We know that our leeks need to be gently hilled to increase the edible white portion. But what about the onions?
A few years ago in Ontario, I saw a beautiful field of onions. The baseball-size bulbs were perched on top of the ground with just the very bottom rooted to the ground. This led me to wonder whether they were able to grow so large because they were not hilled, or whether there were other conditions.
I found the following opinions saying they should not be covered. If you know otherwise, please weigh in.
1. As the onion begins to bulb the soil around the bulb should be loose so the onion is free to expand. Do not move dirt on top of the onion since this will prevent the onion from forming its natural bulb.
2. Do not hill up soil on onions as this can encourage stem rot.
3. Onion bulbs should sit on the surface of the soil. Do not cover.