The Maryland State Highway Administration Wildflower Program started in 1986 to reduce mowing, reduce air pollution, provide wildlife habitat, and enhance the aesthetics of the local highways. Over 300 acres of native and naturalized wildflowers have been planted along the roadsides and in medians of the state highways.
Our wildflower mixtures are formulated for planting in full or partial sun. Most of the species adapt readily to different soil types provided the rainfall is adequate. The State Highway wildflower mix has included one third of the mix with annual seed to establish quick cover and to give color the first year. Biennials will reseed but annuals usually do not. Perennial plants will flower from the second year onward. The SHA seeds 16 to 20 pounds of wildflower seed per acre.
SHA mixtures are blended to give a wide range of color and bloom periods. Wildflowers do not bloom continuously throughout the season. We have included spring, summer and fall blooming species in each mixture. Plant height varies from 1 to 5 feet. See the Wildflower Guide for color and blooming period of each species. Purity on most seed is 95 to 99 % and actual germination is from 40 to 90 %.
The wildflower mix includes a blend of native and naturalized wildflowers that cover a broad range of colors, heights and textures. Different varieties bloom at different times from April to October. The mix is made up of annuals, biennials, and perennials; most of which can be seen growing unaided along roadsides and fields throughout Maryland. The Black-eyed Susan, Maryland's state flower, is the dominant species in the mix. Other species include: Cosmos, Cornflower, White Yarrow, Corn Poppy, Dames Rocket, Evening Primrose, Gaillardia, Lance leaved Coreopsis, Ox-eyed Daisy, Gayfeather, Plains Coreopsis, Purple Coneflower and Rocket Larkspur.
Wildflowers will prosper if you plan ahead to ensure good results.
TIME TO PLANT
We recommend planting in the spring or fall for best results. Spring seeding should be completed as soon as the ground is workable to take advantage of the spring rainfall. Fall planting should be late enough so germination does not occur until the following spring or seedlings will be lost to winter freeze.
The SHA seeding rate is about 16 to 20 pounds per acre. Minimum rate is 5 to 10 pounds per acre and maximum planting rates are 8 to 22 pounds per acre. Avoid using more than the recommended rates since poor perennial establishment may result.
WEED CONTROL PRIOR TO PLANTING
A wildflower planting requires the same weed control as traditional landscaping. Before planting, remove existing weeds by tilling or by using a nonselective herbicide such as Roundup Pro or a combination of these methods.
For seeding large areas over 1 acre, the SHA uses a specially designed wildflower drill seeder (see the enclosed list of contractors with this seeder). Drill to a maximum of ¼ inch and firm soil with a cultipacker. This will ensure good soil/seed contact. On small sites after the site is tilled use a hand cyclone or drop seeder to apply the seed. We recommend using a carrier such as dry sand to mix with the seed to add volume and aid in even distribution. Use 1 or 2 parts sand to 1 part seed. Rake in lightly, covering seeds to a maximum of 2 to 3 times their thickness.
If Mother Nature does not provide ample rainfall to germinate and develop healthy seedlings you should soak the planted areas thoroughly and maintain moisture for 4 to 6 weeks, then gradually reduce waterings. During drought conditions up to ½ inch of supplemental water per week may be required to maintain a good display of flowers.
Fertilization is most beneficial if the soil is sandy or poor in nutrients. When soil quality is unknown it is recommended to perform a soil test. If the soil needs improvement, we use fertilizer with a 10-22-22 (50 % nitrogen from 38-0-0 ureaform) ratio at the rate of 450 lbs. per acre immediately after seeding.
Prior to seeding SHA uses organic matter such as screened composted sewage sludge (spread evenly at depth of a 1/3 of an inch) or tree leaf compost (depth of ½ inch) in the place of fertilizer. The compost is rototilled in the soil at a depth of 3 inches. By adding compost in addition to adding nutrients, the organic materials improve soil texture, water retention and encourage beneficial microorganisms. Avoid over-fertilization, which will promote weed growth and tall foliage instead of flowers.
If the pH is below 6.0, lime should be added to the site prior to cultivation to incorporate the lime into the root zone. One ton of agriculture ground limestone per acre will raise the pH enough to allow for maximum nutrient uptake by the seedling roots.
The SHA is mowing twice a year, once in early summer to remove spring flower seed heads and then again in the fall. If you want to attract birds that feed on the wildflower seed, mow in the late fall after the flowers have gone to seed. Mowing to a height of 6 to 8 inches, will keep down the woody vegetation but leave the perennials to over-winter in the vegetative stage. Leave the residue on the ground; the seed may germinate in the spring.
After the flowers have germinated weeds should be controlled as soon as they can be recognized either by pulling, spot spraying with a selective herbicide or selective cutting with a string trimmer.
Sometimes it is necessary to reseed in the second and additional years if establishment of wildflowers is poor or spotty. The bare areas can be reseeded with the original mixture either in the spring or fall. Loosen soil, provide weed control and watering as needed.
FOR ADDITIONAL INFORMATION CONTACT:
Maryland State Highway Administration
Office of Environmental Design
Landscape Operations Division
707 N. Calvert Street
Mail Stop C-304
Baltimore, MD 21202
e-mail at [email protected].
Click here to see the Highway Wildflower Guide.
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