What is the absolute minimum temp for vegging?

Hitch

Hitch

Well-Known Member
Lots of info on max temps, but I am struggling to find info on MINIMUM temps.

I'm trying to make a separate room for vegging just one or two plants. I have a 1000w HPS for flowering, but not wanting to spend any more $, I plan on using an existing dual socket T12 Floro for vegging a couple more in a separate room. They are 40W each at 6500K.

As the thread title states, I am wondering what the absolute minimum ambient temp is for vegging. It's a basement room with block walls and a cement floor. I think I can keep the room at around 60 degrees Fahrenheit without heat. Would that be warm enough??

Don't get me wrong, I can put in a 500W room heater and keep it whatever temp I want, but that would defeat the purpose of using the floro's to go cheap.

Opinions?
 
S

SSHZ

Well-Known Member
I THINK THE GENERAL RULE IS: Don't let your night time temps drop more than 15 degrees from the daytime highs. So, if you run at 80 degrees during the day, then no less then 65 degrees at night.... No matter what, I never let it get below low 60's in my room at night- I think below that slows down growth because the root medium cools down and slows water absorption.
 
cheechako

cheechako

Well-Known Member
At temps below 60F, growth pretty much stops. AFAIK, 60 is probably the lowest night temp - you want at least 70 in the day, and perhaps higher for Sativas.

Also, you only have about 5000 lumens with that light, and most of it will be pretty far from the plant. That doesn't seem like much at all, even just to veg. So between the cool temps and the low light, growth could be very, very slow - if there even is growth.
 
P

PurpleBuz

Well-Known Member
suggest you get a 4 bulb t5 with some good PAR bulbs and run the T5 as close as you can the plants. The T5 will provide just enough heat to warm the canopy up to 75-85 to make the 60 degree room tolerable.
 
Hitch

Hitch

Well-Known Member
Thank you guys for the info. I wasn't sure if it would be enough light or not, but was hoping it might grow just one or two.

I think before I bought a new fixture for floros, I would just pop the $200 for a 250/400w MH. I just don't have the money right now.

I DO have a space heater, so I guess I'll try that with a couple B.S. schwagg beans just to see what happens.


Maybe just using my 1000w HPS at 12/12 from start is the way to go. Bottom line is I'm doing autos now and want to switch to standard photosensitive girls, but I want to be able to stagger my start dates. If they're not going to grow in veg under that light, it's my only other current alternative (with a zero cost at least)
 
cheechako

cheechako

Well-Known Member
While florescent lights can work, there's a reason T-12s are on the way out. My 5 week-old auto:

0101_bub.jpg

I have 6 CFLs in the cabinet: 4x23W, 2x26W - three are directly above her. So that is 72W or about 4600 lumens. However, unlike your 5000 lumen 4-foot T12 fixture, all of my light is within inches of the leaves. That's the main goal with florescent light. I am going to add a few more bulbs and transition to bloom soon.

If you were to buy straight tubes (instead of using what is free), the HO are the bulbs to get, and the T5 with a well-designed reflector will provide the most lumens per watt.

Your light might be OK for a row of seedlings or clones. I know you asked about temps - but if you have to buy/upgrade light, that can change the temps you will have to deal with.
 
Hitch

Hitch

Well-Known Member
cheechako said:
However, unlike your 5000 lumen 4-foot T12 fixture, all of my light is within inches of the leaves. That's the main goal with florescent light. I am going to add a few more bulbs and transition to bloom soon.
Click to expand...
Ok, now to what is probably a real stupid question...Can I not move my plants within inches of the light? Or are you talking about the lower branches, etc?

but if you have to buy/upgrade light, that can change the temps you will have to deal with.
Click to expand...
So true. My 1000w HPS with the ballast in a similar room keeps the ambient at 72-73 degrees when the outside temps are below freezing.
 
hotrodharley

hotrodharley

Well-Known Member
Here in AK I have experience with low room temps. They survive quite well down to 50. However, bud development really slows and I know this due to multiple repeated grows of some strains. And when I say it slows it I mean it slows it. One poster tossed out 65 degrees and in my own experience that is about it for your plant thriving and not just surviving.
 
Krondizzel

Krondizzel

New Member
hotrodharley said:
Here in AK I have experience with low room temps. They survive quite well down to 50. However, bud development really slows and I know this due to multiple repeated grows of some strains. And when I say it slows it I mean it slows it. One poster tossed out 65 degrees and in my own experience that is about it for your plant thriving and not just surviving.
Click to expand...
They will handle 50, but they don't like it very much. Seems like they are slow to perk up in the morning. 60-65 is about as low as I would go personally.
 
cheechako

cheechako

Well-Known Member
Hitch said:
Ok, now to what is probably a real stupid question...Can I not move my plants within inches of the light? Or are you talking about the lower branches, etc?
Click to expand...
In my picture, the plant is about 1 foot wide. Let's say that it could get useful light from a foot to the side. That is 3 feet total - you just lost 25% of your light. However, that is a simple, conservative estimate. The numbers are more complex than that since the light degrades over distance.

Without any training, very little of the plant will be within a few inches of most of that 4-foot long fixture. CFLs are coiled up so most of the light can be positioned close to the plant. You still don't get it all because of strike-back and whatnot.

Even with the high-end, high-output T5 fixtures, you are probably better off to use SOG or train (LST/SCROG) plants so that they spread out under the light and take full advantage over the entire length of the bulbs, or mount them along the sides.
 
Hitch

Hitch

Well-Known Member
cheechako said:
In my picture, the plant is about 1 foot wide. Let's say that it could get useful light from a foot to the side. That is 3 feet total - you just lost 25% of your light. However, that is a simple, conservative estimate. The numbers are more complex than that since the light degrades over distance.

Without any training, very little of the plant will be within a few inches of most of that 4-foot long fixture. CFLs are coiled up so most of the light can be positioned close to the plant. You still don't get it all because of strike-back and whatnot.

Even with the high-end, high-output T5 fixtures, you are probably better off to use SOG or train (LST/SCROG) plants so that they spread out under the light and take full advantage over the entire length of the bulbs, or mount them along the sides.
Click to expand...
Thanks for the info m8. I think I will just hold off until I can afford a "proper" 2nd lighting system :)
 
Bakatare666

Bakatare666

Well-Known Member
Hitch said:
Lots of info on max temps, but I am struggling to find info on MINIMUM temps.

I'm trying to make a separate room for vegging just one or two plants. I have a 1000w HPS for flowering, but not wanting to spend any more $, I plan on using an existing dual socket T12 Floro for vegging a couple more in a separate room. They are 40W each at 6500K.

As the thread title states, I am wondering what the absolute minimum ambient temp is for vegging. It's a basement room with block walls and a cement floor. I think I can keep the room at around 60 degrees Fahrenheit without heat. Would that be warm enough??

Don't get me wrong, I can put in a 500W room heater and keep it whatever temp I want, but that would defeat the purpose of using the floro's to go cheap.

Opinions?
Click to expand...
Personally, I think if YOU are comfortable, then your plants are too.
I sometimes let mine get as low as 60, but not for more than a few hours at a time.
If you are doing a closet or cabinet grow, replace 1 CFL with an incandescent bulb for a little heat.
I run my lights at night for that reason, and do the same.
 
P

PurpleBuz

Well-Known Member
Hitch said:
Thank you guys for the info. I wasn't sure if it would be enough light or not, but was hoping it might grow just one or two.

I think before I bought a new fixture for floros, I would just pop the $200 for a 250/400w MH. I just don't have the money right now.

I DO have a space heater, so I guess I'll try that with a couple B.S. schwagg beans just to see what happens.


Maybe just using my 1000w HPS at 12/12 from start is the way to go. Bottom line is I'm doing autos now and want to switch to standard photosensitive girls, but I want to be able to stagger my start dates. If they're not going to grow in veg under that light, it's my only other current alternative (with a zero cost at least)
Click to expand...
You can get a decent 4' 4 bulb t5 for around 100-150, which should be good enough to veg a handfull of plants. Keep the T5s within a few inches of the canopy, and you will get plenty of lumens, and save on electricity.
 
Trousers

Trousers

Well-Known Member
Most weed plants want to be as close to 75 at all times.
Plants that are subject to temps below 70 at all times are subject to stunted and delayed growth. Plants that are subjected to low temps are more likely to produce male flowers.
Powdery mildew likes it best between 60-70.

It is variety dependent of course.

With out recent cold spell I had some powdery mildew after the temps stayed below 70 for more than a week. I had seed heater mats under the plants, but that only helped with the roots. I killed everything and started over.

With my low humidity all I have to do is keep it above 70 to keep any powdery mildew from forming.
A $20 ceramic space heater solved the problem.
 
topfuel29

topfuel29

Well-Known Member
The cooler tempature the more dense the buds will be.
some strains will produce more colorful buds deeper purples, and other colors.
alot of these strains origins are plants that grow on the side of a mountain where at night it gets cooler.
I like to run my flower room @low 50's in the dark cycle and @ low 70's in the light cycle.
keep in mind the plant slows down with cooler temps.
 
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