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Roadside Use of Native Plant

Preventing Wildflowers From Becoming Weedy — Wildflowers are Not a Bunch of Weeds

Bonnie L. Harper-Lore, Federal Highway Administration

Weeds are more than plants out of place. Weeds have many definitions. I chose to use one that evolves from State Noxious Weed lists, for which DOTs are responsible. Weeds are invasive plants that compromise agriculture, human health, and/or the environment. States have noxious weed laws to identify and control these problem plants. Because weed problems are escalating across the country and because road corridors often help move weeds across State borders, roadside managers are now beginning to watch for encroaching weeds from adjacent States.

Wildflowers, (per the STURAA requirement), are flowering native herbaceous plants including grasses. They rarely are invasive and rarely make a weed list. On the contrary they are often hanging on to remnant habitats that are being invaded by nonnative plants, or weeds. For example, my native little bluestem lawn border will not move into your Kentucky bluegrass lawn. If it seeded in, it would never take over due to your weekly mowing. However, your nonnative bluegrass is likely to seed into the native area and constrain the native wildflowers.

Native wildflowers do not include naturalized wildflowers like queenanne's lace, which was noted as a European introduction and pest plant to farmers as early as 1919. The plant is not a problem because it is nonnative, but rather that we moved it from its natural conditions, and removed its natural competition. Other naturalized wildflowers, found on noxious weed lists, include: ox- eye daisey, chicory, batchelor buttons, and dame's rocket. Because they are introduced plants that are invasive and now on weed lists, we will consider them weeds for vegetation management purposes. The problems of naturalized species, including the lowly dandelion, far outweigh the benefits of planting more of them as wildflowers.

The "wild" in wildflowers has led to many misconceptions. Native wildflowers are plants that have evolved over time to fit the soils, moisture, and sunlight of any given area. They are adapted and self- reliant in any given region. They have evolved with the local climate and tolerate high, humid temperatures in the Southeast, as well as 30 below more than one year for obvious results. Most of their growth occurs beneath the surface during that first year. Patience wears thin when projects are seeking immediate colorful products. A tip, to please the public, is to include some annual/biennial wildflowers (native when possible).

Finally, a weedy look often occurs when native grasses are not included in the wildflower mix. At low seeding rates, native grasses visually compliment and physically give structure to the wildflower planting. This is the way native wildflowers naturally occur. Planting a monoculture of one flower species, or a mix of flowers can only result in a weedy look, unless a lot of gardening maintenance occurs. We do not have time or funds to garden on roadsides.

The concern about erosion during establishment can be tempered with the use of native grasses as part of the cover crop and/or seed mix. Some of the native wild ryes (Elymus sp.) are annual or short- lived and therefore perform like a nonnative rye in terms of erosion control, but dwindle in importance as the other species establish.

Remember that site preparation, using appropriate seed species, diverse species and native grasses will help avoid the weedy look when using native wildflowers. Always be on guard to control your State's and adjacent State's noxious weeds which can compromise the integrity, the public relations, and the success of your wildflower project.

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Questions and feedback should be directed to Deirdre Remley (deirdre.remley@dot.gov, 202-366-0524).

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