Canoeing leaves = Light/ heat stress?


Plant is almost 14 weeks old. Thing is i’ve never been able to crank up the light strength even when the plant was vegging, come flowering it shows the same stress symptoms when i try to up the dimmer.

The above is only a reference for temperature purposes. Highs of 27 D Celsius with lows of 21 D Celsius through out the day when it was vegging. Increasing the light intensity caused the above symptoms.

Come flowering, i am trying to up the light intensity and again the symptoms re-appeared, considering it was/ is heat stress, why did it happen when the temperature was most favorable while it was vegging.

Now the i have highs of 33 D Celsius and lows of 30 D Celsius (Hot as hell), but the plant didn’t show any signs of heat stress till i upped the strength.

Changes i’ve made to reduce transpiration rates and prevent the drying out of leaves ( i think my leaves are drying out), moved fan so it doesnt directly blow over the plant, increased feed cycles to 12 from 6 (15 min on and 45mins off, for each hour the light is on).

Current pictures

Yes there are signs of nutrient burn, but that was because i was pushing the plant in vegging phase.

The thing i can’t for the life of me is figure out:

When i research Canoeing of leaves: ( They all point towards increased transpiration and ofc my symptoms have come up only after increasing light strength so that’s something to note )

  1. The temperature is too much, light opens up the stomata causing more transpiration and hence drying canoeing of leaves.
  2. Direct fans blowing on the plant, causing the leaves to dry out faster.

Remedy im trying:

  1. Increased distance between the canopy and light by a foot. (26 inches total)

  2. Placed fan so it doesn’t hit leaves directly.

  3. Increased feed cycles (15 min on, 45min off, im using clay pebbles only the roots are okay) to 12 cycles a day when the light is on.

What is bothering me the most is if it is heat/ light stress, the temps were favorable 2 months ago, still upping the intensity caused canoeing.

When i have to move my light up the DLI figures aren’t favorable, ( right now the most light hitting the top most part of my canopy is 17 ).

Is my harvest doomed to fail?

edit: profanity

I think you are seeing canoeing due to high temps and not light stress. A bit of taco on top leaves won’t cause any issues and is pretty common with some plants. I would try hard to get temps down into a better range.


Turning down the temps isn’t an option just yet.

Don’t mean to condescend but the heat issue just doesn’t sit with me. I was in good temp, ranges 2 months back, increasing the light strength ( Maybe it was too much of an increase 70 to 100 perc ) still caused canoeing.

Maybe i should have raised my light too, idk, that’s the one of the things i wasn’t measuring. I was looking at node spacing when setting light strength. Now i’m regretting it.

If the canoeing doesnt progress? I’m in the green?

Other than the plant looking a bit hungry I’d say it’s doing okay. Again; some canoeing is common, light distance definitely factors in.

Your cycle times could likely be reduced to 8 times/day (I’m currently doing twice a day FYI) which helps oxygenate root zone with ebb and flow. Not knowing the nutrient line I’d still suggest bumping feed numbers up a bit as plant appears hungry.

I’m not good with the foreign temps, but it looks to hot, with to much light to me, but sounds like you already know what you’re doing. I’ve read with led’s, the sweet spot is 80 to 83 degrees to get the optimum photosynthesis.

I’ve cut back on the nutes, using early flowering ratios. PPM is currently at 700, just a touch of calcium nitrate.

Magnesium sulfate
Calcium Nitrate
And Masterblend 4-18-38 base
I love to be able to manipulate these throughout the grow. For instance I’ll go
Early veg per 5 gallons
3g magnesium sulfate
6g Calcium Nitrate
6g Masterblend base
12 ml silica
12 ml hydroguard
Late veg per 5 gallons
5g magnesium sulfate
10g Calcium Nitrate
10g Masterblend base
12 ml silica
12ml hydroguard
For early flowering (week 3) per 5 gallons
8g magnesium sulfate
2g calcium nitrate
8g Masterblend base
1/2 dose Flower Fuel
Mid flowering weeks 4-6 per 5 gallons
10g magnesium sulfate
1g Calcium Nitrate
10g Masterblend base
Full Flower Fuel dose
Week before flush
5g magnesium sulfate
5g Masterblend base
1/2 dose Flower Fuel
flush for a week or so or until ppms come out under 200

Ill def, reduce to 8 times a day.

How about root zone temps? Good you are using Hydroguard but may be additional O issues with high temps: not to mention things like root rot.

May want to bump the TDS up to 1,000 ppm or so as well as plant looks a bit hungry.

My bad im only using the nutes, no hydroguard or silica. No flower fuel either. I tried to use mycorrhizae but they don’t do well in clay pebbles only.

The nute solution remains at a cool 18 D Celsius, in between the drain cycle (the root zone) i dont know, maybe it goes back to ambient room temp i.e. 30 D Celsius or more.

How-ever im using a hardcore bubbler, on all times, underneath the fabric pot for oxygenation purposes even during flooding.

I’ll cut back on the feed cycles, chop it down to maybe 8 cycles. That would mean 15 mins on and 75 mins off. For 8 cycles till the light is on.

Ill bump the PPM too but cutting back on the nitrogen one can expect a hungry plant ?

That really depends on where in the life cycle of the plant you are. Late flower for example would require little if any N. Leaf production falls off within a few weeks of flower initiation.

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Week two of flowering schedule. Fingers crossed, maybe this will be my first indoor harvest.

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So you crank “the light” to 100% and the temps in your tent went up. You had to raise the light so you wouldn’t burn them. Can you lower the light intensity, and then also lower it closer to the canopy? They will still get their required light, but you won’t be throwing out as much heat.
What type of “light” is it, and how big is your tent? (sorry, I smoke too much weed and can’t keep track of who has what from other threads! Lol!).
And your leaves don’t look that bad, imho, a little light green, probably hungry!

  • KingBrite 240 W Samsung LM301H mix Epistar 660nm Red KingBright Pre-assembled LED Grow Light

Right now im trying the opposite increasing the light intensity with increasing the distance from canopy.

According to flowering chart, i need a DLI of 25, right now im at 17 DLI smack dab in the middle, the corners are receiving only between 7 to 10 DLI.

I feel like i wanna chop those parts… but im just meh, this light problem got me stressed out.

Dont know how to post yet so I’m cutting in… Any ideas what these spots are . First time grower

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Could be water splash marks. What type of medium are you using? Coco, soil, organic…
What type of nutrients?
Any and all info will help for providing you with the correct answer.

Not knowing anything about your grow and seeing the age of your plant, my first guess would be to add cal/mag. But with your answers this quick assessment might change…

And welcome to the community. This truly is the best place to learn how to grow. Tons of knowledgeable people here who want to see you succeed. Don’t hesitate to ask any questions you can think of. I guarantee there is someone here who can answer it.