Under canopy led lights

[kaw900r]

Have any of you tried a under canopy light? I m looking at them and was wondering if it's worth it to produce quality bud underneath.

T/u

 

[BigBudsBunny]

no, but have used side lighting which had a huge beneficial effect to all the lower buds.

 

[Sativa1970]

I don't remember the exact amount but the bottom side of a leaf is 20-30% as photo active as the top side. So underlighting is wasting roughly 75% of the energy. Side lighting that hits the tops of the lower leaves is vary efficient. If you are just trying to max out a plant for fun and already have top and side light it can gain that last little bit. If you have more lights and energy to throw at a plant do the top then sides and under lights last if at all.

 

[Fenderbender]

I've tried underlighting on the previous grow, no complaints at all, I mean the sides of leaves don't have much surface area so I prefer under, well it's a bit sideways shining up in the canopy.

Absorption profile high nitrogen cannabis leaf, adaxial top surface

Abaxial side

 

[Puszcza]

Side lighting is also worth to be considered. Especially with modern full spectrum LED bars.

 

[Fenderbender]

Side lighting is also worth to be considered. Especially with modern full spectrum LED bars.

Sure, both work, I don't come in straight from the bottom either and leaves do an up and down motion anyways so even with side lighting the leaves will get exposed from below and from above depending on their position.
And well even the stems are somewhat photoactive.
It's just from below is easy for me as side lighting well you need some distance to the walls unless you are using low power bars that the plant can grow against.

 

[Sativa1970]

I guess if you don't have space for side light under light is the next best thing. Didn't consider space.

 

[bluter]

under lighting should be used as often as the sun shines from underneath a plant on earth.

plants get 180 degree lighting in nature. side lighting is good. under lighting not so much.

 

[Fenderbender]

Which should be plentiful for people growing on a mountaintop

Here's my Mount Everest plant with under/side light, 190W from the top 140W from below and I got a gram per Watt. So I really don't think it matters all that much, and side lighting will also illuminate leaves from below.
Again light goes into the leaf, bounces around in the chloroplast and gets absorbed, the light from below will do the same with just slight less efficiency.

Understanding Under-Canopy and Side Lighting for Cannabis - RQS Blog

In this article, we explore the use of under-canopy and side lighting to maximise the yields of cannabis crops. Find out more with Royal Queen Seeds.

www.royalqueenseeds.com

 

[bluter]

Here's my Mount Everest plant with under/side light, 190W from the top 140W from below and I got a gram per Watt.

something that weak probably isn't all that bad. you'll get light aversion and stress issues if using a rig with any intensity underneath.
space buckets use 180 degree lighting very effectively, even the old phototrons of the 70's were centered on it. the first "professional" rig i had used 180 degree lighting, a t5 rig in the early 80's i got from my cousin. if you search there are still a few pics of those rigs on the board.

before there was high power it was the best way to get light to the plant.

 

[Sativa1970]

Light is either absorbed or reflected. Light can be absorbed as heat or collected by chloroplasts for photosynthesis. Roughly 75% of a leaves chloroplast are on the top side of the leaf. This varies some by strain. The top of the leaf is not only more photoactive, it also absorbs more light energy. These are the amount of light reflected back off a leaf. Any light not reflected was absorbed in photosynthesis or as heat. So total absorbed energy.

Top side of a cannabis leaf absorbs 90% up to 700nm. Turning 75% of that into glucose and 25% heat.

Bottom side of a cannabis leaf absorbs 75% of the energy up to 700nm. Turning 25% into glucose and 75% into heat.

That 75% could bounce off the bottom of a leaf and hit the top of another. But the longer distance would also apply the inverse square law of light energy. Adding one foot is 1/4th energy 2 foot is 1/9th the energy.

 

[kaw900r]

something that weak probably isn't all that bad. you'll get light aversion and stress issues if using a rig with any intensity underneath.
space buckets use 180 degree lighting very effectively, even the old phototrons of the 70's were centered on it. the first "professional" rig i had used 180 degree lighting, a t5 rig in the early 80's i got from my cousin. if you search there are still a few pics of those rigs on the board.

before there was high power it was the best way to get light to the plant.

I still have 1 of the old photophobia with the side bulbs

 

[Fenderbender]

Okay but say your plant leaves are straight what is the side light lighting?
It's like lighting a piece of A4 paper from its thickness of 0,1mm and shining over or under the 29x21cm surface.
If my leaves are praying the side lighting is still lighting the abaxial side.
Only droopy leaves would get top light when it comes straight from the side.

 

[Sativa1970]

The leaves are praying to the closest light. When you side light they prey to the sides too. Rather than just the tops, you get a 180 deg prayer circle.

 

[bluter]

Okay but say your plant leaves are straight what is the side light lighting?
It's like lighting a piece of A4 paper from its thickness of 0,1mm and shining over or under the 29x21cm surface.
If my leaves are praying the side lighting is still lighting the abaxial side.
Only droopy leaves would get top light when it comes straight from the side.

it was more about canopy penetration. still is really. we used to place the fluorescents right against the plants, maybe only an inch or two away, it wouldn't burn them.
you can do the same or similar with weak led too, space buckets depend on it. works fantastic too. wish we had more examples on the board.

hid and high power led recommend a minimum of 18 to 24 inches from the canopy depending on whether in veg or flower stage.

The leaves are praying to the closest light. When you side light they prey to the sides too. Rather than just the tops, you get a 180 deg prayer circle.

that's the idea. placing light directly under the plant runs counter to where the leaves like to reach toward. google phototropism for a better explanation than i can give.

 

[gr865]

Not sure if this counts as Under Canopy. Had a CLW LED above and these hanging into the canopy.

Here they are in flower.

And at harvest.

This grow was in a home made 4 X 2.5 X 6.5 cabinet.

The grow was in the garage and it was hot, had air feed from the AC in the house, and it was still very warm. This is what led me to start the adventure and get a grow tent. Went from this in the garage, to a 4 x 4 Gorilla Grow tent in a closet in the house.

And from there to my 15 x 20 man cave/shop, sprayed with insulation, AC installed and ready to rock.
Made this change in 2021 and love it. Wish I lived in a legal state and I would do away with the tent and use the whole bldg for the grows.

 

[Fenderbender]

The leaves are praying to the closest light. When you side light they prey to the sides too. Rather than just the tops, you get a 180 deg prayer circle.

Well but we're talking supplemental lighting not main lighting no? so I feel they'd still prefer the stronger source.
I guess once there's buds the buds have leaves points sticking out all around. So you're shining straight on the buds from the sides that's okay.

Did you find studies on cannabis leaves?
I went down this rabbit hole once before reading a lot of studies.
And on other plants there's a whole array of effects when abaxial & adaxial lighting or even alternating them is used.
In certain plants they found higher carbon fixation when both sides were lighted or alternated, in some leaves they found a limit or even a reduction when lighting was used from both sides I think that was spinach.
With sunflowers they found a higher stomatal conductance when both sides were illuminated evenly even higher than at any intensity from just the topside.
But I cannae find it for maryjane.
So it would be nice to know how our plant responds once and for all.

 

[kaw900r]

Not sure if this counts as Under Canopy. Had a CLW LED above and these hanging into the canopy.

Here they are in flower.

And at harvest.

This grow was in a home made 4 X 2.5 X 6.5 cabinet.

The grow was in the garage and it was hot, had air feed from the AC in the house, and it was still very warm. This is what led me to start the adventure and get a grow tent. Went from this in the garage, to a 4 x 4 Gorilla Grow tent in a closet in the house.

And from there to my 15 x 20 man cave/shop, sprayed with insulation, AC installed and ready to rock.
Made this change in 2021 and love it. Wish I lived in a legal state and I would do away with the tent and use the whole bldg for the grows.

I was thinking about hanging lights down and probably would work best