A plant ready for repotting should slide out with the soil in one piece. If much of the soil falls free of the roots, the plant may not need repotting. If it does, there will likely be a solid soil-and-root mass in the shape of the just-removed pot. Roots should be white or light-colored. Black, dark-colored, or foul-smelling roots are usually signs of a serious problem, such as fungal disease.
Recognizing when it’s time to repot is the first step. Telltale signs include soil that dries out quickly or has become degraded; roots tightly packed within a pot or protruding from drainage holes; and water sitting on the soil surface too long after watering. Often a plant simply looks top-heavy or as if it might burst out of its pot. The best time to repot most plants is when they’re actively growing, in the spring or summer. However, plants can usually handle repotting whenever the situation warrants it.
To keep soil from leaking out the bottom of the pot, cover its drainage hole(s) with a paper towel, coffee filter, mesh screen, or pot shard. If you use a pot shard, place it convex side up to avoid sealing the hole. While it’s common practice to put gravel or charcoal in the bottom of pots, they don’t help with drainage and take up valuable space, so I don’t recommend using them.
Roots packed tightly in a pot don’t take up nutrients efficiently. To promote good nutrient absorption, trim the roots and loosen up the root ball before replanting. Use a sharp knife or pruning shears for this job, removing as much as the bottom third of the root ball if necessary. Don’t be surprised if what you cut off is a thick tangle of root tissue. Also make three or four vertical cuts about a third of the way up the remaining root ball.
Cut through any roots growing in a circular pattern to help prevent the plant from strangling itself with its own roots as it grows. If the roots are thick along the sides of the root ball, shave or peel away the outer layer. Or gently untangle the root ball with your fingers as if you were mussing someone’s hair. Do this along the top edge of the root ball, too.
To repot a small plant that’s easy to lift, put a few inches of moist soil in the pot and tamp it down lightly. Place the plant in the pot, centering it. The goal is to get the top of the root ball to sit about an inch below the rim of the pot. If the plant is in too deep, gently raise it and add more soil. If it sits too high, remove the plant and dig out some soil, or just dump the soil out and start over.
The proper size of the new pot depends on the plant and its potential growth rate, how well it’s growing under current conditions, and the ultimate size desired for the plant. Rely on your own idea of what a healthy specimen of a particular species should look like. When in doubt, go with a pot the next size up.
The second step is to get a plant out of its pot. If a plant is rootbound, it helps to water the root ball thoroughly in advance. For plants in small to medium pots, invert the pot and support the top of the root ball with one hand. Put your other hand on the bottom of the pot and use a downward throwing motion with an abrupt stop. Many plants will slip out after one or two throws. If not, knock the edge of the pot against a sturdy surface, such as a potting bench, still holding the pot with both hands. It may take a few good whacks to release the plant; be careful not to break the pot.
Most healthy container garden plants eventually outgrow their pots. A good way to reinvigorate a rootbound plant is to repot it. In my former job as a greenhouse manager, I spent a lot of time repotting container plants.
Trimming the roots and refreshing the soil give potbound plants a new lease on life
Young plants should originally be sowed in a container about the size of a Solo cup. This starting pot should be adequate for a few weeks before transplanting is needed. Once again, the very first transplant should occur after the seedlings have sprouted their 4th or 5th leaf set.
- Always monitor plants for symptoms of distress or overcrowded roots.
- Growers administering nutrients should cut the input in half before transplanting to avoid shock.
- Avoid overpacking the grow medium into a container during and after the transplant. This can compromise drainage and may damage root systems.
Once your cannabis seeds are germinated, they are ready to be put in their first container. At this point, the grower must decide how and when transplanting will occur.
A plant that is root bound may also appear under-watered. If a plant requires watering once or more a day, this may mean a transplant is needed. Plants that continue to grow while root bound are at risk of growth deficiency and disease, and may die off.
Some growers initially sow their seeds in large containers in order to bypass the transplanting process. The setback is that the roots will be suspended in a large amount of soil and may not absorb all of the moisture. This sitting moisture can then lead to root rot.
Not only do certain cannabis strains require more space than others, but growers will inevitably be working within their own garden’s parameters. How much room do you have available in your grow space?
When in doubt, always opt for slightly more space than needed. A plant tends to require 2 gallons of soil for each 12 inches of growth it achieves during its vegetative cycle. Knowing the potential height of the strain you’re planning to grow is a helpful consideration. (Note: information on a strain’s typical height can be found on most Leafly strain pages under Grow Info.)
Here are some indicators that your cannabis is ready for a new container:
Medium-sized indoor plants tend not to need anything more than a 3-to-5-gallon container as a finishing pot in the flowering stage. On the other hand, large outdoor plants may require several-hundred-gallon containers to reach their behemoth potential.
Transplanting cannabis is important if you’re using a pot or container to grow. Learn how and when to transplant, as well as how to avoid transplant shock in your cannabis plant.