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I have some Mammoth sunflowers that I began to harvest today. Many of the seeds are empty inside, but not all. Maybe 50/50.

I'd like to keep many of them to sow next year.

Is there an easy and reliable way to determine which are worth keeping? I have five plants, each with hundreds of seeds, so checking them one by one seems awfully tedious.

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  • Do the empty seeds float?
    – csk
    Aug 23, 2021 at 1:15
  • If convenient, see if the quality of the seeds in the centre of the flower are different from those near the edge and get back to us. Aug 23, 2021 at 1:19
  • @csk I had thought about trying that. I just chopped the heads this afternoon so they still need a few more days before I can try that. As well, I wasn't really sure if drying them and then getting them wet again was a good idea.
    – pspahn
    Aug 23, 2021 at 2:42
  • @PolypipeWrangler I've only cut two heads so far, but it does appear the ones in the center are less mature than those near the edge.
    – pspahn
    Aug 23, 2021 at 2:43
  • In nature, the head would stand there through all weather, drying out and getting rained on more than once. So I wouldn't think it would harm the seeds to wet them after drying them. But it might be inconvenient for you, to have to dry them twice. You might also try putting the loose seeds in a bowl and shaking them; lighter-weight ones might rise to the top and heavier ones sink to the bottom.
    – csk
    Aug 24, 2021 at 1:57

1 Answer 1

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What you want to look up is "winnowing". You can do it with just a big bowl and a bit of wind. Search for "sunflower winnowing".

Youtube has lots of videos with different techniques but most are fundamentally the same: shake a bowl of seed near the edge of the bowl and let the light ones fly out from the wind.

The process of removing the seed from the flower head is called threshing. For large fields, there are mechanical threshers. They're quite interesting to see in action!

I've had similar problems when I've grown just a few sunflowers by themselves. I guess there wasn't enough pollination going around. When I collect seeds for roasting I'm now growing multi-headed flowers nearby and a handful of the mammoths together. It's helped yield a lot.

If you're saving seed to regrow, don't mix varieties (so no small multiheaded sunflowers). Otherwise they hybridize and you lose the mammoth genes. You'll just have to grow more of them close together and hope they flower around the same time.

Hope you have better luck next year!

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    Thanks, I'll be giving this a try after I cut down the main flowers on my biggest stalks over the next week or two. I'm not 100% expecting the seeds to be true to their genes, since there's quite a few volunteers in the area that I don't have control over. None of them were very close to my mammoths, but were within maybe 100 feet or so. I was actually hoping to see what I got when hybridizing them with some deep red/purple sunflowers I had at home in containers, but they only began flowering recently while the mammoths flowered awhile ago.
    – pspahn
    Aug 25, 2021 at 2:08
  • 100ft is still close enough for the bees! It's fun seeing what grows out of hybrid seeds sometimes. Not great if you're trying to keep a heirloom exactly the same, but I enjoy it.
    – Josh
    Aug 25, 2021 at 5:27

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