I made the same mistake and tried to establish a chicory field this spring. I don't know how many times I've told folks not to plant a perennial like clover or chicory in the spring in my area because of weed competition. Frost seeding is the same. It works great to help fill in an established field, but there is just too much summer competition for establishment.
Like everyone else, I just got anxious. It was only one small field, but I wasted my time. I should have simply planted buckwheat for weed control and the rotated to chicory in the fall. Well, I guess I'll just see what happens and likely start over with it this fall.
Thanks,
Jack