Today I will transplant bunching onion seedlings from their seed tray outdoors into a raised bed. I sowed the Ishikura Bunching Onion seeds in a 72-cell tray in the greenhouse on February 23rd, and they sprouted on the 28th. They have been growing in the greenhouse until today, and for the past week I have been hardening them off by putting them outside for several hours a day. The seedlings have grown so fast that I have had to trim the tops off several times. Each time cut them down to about 2" high, and they quickly grew back up to 4" to 5".
Bunching onions, such as the Ishikura, can be multi-sowed to provide more harvestable onions within much less space. I sowed approximately 300 onion seeds in a 72-cell tray, which means that there was an average of 4 seedlings per cell. Some cells only had 2 or 3, while other trays had 5 or 6, but the average was 4.