Questionabout flowering PAR

[tmold44]

First run with LEDs and also have a PAR meter. My question is I'm pushing close to 1000 PAR on a lot of my canopy. I'm not running co2. The plants seem very happy and no signs of light/heat stress. So my question is do I reduce the intensity simply because I'm at or near the magic 1000 number most say to stay below without co2 or do I let the plants speak for themselves and guide me?

 

[flylowgethigh]

The flat canopy works in your favor. Is that number in the middle of the light at the top of the leaves? That would give the edges less, maybe 800. You are on the high side, but let the plants decide. If you are gonna push power that hard, why not also get a laser aiming non-contact thermometer, and measure leaf temps too?

 

[tmold44]

The high numbers are at the tallest budsites....mostly on the back side of canopy. I've angled light slightly and done my best with lst to keep as even as possible. The lowest readings are around 700 at the front right area which is the plant that has lagged slightly behind in stretch. The middle is actually good at around 850 only because I've been able to train that area down a little easier. I like the laser temp gun idea! I'm trying to push it a little so I have decent intensity at the lower busites that require a little deeper penetration.

 

[Mattbho]

If u have the experience always go by the plants

Your plants are telling me too much heat or not enough humidity . Or combination of both. I only mention this because imo it will only get worse the closer the growth gets to the light

 

[tmold44]

I dont have a specific temp at the actual leaves which I need to get. The room temp is 78 with 60% humidity. Ph has been running slightly high at 6.4 and tds is around 1100ppm running full remo nutrients bloom recipe. Using RO water and also using hydroguard and slf.

 

[Creeperpark]

More light equals more buds. When your plants start flowering you can add more wattage. Low lighting will grow a lot of stem weight whereas more light will make less stem and more bud weight. Your setup is looking good.

 

[Creeperpark]

Just talking about my stupidity I have been running a digital 400 watt ballast only 75 % not knowing it, thinking it was full blast. The last time I used it I didn't know. Damn those last plants seem smaller for some reason and now I know why. I fired it back up to the full blast 100%.

 

[Corpselover Fat]

There are no magic numbers. Some plants can take more light than others.

 

[tmold44]

I took your advice and got a laser temp gun today. I was impressed that I've been able to dissipate heat as well as the results showed. I am between 750 and 900 on PAR accross canopy and budsite temps are allbetween 75-77 degrees.

 

[tmold44]

The flat canopy works in your favor. Is that number in the middle of the light at the top of the leaves? That would give the edges less, maybe 800. You are on the high side, but let the plants decide. If you are gonna push power that hard, why not also get a laser aiming non-contact thermometer, and measure leaf temps too?

I took your advice and received a laser temp gun today. I was surprised how well I've been able to dissipate heat from this light. I'm now averaging 750-950 PAR accross canopy with a budsite average temp of 75-77 degrees. Humidity holding at 60%. Ph 6.1 to 6.2 with tds at 1200ppm. Today is day 13 of flower and pistils are now showing at all budsites.

 

[snakedope]

Give as much light as you can without burning them, there is no such thing as light stress, light stress = heat stress.
You can blast well over 2000 ppfd, no problem if u manage the heat well.

 

[delta9nxs]

@tmold44

howdy, first off your plants look fine! some strains just grow with a little upturned leaf edge. c-99 is famous for it as well as variegated leaves.

the leaf posture shown in the first photo is perfectly normal for a leaf with high turgor growing properly. they address the light as they should.

for about the last year i have been growing with extremely powerful homemade led fixtures.

my big light can produce 1500 umols of flow at 30" for instance.

i too, have a par meter and an infrared thermometer.

like everybody else, i'm trying to understand led lighting.

the only reason everyone is using 1000 umols of flow is that they are lighting for the entire 12 hour period.

1000 umols for 12 hours = 43.2 moles of accumulated light per period.

but, 1500 umols for 8 hours is also 43.2 moles.

i have been flowering for 8 hours with a 16-hour dark period.

so, knowing that the most sunlit places on the planet top out around 72 moles per day, i have really been pushing the light.

instead of applying 1500 umols statically i will set the light to produce 1500 initially and let the plant grow into the light field.

up to 2000 umols. this is the point dr bruce bugbee, a crop physiologist from the u of utah and others have clearly demonstrated light stress begins occurring.

i have, personally, lately, let a plant grow past that point just to see what happens.
for about the first 3 days nothing showed but then a general bronzing of the fan leaf began occurring.

leaves drooped as it avoids light. the bronzed leaves were shiny and metallic looking.

so, yes indeed, you can give the plants too much light and light stress is very real.

on the subject of co2, i'm not running any. i am applying a minimum of 1500 umols during the 8 hour light period. so you do not actually have to use co2 if you are not going below ambient levels which are typically around 400 ppm in most urban areas.

this is because co2 is consumed by the plant on a per-unit basis. you supplement if you are running a sealed room or are in a situation where you have so many plants in a space that they are consuming it faster than it can be naturally replenished.


the formula for computing moles per day is;

3600 (numbers of sec per hr) x photoperiod in hours x intensity in umols divided by 1,000,000.

also, whatever you do, please don't listen to a single word snakedope has to say about growing as he is clueless.

later d9

 

[tmold44]

Thanks so much for the detailed info.
I've continued to push on with this grow and now amapproaching week 5 of flower. Makes me think I potentially could have brought light a bit closer to the canopy but im definitely not unhappy with the progress. Here are a couple updated pics...one of the canopy and one of budsite. Sorry these were taken under the led light so color is distorted.

 

[delta9nxs]

very nice trich development! what is that? here's my latest, rare lemonhead. grown with 8 hour photoperiod at 1500 umols plus

 

[tmold44]

Very nice!!! I am still at a 12/12. You think it would be beneficial to reduce photo period and increase intensity the last few weeks? or should I expirement next run? It's cherry lime runtz.

 

[flylowgethigh]

Delta9, I get readings of 1700 outside on bad days, but the limit in the tent is temperature. That keeps me limited in power that can applied. For this reason I have held on to the hours of daylight, while still kicking off the photo-period reaction of flowering.

Dropping the lung room temp with a banger and forcing in filtered air from there helps turn up the lights. In my 4x4 it is hard to get the lights over 500 watts and keep the temps in check. I am running 900+ umoles at the tops with about 14” gap, flower sites 77*f, and the light is only 530 watts.

I increase the umoles they get as they grow and mature, giving the roots a chance to develop. When they are late in flower I need to turn down the power and heat, so maybe the smells stick around.

 

[delta9nxs]

Very nice!!! I am still at a 12/12. You think it would be beneficial to reduce photo period and increase intensity the last few weeks? or should I expirement next run? It's cherry lime runtz.

you're doing so well maybe you should just continue with your present routine on this one.

whether you try the 8 on, 16 off routine probably revolves around what you're using for light.

is your lighting capable of producing 1500 umols at a distance where it is not projecting a lot of heat downward?

one of mine is capable of 1512 watts which produces 1500 umols at 30" so i get very little heat at the tops. i have a fan pulling air up through the fixture.

with an air temp of 80f i will have about 77-78f at the tops.

 

[delta9nxs]

Delta9, I get readings of 1700 outside on bad days, but the limit in the tent is temperature. That keeps me limited in power that can applied. For this reason I have held on to the hours of daylight, while still kicking off the photo-period reaction of flowering.

Dropping the lung room temp with a banger and forcing in filtered air from there helps turn up the lights. In my 4x4 it is hard to get the lights over 500 watts and keep the temps in check. I am running 900+ umoles at the tops with about 14” gap, flower sites 77*f, and the light is only 530 watts.

I increase the umoles they get as they grow and mature, giving the roots a chance to develop. When they are late in flower I need to turn down the power and heat, so maybe the smells stick around.

yep, we are all dealing with unique situations while growing. each grower has to make compromises based on real circumstances. terpene preservation ain't easy. the public is becoming increasingly sophisticated and critical. and fickle too! no such thing as brand loyalty.

 

[delta9nxs]

oh yeah, tmold44, what kind of cat do you have?

 

[tmold44]

I am about 18" above to get 1000+ so actually getting closer probably would be pushing temps. I have about same room temp and flower top temps as you by using fans as well. 82 room and 79 flower top temp tonight at feeding time. I have the mars hydro fc8000 and am running it at 100% 12 on 12 off. It's a 4x4 fixture and fits perfectly over top my little bigger than 4x4 trellised off area in a grow room not tent. Unfortunately room obviously isn't air tight as you got me "delta9"....wifes cats damn hair somehow makes it in there no matter how hard I try....lol