400W 4'x4' how many can fit?

Hey everybody, this is my first legit grow(had one plant under cfl before) and I'm doing it with a 400W MH in a 4'x4' area and am using 3-4gal. 10"-12" pots and promix as my medium. SO in total thats 16 square ft. Now here's the big question to everyone out there, How many plants should be grown in this space?

At first I was planning on following the 1plant per foot rule but it seemed like it would be a little much for a 400W. Anything is appreciated and happy growing.

My experience with a 400 watt tells me that I can cover a 3' x 3' area very good with it. You can cover a 4' x 4' area but the outer most plants wont get much light. You really need a 600 watt for a 4 x 4 area but a 400 can work fine. I use a 400 watt in my 4' x 4' tent.

Using your 10" to 12" pot size I would recommend only a 3 x 3 matrix for a total of 9 plants. You can do a 4 x 4 matrix but the outside plants will hurt for light. I supplement this by hanging 4 extra 27 watt cool blue cfl's on one side and move the reflector over about 4".

If you do that you can up the matrix to 4 x 4 for a total of 16.

Hotwired said:

My experience with a 400 watt tells me that I can cover a 3' x 3' area very good with it. You can cover a 4' x 4' area but the outer most plants wont get much light. You really need a 600 watt for a 4 x 4 area but a 400 can work fine. I use a 400 watt in my 4' x 4' tent.

Using your 10" to 12" pot size I would recommend only a 3 x 3 matrix for a total of 9 plants. You can do a 4 x 4 matrix but the outside plants will hurt for light. I supplement this by hanging 4 extra 27 watt cool blue cfl's on one side and move the reflector over about 4".

If you do that you can up the matrix to 4 x 4 for a total of 16.

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yah, i would do the 4x4 set-up.

I dont think 4 30 watt cfls sitting right next to a 400 is adding much of a difference.

FullMetalJacket said:

I dont think 4 30 watt cfls sitting right next to a 400 is adding much of a difference.

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not a huge difference, no. But honestly, why not? He will get maybe 10 good plants and 6 weaker mids. i guess if he did 3x3, he would have the benifet of more intense light bouncing off the walls.

The sun isnt stationary in the sky and your lights shouldnt be either, Move the plants around, outside to in, inside to out. A 400w will cover a 4x4 area just fine if you have good reflective material surrounding. A combo of movin the plants and good reflective surround will do wonders.

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macdadyabc said:

not a huge difference, no. But honestly, why not?

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You will see no difference in yield and you will increase heat and energy consumption.

If you put a small source of light into the space that a more powerful source of light is already lighting, you'll get no additional light available to the plants. (this is what people really mean when they say "lumens do not add up".

However, if you carefully position these lights into the shaded areas of the garden, they then become the greatest source of light in that area and 'the lumens do add up' (well sort of).

With CFLs, you need to keep them very close to the canopy, but they will burn your plants if they touch them.

IMO, the best form of supplementary lighting comes from t5ho strip lights. They are available for about $30 ea and produce more light and less heat than CFLs. They also take a long time to damage a plant, even when touching.

Positioning 4 of the 4 foot fixtures around the sides of your garden will increase your yield as compared to just the 400, and you won't have to worry about juggling plants as much.

This also comes with an additional 218w power draw though. Heat won't really be an issue as compared to if you added 8 26w CFLs.

Want some good info on CFLs and lighting, go here: Info on CFLs by Roseman

just go get a 1000 hps, you will be happy you did.

FullMetalJacket said:

just go get a 1000 hps, you will be happy you did.

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in a 4x4 area you must be crazy that would be a waste i would stick with the 400 in a 4x4 with 16 plants or maybe 4 bigger lsted plants

i may be crazy, but if i ever go 4 x 4 it ill be 1000 for sure. Not a waste.

yea really 1000 is min for 4x4 = 62wpsf a 600 for a 3x3 66wpsf and with a 400 a little less than 3x3

I had a 400w in a 3x4 mylar lined area and it covered it really well. I grew 4 full sized plants and the inside of my cab looked like a full bush.

boneman, your avatar is hilarious. i was a still a kid when that show came around, and i remember the "can we fix? yes we can!" thank you for the laugh

Atombomb is spot on , about moving plants around and having the right reflective material, but the Metal Halide...nah, go with an HPS bulb, even if your ballast is MH only, you can still buy an HPS bulb designed for an MH ballast, called a CONVERSION bulb , like this bulb here at this link> http://www.discount-hydro.com/productdisp.php?pid=264&navid=45

Your Metal Halide bulb is rated at around 36,000 lumens and the HPS conversion bulbs like the one above is rated at 45,000 lumens , you definitely need those extra lumens for the space your trying to cover, and if your ballast is MH only ....its still worth the 80 bucks to have those extra lumens. I've got a 400 watt Sunlight Supply switchable ballast so I don't need conversion bulbs and I've grown with both types of bulbs, I don't even bother with MH bulbs anymore because the lumen output just isn't high enough,as a side issue even Ed Rosenthal uses HPS bulbs thru the VEGGING stage, though the nodes grow slightly spaced apart...its still miniscule. My point is go with an HPS bulb ..I swear you will see a difference and I grow in a 3.5 ft. x 3 ft. space, using mylar , a sunleaves sun spot 6 reflector that is awesome , soilless mix in 3 gal. containers. There will be a HUGE difference in bud thickness if your using a 400 HPS for a 4x4 space compared to using a 400 MH for a 4x4 space, I know this from hands on, dude....get a 400 HPS conversion bulb for your MH ballast...you won't be sorry, I'm surprised no one has already mentioned this.

FullMetalJacket said:

i may be crazy, but if i ever go 4 x 4 it ill be 1000 for sure. Not a waste.

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super huge waste of money you are paying for electricity and then the money your loosing by not useing the light to its full potential think of all the plants you could be growing but your not cause you got a wastefull 1000 watts in a 4x4 room.......... 3x3-4x4 use a 400w 4x4-5x5 use a 600 thats how it is... if you dnt know how to use your light you need to go back to indoor growing 101.........5-7000 psf lumens is all you need , why would you need more light than the sun produces.... its bullshit learn to use your light corectly and until than keep your opinion to yourself

mrred said:

yea really 1000 is min for 4x4 = 62wpsf a 600 for a 3x3 66wpsf and with a 400 a little less than 3x3

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your wrong too where do you ppl get this information.... go back to grow school homie

tusseltussel said:

your wrong too where do you ppl get this information.... go back to grow school homie

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I don't think there is anything wrong with using 1000w over a tall canopy in a 4x4 area during flowering - so long as you can handle the heat.

Why do you insist that there is anything wrong with this?

Yield is proportionate to light. If you're canopy isn't too short (light blasting right through to the floor), your plants will make use of this light and they will yield more because of it.

I completely disagree with you on this. I believe that a 1000w light is perfect for a 4 x 4 to 5 x 5 area where the canopy will be 2 or more feet deep.

If you're using a 400w light on a canopy that is 2' deep or deeper, you get almost no usable light to your lower bud sites.

The numbers you've stated are generalities for indoor gardening, MJ is a light loving plant and will repay you for additional lighting.

In addition, if you're supplementing CO2, you will need to maintain these extravagant amounts of light (7500-10000 lpsf) to take full advantage of the metabolic increase. 5000 lpsf just aint gonna cut it.

Why use more than the sun? I don't duplicate nature, I better it.

It was unneccesary for you to lash out stating "keep your opinion to yourself" and "go back to school". There are many successful grows logged using near 10000lpsf.

I'm not saying that you can't grow good weed with what you're saying, just as you shouldn't say that it's a "super huge waste" to use this amount of light.

AeroKing said:

I don't think there is anything wrong with using 1000w over a tall canopy in a 4x4 area during flowering - so long as you can handle the heat.

Why do you insist that there is anything wrong with this?

Yield is proportionate to light. If you're canopy isn't too short (light blasting right through to the floor), your plants will make use of this light and they will yield more because of it.

I completely disagree with you on this. I believe that a 1000w light is perfect for a 4 x 4 to 5 x 5 area where the canopy will be 2 or more feet deep.

If you're using a 400w light on a canopy that is 2' deep or deeper, you get almost no usable light to your lower bud sites.

The numbers you've stated are generalities for indoor gardening, MJ is a light loving plant and will repay you for additional lighting.

In addition, if you're supplementing CO2, you will need to maintain these extravagant amounts of light (7500-10000 lpsf) to take full advantage of the metabolic increase. 5000 lpsf just aint gonna cut it.

Why use more than the sun? I don't duplicate nature, I better it.

It was unneccesary for you to lash out stating "keep your opinion to yourself" and "go back to school". There are many successful grows logged using near 10000lpsf.

I'm not saying that you can't grow good weed with what you're saying, just as you shouldn't say that it's a "super huge waste" to use this amount of light.

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if thats how you wanna play thats fine but if ya wanna grow tall plants grow outdoors you can get more out of you 1000w light if you train your plants and put it in the right sized room than you will out of 2 giant craptacular plants in a 4x4 room its just the way it adds up... ive grown indoor monsters ive grown sog ive grown lst ive only done a scrog once than decided to go back to soil and lst but either way its a proven fact that you yeild more from a sog indoors granted you do get more penetration but you dnt need it if ya do it right monsters belong outside not inside you do what you want but i know i can pull a grade A harvest of grade a weed. it is a super huge waste you could get so much higher yeilds out of that 1000w in the right setting but sure if you wanna lose all that good smoke go for it, penetration will get you half way there good luck... ive been doin this a long time ive seen a lot of grows ive done a lot of grows and i have had 1000watter 600watters and now have a 400 watter and its all i need in my 3.5x4 grow room. i easily pull 10 oz off that light every 2 months sometimes 3 depending on my life schedual and could do more if i wanted to veg longer..... it keeps me happy.. i dont see why i would need any more.. my nuggets come out perfect... have you ever read up on photosynthasis and how excess light is expelled from the plant as heat do some research you may learn that you can have too much light and it slows down photosynthasis.... good luck make sure you tell all the noobies to go overkill for ther first grow so they spend all there money then give up cause all the plants die from the heat.

tusseltussel said:

super huge waste of money you are paying for electricity and then the money your loosing by not useing the light to its full potential think of all the plants you could be growing but your not cause you got a wastefull 1000 watts in a 4x4 room.......... 3x3-4x4 use a 400w 4x4-5x5 use a 600 thats how it is... if you dnt know how to use your light you need to go back to indoor growing 101.........5-7000 psf lumens is all you need , why would you need more light than the sun produces.... its bullshit learn to use your light corectly and until than keep your opinion to yourself

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lol, you're a goofball oh wise one