While you can winnow the seeds as soon as the heads are harvested there is a risk that the seeds will be too damp to be able to store them properly. To avoid this, it is best to first bag dry the seed heads before winnowing them. Bag drying also allows you to harvest the seeds a little earlier, which reduces the risk of the seeds becoming overripe and being blown away by the wind before you have a chance to harvest them.
Any seeds that have to be dried before being stored can be bag dried. Vegetable varieties that can be bag dried include lettuce, endive, basil, beetroot, rocket, Pak choi, Mizuna, broccoli, Brussels sprouts, silverbeet, carrot, peas, beans, and broad beans.
Instead of crushing the seed heads in a bowl and winnowing them as soon as you harvest the seed heads, place the seed heads in a large paper bag and hang them up in a well ventilated dry place away from direct sunlight for a couple of weeks to allow them to complete the drying process. Once they are completely dry you can process the seeds as per the method explained in Saving Lettuce Seeds.
Harvested lettuce seed heads being placed into a supermarket shopping paper bag.
Harvested seed heads hanging up in my garage. They should be left hanging up until the seeds are completely dry, which usually takes two to three weeks. Once they are completely dry you can process the seeds as per the method explained in Saving Lettuce Seeds. Note that it is also important to write the name of the variety of seed being saved on the bag so when you come to package up the seeds they can be labelled correctly.
Any large bag that allows the seeds to dry out and is strong enough to hold the weight of the seed heads can be used. Some options are:-
Supermarket shopping bags and takeaway food bags are ideal for bag drying seeds.
Larger seeds such as beans and peas can be hung up in onion bags or bags made using fine bird netting.
If you do not have any large paper bags handy you can make your own bags out of newspaper. To do this take a couple of sheets of newspaper, fold the side edges over and staple them together. Though note that they are not as sturdy or spacious as supermarket shopping paper bags.
Making a seed bag using two sheets of folded newspaper.
