Prepared by Bob Polomski, Extension Consumer Horticulturist, and Lisa Wagner, Education Director, SC Botanical Garden, Clemson University. (New 05/99.)
Growing wildflowers in gardens and landscapes continues to rise in popularity for several reasons. Wildflowers add interest and beauty to any landscape. They often attract birds and other wildlife. Some species can be used as cut or dried flowers.
What is a wildflower? A horticultural definition is a flowering plant that grows in a natural uncultivated state or survives in a given area with little care. They may be annuals, biennials or perennials. Most are native to the United States.
Although wildflowers require little maintenance, especially when compared to traditional cultivated gardens, they do require some level of effort. You need to spend some time on the proper selection of wildflowers, knowing that the success of a wildflower species or mixture depends on the adaptability of the species to its environment. Select the right wildflowers for your area. Be aware that many wildflowers have specific needs regarding soil, light and moisture. In some cases, the conditions can be changed to create more favorable growing conditions, but in the long run, it is always easier to select wildflowers that are suited for the existing location.
Wildflowers vary in their moisture requirements depending on their natural habitat. There are drought-tolerant wildflowers such as black-eyed Susan (Rudbeckia hirta), butterfly weed (Asclepias tuberosa) and wooly mullein (Verbascum thapsis). Moisture-loving wildflowers such as cardinal flower (Lobelia cardinalis), rose turtle-head (Chelone obliqua) and pale gentian (Gentiana villosa) are best cultivated in low, moist areas of the garden, including bogs and along stream banks.
Consider the low maintenance approach to wildflower gardening by choosing species that are drought-tolerant, knowing that watering may be necessary to help them get established. Once they are established they will not require supplemental irrigation. Avoid wildflower species that have high moisture requirements unless those conditions exist naturally in your landscape.
Many wildflowers have specific soil requirements. Most prefer well-drained soils, while other species can be grown in poorly drained, boggy conditions. Woodland wildflowers prefer soils high in organic matter; meadow species prefer less fertile soil. To choose the right wildflowers for your situation, familiarize yourself with the site and the cultural requirements of the particular wildflowers.
To improve the growing conditions for your wildflowers, maintain the proper soil pH by having your soil tested through your local Clemson Extension service. See HGIC 1650, Changing the pH of Your Soil, for an explanation of soil pH, and HGIC 1652, Soil Testing, to learn how to take a soil test.
Wildflowers can be propagated or reproduced through sexual (seed) and asexual (vegetative) means. Seed propagation is easier and less expensive than vegetative propagation by division or stem or root cuttings. You can, however, expect a certain amount of variability among the seedlings.
Propagating wildflowers from seed is similar to propagating cultivated annuals and perennials. Many seeds will germinate as soon as they ripen or dry. Others may require a period of stratification - moist, cool temperatures of six to 12 weeks at around 40 °F. Stratification satisfies the dormancy requirements of the seeds that cause germination to occur.
Some seeds with hard seed coats need to be scarified - a chemical or physical treatment which breaks down the seed coat to allow the seed to absorb water. Some wildflower species may require both stratification and scarification. Before seeding, learn about the specific germination requirements of the species.
For slow-germinating wildflower seeds, seedlings that are slow to develop and those with few available or rare expensive seeds, sow the seeds in flats or other containers instead of directly to a bed outdoors. Select a well-drained, well-aerated medium that holds adequate moisture, such as a mixture of peat and sand or commercially available peat-lite mixes. The seedlings can be transplanted to individual containers or directly to beds after they have reached sufficient size.
Soil Preparation: Wildflowers germinate and grow best in soils that have been prepared prior to seeding and have plenty of moisture available. In South Carolina, sow seed from September through November when the soil temperatures are cool. This time is ideal for spring- and early summer-flowering wildflowers. Seeding in the fall takes advantage of rains and cooler soil temperatures. The seedlings, especially winter annuals and perennials, can become established during this favorable time.
Spring plantings from March to late April are fine if you pay attention to meeting the moisture demands of the young seedlings. Perennials planted in the spring generally will not flower until the second growing season.
Transplants or container-grown wildflowers that flower in early spring are usually best transplanted in the fall. Those that flower late in the year are best transplanted in spring. Late spring- and summer-flowering species can usually be planted in spring or fall. There are, of course, many exceptions depending on the time of year the plant is active or dormant.
Once you select the planting site, submit a soil sample to your county Extension agent four to six weeks before planting to determine the soil pH and fertility levels of the site. Wildflowers tend to thrive at a soil pH from 5.5 to 7.0.
For meadow plantings, closely mow the area to be planted. After the regrowth reaches 6 to 8 inches high, spray with a nonselective postemergent herbicide containing glyphosate (Roundup) according to label directions. Wait several weeks before lightly cultivating the soil. If green vegetation is still present, make a second application of the postemergent herbicide. Avoid deep tilling which can bring more weed seeds to the soil surface.
When preparing a site for moisture-loving woodland wildflowers, it may be necessary to cultivate the soil more deeply to a depth of 8 to 12 inches deep and add generous amounts of rotted leaves or peat moss to retain moisture.
Generally, fertilizers should not be applied to planting sites because the added fertility will stimulate the growth of competing weeds. Also, do not use topsoil as an amendment because it contains weed seeds.Direct Seeding: Select wildflower species and mixes adapted to your area and planting site. For large areas use the seeding rate recommended for the individual wildflower mix or species, which is usually 10 pounds per acre. For smaller areas seed at the rate of 4 to 5 ounces per 1,000 square feet.
Mix the seeds with sand or perlite before broadcasting for easy and uniform application. Seeding large areas may be accomplished with a special drill seeder or by mixing seed with dry sand and then spreading with either a drop-type or rotary spreader. To ensure good seed-to-soil contact after seeding, lightly rake and tamp or roll the area. Following seeding, apply a light mulch of straw, pine needles or wood chips to conserve soil moisture and protect young seedlings.
Keep the planted area moist for four to six weeks during seedling germination and development. Planting when normal seasonal rains occur is ideal.
Transplanting: The transplanting techniques are similar to those for cultivated plants. Set the plant at the same depth it was growing in the nursery; for most wildflowers, the crown should be even with or just below the soil surface. Also, pay careful attention to watering during the first few weeks of establishment. Mulch to help conserve moisture and keep the roots cool. Some wildflowers with rhizomes or running underground stems benefit from several applications of a leaf mulch during the year to help conserve moisture and enrich the soil.
Wildflowers are "low maintenance," not "no maintenance." Without some attention, most will not flourish for long.
Weeding: Meadow wildflower gardens pose special maintenance requirements because of the potential for weed invasion. While a meadow garden does not have to be weed-free to be attractive, extremely vigorous or invasive weeds may require control. Isolated weeds can be removed by hand, and herbicides may be more effective in certain situations. Read the label carefully and exercise caution in the use of herbicides to avoid injuring desirable plants.
Fertilizing: Wildflower seedlings can be lightly fertilized when nutrient deficiencies are evident. Broadcast applications of 500 to 1,000 pounds per acre of general purpose fertilizer in spring or early summer can benefit wildflower plantings in typically infertile sites.
Mowing: Generally, meadow gardens should be mowed at least once a year in late fall or early spring at a height of four to six inches. Small areas can be cut with a swing blade or scythe. During the growing season several mowings may be needed around the outside of meadow plantings to better define the wildflower beds.
Wildflowers are not pest-free. Wildflowers persist in given areas largely because they adapt to soil and climatic conditions and are less prone to serious insect and disease problems. Thus, an important consideration in choosing wildflowers is their relative freedom from pests.
Many commercial wildflower mixes for meadows are available that have been designed for the Southeast. Ideally, the annuals and biennials reseed themselves, and the perennials go on blooming year after year. In practice, however, some species disappear while others flourish, so that the mix of species and colors is likely to change with time and seasonal growing conditions.
For more information about specific woodland and meadow wildflowers that are suited for the southeast, refer to the following publications: Growing and Propagating Wild Flowers by Harry R. Phillips (1985, the University of North Carolina Press); Wildflower Gardening in South Carolina by J. B. Aitken (1994, Clemson University Cooperative Extension Service, EC 680); and Wildflowers by W.L. Corley and others (1995, University of Georgia Cooperative Extension Service Bulletin 994).
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This information is supplied with the understanding that no discrimination is intended and no endorsement by the Clemson University Cooperative Extension Service is implied. All recommendations are for South Carolina conditions and may not apply to other areas. Use pesticides only according to the directions on the label. All recommendations for pesticide use are for South Carolina only and were legal at the time of publication, but the status of registration and use patterns are subject to change by action of state and federal regulatory agencies. Follow all directions, precautions and restrictions that are listed.