calculating w/sq.ft. or w/plant - could use advice

[Carlos Danger]

Hey ic, I'm trying to figure light usage. Let's say CMH horizontal, 20 plants in 10gal soil each. I'm trying to figure out what wattage people would suggest - I've heard as low as 50w/sq.ft. to as high as 150w/sq.ft. but I don't know enough about light to make an informed suggestion.

 

[Mister_D]

30-75 wpsft is a good range to stay in. 50 wpsft is what myself and others recommend, as experience has taught us the return from using more light doesn't justify the added cost beyond that point. People I know that have seriously tested this found anything above 75 wpsf to cause light bleaching in a majority of strains tested, and anything under 30 wpsf lead to lower yields, noticeably decreased potency, and less resistance to bugs.

 

[Carlos Danger]

Thanks for the input!

 

[Stonefree69]

Once again Mister_D right on the money. Going by watts/plant only confuses things. 50 watts per sq ft for HPS is considered pretty ideal for those big dense nugs. How many plants you want to use is really up to you, the more plants the shorter veg times you'll need for that same space. So IOW 50 watts/sq ft is great for your plant canopy especially in flower, regardless of grow method indoors.

 

[gus738]

how do people calculate the 75watts per sqft ? was there a chart ? i have a 600w bulb with a magnum xxl 6 that i want to hook up on rooted clones that been going over a month

 

[00420]

3x3=9/600=66.66

 

[Stonefree69]

how do people calculate the 75watts per sqft ? was there a chart ? i have a 600w bulb with a magnum xxl 6 that i want to hook up on rooted clones that been going over a month

That 600 watt bulb is going to cover 12 sq ft nominally with 50 watts per sq ft. IDK where you came up with 75 watts/ sq ft, that is overkill for good lighting. 50 watts/ sq ft with HPS bulbs is the general rule for good buds & yield. You start to get diminishing returns on your light wattage when you hit about 65 watts/sq ft and above.

 

[gus738]

3x3=9/600=66.66

so best size to cover is a 3 x3 area correct? 66 watts ?

That 600 watt bulb is going to cover 12 sq ft nominally with 50 watts per sq ft. IDK where you came up with 75 watts/ sq ft, that is overkill for good lighting. 50 watts/ sq ft with HPS bulbs is the general rule for good buds & yield. You start to get diminishing returns on your light wattage when you hit about 65 watts/sq ft and above.

i can just set up a 3x3? and im going to have the bulb on for 20 hrs i will veg until the beg of next year .

thanks in advance guys

 

[Granger2]

Yes a 3x3=9. 600/9=66.67 w/sq. ft.

Why are you going to veg for 3 months? No need to veg any longer than it takes for the plants to reach a height of about 2 ft. If taller, the lower parts of the plants won't get enough light to produce much, and it will be low quality. Good luck. -granger

 

[00420]

so best size to cover is a 3 x3 area correct? 66 watts ?

never said that, was just showing the math

i can just set up a 3x3? and im going to have the bulb on for 20 hrs i will veg until the beg of next year .

thanks in advance guys

that's a long veg really long lol

 

[gus738]

a long veg so all the cannabinoids will mature but at least 2 months of veg edit : essential oils ? i cannot use outdoor anymore i dont have space at all outdoor.

 

[00420]

a long veg so all the cannabinoids will mature but at least 2 months of veg

 

[Jhhnn]

That 600 watt bulb is going to cover 12 sq ft nominally with 50 watts per sq ft. IDK where you came up with 75 watts/ sq ft, that is overkill for good lighting. 50 watts/ sq ft with HPS bulbs is the general rule for good buds & yield. You start to get diminishing returns on your light wattage when you hit about 65 watts/sq ft and above.

That 50-65w/sq ft seems right. A 1000w bulb in a 4'x4' area works great, which is 62.5w/sq ft.

Veg time depends on the strain & grow space/style. If I vegged for 2 months, some stretchy strains would surely be up in the light w/o extensive pruning & shaping early on. Several have stretched to more than 3x their height after switching to 12/12. I have no experience with Haze strains, but they're supposedly even stretchier.

 

[gus738]

i also have a 1000w hps and a mh . i dont care how much height they grow i;ve grown 5 half or 6 somethinig footers im starting them at 3 gal i have 45 gal smart pots as well . i've used 25 gal before on outdoor . but like i said i cant do out door not for many months.

i think most clones are indica or hybrid with indica being most

 

[vapor]

111.1111 my lucky number

 

[Stonefree69]

a long veg so all the cannabinoids will mature but at least 2 months of veg edit : essential oils ? i cannot use outdoor anymore i dont have space at all outdoor.

I like longer veg times too but it's the flower period that really effects cannabinoid and terpene... development. Pure sativa strains can be a PITA when your waiting up to 16 weeks for them to fully flower right. I know that just from my bros old bagseed that was stubborn like that. I like the Indica dom strains so I'm lucky in that regard.

Maybe that's why clones are popular too, as they can get bigger faster in veg 4 weeks than a seed can. So the turnaround time is cut by some 30 days too. I veg seeds some 8 weeks and the vigor they have over clones makes up for some of that. One day I'll clone a strain that I really like - and/or make a lot of seeds in a grow cycle.

 

[gus738]

most indica dom are fully mature flower in 60 days indoor?

 

[Stonefree69]

most indica dom are fully mature flower in 60 days indoor?

8-10 weeks generally. So yes 60 days would be about 8 1/2 weeks (8 weeks x 7 = 56 days + 4 = 60 days). I like 9 weeks minimum to be safe even it the strain says 8 on the label.

Sativa dom to grow is nice one in a while for me for day & night use. Then that ups flower time to a good 10-12 weeks.

Being I have a veg & flower area I cut that time. Using seeds I should have a 3rd area for the 1st 4 weeks (early veg) that would make up for the time vs using clones which have a good 30 day head start. Problem is my plant count and I'd like to stay legal. They say plant count dictates yield.

Seeds do have more vigor generally but a good clone is chosen from a good mother (if having adequate selection to choose from) and have better chosen genetics than random seeds of same strain.

 

[00420]

I like 9 weeks minimum to be safe even it the strain says 8 on the label.

 

[gus738]

we must think alike i too rather be safe then sorry with an extra week , truth be told im starting all over again now that i have solar power (granted on the grid) but solar nonetheless and been pretty much outdoor guy . and i would just want have something . so 60 plus 2 weeks dry 2 weeks cure . veg time ? so 90 or so days would be normal for an indoor guy ?

8-10 weeks generally. So yes 60 days would be about 8 1/2 weeks (8 weeks x 7 = 56 days + 4 = 60 days). I like 9 weeks minimum to be safe even it the strain says 8 on the label.

Sativa dom to grow is nice one in a while for me for day & night use. Then that ups flower time to a good 10-12 weeks.

Being I have a veg & flower area I cut that time. Using seeds I should have a 3rd area for the 1st 4 weeks (early veg) that would make up for the time vs using clones which have a good 30 day head start. Problem is my plant count and I'd like to stay legal. They say plant count dictates yield.

Seeds do have more vigor generally but a good clone is chosen from a good mother (if having adequate selection to choose from) and have better chosen genetics than random seeds of same strain.