yellow sweet clover is done

I do not know for your area, but here once you have sweet clover go to seed you have it for ever. It would be impossible to plant alsike clover where the sweet clover had been. When mine is through blooming I mow it down and do not till. The next spring it will come up like hair on a dogs back.
Dave

Humm, I have about an acre of white clover next to my house, it's been raining on a regular basis here, so my neighbors mow it down, and a new crop appears, my girls are all over this clover, lucky year for me, usually, after July 1st, things dry up, but not this year, everything is doing great.

Let it go to seed. Did you only plant it once? if so, you should have planted some more this spring as it's a biennial and blooms once every two years. No need to plant this year if you let it go to seed, but you should plant some next fall. If you plant an equal amount of white sweet clover, it will bloom two weeks later and last two weeks longer. Our yellow is done here as well, but the white is going strong.