Size matters

In the business of growing cannabis, pot size might not come up as often as irrigation and lighting – but that doesn’t mean it’s not important. Commercial cultivators are tasked with maintaining the optimal environment for their plants, and that means regularly assessing whether they’re using the best pot size for cannabis by growth phase. As plants grow their needs change, but choosing the best size pot for cannabis isn’t just about the plants. It’s also an example of how making incremental changes can save your team valuable time and labor in the long run.

The Best Pot Size for Cannabis Cultivators

When it comes to determining what size pots to grow cannabis, the plants can tell you a lot. As plants grow their pots stay uniform, so the best-size pots for cannabis seedlings may not work once they’ve reached the flowering phase. But how do you know for sure? Outside of pulling data from substrate sensors, your own labor could be a strong indicator.

Let’s say your potted plants are in a growth period that requires giving them an additional irrigation shot during the dark period at night. Adding this nighttime feeding, or P3, is less than ideal because it means the plants aren’t getting enough water during the day to be able to support their needs at night  – and that’s most likely because they’re too big for their pots. 

Remember, roots need room to grow, so when a plant has outgrown its container, its ability to retain nutrients becomes a lot more difficult. This ultimately has to do with volumetric water content (VWC). Drybacks mark the decrease in VWC percentages between the last irrigation event of a given day and the first irrigation event of the next day. As cultivators look to steer their plants toward particular vegetative or generative outcomes, growing plants in the wrong-sized pots could have a negative impact on drybacks and ultimately yields. Plus, your grow team could be having to perform more tasks (like adding a P3 shot) to keep the plants growing in the right direction. 

Sometimes Bigger Is Better (But It Depends)

In the above scenario, going with a larger pot size is better for the plants and could eliminate the need for a P3. That’s one less chore on cultivators’ to-do lists, and less water used for irrigation – that’s the kind of resource-saving that all producers can get behind. But a bigger pot won't always be the solution; going smaller may make more sense in facilities dealing with space limitations, for example.

The point is, picking a pot size isn't a one-and-done decision. Choosing containers that accommodate what’s happening in the root zone at all phases can go a long way toward setting your plants (and you) up for success. For more on the importance of choosing the right pot size, check out this segment from Office Hours Episode 44.