Site Preparation and Weed Control
Choose a mix suitable for specific site conditions, such as dry, hot, south exposures; cooler, shaded, north and east exposures; or moist meadows. These conditions require different plant species. Seed companies often formulate their mixes for different site conditions. Most wildflowers grow best on well-drained, well-aerated soils. Others are adapted to moist meadows. On sites with poor or compacted soil or extensive weed populations, considerable soil preparation and weed control are necessary.
If weeds predominate on the site or if the soil has been disturbed by rototilling or construction activity, it may take up to a year to control weeds before you can plant wildflowers. Eliminating weeds prior to planting wildflowers is easier and less expensive than identifying and controlling them in newly seeded sites. Water the area to stimulate weed-seed germination and growth and then spray or pull the resulting weeds.
One method of sowing wildflower seeds with minimal soil preparation is to lightly cultivate or break the soil with a rake prior to sowing. If the soil is compacted, heavy clay, you may need to do some soil improvement. Incorporate organic matter, such as compost or sphagnum peat moss, into the top 6 inches. Three cubic yards of organic matter per 1,000 square feet, or about enough to cover soil 1 inch deep, generally is sufficient.
After incorporating organic matter, water the area to germinate any existing weed seeds. Spray these weed seedlings with glyphosate (Roundup), glufosinate (Finale) or another appropriate herbicide. As with any pesticide, read and follow label directions. Remove dead weed debris prior to planting wildflowers. The number of times you need to repeat this water/spray process depends on the degree of weed infestation and types of weeds prevalent.
On sites where other desirable vegetation exists, cultivate the soil lightly or break it with a rake, then sow wildflower seeds so they contact the soil.
Seeding
Fall is a good time to sow wildflower seed because subsequent winter cold and snow (moisture) will promote seed germination the following spring. You may need to water in the spring to germinate seeds if winter moisture is insufficient. For spring or summer seedings, water to germinate seeds if rains are insufficient.
To prevent seed from blowing, provide additional protection on exposed, windy sites. Seedlings emerging in late summer may not become well established and may be killed by fall frosts.
Depending on the mix or species selected, sow 4 to 8 ounces of seed per 1,000 square feet. Exceeding recommended seeding rates may result in poor stands, especially of perennials shaded out by too-dense annuals.
For an even distribution of wildflower seed, mix six parts dry sand with one part seed. For small areas, spread the mix by hand. On larger areas, use a cyclone-type fertilizer/seed spreader. For small areas, light raking can help ensure good seed contact with soil. For large areas, it's faster to pull a section of chain-link fence behind a tractor.
Wildflower "sod" is available as an alternative to seeding. Although considerably more expensive than seeding, you may wish to use it on steep slopes or where you want quick establishment of wildflowers.
Maintenance
After wildflowers are established, pull weeds as soon as they can be identified and before they set seed. During extended dry spells, supplemental water can help wildflowers look their best. If initial soil preparation was done, little if any fertilizer is required. After plants brown from killing frost, mow wildflower areas to distribute seeds set by plants. Cut stalks to 4 to 6 inches and leave clippings on the ground. In the second and succeeding years, the appearance of the wildflower planting may differ due to bloom of biennial and perennial species. Additional seeding can be beneficial if your wildflower stand is not satisfactory or plant growth was spotty or poor. Some species of wildflowers are toxic to grazing livestock (e.g., lupines and larkspurs). Observe which wildflowers escape from your landscape to rangeland, open space, wetlands or other natural areas. Remove escaped plants and replace them with less aggressive species.
For more information, please see fact sheet 7.233, Wildflowers in Colorado.
