Q&A for How to Grow Marijuana Hydroponically

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  • Question
    Where can I get the seeds?
    Lauren Kurtz
    Professional Gardener
    Lauren Kurtz is a Naturalist and Horticultural Specialist. Lauren has worked for Aurora, Colorado managing the Water-Wise Garden at Aurora Municipal Center for the Water Conservation Department. She earned a BA in Environmental and Sustainability Studies from Western Michigan University in 2014.
    Professional Gardener
    Expert Answer
    In places where marijuana is legal, you can get seeds from a dispensary that sells marijuana products.
  • Question
    In a 24 inch grow box, how tall should I start the blooming?
    Lauren Kurtz
    Professional Gardener
    Lauren Kurtz is a Naturalist and Horticultural Specialist. Lauren has worked for Aurora, Colorado managing the Water-Wise Garden at Aurora Municipal Center for the Water Conservation Department. She earned a BA in Environmental and Sustainability Studies from Western Michigan University in 2014.
    Professional Gardener
    Expert Answer
    24 inches is not large enough to flower marijuana.
  • Question
    Is weed illegal?
    Community Answer
    If non-medically used in certain states, yes. If you are over 21 in Colorado or Washington, you can recreationally use marijuana legally.
  • Question
    I have the correct light in the correct room areas, but the plants are very skinny and spindly. What can I do?
    Community Answer
    As long as the light you use is not hot, lower it and put a small fan on the plants. The fan will help the plant to be stronger and the lower light will keep it from trying to stretch up to reach the light source.
  • Question
    When should I top my plants to get more buds?
    Community Answer
    Top the plant when it reaches 5-6 inches tall and continue to do so after each previous top has grown three inches. This will produce a fat, bushy plant. You will need to put some lights lower down after the plant begins to fatten up.
  • Question
    What NPK ratio should I use for hydro weed to bud?
    Community Answer
    Find a brand of nutrients for hydroponic plants, and follow their nutrient schedule. The schedule will vary as you go through the growing cycle. NPK ratios will also change. Even then, you may have to tweak this depending on what you are growing.
  • Question
    Which is better: hydroponics or normal, soil-based growth?
    Community Answer
    Hydroponics will bring bigger, faster yields, but it's a science and mistakes are difficult to correct. Soil is grower-friendly; mistakes can be mended and a simple flushing of soil will usually fix the issue. So it really depends on your preferred level of difficulty.
  • Question
    If the plants are in the budding stage, but I need to do some maintenance when the bulbs are off, will a little bit of regular light from a small ceiling light bulb shock or hurt them?
    Community Answer
    Yes, any light whatsoever, even a flashlight, can shock them. They need to be kept in total darkness.
  • Question
    I have a deep culture system, and have 2 12" bubble stones. Should I have the net pots submerged at all or just above the water level to let the bubbles splash them on the roots?
    Community Answer
    Just an inch or so above the water, the goal is to have the roots eventually drop into the water, which will cause a massive growth spurt when it finally happens.
  • Question
    Is rain water okay to use in my hydroponic system?
    Community Answer
    Perhaps, but using distilled water would be better.
  • Question
    Once it's time to trim and harvest, should I clip clones for the next run? How would I do that?
    Community Answer
    You should clip clones before you start the flowering stage. It's best to take clones in the veg state.
  • Question
    How do I adjust the pH level in the water?
    Community Answer
    Use Sunshine soil less mix. Mix a very light food to water ratio and water small amounts every day, and only water for the last two weeks. Fill 2-liter bottles with water and let them sit for two days before using. Have 6 bottles in line so that each one is settled and ready when needed.
  • Question
    How long does it take to grow marijuana hydroponically?
    Community Answer
    A few months, generally.
  • Question
    Should I trim the leaves while the plant is flowering?
    Community Answer
    If in the vegetative stage, yes, but not in the flowering stage.
  • Question
    Why should germination be outside the hydroponic system?
    Community Answer
    If you’re growing in a deep water system, the rock wool won’t get wet enough to germinate the seed. It shouldn't be a problem If you’re growing in coconut fiber (as long as you keep it moist enough), it’s just not optimal.
  • Question
    Do I have to use dirt or just water when growing marijuana hydroponically?
    Community Answer
    You can't use dirt and grow hydroponically. Hydroponics means without soil.
  • Question
    Can plants that develop mold while being cured in air tight containers be consumed?
    Community Answer
    No, you should not consume plants that develop mold.
  • Question
    Why are my plants not showing their sex organs at 8 weeks of age?
    Jay Ess
    Community Answer
    Plants don’t show their sex until in the flowering stage. A few weeks of 12/12 lighting should cause them to show.
  • Question
    At what point should I begin fertilizing my plants?
    Jay Ess
    Community Answer
    After the first week of plain water, start at 1/4 of recommended nutrients. Gradually increase to full nutrients over the next 2 weeks.
  • Question
    How often do I add nutrients or change water?
    Community Answer
    If you are growing hydroponically, you'll want to change your water once a week. Up the nutrients and then you'll need to flush your plant once you get about two weeks before harvesting. That's when you'll use pH water without any nutrients. If you don't, your smoke will be extremely harsh and have a chemical aftertaste.
  • Question
    How do I tell male marijuana seeds from female seeds?
    Community Answer
    If you place the seed under a microscope, you'll notice the ends of the female seeds look like volcano openings.
  • Question
    Is growing marijuana hydroponically illegal?
    Community Answer
    Only if growing cannabis in general is illegal in your area. If it is legal to grow marijuana, then it doesn't matter how you grow it.
  • Question
    Our plant is about 3 1/2 inches tall. How much time should it spend under a light?
    Community Answer
    It should get about 18 - 24 hrs a day until it reaches a mature size (half the height of your growing area). Then it should be switched to 12/12 hours in order to flower.
  • Question
    What size pot should I use when I transfer the plant and should I fill it with more coco coir or soil?
    Community Answer
    At least 5 gallon felt pots should be used. These pots would allow air to flow to the roots. Coco would be ideal.
  • Question
    What can I do if a plant was over watered?
    Community Answer
    Let it heal by not watering it for a couple days, then see if it is back to normal, if not repeat the days until it looks better.
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