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Plants don't grow under the LEDTonic Z5 LED grow light. What's wrong?

May 31, 2020 - 9:28 AM

  • I bought your Z5 last January, my plant was in bloom stage when I received your light in the mail, I was using a 200W 6400 K with 17,600 lumens compact fluorescent light before I got the Z5, I put the Z5 light in and finished the grow and it turned out amazing. So now I started an autoflowering cannabis plant under the Z5, it’s been 3 weeks and there is utterly no change in the start, the plant doesn’t seem to be maturing at all. Do you think the Z5 isn’t strong enough for starts? It’s in a 2x2x4 grow tent and the Z5 is only hanging 5” from the canopy but the plant doesn’t seem to be maturing.

  • For seedlings, we recommend providing somewhere between 100 and 200 PPFD. You can have both more and less than this, but it might not be ideal.
    Full sunlight in the middle of the summer and the middle of the day, is somewhere between 1500-2000 PPFD, depending on where you live.
    The Z5 produces 1600 PPFD at a distance of 6"/15cm. Giving your seedling this much light (or even any adult plant) for extended periods each day, will be damaging. Your plant is in survival mode.

    We have recently measured our Z5 LED grow light in a 2x2'/60x60cm reflective space. Direct link:

    It shows what PPFD values are produced at three different distances in a 2x2' space with both buttons activated. Looking at 12" distance, there is a center intensity of over 900 PPFD and this is around our recommended maximum for cannabis plants during the mid and late stage of flowering.

    To achieve 150-200 PPFD, you need 2.5-3' distance between the lamp and plant canopy, if both power switches are activated on the lamp.

    The blue switch activates 40% of its total light output.
    The red switch activates the other 60%.

    As your grow space isn't very tall, you can hang the lamp at 18-20" above the canopy and only use the blue switch. This will give you between 150-200 PPFD.

    You can activate both light switches when your plant has grown in size. It can take roughly twice the intensity when it is a couple of weeks old and/or 8-10" tall.

    We're glad you reached out and hope that this information helped.
    Please let us know if you have any other questions or if we can help you in any other way.

  • How do you raise or lower humidity in the tent

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