In our previous article on how, why, and when you transplant marijuana plants, we learned that if you’re doing container growing rather than pure hydroponics growing (deep water culture, etc.), you need to transplant marijuana plants at least twice if not more during a complete crop cycle.
We also mentioned that you want to keep your pot size slightly but not massively larger than your plant’s root size.
I start my marijuana plants in cubes or rooters, then transplant them into a one gallon pot when they have visible roots.
After a couple of weeks to a month, healthy cannabis plants have filled a one gallon pot with roots.
They then want more space and more material to spread into. If you don’t transplant into a larger container, your cannabis plants become rootbound.
If they become rootbound, the roots strangle and suffocate themselves.
Your marijuana plants become stunted, creating problems with wilting, slow growth, and nutrients intake.
My rule is to have one gallon of pot size for every foot of plant growth aboveground.
I transplant marijuana seedlings or clones into one gallon pots as early as I can.
About a month later or whenever they’re a foot tall, I transplant them into 3-5 gallon pots.
Just before flowering, if I anticipate for example that my cannabis plants will top out at 4-5 feet tall during bloom phase, I transplant into 5-10 gallon pots.
I stay ahead of the roots, giving them enough room to expand, but not too much room.
Too much room is almost as bad as not enough room.
Why? Because vast areas of real estate sitting in the pot under your marijuana roots, that material easily becomes waterlogged and stuffed with nutrients, and cause problems for your cannabis roots.
When you transplant marijuana plants, you have specific opportunities to enhance your marijuana plants’ root health, and their overall chances for success.
After my clones or seedlings are established and I’m ready to upgrade their pots, during the transplanting I do root pruning.
This means I remove brown or stunted roots, and I free stifled roots.
What I mean by stifled roots are roots that have had to turn sharp corners, are crunched, bunched, stacked, impacted, or otherwise assume unnatural patterns, especially if it’s because they bumped up against the walls of your container.
Any time your marijuana roots run up against a pot wall or bottom in a square or rectangular pot, they bend at a sharp angle.
If you envision marijuana roots the same way you’d think of a plumbing pipe or hydraulic tube, any time you have a sharp bend, crimp, or kink in the line, you get flow restriction and constriction.
This blocks the hydraulics of your marijuana roots, lessening the efficient movement of water and nutrients from your roots into your plants.
Many growers use round cloth pots that provide more aeration and oxygenation for roots.
Cloth pots also provide root pruning so roots don’t circle upon themselves and suffocate.
When you transplant marijuana if you see brown mushy circling roots, carefully and gently remove marijuana roots on the outer surface of the root mass if they’re brown, mushy, or if they’re rootbound.
Don’t rip the roots off.
Use precision trimming shears, and cut them, then gently separate them from healthy roots.
Brown and/or rotted roots are a sign of overwatering, lack of oxygen in the root zone, rootbound conditions, root zone toxicity, temperature issues, bad water, fertilizer burn, or any or all of the above.
In fact, when you transplant marijuana plants it’s a rare opportunity to examine root health as an indicator of various gardening parameters.
For example, if you’re using soilless mix or soil and your root zone is dripping wet and roots are rotting, this indicates overwatering, but could also indicate that your mix or soil is too dense.
If it’s your mix or soil that’s at fault, shake the loose material off your marijuana roots, do root pruning if needed, then make sure to add perlite or grow rocks to aerate the material you use for transplanting into.
In our next article in this series, we’ll tell you about soil formulations, feeding, and other prep so your transplanting creates healthier marijuana roots for bigger harvests of stickier buds!