Hi there. It could be many different things of course, but the quality of the sets DOES come into play. So it could be that. Also, as my neighbor planting HIS first onions found out after I explained, you should not let the onions make seed clusters on top. They are gorgeous to look at and his are numerous and huge (over 3 inches). It looks like flowers from my window. He, however, has very little onions.

Once the onions start showing above the ground (that is how they grow, so like beets, just let them do their thing and don't mound dirt over them) you can see their size. Toward the end of summer the tops should start to fall over signifying that they are getting done with their growing.

You can push the necks (stems) over and even walk on them to help this process. You want all the energy to go into the bulb, not the top. When the onions are done growing, the necks should be very tiny and shriveled. Any onions with fat necks won't last well, so eat them first.

When you pull up your onions, you can let them dry above ground or in a shaded garage for a bit longer. Braid and hang them if you are into cool kitchen props or cut off the necks. Be sure and leave a couple of inches of neck on there. They will last better.

Hope that helps some. Weather makes a difference too of course. I had both marginal sets (other planted the same ones with unhappy results) and pretty much NO summer in Oregon. So my green onions were great, but the keepers? Not so much.

Good luck next year!

That was so helpful - thank you so much. I'm saving your info for next year as I'll definately try this again!

Are you trying to grow onions like you slice for burgers? Large onions? Maybe you need to start out with onion plants not onion sets.