Prior to modern cultivation, pasturing and development, wildflowers and warm season grasses covered much of the country. Called wild because they grew wild, that does not mean that they grew without maintenance. Actually they received much of what they needed through several natural processes. Wild fires were essential in destroying woody growth and other competitors. Animals such as bison added to the natural benefits as well. Today, gardeners get satisfaction from growing wildflowers because the flowers are pretty, and people feel that they are growing something that is part of nature. However, without the once naturally occurring maintenance, wildflower plantings are not easy to establish, requiring in most regions of the country efforts beyond tillage and seeding.
First, select the wildflower seeds. Good selections of single-species or blends of seeds are available from vendors nationwide. Blends may include twenty or more species, but only a few contribute colorfully to the stand. Some writers often downplay annuals; however, they are an important component of a mix, for they add color in the first year of planting. Biennials and perennials do not contribute to bloom until the second and following years. Spring seeding is recommended to ensure a stand of annuals blooming the first year. Seedlings in May will bloom by mid-summer. The area for planting should be mowed closely or tilled shallowly. How you prepare the ground for planting is not important, since weed control is inherent in this procedure and seeding is into a mulch of compost rather than directly onto the soil surface.
Many weeds and grasses exist today that are either exotic to the area or much too competitive for wildflowers to succeed. You must lay a weed-suppressing barrier on the soil. This layer can be 4 sheets of newspaper, 1 sheet of craft paper, or 1 film of landscaping fabric (spun bonded polyester) or other root-permeable sheeting. Compost is placed directly on the weed-suppressing mulch. A ½ to 1-inch thick layer of compost is recommended to hide the underlying barrier and to give a good medium for seed germination. With a 2-inch layer of compost, no barrier may be needed, for this thickness will likely suppress weed emergence. The research demonstrated that plantings of wildflowers in compost overlying barrier mulch are virtually weed free, controlling even aggressive perennial weeds. Composts of biosolids and woodchips or farm manures and crop residues are recommended. Leaf and yard waste composts are acceptable but likely contain weed seeds and are poor in nutrients, requiring extra fertilization.
Seed the wildflowers directly in the compost mulch; rake lightly after seeding. Use the seeding rate recommended by the vendor, but roughly, 1 ox. of seed will cover 150 to 200 sq ft. Daily watering by rainfall or by irrigation is required for at least 3 weeks after seeding. Plantings require about ½ inch of water weekly after roots have grown through the compost and into the soil.
A seasonal and annual succession of bloom occurs with plantings of mixed species: annuals bloom in the summer and fall up to a killing frost in the first year; biennial and perennial species, notable Dame's rocket, Siberian wallflower, and Ox-eye daisy, dominate in the spring of the second year, followed by a summer and fall bloom of Black-eyed Susan; perennials dominate in the third year. A monoculture of Ox-eye daisy is common in 3 year old stands. Some intervention by the gardener is necessary to maintain a diversity of species. Short of complete renovation and starting over, mowing, scalping, and over seeding may be needed. Gardeners should not be disappointed if they get three years of beautiful flowers before renovation is needed.