Too much light intensity?

So, this is my second run with this strain. First one was under cobs, and I noticed the leaf canoeing, and fading, when I turned up the light. Now i have a bar light, and imo, better spread. I turned the dimmer up from 40% to 50% last night, and now I get canoeing again. My meter reads in between 500-600 ppfd. My temps are ~88° - 89°f, humidity 55 - 57%. What says y'all?

























canoeing is usually a transpiration issue. light intensity can be the source of this even when temps are technically within tolerance but for indoor grows you're getting up there without CO2 supplementation at 89°F. You can try an aloe foliar but you might want to also check air circulation at the leaves. You can check soil moisture too if overwatering is a possibility but that doesn't sound like it here. Whats the feeding look like for these?

At those temps transpiration is pretty elevated at that RH so either lower the temp or increase RH to slow transpiration. The top leaves are sweating faster due to radiant heat from the lights. Do you have a laser thermometer to check leaf temps?

You'll probably start getting signs of nute burn, (toxic salts buildup), in the most affected leaves if this continues. I have chronic low RH so have had to deal with it for 20 years.

Dr.J20 said:

canoeing is usually a transpiration issue. light intensity can be the source of this even when temps are technically within tolerance but for indoor grows you're getting up there without CO2 supplementation at 89°F. You can try an aloe foliar but you might want to also check air circulation at the leaves. You can check soil moisture too if overwatering is a possibility but that doesn't sound like it here. Whats the feeding look like for these?

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coco. 5 gallon container. Water in ~1 gallon, twice a day. H3ad formula. 1.8ec, 6.0 pH.
I'm thinking vpd maybe now? Just seems funny it started after turning up the light, just like last time.

Hollatchaboy said:

I do have a ir thermometer. Not exactly sure where on the canopy to take a measurement. In the center?

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Check multiple spots on the top leaves especially where they seem most affected.With your room temp close to 90 they should show a little higher than that but because water is being evaporated from them that has a cooling effect so they could be a couple degrees cooler from that.

Usually the first sign of heat stress is the jagged edges of the leaves lifting up giving them a 'toothy' look. As it gets worse they 'canoe' or 'taco' depending on whether you're in the US or Canukistan.

Because they are drawing up more water to cool themselves they also draw up more nutrient salts that they can't use up so it gets stored in the leaves causing the dreaded toxic salts buildup that eventually causes leaves to burn all over rather than just along the edges. Always showed up for me in older fan leaves first around the middle of flower but by chopping time even the tiny bud leaves would be affected. With heat stress like you are having the upper leaves are showing signs first and the rest of the plant further from the light may have no problems at all. Your RH would be great if the temps were lower. Here it's low most of the year and I've learned to deal with it by using lower ppm in hydro and not letting my semi-organic mixes be too hot. Like now the rh in the house is only 20% and 29% in my upstairs grow tent. Even running my humidifier only gets it up 10% and uses a gallon of RO water a day which adds about $5 a week to my growing costs. Power costs the most tho at over 30¢/kwh.

Are you in the southern hemisphere to have such high grow temps?

Hollatchaboy said:

Just seems funny it started after turning up the light, just like last time.

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Most likely you're crossing the border line when you up the light intensity. The straw that breaks the camel's back.

Forgot to mention that if my plants are getting too close to my HID light I hang it off my Light Rail and keep the light moving so it's not just baking some of the tops and I've run a 1000W HPS just a foot from the canopy like that no problems.

I'm sorry....I meant 78° - 79°. Just under 80.

Hollatchaboy said:

I'm sorry....I meant 78° - 79°. Just under 80.

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Room temp shouldn't be a problem then. I like my temp to be 75 - 80 max without CO2 but 10° higher with CO2.

Sounds more like a light issue than temp. Maybe too much IR from your light. ¯\_(ツ)_/¯

I liked your idea about vpd. I raised my humidity to closer to 70%. I'll see if there's a change in about an hour at lights on.

Also my light has ir diodes, but I don't feel ir diodes put off a lot of ir, but I only have it at 50% intensity, so I dunno either. Lol

So, no change with higher humidity. Actually she seems like she doesn't like it that high. This strain has been a PITA. I think I'm gonna chop it and start a different strain.

I turned the light back down to 40%. I'll see what that does.

Hollatchaboy said:

I liked your idea about vpd. I raised my humidity to closer to 70%. I'll see if there's a change in about an hour at lights on.

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You're not going to see an immediate change raising your VPN. If the RH is higher then the plant's transpiration will slow and after a few days the leaves should relax and be less taco. Possibly not if it's a heat issue caused by the lighting and that doesn't change. It can take a while after making any change for the plants to show it. I would be watching new top growth carefully to see how they react to the change.

Hollatchaboy said:

Also my light has ir diodes, but I don't feel ir diodes put off a lot of ir, but I only have it at 50% intensity, so I dunno either. Lol

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I don't use LEDs other than my cheap 5 bulb COB light and a DIY fixture with 11 9W LED bulbs with the domes popped off for use in my 2x4' tent. I've used HIDs for 40 years and start my seedlings/clones under fluoros like my old DIY 8 tube T-12 fixture I built 22 years ago and used for my first DWC grow. Wife uses it now for starting her tomatoes and peppers that she's getting ready to go next month. Many seed packs showing up in the mail lately. I want to start some opium poppies this year to plant out in the pot patch I can no longer use because of hemp fields down the road now. Finally start to grow autos outside and get shut down in my 3rd year.

Do the ir diodes have their own switch so you could shut them off? Some do I believe but then I don't know lots about LEDs.

Hollatchaboy said:

So, no change with higher humidity. Actually she seems like she doesn't like it that high. This strain has been a PITA. I think I'm gonna chop it and start a different strain.

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You could expect the plants to be droopy with the higher RH until they become acclimated to it which can take a bit and the already affected leaves may not fully heal so new growth tells the tale. What strain is this? I think I would soldier on and try to fix this issue or you may find the same problem with a different strain and have lost time getting a crop. I've grown some crappy looking plants over the years that have fire in their buds when finally cropped. My focus now is more on the medicinal properties of a strain whether it has 5% or 30. Lots of resin is also a quality I want if it's helping with my and others issues as I make almost everything into oils.

Hollatchaboy said:

I turned the light back down to 40%. I'll see what that does.

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Probably won't hurt and may help so see how they are in a few days.