In this installment, we explain why progressive transplanting is important, while offering insight into why various container sizes benefit certain growth stages. Finally, we’ll review some techniques for successfully transplanting cannabis.
Why Is Transplanting Important?
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.
For this reason, most growers opt to start seedlings in smaller containers before gradually transplanting them into their “finishing pots.”
When growing cannabis in containers, the number one limitation for plant development lies with root expansion. Roots need to expand and develop in order for a plant to grow and flourish. Containers determine the amount of space available for roots to grow, and cannabis requires transplanting in order to reach its full potential.
Furthermore, when root systems outgrow their environment and do not have enough room to expand, it may become “root bound.” The symptoms of a root-bound plant include:
- Flimsy new growth
- Stunted flower production
- Stem discoloration (reddening)
- Nutrient sensitivity
- Nutrient deficiency
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.
Gradually moving plants from smaller containers to slightly larger ones will allow the roots to develop, while getting the most from their containers. When the plants are ready to move into the flowering stage, they should have plenty of room in their finishing pots for the roots to flourish.
When Is the Right Time to Transplant?
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.
Here are some indicators that your cannabis is ready for a new container:
- Number of Leaves: Young plants sowed in small containers are ready to be transplanted after they’ve sprouted 4-5 sets of leaves (not including the cotyledon). This may vary in some strains, but at this point, roots have typically overgrown their starter cup.
- Root Development: When checking perforations at the bottom of a container, a plant should have a healthy and visibly white root system. Any discoloration or darkening may indicate that the plant has become root bound, and a transplant must take place immediately.
- Vegetative Stage: Many opt to transplant to a finishing pot in the final two weeks of vegetative growth before a plant transitions into the flowering phase. At this point, a plant will explode both in size and volume and will require a substantial amount of space for root development.
How Much Space Does Cannabis Need?
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?
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.
A plant tends to require 2 gallons of soil for each 12 inches of growth it achieves during its vegetative cycle.
When transplanting, it’s advised to give the plants at least double the space of their previous container. This reduces the number of times you must transplant, and therefore minimizes the risk of “transplant shock,” which may occur when a plant experiences extreme stress from root disturbance.
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.)
How to Transplant Cannabis
The process of transplanting does not come without risk. Transplant shock can be incredibly detrimental to the growth and development of a plant, even deadly in some cases. However, through proper execution, the process of transplanting should benefit the plant, leading to stronger root development and healthier flower production.
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.
After checking the root development and confirming that the plant is beginning to fill the basin with healthy roots, it is time to choose a successor container.
- Wash your hands and/or wear gloves to prevent contamination of the delicate roots. Keep the surroundings as sanitary as possible.
- Try not to water plants the day before their transplant. This will allow the soil to stick a bit when being removed from the starter container.
- Make sure the receiving pot has been filled with your grow medium and there is enough space to safely transplant.
- Do not disturb or damage the roots when transplanting. The first transplant poses the greatest risk for shock, and this occurs as a direct result of root damage and agitation.
- Avoid intense light when transplanting. This will help prevent transplant shock as well.
- Always administer a healthy amount of water after a transplant.
After the initial transplant, all others should be based on root expansion until a finishing container is selected. Remember, a plant tends to require 2 gallons of soil for each 12 inches of growth it achieves during its vegetative cycle.
Plants should maximize the space in their current containers before a new one is chosen. This process may continue for as long as a grower intends to keep their plant in a vegetative state. Oftentimes “mother” plants–used for cloning–are transplanted into larger pots so that they may continue to vegetate for long periods of time.
- 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.
A finishing container is the final holding place for a plant during its flowering cycle. This will be the largest container used during the grow, and it is highly recommended that plants are placed in finishing pots prior to the flowering stage.
- Do not transplant after the plant’s flowering cycle has begun. Transplant shock can cripple the early development a plant undergoes during this phase.
- Give the plant at least 1-2 weeks after a transplant before initiating flowering.
- Have plenty of space available in the final container for a plant to fully develop. For indoors, this means 3-5 gallons depending on strain selection. For outdoors, 5+ gallon containers are recommended (again, depending on the strain).
- Larger plants may require stakes and other supporting mechanisms to avoid structural damage during and after transplants.
If performed correctly, the benefits of transplanting can be profound. There is a lot of room for customization when it comes to transplanting progression, with different systems suiting various grow styles and container options. The most important aspect of a successful transplanting routine is that grower gets what they want from their garden and gets the most out of the containers they choose to grow with.