Our onions are started in January to give them enough time to become stout transplants when moved to the field. Most of the onions that we grow are what are called long day onions (which realy means short night but thats another story). This means they have to put on a lot of growth before bulbing is induced. Up here that happens around June 20th or so. We do all we can to give them a head start inside. Trimming the onions helps them thicken up while still in the speedling tray.
First we sow our onions into speedling 200 trays about 1/4in. deep, 0ne to three seeds per cell depending on variety. They are germinated at 65 F. and begin to emerge ten to fourteen days later.
It's not long before they start to put on some serious growth
We do an early trimming that is hard to get through because they are so wispy. This early trimming pays off because they bounce back quickly and begin to thicken into what look more like onions.
By this time it's time to make room in the front house for other things. We time the second cutting of the onions with moving day so that we handle them only once. We use an electric hedge trimer like you might use on the shrubs around your house.
We then move all the onions into the early Tomato house so that they stay nice and warm and can thicken up again.
Depending on the way the year is going these onions may be trimmed again or they may simply be moved out side for planting. If it looks like we won't be able to get out onto the fields for awhile it pays to trim the onions again. If we will be able to plant the first week of April we generally let them grow on and keep growing to they have momentum going out in the field.