Best Under Canopy Lights: Picks, PPF Figures and Setup
The best under canopy lights are red-heavy bars for commercial flower rooms bulking lower buds under a strong top light, and full-spectrum bars for tents where one fixture has to do more. The Faven Chroma is the pick for adjustable spectrum, the GrowPros Model 3 for a dual-channel 8 ft run, and the VIVOSUN LumaRay for a first tent setup. Under canopy light adds to a top light. It never replaces one.
The Best Under Canopy Lights
Under canopy lighting is extra LED light mounted at or near the floor, pointed up into the lower canopy your top fixture can't reach. You use it in flower, it runs on the same schedule as the overhead light, and it pays you back by finishing lower flowers instead of sending them to the trim bin.
The physics explains the gap: the upper canopy shades the leaves below it, so the bottom third of a tall plant sees a fraction of what the top cola sees, and red photons drive flower development efficiently per watt. You're filling a light deficit, not lighting a second room.
Under top lighting alone, PAR roughly halves from the apical to the middle canopy and halves again to the basal level, so the goal is topping up that lower level rather than matching the top. Check any target with a meter at the floor. The published research on canopy light intensity found dry inflorescence yield rising linearly with canopy-level PPFD, and the subcanopy studies below make the case for adding light down low at all.
Our Under Canopy Picks at a Glance
The Picks
Faven Lighting Chroma Under Canopy Light: best adjustable spectrum
The Faven Lighting Chroma is the pick for a commercial room that wants to tune the lower-canopy recipe run by run instead of committing to one fixed blend. It runs 120W plus a 15W independent far-red channel, and the spectrum is adjustable across R4 through R9. It measures 46 in long and carries an IP66 rating with ETL and DLC certification, so it survives washdown and qualifies for the rebate paperwork.
Faven publishes a 10-bar daisy chain at 120V, which is more fixtures on one circuit than most rooms need per row. Best for a head grower who already runs a controller and wants far-red on its own schedule. If you just want red photons on a single channel, save the money and take a Model 2.
GrowPros Solutions Model 3 Dual Channel: best for long benches
The GrowPros Solutions Model 3 lets one fixture run blue-heavy through stretch and lean into red from mid-flower through harvest. The GrowPros Solutions Model 3 comes in 4 ft and 8 ft lengths; the 8 ft bar runs 300W total, split into two dimmable 150W channels: UVA, blue and 5000K on one, deep red, far red and 3000K on the other. It publishes PPF 900 µmol/s and 3.0 µmol/J, with IP65 and DLC/ETL listing. The 4 ft bar is 150W, split 75W / 75W.
Best for a bench that runs 8 ft or longer, where a 4 ft bar leaves dark gaps between fixtures. The 8 ft version daisy chains 4 bars at 120V, or step to 240V if the room has it. Cords and controller are separate, so budget one line for the controller and power runs.
GrowPros Solutions Model 2 Deep Red: best red-only value
The Model 2 is the value pick, sold as a two-pack of 4 ft bars at 125W each. The spectrum is 80% deep red plus full spectrum, PPF 414 µmol/s per bar, 3.31 µmol/J, single channel, IP65. There is no UV and only one channel, and it needs a controller to turn on. It does one job well: pour red photons into the lower canopy during flower.
Best for a commercial room already running strong full-spectrum top lights, where the only gap is the red that never reaches the floor. If you need a veg-capable or adjustable fixture, this is not it. If you want the cheapest way to light a row of lower flowers, it is hard to beat.
ION LED 135W Under Canopy: best full-spectrum coverage
The ION 135W puts the lower canopy under the same full-spectrum blend as the top light, for a grower who does not want a red-lit underside. It runs a full-spectrum FSG blend at 2.7 µmol/J and 370 µmol/s, DLC-listed and ETL-rated, with IP66 water resistance and 0-10V dimming. It is 1,160 mm long, so it covers a long narrow strip with even light rather than a hotspot.
Best for a mixed-light room or a veg-to-flower space where one fixture has to serve both. The stand is sold separately, so plan your mounting before you order. It weighs 6.2 lbs.
VIVOSUN LumaRay: best first tent setup
The VIVOSUN LumaRay is the entry-tier under canopy light. It is 100W, full-spectrum with 60% red, 2.38 µmol/J, IP54, and mounts with magnetic clamps and three selectable heights, which is what makes it the right first bar. You can clamp it to a tent wall or sit it on the floor without drilling. It connects to VIVOSUN's SGS system through an E42A+ or E25 controller, sold separately, and daisy chains six units.
Best for a home grower who wants to test whether under canopy lighting pays back on their setup before spending on commercial fixtures. The IP54 rating and 25,000-hour lifespan tell you it is a home-scale bar, not a washdown commercial one, so keep it in the tent.
Iluminar 160W Red Spectrum: best output per 4 ft-class bar
The Iluminar 160W is the highest-output 4 ft-class bar here, publishing PPF 495 µmol/s at 3.09 µmol/J in an R spectrum tuned for synergy with full-spectrum top lights. It is 1,150 mm long, IP65, 0-10V dimmable, and daisy chains up to 12 units at 120V. Best for a commercial room replacing an older under canopy fleet, where the measured PPF off the floor decides the purchase.
Are Under Canopy Lights Worth It?
The worthwhile case rests on published research. A HortScience study on subcanopy lighting found both Red-Blue and RGB supplemental subcanopy light "significantly increased yield and concentration of total Δ9-tetrahydrocannabinol (Δ9-THC) in bud tissue from the lower plant canopy" (Hawley et al., 2018). That is exactly the tissue a top light cannot reach. A 2025 study comparing subcanopy and inter-canopy light reported dry inflorescence yield gains of 24.58% from subcanopy and 29.95% from inter-canopy light, with THC yield up 18.67% and 24.42%, and both supplemental treatments "reduced the coefficients of variation, yielding more standardized products" (Plants, 2025).
I'd underline that last point for a commercial buyer. Yield gain matters, but batch-to-batch consistency is where a legal market actually grades your flower, and less variability between plants is worth more than a headline percentage. The Frontiers work shows dry inflorescence yield increasing linearly with canopy-level PPFD, which is why under canopy light works at all. You're raising the PPFD the lower flowers see.
The objection I hear from experienced growers is that a bar pointed upward mostly lights the underside of a leaf, which absorbs worse than the top surface, so a chunk of the photon budget is wasted. That inefficiency is real, and it is why under canopy bars run at a fraction of top-light wattage and get angled rather than fired straight up. The physics still clears the bar for tall plants with a deep lower canopy. On a short, squat plant the gain is smaller and the energy case is weaker.
When it pays: tall plants, dense canopy, a strong top light already in place, and a room where lower flower quality is the bottleneck. When it does not: short plants, a top light that already saturates the floor, or a grower who has not fixed the environment first. Under canopy heat and humidity load adds to the room, so the dehumidifier has to handle it.
Red-Heavy vs Full Spectrum Under Canopy Bars
Pick red-heavy when the room already has a full-spectrum top light doing the heavy lifting. The lower canopy's job in flower is bulking, and deep red plus far red is efficient at that per watt. The GrowPros Model 2 at 80% deep red and the Iluminar R spectrum are the two purest versions of this approach.
Pick full spectrum when the bottom has to look like the top: a mixed-light room, a veg run, or a tent where the same bar does two jobs. The ION 135W and the VIVOSUN LumaRay cover this ground. Full spectrum trades a little flowering efficiency for versatility. If you already run supplemental LED grow lights up top, the bottom bar can stay red.
Adjustable is the third option. The Faven Chroma and the GrowPros Model 3 let you shift between the two, which is what most commercial rooms eventually want as they dial in a recipe.
How Much Under Canopy Light Do You Need
Place bars in the rows between plants, running the length of the bench. Faven's sizing rule: convert bench length to inches and divide by 46 for lights per row, then multiply by the number of rows between plants (a 14 ft bench three plants wide takes 3 lights per row x 2 rows = 6 lights).
Faven publishes its own coverage math: bench length in inches divided by 46 gives lights per row. Use that as your baseline, from the 4 x 4 tent upward, then adjust for the PPFD you read at the lower flower sites.
Setup: Mounting
Mount the bars low, at or just above the floor, so they angle up into the lower canopy rather than firing horizontally across the room. The VIVOSUN LumaRay mounts with magnetic clamps to a tent wall and offers three adjustable heights. ION sells the stand for its 135W separately. For a production bench, dedicated under canopy lighting stands get the bar off the wet floor and hold a fixed angle.
Leave enough room around the bar that it does not press into the pots or block irrigation. A warm bar against plant tissue can stress the closest buds, so keep it at least 6 inches from plastic pots, trays and other combustible materials, as GrowPros requires for its bars, and check the surface temperature with an infrared thermometer on the first run.
Angle
Aim the bar up and slightly inward so the cone hits the inner lower branches, not the wall. A pure 90-degree straight-up mount wastes photons on the underside of leaves and casts a narrow hot spot directly above the bar. A slight inward tilt throws the light across more flower sites and blends better with the top light.
The other angle to check is the top light's. If your overhead fixture already throws strong PPFD to the floor at the canopy edges, put the under canopy bar on the interior rows where the deficit is worst, not on the outer rows.
Schedule and Wiring
Run the under canopy bars on the same schedule as the overhead light. During flower that is 12 hours on, and the lower canopy needs the same dark period the top does. If you stagger anything, delay the under canopy channel by a few minutes so the controllers sequence cleanly, but do not run the bars into the dark period.
Wiring is where commercial and home diverge. The Faven Chroma daisy chains 10 units at 120V. The GrowPros Model 3 8 ft chains 4 at 120V. The Iluminar chains 12 at 120V, and the VIVOSUN LumaRay chains 6. The Faven, GrowPros and Iluminar chains are longer at higher voltage, so on a commercial circuit run the bars at the higher voltage and halve the amperage. Controllers matter too: the Faven wants GrowFlux or an RS485/0-10V adapter, the GrowPros uses an RJ12 data cable, and the ION and Iluminar use 0-10V dimming. Match the controller to the fixture before you buy the controller.
If you are still setting your overall photoperiod, our guide to how long grow lights should be on covers the schedules by stage, and the broader full spectrum grow lights guide explains what the top fixture's blend already delivers so you know what the bottom bar adds.
Under Canopy vs Inter-Canopy
Under canopy light sits at or near the floor and fires up. Inter-canopy light adds dedicated light inside the canopy, at both the middle and basal levels. Under canopy targets the very bottom of tall plants. Inter-canopy gives more even coverage through the middle and basal levels. In the 2025 study, inter-canopy light produced the larger yield gain, while subcanopy light was more power-efficient per gram of flower and THC. Our comparison of under-canopy vs inter-canopy lighting walks through the trade-off in detail, and our inter-canopy lighting lineup shows what the mid-canopy option looks like.
Frequently Asked Questions
- Are under canopy lights worth it?
- For tall, dense plants under a strong top light, yes. Research on subcanopy lighting found higher yield and THC in the lower canopy buds, and a 2025 study reported a 24.58% dry inflorescence yield gain from subcanopy light. On short plants, or where the top light already lights the floor, the energy case is weaker.
- Can you run under canopy lights in a tent?
- Yes. A 4 ft bar fits a 4 x 4 or larger tent, and the VIVOSUN LumaRay is built for exactly this with magnetic tent-wall clamps and three heights. Keep it out of the way of your irrigation and keep the bar clear of the pots and the closest buds.
- Do under canopy lights help popcorn buds?
- They target the lower flower sites that would otherwise finish small. By adding red photons to the lower canopy, under canopy bars finish more of the smaller B-buds into usable flower, which is the reason commercial rooms add them during flower instead of stripping the lower canopy bare.
- How many under canopy lights do I need for a 4x4?
- One 4 ft bar down the center or along one wall is the standard starting point in a 4 x 4 tent. Add a second on the opposite wall if your canopy is wide. Measure PPFD at the lower buds and add a bar if the floor reads below your target.
- When should I turn on under canopy lights?
- During flower, and on the same 12-hour schedule as the top light. The lower canopy needs the same photoperiod and the same dark period as the rest of the plant.
- Red or full spectrum for under canopy?
- Red-heavy when the top light already runs full spectrum and the job is bulking lower flowers. Full spectrum when the bar has to serve veg or a mixed-light room. Adjustable fixtures let you shift between the two as the run progresses.
- Will under canopy lights increase the room's heat and humidity?
- Yes, they add some of both. Each bar puts a small amount of heat back into the room and the extra light drives transpiration. Size the dehumidifier to the full load including the under canopy bars, not just the top lights.
The Bottom Line
Under canopy lighting earns its place on tall flower in a commercial room and on a tent where you want to test the idea before spending on a fleet. The GrowPros Model 2 is the cleanest value buy if you already run a strong full-spectrum top light. The Faven Chroma is the fixture for a room that wants to tune the recipe. On a home tent, start with the VIVOSUN LumaRay and see if the lower canopy responds before you scale.
If you are still choosing the overhead fixture, our best grow lights guide covers the efficiency and PPE comparison, and the LED grow lights lineup has the current fixtures by tier. When you are ready to add the bottom bars, browse the full under canopy lighting range and match the fixture to your row length and controller.
Related Guides
- Under-Canopy vs. Inter-Canopy Lighting: Which Supplemental Setup Does Your Grow Need?
- Best LED Grow Lights 2026: Efficiency and PPE Compared
- How Long Should Grow Lights Be On? Schedules by Growth Stage
- What Are Full Spectrum Grow Lights? Spectrum Explained
- Why Every Indoor Grower Should Consider Under Canopy Lighting
