See site preparation and planting instructions for more details on weed control and elimination. However, don't expect wildflowers to grow in an area that has no vegetation growing in it now. If the soil is too poor for weeds, it will not support wildflowers either. Sow your seeds at the proper depth. Water your seeds regularly and gently.
Germination can take place in just a few days, or can take several weeks.
Whatever the case, your seeds need moisture on a daily basis in order to sprout, and for 4-6 weeks afterward, too. Remove weeds on a regular basis. The reason for mowing is to keep weeds from setting seeds and from smothering out your seedlings. It depends on your site location and weather patterns. Generally, it's best to go by the amount of seasonal precipitation in your area rather than temperature.