When should you fold over the tops of your Onions to encourage them to start to ripen in readiness for pulling? Well, the answer is, when they start to do it themselves anyway. Once the bulbs are big enough and the tops are heavy then the plants will naturally start to bow their tops over. You can give them a helping hand by doing it for them and creating neat rows rather than messy beds.
When you do decide to bow the tops over make sure to do it gently and if you have more than one row bend the heads in different directions to get as much sunlight to the bulbs as possible. Remember the intention here is to ripen the bulbs and encourage the tops to dry out.
Once the leaves have dried out and you can pull the bulbs easily from the soil then your onions are ready for storing.