1. We are currently experiencing issues with viewing and uploading images, our team is working on the issue.
    Dismiss Notice

How many plants can I put under a 400 watt HPS?

Discussion in 'Indoor Growing' started by Trader Bill, Apr 20, 2008.

    Trader Bill

    Trader Bill Active Member

    Hi all. I'm new to the board.

    Here's my situation.
    I have a 400watt HPS mounted to a hood attached to a 6ft PVC frame that I built so I could raise and lower my light as needed via the chains that attach the hood to the frame.

    I'm running a deep water hydroponic system that features four 20 gallon tubs that have spots for 4 plants per tub. So as it stands right now I can have 16 plants going at once.

    My plants are growing incerdibly fast and it seems to me that 16 plants under one 400 watt HPS might be too much. They're already crowding each other and im just under a month into my operation.

    So can I have 16 plants under one 400 watt HPS?

    How close can you crowd the plants together?

    Will I get better yield from fewer plants that I grow larger? Or should I crowd up smaller plants and get a fast harvest of many plants? This is my first time growing so thanks for the info.

    High4Life Well-Known Member

    4-6 Plants Work Best Under A 400w . I Found 6 Is Tightly Packed With Not Much Ligh Getting Through To The Sides , 4 Plants Works Perfect ..h4l

    surfnsk8er Active Member

    ya i would have to agree with 4 is perfect. i currently have 5 and it's a bit too crowded

    Dutch1976 Well-Known Member

    I say 9 small-medium sized plants. Top the plants as soon as you see the 4th node. A few days before you put them into flowering, strip the lower half of the plant and watch those colas explode.

    kearners Well-Known Member

    thanks man this really helped me i was going 2 make a thread to find out how many plants i could have!! ill be checking this out again soon!thanks...

    jEthereal Active Member

    It all depends on how TALL the plants are when you switch to 12/12.

    You could EASILY do 16 plants under a 400w HPS. How so, you ask?

    FLOWER AT 6"!!

    If it is done right then you'll be able to have a bunch of mini-cola plants.

    16 plants x 1/2oz expected yield =

    One question - What's the 'footprint' of your tubs? ie - How much space (LxW) do your tubs take up when you have them arranged how you want? 4x4? 5x5? etc....

    Your spatial 'footprint' when growing with a 400w HPS should be around 4x4. It's YOUR choice on how to accommodate your plants into that space.

    There isn't really a 'set' number of plants that are appropriate with a certain wattage.

    So to say 4-6 plants WITHOUT offering the SIZE of said plants is a very inaccurate statement when trying to help a newbie.


    High4Life Well-Known Member

    Unless your doing a sea of green for advantced newbies or mini growers *

    4-6 normal plants is all a 400whps is good for

    kearners Well-Known Member

    thanks a lot i just spent a long long time looking for advice on this area but ye really helpd, i owe ye one!! peace out!!
    White Widow Woman

    White Widow Woman Well-Known Member

    Yes, you could get a better yield from letting fewer plants grow taller/vegging longer for height - but you can also get a great yield from growing lots of smaller plants (SOG). That dear sir is all personal preference. But I have never heard of this 'Fast Harvest' that you speak of. The plants are gonna take 7-8+ weeks of flowering reguardless of their height - unless you have chosen a strain that finishes sooner.

    Let me finish by saying that 8 plants under a 400w light, creates some pretty good buds - go down to only 4 plants and you get some great perfect buds!

    Ace Smoking likes this.

    kearners Well-Known Member

    u can get a 250watt hps right?
    Trader Bill

    Trader Bill Active Member

    Hi all. Sorry it took me so long to respond.

    I have all four of my tubs pressed together into one rectangle that is 45in x 31in.

    The biggest plant is 19.5 inches. The rest of the plants range from 18 inches to 13 inches.
    Trader Bill

    Trader Bill Active Member

    Hiya. When I mentioned getting a faster harvest with smaller plants I was speaking in the context of having a shorter vegetative period before going to 12 on 12 off to make em flower.

    I think i'm going to try for 4 plants per HPS, and get myself a second HPS so I can do 8 at a time.

    Dabu Well-Known Member

    150watt hps complete system for $69.75
    High Tech Garden Supply

    250watt hps complete system for $117.45
    High Tech Garden Supply

    Hope that answers your question. I have a 150watt on the way in the mail at the moment.

    kearners Well-Known Member

    nice one dabu, what you planning on putting under d 150watter??

    tpemiles Active Member

    for a 400w hps, should it still be around 2 in. away from the top of the plant during vegetation? and then how far should it be from the top of the plant during budding? and with a 400w hps with 30w extra blue spectrum, thats all i would need right? sorry about all the questions. just dont want to fuck up lol
    mared juwan

    mared juwan Well-Known Member

    an hps needs to be AT LEAST 14 in away from your plants. That 2 inch stuff is for CFLs. Please don't put your light that close. You will kill your plant quick.

    tpemiles Active Member

    it won't grow too high too fast if its 14 in away?
    and how much does it normally grow after you start budding? i just want to make sure i have the right height when i build my room. i only want a small garden, just for personal use.

    jEthereal Active Member

    You can expect to double or TRIPLE in height. Sativas will stretch more. Indicas usually double their height, if even that.

    tpemiles Active Member

    i thought it would get too stretched out and not bud well but i honestly dont know anything so thank you!
    should the light still be at least 14 in for budding? Is it all the same distance with hps?

    High4Life Well-Known Member

    14 inchs would be about right man , 2 inches would burn the crap out of them ,

Share This Page