Cleaning Onion Seeds

Hello! I was looking to see if there was anything on here about how to thresh/winnow Onion Seeds, but didn’t find anything. I was talking to someone the other day about how I clean my seeds, and he seemed surprised at how quickly it went. So here’s my process, if it would interest anyone. I cleaned about 180 grams of seed (~40k seeds) in about an hour.

I rub the very dry seed heads between my hands wearing silicone grill gloves to thresh the pods. Take from one bucket, thresh into a second bucket. Repeat 2 or 3 times until it looks like all of them are empty. Then I take the bucket to my water hydrant and fill it most of the way with water. All the chaff and bad seed floats to the top and the viable seeds sinks after about 15 seconds. You could wait a little bit longer. Then I scoop the chaff and bad seed off the top and decant the water off the top of the seed. Repeat until water runs clear and no more chaff. This really doesn’t take very long.

I dry them by spreading out on doubled paper towels and turn a low speed fan on them. Stir them around and change the paper towel several times until the seeds are dry. Takes less than hour to dry in my kitchen. YMMV. Trick is to make sure they are wet for as short a time as possible. But this removes the chaff AND removes non-viable seed very quickly.

Thoughts? How do you clean your onion seed? How long does it usually take?

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I was regrowing green onion heels after chopping the tops of store bought ones for use in the kitchen (I always try to plant them out as they work great as perennial markers of garden bed locations, etc.) and after a strong year of growth they flowered. I waited until most of the umbel was open and dry but not until the seed was blowing out, then clipped it off and rubbed everything between my dry hands over a clean container like the Chinese takeout restaurants in this area use for a quart of soup.


I pursed my lips and gently blew the chaff off the top, swirled the remaining seed to bring more of the paper shell of the seed to the top and did it again, just until I felt that it was clean enough for my liking. I’d reckon it was about five minutes I spent for the two onions that had grown large seed heads.