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Activity Forums Grow Tips Light Height

  • Light Height

    Posted by Deleted User on September 17, 2021 at 1:45 pm

    Newbie here, just trying to get my plant (animal cookies bag seed, 28 days since it broke ground) the right amount of light. It started under a viparspectra p1000 but I knew I wanted something else so I picked up a Mars-Hydro SP3000. My plant is happy 15″-18″ from the light @ 30% power but I have read now that there are consequences to using heavily “dimmed” lights. I tried raising the light and using more power but my plant doesn’t seem to like the added power (60%) until I get the light up to about 48″ above the canopy. That gives me the same par reading on my little Light/moisture/PH meter and the plant doesn’t hate it, but it’s not praying to the light and that is way out of the height range recommended in the documentation for the light. The manual says 12″-18″ and 75%-100% power for a vegging plant. I know that would cook my plant quick.

    boris.kogan replied 1 year, 7 months ago 3 Members · 4 Replies
  • 4 Replies
  • marcoeldragon

    September 17, 2021 at 9:39 pm

    I was hoping that some of the more experienced people would join in this discussion. I too have similar questions. I recently started back growing after a 20 year break. The technology, genetics and practicality everything else has changed so much I might as well be a first time grower.I am using 2 Spyder Farmer SF 1000s. They are working but I doubt I am using them as effectively as possible.

  • Deleted User

    Deleted User
    September 17, 2021 at 10:25 pm

    I set it back down the way it was (30% on the SP3000 @ 15″ from the canopy and it is happy again. My ballpark math says it should be getting around 410 umol/s there. Should I be trying to dial up it’s light tolerance or will it be ready for more light when it’s time? I am just surprised that the manufacturer recommendation is so far past what my healthy looking plant can take.

  • marcoeldragon

    September 18, 2021 at 10:24 am

    When I first bought my SF1000s I started at about 40% and a few days later 1 of my 4 seedlings bent over. I propped it up with a stick and a day later it was bending over again. It was trying to get away from the light. I turned the light down to about 30 % and slowly cranked it up over the course of a week to 50 %. Another 2 weeks and I slowly worked it up to 75%. Only the 1 of 4 seemed to have any problems the rest didn’t seem to care one way or the other. By the time they were 6 weeks old I was blasting away at full power.

  • boris.kogan

    September 12, 2022 at 6:22 pm

    i know i am coming too late to the discussion but hoping it will help others in the future. the thing you need to know about par and ppfd is that your plants need different amounts at different stages of growth. also, your environment will greatly affect how much light your plants can use. are you running co2? if so, your plants should be able to use a hell of a lot more light. in any case use the following table to determine how much light a plant should receive;

    clones – no direct light and no more than 100 ppfd

    early veg – 200 – 400 ppfd

    late veg – 400 – 600 ppfd

    flower – 600 – 900 ppfd (no co2) 1400 ppfd (with co2)

    in order to determine ppfd at the canopy level you need a par meter. the good ones are ridiculously expensive. this is the one i use; https://www.amazon.com/Apogee-Instruments-Full-Spectrum-Quantum-Telescopic/dp/B09MYDTW5C/ref=sr_1_3?keywords=apogee+ppfd+meter&qid=1663021274&sprefix=ppfd+meter+a%2Caps%2C87&sr=8-3