Growing Onions in Clay
I tried to grow onions two years ago from seed. It didn't go well. Onion seedlings are very tiny and pretty much impossible to keep weeded, so they died. Sorry little fellows.
I decided this year to try onions from sets - small onion bulbs that mature into larger edible onion bulbs. I purchased a healthy row's worth from Jesse Israel in March and planted them in the garden.
The thing about onions is that the bulbs need to have room to grow, and they need to be able to penetrate the soil in order to grow. With heavy clay like ours, that is quite a task for them, as I found out a couple weeks ago when I dug around a plant to see if it was ready for harvest. It's been three months and their foliage is starting to yellow, so they should be ready soon.
You can see that the bulb of this yellow onion has not grown to the size you would expect to find in a store, but looks more like one of those little "green onions" that my grandpa always dipped into salt and munched on at dinnertime.
At the farmer's market this weekend, I paid close attention to the local onions being sold. They were all shaped just like mine - no bulbous onions to be found.
I presented this quandry to Ian's grand-dad who has been farming for 60+ years, and he said you have to dig out around the bulb, leaving just the roots planted in the soil to encourage the bulb to ripen. He lives in Florida and grows in sandy soil, so if his onions won't mature on their own, my clay-bound onions have no chance. So, I grabbed my spade and dug those suckers out.
Time will tell if it works. I hope so, because I need some onions to go with my squash!