If you’re not sure how much water is too much water, keep in mind that you want the growing medium (AKA the soil) to be damp and moist — not soaked and oversaturated.
The seedling stage can be an especially vulnerable time in the growing process. The cannabis seedling is in need of a lot of TLC to grow into a healthy cannabis plant.
Choosing the right pot is an essential part of caring for your growing plant. You need a pot that’s going to give the root system space to grow, but not so much space that the roots won’t be able to absorb all the water in the soil. You should also make sure the pot has drainage holes to get rid of any excess water that could overwhelm the plant.
Know the signs of nutrient deficiencies
But what does that TLC look like? What steps do you need to take to support your cannabis seedlings through the seedling stage and as they grow into mature marijuana plants?
When you’re growing cannabis, you want to keep your plants strong and healthy through every stage of the growing process — and that includes the seedling stage.
Environmental conditions are essential to growing healthy cannabis seedlings, and some of the most important conditions to control are temperature and humidity.
The root system of a seedling isn’t elaborate; the roots are small and don’t need much water to grow. Misting the plants with water once or twice a day should be plenty to give them the hydration they need to grow.
While cannabis seedlings like warm, humid conditions, too much heat can cause a plant’s leaves to grow slower than its stem, resulting in tall and stretchy growth. To promote healthy seedling growth, we recommend keeping the temperatures in your grow room or dome at 19–20°C during the day and roughly 13°C at night.
Fix stretching in cannabis seedlings, and prevent it from happening again.
In the same way taproots dig for water and nutrients, the top part of the plant will stretch vigorously if it’s not receiving enough light. It’s a survival mechanism in which a plant uses up all its stored energy to rise above competing flora. In the case of indoor growing, there is no competition, but the seedling will perceive it this way. For instance, leaving the pot under a windowsill in the shade will likely trigger this behaviour. Things can get even more dramatic under artificial light.
Other Potential Causes of Stretchy Cannabis Seedlings
Just like baby humans, cannabis seedlings are super fragile and need plenty of tender loving care to flourish. Unfortunately, many growers run into the same issue during the early stages of their cannabis plants’ lives; their seedlings grow long, stretchy, and weak stems. This, in turn, can lead to a host of issues that put your crop at risk of delivering subpar results.
Long, stretchy stems are one of the most common problems growers face during the seedling stage. Luckily, there are a few simple ways to prevent and fix stretching in cannabis seedlings.
Thinning is a common agricultural technique that’s often forgotten among cannabis growers. As the name suggests, thinning is all about reducing competition among your plants by “thinning” out the population.
More precisely, cannabis seedlings benefit from nitrate-derived nitrogen. Unlike ammoniacal nitrogen, nitrate-nitrogen is a lot easier for plants to absorb and fuels shorter, bushier vegetative growth. If your seedlings are stretching despite ideal light conditions, we highly recommend checking the ammoniacal nitrogen content in your soil and fertiliser.
First, you need to get a general idea of the final container size which will be based on how big you want your plants to grow. The less often you transplant, the bigger the final size pot you'll need because the roots will tend to grow out and cover the whole container if left too long. You can help avoid problems with roots getting rootbound by using a fabric pot (also known as a "Smart Pot") or an air pot.
Too Much Light = Burned, Crinkled Leaves
If the seedling isn't transferred to a bigger container in time, it can cause symptoms of overwatering, nutrient deficiencies, wilting, and sometimes very strange and unpredictable symptoms.
These small cannabis plants (below) were put in big pots, and were given enough water to support a much larger plant. The plants couldn’t drink all the water that was given to them and as a result, their roots weren’t able to get the oxygen they needed and started "drowning." Once the roots are out of commission, the leaves start drooping.
Planting in too big a container is sometimes called “overpotting.” It’s possible to get around this with special watering techniques (for example by giving plants just a little bit of water until they start “growing into” their containers) but starting plants in small containers and transplanting as needed can be a more straightforward way for some growers. Overpotting plants is also a waste of growing medium and nutrients, especially if the plants never get big enough to fully use their containers.