How to Successfully Transplant Cannabis Seedlings
Cannabis plants are, in general, fairly resilient. However, those in the seedling stage are more susceptible to issues from shock or distress. Cannabis seedlings are like baby cannabis plants and should be handled with the utmost care. The lifecycle of a plant is shaped by the earliest stages, so the seedling stage is arguably the most influential and important stage of growth in a cannabis garden. Growers who master a stress-free environment during this stage will be rewarded in spades by vibrant vegetative growth and, eventually, prolific blooms.
One crucial task in the seedling stage is the transplanting of young plants. When done correctly, a cannabis plant can seamlessly transition to its next chapter of life. When done incorrectly, a cannabis plant can lag behind; never fully catching up to its potential or, worse, meeting the catastrophic fate of dying before ever having a proper chance.
Ideal Conditions for Seedlings
Once the germination process is complete, the main goal for the seedling stage is healthy root development. This can be achieved by giving the seedlings a well-aerated starter substrate and as close to the optimal environmental conditions as possible. To ensure a cannabis seedling gets off to a solid start, a quality, highly oxygenated medium should be used.
For hydroponic growers, stonewool or coco can provide the well-aerated, yet moist, conditions for healthy root development. Stonewool also makes transplanting simple for those hydroponic growers who are using it in the later stages of growth. As the roots grow through the wool, the cannabis plant can be layered or inserted into the next size stonewool cube until the finishing size is reached.
Stonewool is not ideal for soil growers as even the smallest cube will have different water retention properties than the soil, which could cause a whole slew of problems once combined. Soil growers should instead rely on a well-aerated seed starter mix. In other words, a mix with a small amount of balanced nutrients and a high-oxygen holding capacity. A small planting container for seedlings is also highly recommended. Personally, I use a solo cup (8-12 oz) sized container for seedlings filled with a specific seed starting soil mix. Most seed-specific soil mixes will have upwards of 40 percent or more perlite or other aerating additive. This allows for a high oxygen capacity, which is imperative for healthy root development. It is also important (especially if using plastic cups or other homemade planting containers) to cut plenty of drainage holes in the bottom of the container. Proper drainage ensures oxygen gets “pulled in” when watering the medium. It also ensures the container will not hold too much water for too long. Seedlings do not do well in a waterlogged medium.
Environmental Conditions for Seedlings
In my opinion, it is best to use a florescent or LED lighting system for seedlings as the chance of overheating or scorching is minimized. Some growers prefer metal halides, but caution should be taken if using HID lighting with seedlings. Again, seedlings are very delicate and, if not used carefully, HID lighting can quickly burn or dry out seedlings to the point of irreversible damage.
As far as the actual light cycle goes, it is important to remember root growth occurs mainly during the dark cycle. It is not advisable to use a 24-hour lights-on cycle with seedlings. Instead, many growers find an 18-hours-on, six-hours-off light cycle the best for maximizing the growth of both foliage and roots. A full-spectrum light source, or white light, is ideal for seedling development.
Although some genetics are “stretchier” than others, a tell-tale sign that a light source is too weak or too far away is leggy seedlings. Most lower-wattage florescent and LEDs can be safety placed 6-12 inches above the seedlings. It is always better to start on the safe side, and a little higher up, and then move the light closer if it’s your first time with a particular set up.
The optimal temperature range for cannabis seedlings is 72-78°F with a relative humidity of around 70 percent. Depending on the individual indoor garden, a propagation dome and spray bottle are tools that make these conditions much easier to achieve. Also, a digital hygrometer is an invaluable tool during all stages of a cannabis plant’s lifecycle, but especially during the seedling stage. Make sure to monitor the humidity and temperature multiple times a day to ensure consistency. Cannabis plants thrive with consistency and cannabis seedlings are no different.
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Transplanting Seedlings
Knowing exactly when to transplant is an art form and experience is the best teacher. The correct time to transplant is just before the seedlings outgrow their current containers. For stonewool growers, this is easy to gauge as the grower will see white roots poking through the bottom of the cube. For soil growers, close attention should be paid to the seedling itself and its foliage development. As the seedling’s true leaves emerge, a good indicator of transplant time is when those leaves overtake the circumference of the top of the cup or planting container.
Another common indicator is when the seedling’s height has overtaken the height of the planting container (assuming the seedling is receiving adequate lighting). In some cases, the roots poking out of the drainage holes of the planting container can be used as an indicator for it being time to transplant. However, be careful not to wait too long as root-bound plants will take extra time to recover and may become stunted to the point where they never fully recover. Another general rule of thumb is the duration a seedling has been in its starting container. After the first set of “true leaves” develop, a seedling will typically need transplanting (from an 8-12 oz planting container) in 7-14 days.
Transplanting Techniques
When a seedling is ready for transplanting, start by prepping its new container. Do this by putting soil in the container, allowing extra room for the plant and the soil/coco coming with it. Create a hole a little larger than the circumference of the seedling’s current container. Make sure the soil is damp, but not oversaturated. Also, be sure to avoid packing the soil in the new container too tightly.
The goal is a nice, loose soil that makes way for new, healthy root development. The moisture level of the seedling’s current container should also be damp, but not soaking wet. This will make it much easier to work with during transplanting as the soil will be less likely to crumble. After the new container is prepared, take the seedling’s current container and flip it upside down while holding on to the top of the soil/plant stem so it doesn’t fall to the ground. Then, lightly tap or squeeze the container until gravity does its part and the seedling, along with the soil, drops out. Once in your hand, carefully flip the plant and root mass right-side up into the new container with the roots pointed downward. While continuing to stabilize the seedling with one hand, take a few handfuls of fresh soil with the other hand and gently spread it around the seedling until the new soil stabilizes the plant. Lightly press the fresh soil around the old soil’s perimeter and add more fresh soil if needed (do not pack the soil too tightly). Finally, lightly water the freshly transplanted seedling in its new container. The transplanting process can be repeated as needed as the plant continues to grow until the desired or final size container is reached.
Final Thoughts
Many cannabis growers like to minimize the number of times a plant needs transplanting as the transplanting process always produces some plant stress. However, there is a fine line to walk when trying to maximize the space of an indoor garden while minimizing stress. Many people wonder why not just plant the seedling directly into the larger, finishing size container? Again, the space in an indoor garden is valuable real estate. The more efficiently a grower can use his or her space, the more efficiently he or she will use the artificial light source. Efficient use of the light source, in turn, equates to better overall success. Planting directly in a large container also creates a situation where it takes too long for the medium to dry out between watering.
When considering the value of garden space and fear of an oversaturated medium, transplanting at least a few times during a cannabis plant’s lifecycle is generally the better choice. When done carefully and properly, cannabis plants (even in the seedling stage) can be transplanted seamlessly into a new container and continue to grow and thrive. Like all aspects of indoor horticulture, practice makes perfect. After a grower transplants a bunch of cannabis seedlings, it will become second nature.
Preparing the work space before beginning and taking your time during the transplanting process will go a long way in securing success.
