What Size Pot Should I Use?
When growing cannabis plants in a container, you have to choose the size of your pot. A general guide is to have about 2 gallons per 12″ of height. This isn’t perfect, since plants often grow differently, but this is a good rule of thumb.
When in doubt, get a bigger final container size as opposed to a smaller one. Plants that get rootbound from being in a too-small container will grow more slowly and be prone to problems.
It’s not good to transfer plants during the flowering/budding stage, so you want to have your cannabis plants in their final container at least 2 weeks before the beginning of flowering/budding.
Final Container for Desired Plant Size – General guide
- 12″ ~ 2-3 gallon container
- 24″ ~ 3-5 gallon container
- 36″ ~ 5-7 gallon container
- 48″ ~ 6-10 gallon container
- 60″ ~ 8-10+ gallon container
But what size pot should you use for your seedlings?
For fastest growth rates, it’s better to plant young seedlings or clones in a very small container, like a disposable plastic solo cup.
For new seedlings and clones, use a small container if possible
The reason you want to start with a small container is that your plant’s young roots thrive on oxygen. Cannabis plant roots “breathe” oxygen, just like we breathe air, and it’s important that young cannabis roots get plenty of oxygen so the plant can grow as fast as possible.
However, young plant roots do not drink much water yet. When you water seedlings or clones in a very big container, they will use up all the oxygen quickly, and the large size of the container will prevent the growing medium from drying out.
A big plant will drink up all the water quickly, but with seedlings, you’re basically waiting for the growing medium to dry out by itself. While you’re waiting for the container to dry out, your cannabis roots are sitting in a wet environment and not getting much oxygen, slowing down their growth rates.
Poke holes in the bottom of your cup so water can drain out easily!
By planting young seeds in a small container with holes in the bottom, the growing medium will dry out much more quickly, allowing you to water more often. The young cannabis will get plenty of oxygen and water.
Alternative to Solo Cup: Start plants in seedling cube
If you don’t want to have to transplant your young plants, you can start them in a seedling plug or cube and wait until you start seeing roots come out the bottom. At that point, they will be ready to be transferred to a larger container.
What happens if I plant seeds or clones in a big container?
Your cannabis seedlings and clones will definitely survive in a bigger container; they just won’t grow as fast for the first few days or weeks because they aren’t getting as much oxygen. With a bigger container, you will need to wait longer between waterings, and during that time your plant roots will be getting reduced oxygen.
If you’ve planted your young plant in a large container, try to give only a little bit of water at a time (enough to wet the area around the seedling roots) until the plant is growing vigorously. Once the plant has grown a few sets of leaves, you should start watering cannabis normally so that water drains out the bottom.