I grew crimson clover in a large plot several years ago and it did well as a green manure when turned under in the Spring. I'd allow it to bloom it's purplish/pink flower tops to attract beneficials before plowing or turning it under to breakdown 5-6 weeks or so before planting other crops. That way it never went to seed and it never spread for me.

The seed of Melilotus alba and M officinalis, yellow and white sweet clover, is not wind dispersed. Nor is that of Trifolium incarnatum, crimson clover. The seed is too heavy and has no wind dispersal mechanism but it can be dispersed by animals.

if your garden area is well defined by a sharp cut edge then it shouldn't be possible to confuse it with the lawn and the city should not chase you about it.

Well, here in Texas they're dispersed by water and wind. Go figure.

https://www.texasinvasives.org/plant_database/detail.php?symbol=MEOF

It is true that the seeds lack appendages for optimal wind dispersal, but they'll migrate handily at least with animals and water.

Maybe the wind in Texas is stronger than in the rest of the world.

Seed dispersal: Because sweetclover lacks appendages for wind dispersal, most seed falls near the parent plant (review by [49]), but observations and experiments indicate that long-distance dispersal by animals and water is possible. Long-distance dispersal may also occur through the transport of contaminated seed or animal feed ([14], review by [49]).

https://www.fs.fed.us/database/feis/plants/forb/melspp/all.html#DISTRIBUTION%20AND%20OCCURRENCE

Of course, all it takes is for one seed to be dispersed. That's all an "invasion" really needs. But I agree that turning it under before seed heads form is a smart approach. The stuff is a powerful nutrient scavenger, and offers nitrogen fixing and improved soil structure.

The yellow sweetclover is a bi-annual and dies after seeding. Some clovers live longer and are harder to deal with...getting the roots worked up.

Beware that clover can also attract pest insects. Bean aphids are one example that can then migrate to your patch of green beans and spread bean mosaic virus. I have quite a bit of clover around my gardens and have to grow bean varieties that are resistant to bean mosaic virus.

Buckwheat is a good fast growing cover crop for spring and summer. It will readily reseed itself if allowed too but is not wind dispersed. It also attracts bees better than any anything I've ever seen. Mining Phosphorus from the sub soil is it's forte.

Of some interest is that fact that sweetclover seeds can survive for many decades in soil. So they have plenty of time to disperse. Infestations can persist for a long time.

Thanks for all the helpful comments everyone. When I called my seed supplier (Rohrer's in Lancaster), they said try berseem clover. It outproduces yellow sweet clover and others: https://www.sare.org/Learning-Center/Books/Managing-Cover-Crops-Profitably-3rd-Edition/Text-Version/Legume-Cover-Crops/Berseem-Clover