Temps and stretching question?


New Member
Hello I have some young WW seedlings (3 nodes) I'm in the UK but it's hot here and the temps in my veg room are around 28-30 for big amounts of time, i'm on 18/6 and the 6 hours off are 1PM to 7PM to help in the hottest part of the day we normally start with a 125w CFL but that was making the temps hotter than using a air cooled 250w MH at a distance.

Basically I have read that if the temps regularly go above 29c (84f) it can make the plants stretch between the nodes which I do not want as the growth in our aqua farm set up is so ferocious that its hard to keep
full indica's being topped once and heavirly LST'd
height down even with a fair amount of head room in our flowering room.

Sorry for the long post but how severe do you think these high temps will be in regards to stretching? also this is England so I doubt it will be hot for a long time but I can already notice they seem to be growing a bit slower than when I had it ad perfect temps.
Re: Temps and stretching question??

When I first started it was summer and I'm from south America so temps in summer go up as high as 37°C (98°F), fortunately the temps inside my room weren't as high but still they could go up to 33°C (91°F) during lights on. That was for the flower side, the veg side was a little cooler but still high 20's sometimes low 30's.

I have not read anywhere that temps affect height, what does make the plants stretch is putting the light too far away. I keep my veg plants, which grow under T5s and CFLs, at about 4" or less from the tops, they don't generate enough heat to make any damage and this keeps the plant from stretching and instead they grow very bushy with a minimal internodal distance and a shit load of bud sites. I'll try to post a pic tomorrow of my 2 months old (from seed) Aurora Indica and Blue Mystic which are ready for flower. Today they measured about 40cm (about 16") which may not sound like a lot but she's going to double or triple in size when in flower, so far it has about 16-19 sets of branches so she's gonna give one hell of a yield by late September-early October.

So in short, I don't know if temps have to do with the stretch rate, but I don't think it does based on my experience (growing with intense heat yet not experience any stretching).

Hope it helps.
Re: Temps and stretching question??

trichomes, yeah i have a 2 Antec PC fans for each plant running off a 19v laptop charger! they are in fairly heavy wind, I do like to sturdy/stockiness as soon as possible with seedlings.

Rodrigo, Thanks for the advice/reassurance, yeah i'm hoping the temps won't be to detrimental i'm going to stat LST'n a bit earlier then I normally do to further help them be stocky with lots of bud sites. I leave the cupboard doors open as much as i can now as it's giving slightly kinder temps 28-29c (84-85f) .

Here are some pics like i said this a 250w MH so no stretching will happen due to lack of light.

Re: Temps and stretching question??

Nice clean setup :bravo:
However at the distance you have the light now I believe you will experience stretching. One of the reasons I believe that CFLs and T5s are perfect for vegging is because they allow me to put the lights extremely close without causing damage, thus minimizing internodal space and stretching and increasing bushiness and bud sites. But I've never worked with MH so maybe at the distance you have it now it's the equivalent of keeping the CFLs at 4" in the amount of light they receive. However to minimze stretching see how close you can put the light without causing too much heat near the tops.

How far up can you put the light? meaning how much available space you get with that big blower and light fixture.
Re: Temps and stretching question??

Yeah i like a tidy set up makes maintenance less of a pain!

Trust me that air cooled 250MH will definitely equal a CFL at that distance CFL's are good but really lack the penetration that you get from a MH like i said at the beginning of this post is that we normally use CFL's at this stage but it's even hotter than the air cooled MH which is only a problem now as our outside temps are quite high, I know seedlings like MH if the propper distance is met on one of the 1st few pages of my 1st grow journal you can see I used a 600w MH on 10 seedlings all in 11 litre pots clustered together it was just over a meter away from the plants.
Re: Temps and stretching question??

Yeah I know that MH is better than CFL when it comes to the 'quality' of the light, but my point was that if you have a small space and are worried about stretching then you might want to think about optimizing the available vertical space so the plant can grow as much as it can without coming too close to the light. That happened to me the first time since I didn't really expect the plant to grow that much (and I started with the light too far away so it stretched way more than desired), it came too close to the light and my light system was inadequate at the time so I had it as high as I could but still the tops were just a few inches from the light.

Anyway you know your measures (which I can't tell completely from the pic) so good luck and I hope it turns out good for you.
Re: Temps and stretching question??

There is no carbon filter as this is my veg room when the others in the flowering room get the chop they move into there so not much smell to hide also there is no muffler as it isn't that noisy from outside. Check out my perpetual grow in my sig if you would like to see the flowering room you won't see a carbon filter or fan in there as we cut a hole in the ceiling and put a piece of solid 150mm tubing through so the fan and filter are in the loft/attic then we connected the ducting to the solid pipe in the flowering room to the cool tubes, we also have a intake fan drawing in fresh air from outside, both fans are wired in to a primair controller for stable temp control.
hi, your plants look nice and healthy, im also in the UK and i stared growing with cfls due to the very tight node spacing and due to the lack of funds, i flipped to hid lighting and found the plants stretch more due to the distance of light,

now plants will stretch due to high temps as their trying to reach cooler air which is usually higher up, so they do stretch when temps are up and they do stretch when the light is to far away, but as long as you got a couple of fans running you wont have any problems, im also struggling with high temps and my grow space is pretty much the same as yours and im running a dual spec 400 watt hps, my grow door is open during the lights on period and i have small 12v fans running constant, but the plants are doing ok and the temps are not affecting them to much, id say the biggest cause of stretch is the distance from the light,

so even though i use a dual spec hps i still start my seedlings and clones under cfls, they keep the nodes very tight so the first 2 weeks the plants are under cfls as the cfls can be within an inch or 2 of the plants so node spacing is very tight, then i put them under the dual spec hps,

usually i dont have a problem with stretch as i can keep the hps pretty damn close, a regular hps bulb will cause some stretch as it dont contain the blue light needed for veg like the mh does and like the 6400kelvin cfls, but the dual spectrum sunmaster hps bulb contains both the blue and red light so its good for both stages of growth, but due to this heat wave i have had to raise the hps as its not a cooled hood type so my plants did suffer from some stretching, not a huge problem but it means ive got bigger plants than i normally have,

but i dont think its a huge problem, your plants look great so im sure you will be ok,

the only time high temps are a huge problem is in flower, if the temps are to high in flower then the buds stretch to reach cool air, so you can end up with very airy buds.
Hello donpaul.p I LST'd shortly after the pics above were taken they aren't stretching at all and the nodes are very tight I have about 6-7 nodes all less than 1 inch apart. I will put some pictures up later. They are definitely growing slower than when the outside temps were kinder. The distance of my light is fine I have used a 250w MH at this stage before and know what distance is good.

Where did you read that plants stretch for cooler air? I thought hot air riser?
plants stretch to reach cooler air, indoors heat rises and its hotter higher up, outdoors the taller a plant is the more likely it is to get a good breeze, so a taller plant gets the cooler air if it was in a field full of plants,

plus i know in flower when my temps get high the buds stretch and its not far off how foxtailing looks, but it happes earlier in flower if the temps are to high,

so heat does rise and indoors this means as the plant stretches it gets into warmer air so keeps stretching, outdoors it stretches so it can be taller than the plants around it and this then allows it to get to the cooler air where the breeze is likely to be,

plants also stretch under 12-12 as you know, they do this because their looking for the light, if a plant is in the shade then you will notice it stretches like crazy and node spacing can be anything upto 1ft between nodes if its in the shade, so when the lights go off the plant strethches a it thinks its in the shade, plants under 24-0 dont stretch as much but i find plants dont grow as quick under 24-0, i have tried all lighting schedules and found on balance that between 17-7 and 20-4 is about where these plants should be, this time round i went 17-7 and my plants are in flower schedule now a lot earlier and are much bigger than the same plants grown under 20-4 or 24-0, i could of done with putting my plants in flower a lot sooner but i gave them same age in days and their much bigger this time round across all strains, so they benefit from a good dark period as at night they grow roots, repair damage and they also grow to find the light,

plants can take time to recover from lst as well, usually its a quick recovery unless you have pulled branches down lower than they was then this takes the plant time to recover, if you pull down the top branch lower than the branches below it then the branches that was below the top branch then become the top of the plant so they then get the most growth,

to make plants more bushy i have used a form of defol method, if you remove the top set of fan leaves on the main stem then this stops upwards growth on the main stem and allows the lower branches to keep growing and catch up, then once the next set of fan leaves have grown at the top of the plant if you remove this set then all the branches catch up and you end up with a plant with many tops but without actually topping it.

so your right indoors heat rises so its hotter the higher the plant is, but outdoors the plants stretch to reach cooler air where their likely to get more of a breeze,
Cheers for the info donpaul.p, I didn't really think about them stretching for chance of a cool breeze but I guess that makes sense, bit of a catch 22 indoors because like you said it would stretch for cooler air but in the unnatural indoor conditions it would stretch for that breeze and reach even higher temps.

I'm in the UK so I don't really have to worry too much about temps all thou the high outdoor temps kicked in here when I had to start new seedlings which I didn't like as I have a heated propagator on a thermostat and when the weather here is cooler I can use the propagator and maintain a stable 23c (73f) lights on and off and as you will now seedlings love stability.

I have LST'd every plant I have grown and got a good feel for it and how to shape the plant the way I want it, they have been untied now for 2 days to get over the minor shock of the LST then in the short future I will either top or FIM them.
not a problem, the weather has been a bit hot here the last few weeks but seems to of cooled down a bit now, so ive managed to lower my light again back to where i like it but if the temps go back up again then so will the light,

i would of planted outdoors but last year my plants got water logged and died, this year they would of done really well but you just got predict the great outdoors in the UK, :)
no not that i know of, is it something you have to subscribe to, at least its not something ive seen anywhere, im in the midlands or their abouts but lived down south on the good old isle of wight for a good few years, crazy place down their,
Nah you don't have to subscribe to it I can pick it up from one of 2 grow shops near me, they are free as well, they aren't really suppose to have them there as people can say they are promoting the idea of growing cannabis, if you have a local grow shop you go to then it's worth a ask as they often keep them tucked away somewhere and give them out when requested.

You can read it online here The original cannabis newspaper for growers and smokers, since 1985.
ok cool, thanks for the link, ill have a read, ill see if the hydro shop sells it near me but its only just opened up so not sure if its totally safe to use just yet, you know how the police like to open second hand shops and catch burglars well it could be the same sort of deal as their are a few growers around here so would be an easy option for police to find out who is doing what,

i might send a friend in to ask, until i know its safe to use i wont be going in their,

thanks for the links,
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