Answer: You'll need to eliminate the grasses first because they'll outcompete the wildflowers. Many wildflower seeds need a period of cold to germinate, so autumn sowing is usually best. If you can't prep the area until next spring, chill wildflower seeds in the freezer for a couple of days, then thaw for a day before planting. This breaks seed dormancy and improves germination rates.
Here's how to prepare the site: mow and till the area shallowly (2"), to raise as few weed seeds to the surface as possible. Water the area a couple of times to get weeds to sprout, and do another shallow tilling to kill them. If you repeat this step a couple of times, you further reduce the amount of grass/weed seed left in the soil to compete with your wildflower seedlings. Broadcast the seed as recommended on the package label (they often recommend mixing seed with sand for even distribution), and then cover by raking. Snow melt and spring rains should provide enough moisture for germination, but if it's an extremely dry year, you may have to water.
Once the flowers are established, cut them back only after the first hard frost and drop the plant material there to spill seed. This annual cutting also removes any weed shrubs and trees that sprout. Never cut the field back in the spring, because many of the wildflowers are spring bloomers. If you cut it back then, not only do you lose your flowers, but you lose your seeds for next years bloom...and perhaps, since many are annual, you lose them all together! Above all, remember that wildflowers are essentially weeds! Don't be discouraged by their scruffy looks. That's the way they look out in the meadows where they grow naturally. In fact, most wildflowers do better and bloom more on relatively poor soils, so don't add fertilizer to the area unless a soil test reveals severe deficiency.
Some more considerations for wildflower plantings:
1. The balance of annuals to perennials: The first year you may have great success with the annual varieties, but when it's time for the perennials to take over the second year, annuals often decline in number.
2. The proportion of flower seed vs. grasses in the mix: Many wildflower mixes contain a relatively large percentage of grass seed. This grass can really take over a planting. It's best to use a 100% wildflower mix. It's more expensive, but you'll get more flowers. Plenty of grass will find its way into your flowers anyway.
3. Choose a regional mix that suits your climate. A good wildflower meadow should last for several years (or more). The only real maintenance should be an annual mowing, just after the first frost, to knock down brush and scatter seeds.
Q&A Library Searching Tips