Got a question I’m a newbie to growing I germinated seeds now in soil sprouts are present. I am currently NOT using grow light yet should I? And I am using a good heat mat under them ? Right or wrong? Thanks all 
If you had a good sunny spot by a window would do the trick
I put my seedlings straight under 1000 mph after first week and they are thriveing
Hello I’m growing in a 4×4 tent with marshydro ts 1000 light I live in a state where humidity stays high I have a dehumidifier and 2 fans and a bowl of rice in my tent my babies are about to be 2 weeks old and they only have the 4 leaves so far. Humidity is at 61 teetering between that and 70 regular temp stays at 70 weekday am I doing wrong? Please help
Marshydro ts1000 is bomb I have one for my 4×4 tent
You could run weaker lights but keepnum.closer to the plant ,weaker lights man ,ud be surprised ,if u have a good.ohone download the lux ammeter app,and that will let u know exzactly.jus how.close.u can git a low powered.led
What temps are you guys actually running?
Have you noticed a point where things start stressing, or can you push it a bit higher if airflow and humidity are dialed in?
I run mine from 80 - 85 F lights on, usually 68 - 75 F lights off.
I had no problem running 85 - 90 but felt that was a bit close to being out of range high. I use 80 - 85 because the plants grow vigorously at that temperature and I have plenty of margin if a sensor fails.
Thanks for the input. My flowering tent is at 23.5C - ±75F. Some of my bud sites are about to touch the light (stalks are too sturdy to bend them down at this stage). I’ve been wary of dialling the light to full intensity because of this, so I’ve just been gradually dialling up to full strength. Would you say it’s safe for me to go full strength? I am running a simple LED that seems to max out at 400 lumens [edit: PPFD] at the ideal range - so as far as I understand that’s still underpowered for flowering?
I initially lost track of my heat sensor and it continuously read out 85F or so, turns out it was resting directly on top of the LED. So in terms of heat I should be fine, but should I still worry about light stress?
I don’t dial my lights down, 100% from seedling to harvest. The seedlings get a lower ppfd as they sit on the floor so are further from the lights. I would say that at 75 F, you are at the bottom of the healthy temperature spectrum for lights on.
To 11 it is! Thank you!
Veg: 78-82f lights on. 68-70f lights off
After week 3 of flower: 75-77f lights on. 65-67f lights off
Cannabis plants typically do best around 80f in the light on period and around 72f lights off. The reasons are, stomata are like our skins pores, the difference is they regulate water movement through the plant through transpiration. When the temperature gets too hot, plants will shut or shrink the stomata to preserve water. Since the water carries the nutrients, this obviously is not ideal. If you dont know what VPD is, this would be a great opportunity to read up on it, so when you look at a VPD chart you know what you are seeing and why it matters. The 72f thing is to reduce large temperature swings which can cause host of other issues, not the least of which is powdery mildew. Now keep in mind that the reason pot grows so well indoors is because we can control VPD very precisely, whereas outdoors you are at the mercy of nature.
There are two types of heat you need to consider, one is ambient room temperature and that really doesn’t fluxuate a whole bunch from bottom of plant to about 3/4 of the height of the plant, and then there is leaf temperature. In flowering we are primarily concerned with leaf temp, because the business end is the tops of the plant now. Too high of a leaf temp will cause burning and damage trichome production. In the future, try to leave at least half the plants height for stretch. You may be able to gently tie/ ben the buds off to the sides to reduce proximity to the light fixture? Just be gentle
This chart has become my ‘square one’ in my line of thinking & order of operations when considering & dialing in temps:
Photosynthetic rate based on Leaf temps:
(Lower line is ambient CO2, upper line is enriched CO2)
I check with a Klein IR-5 & set the emissivity to .98 for green plant matter (important).
Eventually the question becomes ‘How hot is too hot for the buds?’, since they heat-soak & run hotter compared to healthy transpiring leaves.
If youre insane you can actually use this behaviour to determine when to water. Leaf temps will start to climb towards ambient as the plant restricts transpiration. If I remember right leaf temps are typically ~3f under ambient.
@PhotoFinisH Assuming decent airflow, I dont think your buds should ever be at a higher temperature than ambient? Unless theres something Im missing…
My tent has been 61f-65f overnight and ~77-85f during the day for basically the whole grow. I never saw any signs of stress unless the humidity dropped below ~30% at peak temperatures. I keep my 300w light 7-10" above the canopy for the entire flowering stage.
VPD has been ~2-2.3+ during the day and ~1.15 to ~1.3 at night. I should mention my tent is in an office with really bad airflow so its likely that co2 is more concentrated in this room than is normal. I have not measured. I try to run as cool as possible but my 4inch fan cant quite keep up when its hot out.
I notice buds running around ambient or maybe a degree under, but hotter than the leaves when the leaves are transpiring. So I want ambient air temps to be warm enough to get my leaf temps where I want them using the chart above, but without overheating (imho) the buds. Feel free to discuss how hot is too hot for buds, because I don’t really know, but I try to keep them under 83f.
Prayers for your wife and you
Plant looks awesome.