In this video I show the process of trimming the tops off of onion seedlings to keep them from getting leggy and falling over. Keeping them trimmed to less than 3" ensures that the plants will develop sturdy stems. I also thinned the vegetable seedlings to one per pot. The onion seedlings I trim in this video are Bunching Onions, also called Green Onions, which do not form bulbs so they are multi-sowed with 4 or 5 seedlings per cell of the tray. They will be transplanted into the garden still multi-sowed, and the bunch of 4 or 5 onions can be harvested all at once.
I cut the tops off of the onions at about 2" above the soil. Within two weeks they will grow enough to need trimming again before transplanting. When the tops are cut off they are kept for use in salads, or adding to things such as scrambled eggs.