Most of the prairie plants are perennials, and the old garden adage about perennials is that the first year they sleep, the second year they creep, the third year they leap. That you see as much yellow as you do is an excellent sign. You'll see less next year probably, and then the next year you can judge the success of the planting. I'd wait until year three to do anything like add seed, pull up plants, mow, burn. Now it is a waiting game. It does not look awful; it looks like a seed smorgasboard for migrating songbirds. Thanks to you, someone will have enough energy to make it all the way south this year.

If it is a very visible area, you can mow it in November, but you are going to chop some good plants that are sitting there waiting to grow next spring.

Thanks for the advice. I'm so tempted to just mow the thing down now, but I keep repeating "patience...patience" knowing that they'll leap eventually.