When the tops of onions start to turn brown and fall over, they are ready for harvest. You’ll want to carefully dig them up and leave the tops on.
The next step is to cure or dry them. You need to lay them in a single layer in a dry, warm, sunny and well ventilated area. Depending on conditions it may take up to two weeks to fully dry. You will need to turn them so that they cure evenly.
When the onion tops and necks are completely dry and the outer bulb scales start to rustle, they are done. Braid the tops together and hang them in a cool, dry place. Make sure that the storage location gets good air circulation.
The storage life of onions will vary depending on the variety of onion and environmental conditions. So check them often. Any onions showing signs of mold, soft spots or sprouting should be used immediately.