Plant Parenting: How to Know When to Transplant
June 8, 2020
Two common mistakes that new plant propagators make include transplanting young seedlings or clones before they've developed a large enough root system -- or waiting too long to transplant. If you’re not sure how to gauge when a young plant is ready for transplanting to a larger container, the root system will tell you.
After gently removing two plugs from the growing tray, I can see that the tomato seedling on the left has rooted completely to the bottom of the cell and is ready for transplanting. The plug on the right belongs to a slower-growing dwarf variety; its root system hasn’t quite filled the entire plug and some soil has fallen away when I removed it.
If you transplant too soon, you risk failure,since the root system isn't big enough to handle the disruption or a bigger pot with more soil.
Waiting too long may stunt the plant & they may not recover.