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400 Watt HPS - How much space? How many plants?

M

manbearpig

Member
How much space does a 400 Watt HPS effectively cover?
I was under the impression the maximum coverage is 4x4 ft for a 400 watt.

How many plants can you put under a 400 watt HPS without getting too crowded?
Would 1 plant per square foot be too many? (If 4x4 ft area, 1 plant psf, 16 plants total?)

Danke


 
M

manbearpig

Member
Forgot to add, it'd be a SOG style grow. Basically a bunch of 2-3 footers, so I think 1 plant psf is okay what do you think?
 
Truth

Truth

Member
3x3 is proper, but 4x4 is do-able. how many plants depends on their size. I wouldn't put more than 6 plants under a 400w. I like to give around 100w per plant, but 50w is do-able. so 4 plants, for a 400w is excellent if you want space and let them stretch their 'arms'. you don't want your plants to overgrow your light source in flowering, even if you flower from start. it depends on the strain also, the less branchy the strain, and short, the easier you can add more plants. you could fit 10 plants under there if you did 12/12 from near the beginning from seed, but of course, they will still need to be small and not branchy.

400w HPS is basically the bottom line to me for serious growing. I know I can stick 3 DWC plants into flowering at 3 weeks veg (thats how long I veg half the time) and by the end of flowering, they've taken up the 3x3 area. you don't want to put too many if using only one light, you do not want to outgrow your lighting source in the beginning or middle of flowering. if you plan on taking many clones, then it may be fine. you can always trim the 10 plants, but it is sort of counter productive unless you plan on cloning (why take the time to grow out areas you are just going to toss?). also to note, it may not be so bad, if say you planted a whole 10 pack of seeds, you'd expect around half to be female, and if thats the only type you want, you could end up with 5 or so plants, which can do nicely under a 400w.
 
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M

manbearpig

Member
Wow thats not many plants at all... I thought the rule of thumb was 1 plant per sqaure foot???

They'd be vegged for 1-2 weeks maximum then 12/12, so I think I could do 10 like you said,
What kind of yield you think i'd get with 10 females that were flowered after 1-2 weeks of veg? Under a 400 watter

Getting femaleseeds.nl no males :)
 
T

tru-smoker

Member
a 4x4 is to large for a 400w. Try 3x3 and keep the light close...1 plant/psf is standard for most sog's but imho pack em in if your going sog trim em' single cola keep em nice and tight...maybe 16 under ur 3x3, i've seen as many as 25. peace...tru
 
T

tru-smoker

Member
your yeild per plant is hard to say depends on strain and a million other things but around 14-28 g's per (depending on everything) with a week or two veg.
 
MTF-Sandman

MTF-Sandman

OG Refugee
Veteran
Personally, I'd go with 16 plants under a 3x3 canopy...1 gallon pots and 2 weeks veg oughta get you 1/2oz per plant with decent clones.

Make sure that you trim all branches off at the start of flowering and then go back in right after the stretch is slowing and remove any new ones that popped up. Otherwise you'll end up with mini-bushes that are a PITA to manicure.
 
M

manbearpig

Member
Well thank you some very good suggestions here

Am I wrong in assuming I can get .5 grams for each watt? So 200 grams, or a half pound, if I fill my space with the 400 watt?
 
T

tru-smoker

Member
You got it...keep after it... In time find the right strain, dail in your grow and reach 4 that G. per/watt mark. It can be done :joint:
 
M

manbearpig

Member
LOL! Yeah maybe I can achieve G per watt if I have a full scale pro grow room. That's a fantasy, not happening.

But .5 gram per watt is alright in my oppinion! No complaints!
 
marx2k

marx2k

Active member
Veteran
With the vectors mentioned, what do you folks think would be a decent height of the growth space given that we're using 3 gal containers?
 
D

dirtybudz

Member
16 plants at 1/2 oz per plant seems like a large expense of resources and time.
I hate to say it, but I hate to toil. I like clean and simple and easy if possible.
This is why I got away from solid medium grows such as soil except on rare occassions.

In 3gal DWC (4gal containers) with two plants in a 18x48 cab under 400w standard HPS, it is possible to achieve well over 8oz depending on the strain.

I have found the KISS principle works best. As I am still and always learning, it is just easier for me to slowly tweak variables, methods, strains in a small space to see what max I can reach rather than slave over a bunch of plants that might yield less and less quality.


Best of luck :wave:
 
J

JackOneill

Member
I am growing 3 plants in 3 gallons under a 400 watt CMH and I got them a foot away from the bulb itself. the height of the room they are in is only about 4 feet or so but I LSTed to keep them short but man are the wide with so many colas, I got pics in the CMH thread if you want to see for yourself.
 
P

PharmaCan

Active member
Veteran
You can't believe what the light mfgrs tell you about the effective footprint of their lights. What you want to do to determine the physical size of your grow is to use the watts/sq.ft. method - which is what a couple people already did, they just didn't explain the process to you. You want 40 watts per square foot absolute minimum. (I've got 50-70 watts/sq.ft.) So a 3'x3' area = 9 sq.ft. - 400 watts divided by 9 sq.ft. = 44.44 watts per sq.ft.

PC :smoker:
 
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