We've done white clover in our 3 beds, between all the flowers, for the last 2 seasons. We do, still, apply a layer of mulch at first frost but that's because we're Zone 4b. I love my clover, I think it fills the empty spaces really well, it's a nitrogen fixer, so I feel like it's helping the other flowers, and as long as the other plants are already established, the clover hasn't snuffed out the "good" plants, just the "weedy" growth. The only 2 things to keep in mind are (1) I found if I plant small/really young plants while the clover is established, the clover will need to be plucked until the new flower has good growth. And (2) the clover itself can get a little wild, but again, we bring it right down and mulch in the winter. Good luck!