Many growers ask: How high should I hang my lights? Where should I put them for the best uniformity and ideal PPFD? The answer depends on your setup. Let's break it down.
1. Position and Height
For Greenhouse
Grow lights are usually installed overhead above the crop canopy, supplementing natural sunlight. The goal is to provide even PPFD without shading. Lights are typically mounted 2–4 meters above plants (the least height is 30cm, 12''), depending on greenhouse height and crop type. For distance between lights, depends on the lights dimension and greenhouse cross bars. Consult us with picture and floorplan of greenhouse would help a lot.
For Rack System
Rack growing requires close-to-canopy lighting because the vertical space is limited. Fixtures are often placed 15–40 cm above the plants ( the least height is 6''). Uniformity is crucial-tubular bar LEDs are preferred to spread light evenly.
For Indoor Cannabis
Lights should be hung directly above the canopy, with adjustable distance according to growth stage:
Seedlings: 60–90 cm above
Vegetative: 45–60 cm above
Flowering: 30–45 cm above
This ensures maximum PPFD without burning the leaves.
For Tent Cultivation
Because tents are small, reflective walls help redirect photons. Position the fixture in the center of the tent, 30–60 cm above canopy, and adjust as plants stretch. Using ratchet ropes makes it easy to raise or lower lights.
Lights for All Scenario
2. What Happens If Positioned Wrongly?
Too Close → Leaf burn, bleaching, or stunted nursery plants.
Too Far → Plants stretch, weak stems, and lower yields due to insufficient PPFD.
Uneven Angle → One side grows aggressively while the other stays underdeveloped, leading to uneven canopy.
Hot Spots → Excessive intensity in one area reduces uniformity and damages flowers.
3. What Should Growers Prepare Before Positioning Lights?
Clear the Growing Area
Make sure the space above your plants is clean and free from obstacles so lights can be hung securely.
Check Power Supply
Ensure there are enough sockets and safe wiring to handle your grow lights without overloading.
Use Simple Hangers or Ropes
Have adjustable hangers, hooks, or ratchet ropes ready so you can easily move the lights up and down as plants grow.
Leave Room for Adjustment
Don't fix lights too rigidly. Plants will stretch, so prepare some extra space above for raising the lights later.
Observe Plants Regularly
You don't need a meter-just watch the leaves. If they curl, burn, or stretch too much, adjust the height.
Still have no clue to position? Well leave that to us, Westland Tech. will help users to calculate the lights and position the lights with best PPFD. We will apply Dialux software arrange the best position.
If the user will operate Dialux software, it is welcome to ask IES file of fixture from us.