Hand pull the weeds as best you can then next spring you'll want to burn it or mow it very low, but don't mow it now!

actaully you could mow it now...or you could let it grow...

mowing the first year or two is usually recommended to keep weeds from going to seed, so if you are confident that you have weeds under control - you could let it grow.

watch for canada goldenrod though - its shows itself in the fall, its hard to tell from the desirable natives and is definitely one that you dont want to set seed.