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Growing Under LEDs at Temps Above 80F

Fixer

Active member
Thanks I appreciate that. The oil filled heater I've got running keeps the room warm enough both lights on and off. I'm having issues once the lights come on. [FONT=Arial, Helvetica, sans-serif]exploziv has the solution. I just need a more accurate thermostat.
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imadoofus

Active member
Veteran
82f?84f is optimal temp for the canopy. My girls under the gavita 1700e did not like being under 82f.
 

ronbo51

Member
Veteran
Propogation heat mats, widely available online and Lowes/ HD, have been the answer to my low temps in a garage cabinet. Warm roots lead to very happy plants. I have also grown larger plants in 10 gallon smart pots with prop mats under the hot water heater overflow catch basins I use to hold a 10 0r 20 gallon fabric pot.

I think underheat is more effective than raising the air temps in cold rooms.
 

indagroove

Active member
Veteran
Propogation heat mats, widely available online and Lowes/ HD, have been the answer to my low temps in a garage cabinet. Warm roots lead to very happy plants. I have also grown larger plants in 10 gallon smart pots with prop mats under the hot water heater overflow catch basins I use to hold a 10 0r 20 gallon fabric pot.

I think underheat is more effective than raising the air temps in cold rooms.

Underheat doesn't open the stomata the way environmental heat does.
 

Koondense

Well-known member
Veteran
Another important thing i noticed over some seasons growing indoors under leds... especially if you follow the vpd charts.

Absolute humidity of the air(outside) is usually high in hot months and low in cold months, so the range of relative humidity stays similar but as we know hot air can hold a lot more humidity compared to cold air.
This can be a problem with winter grows, as the inside temps are kept in the warm range, the air will be relatively drier thanin summer which can lead to issues with plant transpiration in an off the chart vpd but within a good temp range. So maybe keep the temps a little lower than in summer to prevent issues, if they apear.

Good range in my situations were somewhere 28-32°C and 65-75% rel.hum during summer, 24-26°C and 55-60% rel.hum during winter. With more control you can go higher temps and higher rel.hum in winter but at night time humidity will raise too much if not exhausted.
Sadly most of the time my values were off but the girls didn't mind much.



Cheers
 

ronbo51

Member
Veteran
Underheat doesn't open the stomata the way environmental heat does.



That may be so, but raising the temp of all the mass of soil and plants will effectively raise the ambient air temp while also pushing the soil temps higher by a lot.

If all you do is blow heated air it will be immediately extracted by your fans.
 

f-e

Well-known member
Mentor
Veteran
I'm not sure about radiators. My early grows showed plants beside them would be tall and sparse. I saw it enough to stop using them. Instead using fan heaters which are never pointed at the plants.

Recently I have learnt that the hotter a body, the longer the wavelength of the IR emitted. This means a concentrated heat source such as the coil in my fan heat gives off a longer wavelength of IR than a less concentrated heat source such as a radiator.

Or plants are sensitive to IR just outside the visible spectrum. Here, the fan heater produces less radiation than the radiator (per given thermal unit). The radiator could in fact be a great 730nm emitter. A wavelength known to trigger the stretch/shade response which our plants prioritise above flower production.

It's like a little jigsaw puzzle coming together. Where the science and my viewed responses come together as a good fit.

I would be very wary of radiators. Especially if the plants can see them.


Perhaps further study of a black body radiators emitted wavelength vs temperature is needed. It's really not an area of interest for me though. Just something I keep crossing paths with.
 

Koondense

Well-known member
Veteran
I doubt it's about ir wavelength, more about intensity.
What should be heated is the lung room, not so near the tent.



Cheers
 

f-e

Well-known member
Mentor
Veteran
Intensity and wavelength are linked. The fan heater is more intense so is a less effective emitter at the 730nm wavelength we must consider.

If outside the grow space it's not an issue. lower infrared band radiation in the grow space is a lighting topic though.


Edit: Prompted to think about it further, my source may of got it completely backwards but I have to go out...
 

Koondense

Well-known member
Veteran
Here's a good graph showing at which temperatures black bodies radiate in relation to the visible spectrum. The scale is logaritmic:
sun.org/uploads/images/BlackbodySpectrum_2.png

Fan radiators glow in ir and deep red(par) so of course their glow will have an effect on plant growth.


Cheers
 

indagroove

Active member
Veteran
Underheat doesn't open the stomata the way environmental heat does.



That may be so, but raising the temp of all the mass of soil and plants will effectively raise the ambient air temp while also pushing the soil temps higher by a lot.

If all you do is blow heated air it will be immediately extracted by your fans.

I doubt it's about ir wavelength, more about intensity.
What should be heated is the lung room, not so near the tent.



Cheers
Yes exactly, that's what I do, heat the lung room. That way the heat isn't lost by my extraction fans. It's recirculated.
 

Fixer

Active member
So the heat is up around 83F lights on and 77F lights off RH at 60% I'm getting that crazy foxtailing I got when I was growing at around 80F under the HPS. I'm going to run with it. The Master Kush that's exhibiting foxtailing started under HPS and is now under the new 720W LEds. I have three other strains in the same room that are not as far along. I'll see how they develop.
 

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Koondense

Well-known member
Veteran
Lights off temps seem too high, also trykeeping lower temps if you're so far in flower. The higher temps are really most beneficial in the first half of flowering.


Cheers
 

prune

Active member
Veteran
I doubt it's about ir wavelength, more about intensity.
What should be heated is the lung room, not so near the tent.

I posted a bit about this when I was sampling the 1700e.

Infrared light drives the plant. It heats the leaves directly, driving transpiration and growth, while leaving the surrounding air a relatively cooler and cooling temperature.

Heating the air, to drive transpiration, slogs the plant down without an efficient way to regulate transpiration in a positive manner.

IR is such an efficient driver of transpiration and lush growth that I dropped the led's and pay the DE tax, so as to grow the best bud I can...
 

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