Due to varying characteristics of plants in a wildflower mix, the appearance of the planting may differ from year to year as some species thrive and dominate less aggressive species. The type of wildflower seed mix you choose depends on site conditions and the effect you want to create. Commercial seed mixes may be formulated using a variety of flowers with different heights, colors and bloom times. Usually, a mix of self-seeding annuals, biennials and perennials is most effective. Wildflower mixes also may contain some grass species, which can fill in spaces around flowers, add texture and color contrast, and provide support and protection to wildflowers.
Grasses also can reduce soil erosion and enhance wildlife habitat.
On steep slopes, existing or seeded grasses can reduce soil erosion until wildflowers become established. Use plastic netting, jute twine or straw mulches on the soil surface to help establish wildflowers on steep slopes. Because some wildflowers can be aggressive, you may lose the diversity of a wildflower planting. Their aggressiveness can be compounded by site conditions. Some species invade areas where they are not wanted.