin to dim near the edge of the canopy?

If you recall our guide, How to Plan an Indoor Cannabis Garden, we discussed how to choose the optimal grow light system concerning the grow room’s size and desired number of weed plants.

Whether you grow a single marijuana plant or nine weed plants in a meter squared — the light’s footprint should always extend to the outer border.

If you notice that the cannabis plants at the edge of the grow room are receiving less bright light than those in the middle:

  • Lower the light or bring your cannabis plants closer

If you notice that the cannabis plants are receiving too much light (via bleaching):

  • Raise the light until the grow space is evenly illuminated

We understand — it’s not easy to raise or lower the grow light by mere intuition, which is why we offer grow light distance charts for you to follow.

The Grow Light Distance Chart For HIDs

  • 400-watt HID grow light: 12″-20″ above marijuana plant canopy
  • 600-watt HID grow light: 14″-26″ above marijuana plant canopy
  • 1,000-watt HID grow light: 16″-32″ above marijuana plant canopy

The Grow Light Distance Chart For LEDs

  • 240-400-watt LED grow light: 14-28” above marijuana plant canopy
  • 450-550-watt LED grow light: 18-32” above marijuana plant canopy
  • 600-850-watt LED grow light: 22-36″ above marijuana plant canopy
  • 900-watt LED grow lights and above: 26-46” above marijuana plant canopy

The Grow Light Distance Chart For CFLs and T5s

  • 20-50-watt CFL grow bulbs: 1-2″ above marijuana plant canopy
  • 55-100-watt CFL grow bulbs: 2-4″ above marijuana plant canopy
  • 150-250-watt T5 grow lights: 4-10″ above marijuana plant canopy
  • 300-watt HO T5 grow lights: 10-16″ above marijuana plant canopy

Step Three

The final step is to watch how your cannabis plants respond over the next days and weeks.

Here are positive signs to watch for:

  • Plants are growing quickly
  • The leaves are turned upwards as if “praying” to the light
  • Tight internode spacing
  • Calyx proliferation during the flowering process
  • High resin content

Alternatively, here’s a list of negative signs to look out for:

  • Bleached buds or leaves
  • Scorched buds or leaves
  • Stunted growth
  • Uneven canopy

As long as your cannabis plants are growing happily — you’ve found the sweet spot for your grow lights! If you find your cannabis plants unhappy — it’s time to repeat steps one and two until your green beauties bounce back.

A Special Consideration: The Height Between Grow Lights and Cannabis Seedlings

We have yet to touch upon a special consideration during the entirety of this guide when finding the right height for your grow lights.

Cannabis seedlings are incredibly susceptible to too much or too little light. As you already know, the seedling phase sets the stage for the remainder of the marijuana plant’s life.

Therefore — you must make sure your marijuana seedlings thrive under the proper amount of light.

First and foremost — you will not use a HID grow light system to germinate marijuana seeds. Instead, you will likely use CFLs or a dialed-back LED system.

If using low-wattage CFLs:

  • You may place the grow lights 1-6″ above the weed seedlings

If using a heavier-duty T5 system, such as 150-watts:

  • You may place the grow light 10-14″ above the weed seedlings

As for medium-watt LED systems:

  • You may place the LED 12-18″ above the weed seedlings

Remember, you can also use the back-of-the-hand test to ensure the safety of your marijuana seedlings. By placing your hand at the same level as your marijuana seedlings, and it doesn’t feel hot — it’s likely a safe height.

Let Your Grow Light Shine in Return For Massive Yields

By finding the perfect distance between grow light and plant canopy — you’re on track for a record-busting cannabis harvest.

The journey, however, doesn’t end here. From plant monitoring tips to optimized feed schedules, the world of indoor marijuana cultivation is filled with unique aspects that’ll make your head spin.

By following our guides — you’ll always remain on the path of happy weed plants and resin-coated buds — guaranteed.

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2 years ago

Please…discuss how to water the seedlings to mid to mature plants…

9 months ago

I’m using a 600wat hid for my seedlings so that to much to start them?