I have managed to get harebells, ragged robin, campion and toadflax (thanks, Thifasmom!) to grow this year, but I started them in seed compost in trays then planted out, since I was only preparing a small area. Some companies claim wildflower mixes from seeds such as nigella, cornflower, marigold, which I think of more as hardy garden annuals, I grow these by germinating in in the veg plot and then planting out. Some of the genuine wild flowers are very tiny when they first show and easily mistaken for the chickweed or bittercress type of weed. After all, a weed is only a plant in the wrong place....