When seed starting, it’s easy to focus on what’s happening above ground. But it’s just as important not to forget what’s going on below the surface.
A common question is when young seedlings need to be moved into a larger pot. A usual piece of advice is to repot when roots start poking out of the drainage holes at the bottom. Depending on how the roots grow, this can happen very quickly—while the plant itself is still quite small.
Another useful rule of thumb is that plants, very roughly, build about as much biomass below ground as above ground. So when the above-ground part would be hard to squeeze back into the pot it’s growing in, it’s probably time to repot.
Even if the plant looks healthy, the roots may already be short on space, air, and fresh soil. For trees and shrubs especially, it’s important not to let them grow too long in the same pot, as this can lead to root circling—long roots following the pot wall around and around. Once planted out, those roots can constrict each other and limit the plant’s growth. In those cases, it’s often better to trim roots that can’t be untangled than to leave them as they are.
Keep your tools close at hand and repot a few plants at a time. It’s easy to put it off for too long and suddenly realize how many plants have outgrown their pots.
Good seed starting is all about balance. When plants get the right amount of light, nutrients, water, and warmth, they grow in their natural pace. That makes it easier to see when they need more space—and results in sturdy, resilient plants ready to thrive once planted out.
