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Heat stress?


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Hey Ozstoners,


Hope everyone is well. It has been a long time since I have posted and in the interim I have switched from indoor to outdoor growing. Which is more challenging than i would have thought, it is a lot harder to micromange the plant environment outdoors.


It has been between 40 - 45 degrees celsius some days over the last few weeks, and unfortunately my plants were out in it one of those days. Today I moved them inside, and myself the dog and my plants spent the day in the laundry, which being under the house, is a few degrees cooler (maybe only 40C instead of 45C).  So they only spent the one day out in really brutal heat - I am surprised they survived that to be honest.


I think my problem is entirely heat stress but I would like a 2nd opinion (3rd, 4th and 5th opinions welcomed too) in case there's more to it than that.


I have produced some very nice plants indoors in the past, (I think i maintained a grow journal here of one grow, same strain as this, the parents in fact) but that was many years ago and my green thumb is a little rusty now it would seem.


Indoor/Outdoor: Outdoor
Growing Medium: Soil 70% perlite 30%
Growing Style: Haven't decided yet, I think probably au naturel is best for outdoors, although I am considering scrog style wiring or tying them down, just for the fun of it.
Watering/Feeding Frequency: 2 times a week (whenever soil is dry) + (1/2 strength foliar feed a few days ago)
Nutrient Strength (PPM/EC): 3/4 strength Charlie carp atm

PH Levels: I should check, all my grow stuff is stored somewhere in the garage, I need to find the tester kit.
Temperature/Humidity Levels: Ambient temps are currently 30 - 40C in the shade here atm, when it's above 35 degrees I'm bringing them indoors out of the sun, but it's still VERY hot even inside, stretchy stems seem less greivous than sun stroke though.
Lighting Type (CFL/HPS/MH etc.): Sun
Growth Stage:  A few weeks old (I know, I planted them a bit late, but hoping for a little something to smoke come harvest time, the genetics are VERY nice).
Cannabis Strain:  It's a sat/indica hybrid my friend grew originally which I was lucky enough to find a few seeds in. These I grew and produced the seeds I am using now. These seeds are over 6 years old now, I kept them in the freezer, but electricity has failed on occasion, so seed age may affect the plants' vigour.


The obvious candidate for the damage I am seeing is ofc heat stress. But there are a few other little variables that confuzzle the issue, so I was hoping to get some knowledgeable opinions, so that if there are other problems on top of the heat stress, I can address them too.


Some other factors apart from heat that may or may not be relevant:


The soil I am using is a cheapo coles type. Pretty crap stuff. Back in my serious growing days I would never have considered using it, but I  popped these beans on a whim and this was the soil I had to hand at the time, pH could definitely be an issue with such cheap potting mix. When I repot I will use a better soil.


As mentioned the beans are OLD - 6 or more years old (but such a sweet smoke and was really easy to grow under lights last time around), and I got a good germination rate (about 80% popped, paper towel method)). Although I got a good germination rate, I got a very high mortality rate (over 50%) in the first few days after planting, which again I put down to heat stress.


As I remember it, this strain is a total nute pig, you can see they're looking a little pale now, I gave a weak foliar feed a few days ago hoping to darken them up a bit, wondering if this is an issue, perhaps the 1/2 - 1/3 strength Charlie Carp I used was too strong and compounded my issues?


I have no idea what pH my soil or water is, these are variables I really need to check. It's possible I am getting some nute lock out from either of those.


The plants get full sun from 9am - 4pm, although since it's been so hot I have been bringing them into the laundry to cool down which accounts for the stretching you see. I will bury them a little deeper to account for the strectching when I repot so the stems have a firmer footing.


What I am seeing is lighter/whitish spots between the veins of the leaves, which if it were indoors I would say is possibly light bleaching, but outdoor I have no idea. The margins are a bit browned, leaf tips are very browned (no way some of these will recover, you can see I have cut some browned leaf tips off entirely. There are few brown spots scattered on the damaged leaves too. Older leaves are yellowing, dying and falling off (nute lock out?). A bit of clawing both upwards and downwards. Finally, new growth looks OK, but paler than I would like.


They're also a bit wilty from todays heat and an extra watering I gave them to try to cool them off a bit.


Any and all advice welcomed!






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I found an old thread of mine here featuring the same genetics - the parents of these beans.




You can see what these plants can look like in this thread, bud porn is post 12 XD

As you can see from earlier pics in that thread, I always had trouble keeping up with their nute requirements, they're big feeders.


Was such a nice smoke, hoping to achieve the same with this lot, fingers crossed.

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You want to upsize pots to at leat 50L and like you said that soil your using is pretty average so upgrade that. See if you can get creative with your mix. Info on soil is everywhere.


The only killer heat wise outdoors will be your soil temps so mulch well and add insulation to the sides of your pots or bury them into the ground to keep soil stable and cool.


Thats your basics good luck and thanks for the pics



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Yeah good idea RiverRat,


Upsizing now will give them a bit more of a buffer against the temps. I've got some styrofoam too, I might tape that round the pots for insulation too. It was nearly 46 C today. Hope we don't get too many more days like that. I bought them inside about 11 am, and as you say the soil temps are the killer and that soil was way too hot even that early in the day.


The soil composition is terrible, avoid Coles brand potting mix like the plague. I had intended to save the beans for an indoor grow this winter, so I am very disorganised, and that was the only soil I had to hand.


You're welcome on the pics XD Hopefully I'll be able to post some really nice crystally bud pix some months hence.


Took me ages to remember how to strip all the exif data and load up a proxy, it's been so long since I've posted on a grow site, at least I can remember the fundamentals of security, even if I cant for the life of me remember how to actually grow.


I think I've been bitten by the growing bug again. I've spent the last couple of years not growing, smoking whatever I could get my hands on, pretty hit and miss quality wise, stuff you can buy is never anywhere near as nice as home grown.


I guess I need to pull my finger out, stop being so half arsed and get organised if I want some nice buds.


Soil wise I will head down to bunnings tommorrow, I have the perlite and some blood and bone, so I guess I just need some peat moss and any good quality organic soil should fit the bill, I've had good success in the past with soils marketed toward tomato growing. Really need to unearth that pH tester kit too.


I need to get some proper hydro nutes to foliar feed too.


You think the problem is just heat stress or do I have other issues going on there too mayhap? They look so pale and wan and underfed right now.


Thanks for the advice, much appreciated, good call, upsizing will be a good start for beating the heat.

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W00t, found all my old growing stuffs.


Wow, it's like Xmas day all over again in my garage, so many exciting toys, apparently I have A LOT of growing equipment still, most of my stuff is geared toward indoor growing - lights, fans etc (definitely an indoors grow on the agenda once the weather cools down enough to run the lights), but a lot of stuff that's useful for outdoors too. 


I probably don't have to buy much stuff now, it's all here. Dolomite, rooting hormone, Veg growth Hydro nutes for foliar feeds (Nature's Own Guano Superbloom & Hydro Organic Bio Juice), all manner of other organic nutrients for soil. A bunch of organic pesticides including neem (yay), pyrethrum, as well a few more hardcore chemical ones there's no way I'd want to use once flowering starts. Hopefull I won't need these, I had a small mite problem at one point, but I think I bleached it out of existence. Even have coco coir, nice.


Think I just about have everything I need, bar a bag of good soil and some peat moss, which I will get today.


As luck would have it today is quite cool, so the plants are out enjoying the sun and the wiltyness of yesterdays heat and extra watering is gone, the damage is done on the leaves, but new growth looks fine and perky, if a little pale, a few night time foliar feeds should help there and reading my old thread it looks like this strain did best on 1 and a half times the recommended nute doses.


The pH test kit says my "soil" (if you could call it that, my native Aust plants like coles brand soil, but then again native aussie plants grow in just about anything. Non natives like MJ are a little more finicky) pH is 5.5 - 6, a little lower than ideal. Will fix that when I repot today.


So glad to be growing again, it's been years - I think my last post here was in 2008, that's how long it's been since I've grown my own. My old internets grow forum is alas changed beyond recognition, not even the same URL anymore, all my old internets grow buddies have gone from there, I wonder where? Hopefully they're all well anyway. So I think I will relocate here to Oz Stoners. Although I haven't posted here much befrore, I always had the highest respect for the place and got a lot of good info from lurking here in the past - so here I am, hopefully I will be able to post some pix of lovely healthy plants shortly. :)


Hope everyone has an awesome weekend.

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Hmm sorry for the turbo posting, but it's been so long since I've grown I have forgotten everything I knew so I am hoping if I post my thoughts and plans here that if I am going terribly wrong someoone will point it out & put me back on track.


Plants are looking better today, weather is cooler so I think I will give them the entire day to keep recovering from yesterdays heat and repot tonight.


In terms of upping pH any advice on whether I should use Ca/Mg or dolomite? I think I used to know this stuff, but my brain is leaky and it's knowledge I don't seemed to have retained. XD


Still looking for opinions on whether the damage I am seeing is merely heat stress or perhaps there is something else wrong too?

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Repotted into new medium now.


Medium is 1/3 perlite, the other 2/3rds is soil, compost and peat moss. 3 parts soil to 1 part peat moss to 1 part compost. Also a few handfuls of blood and bone and enough lime to bring the pH up to 7.


It's fairly cool right now so I havent taped the styrofoam insulation around the pot, but will do if temps exceed 30 at any point.


I was a bit reluctant to give her more water, but I can't really repot without it, I left all the new soil dry though, so hopefully she's OK with it. She'll appreciate the nutes even if she doesn't love the water. I'll give a foliar feed when she looks like she's really recovering, all things going well, tomorrow or the next day.


Fingers crossed.

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