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I have a cannabis plant, how long do you leave the blue light only?

Sep 24, 2020 - 9:49 AM

  • Hi till what stage of the cannabis plant do you leave the z5 on the blue light spectrum only, and what distance? Thank you

  • Thanks for asking.

    For many plant species, a dominant blue light will affect photomorphogenesis. This essentially makes plants grow more compact with stronger stems and branches. This is preferred by growers during vegetative state when growing cannabis.
    Red light is mostly beneficial during flowering and will also make plants grow taller and faster. I'd say it is best to use both light spectrums at the same time at any growth stage. Both buttons are made available for growers who want to experiment.

    You can use the blue switch alone, or both light switches together but never use the red light alone as it is less beneficial compared to using both light spectrums..

    As you are growing cannabis, appropriate light intensity depends on many different factors such as strain, temperature, and humidity to name a few.

    Generally, I recommend 150 PPFD (╬╝mol/m2/s) until the second set of leaves are showing. Progress towards 200 PPFD when the first set of leaves grows bigger and keep increasing intensity a little every other day.
    When your plant is about 3"/7cm tall, it should handle 250 PPFD quite well. When it has become a young adult and it is in it's vegetative phase, work your way to 400 PPFD and slowly increase to 500 or slightly higher.

    When switching to flowering, an intensity of 600+ is recommended. When light intensity passes 600, photosynthesis will slowly start to become saturated by the availability of carbon dioxide instead of light. I recommend to not grow in intensities higher than 900 PPFD, as this is where photosynthesis in cannabis more or less becomes completely saturated. But it can be done in the late stage of flowering if you are on point with watering, temperature, nutrition, air humidity, etc.

    150 PPFD is achieved at 36/90cm
    250 PPFD is achieved at 30
    400 PPFD is achieved at 22/55cm
    600 PPFD is achieved at 18
    900 PPFD is achieved at 12"/30cm

    The blue button counts for 38% of all light intensity emitted. To give an example, the lamp produces 343 PPFD with both buttons at 24/60cm. Using the blue button alone at 24/60cm will result in 343*0.38 = 123 PPFD. If you choose to use the blue button alone, in the first week (or weeks) of your plants' life, it would be appropriate to hang the lamp at approximately 55cm, as 400*0.38 = 152 PPFD. The best advice I have is to progress slowly with these recommendations in mind and to listen to your plant as it will tell you how it is doing.

    Our spectrum charts and intensity maps can also be found on our website for both our lamp models. Here are the links:

    Z2: https://www.ledtonic.com/products/ledtonic-z2
    Z5: https://www.ledtonic.com/pages/z5-product-info

    I know light can be tricky in the beginning so please let me know if anything was confusing or if you have any more questions. I am more than happy to fill in where ever it is needed.

    Best regards,

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