How many plants can a 400w HPS handle?

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more then a 200w less then a 600w

^ IDIOT here

honestly dont know but id say between 1-10 depending on size and how your growing them. id say 4-6 would be a good number. but yup this is opinion based on research not on experience. there is a few hundred threads on lighting ive come across in the short time ive been using this site

I would do 2, grow them for around 24 days and then flower. Pick a short indica, no sativa's or hybrids cause they'll get too tall and the bottom 3/4 of the plant won't get enough light.

It will depend on space, grow methods, etc.
https://www.rollitup.org/grow-room-design-setup/61539-400w-club-show-off-your.html

Do more research, learn, and have some fun! Your effective area is about 3x3 under 400w.

If by handle you mean grow big buds, I would say 4. Any more than that and the leaves may not have enough light to bud well since we're talking a grow area of 10 sq feet or less for optimal lighting with a 400w. You can do a SOG with more but it's not really necessary and in fact where I live it's stupid to do that because extra plants may = manufacturing charge instead of personal.

i use 7 under a 1k in a 4x4 and its lil tight, id suggest like 3 max ?? juss my opinion i never used a 400

i would do 4 medium/big plants in a 4x4 in 5g buckets for hydro

If you have to ask that question just do 2 to 4. Probably better with 2 and veg them a bit longer. I personally would throw 4 under her

400w depends on size. And the only way to do so is to gone head and do it. Find out various ways in which you choose to grow by growing that way. This way you gane experience, seems everyone is looking for experienced answers for inexperienced questions from lazy growers. If you fuck up, you fuck up! Have fun!

3x3' area. fill it with buds. if that means a bunch of small plants or just 1. empty spaces within that area will cut your yield.

4 in 3 - 5 gal buckets but it all depends on if you're topping or not topping how long of a veg you give them, how you train them. Remember it's not bad to defoliate gradually, it helps get light to lower branches but also helps to focus the plants energy where it belongs in the buds. I know a guy that has all fan leaves removed by week 7 and his shits amazing!!

I try to keep 6-8 vegging under mine with lst asap anf think no i know can handle few more.

But i just vegg for 5-6 weeks.hope this helps

400w = 3'x3'
600w= 4'x4'
1000w= 5'x5'

if your doing 1 sqft/ plant, then 9, 16, and 25 respectively.

Thought u meant vegging ,if flowering get a hps imho

I run a 400 watt hps with 6 plants. I veg. under the 400 mh for 3 weeks ( this does not include sprout time). Flip 'em to 12/12 when they reach 12-15"s tall. I also run some supplemental 70 watt hps's below the canopy. They produce very little heat and give off pretty good light. Usually yeild 2+ oz's/plant.
Fox Farm soil and grow nutes used as well.

Happy learning bro.

I run 4 DWC plants under a 400w hps. First time I ran 3 big plants and I ended up harvesting 8 oz dried but I had a lot of issues the first round of DWC. Now I only veg my plants for 2 weeks, once the clones have their roots. So 4 plants is a perfect amount for a 400w oh yeh air cooled hoods rock because my light sits 5 in away from the top of the plants.

I'm 400W MH in veg (24 hr light) ...I veg, top and bend till shes bushy. 4-6 weeks after sprouting.
I had 6-8 plants to begin with in big 5gal buckets... killed a few and a few sexed, but I kept sprouting constantly.
so theres always something to replace any empty space immediately.

I also rotate my buckets position bi-weelky and give em a 180 degree turn every day or so....

Flowering under a 600W HPS... hoping that with super-cropping (topping and bending) and a higher wattage bulb for flower, I can get some dense buds.

Oh yeah, and both lights have hoods, some sort of fan blowing through to exhaust and glass or plexi-glass to control heat.
sometimes in the winter I exhaust the heat directly into a corner of the grow room to get more air flow and temp...
but in the summer I hook it to an outside exhaust for ease in cooling....