Marion County, OR Native Plant Program for Roadside & Construction Site Reclamation

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Marion County, OR, US

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Type: Program

Status: Ongoing

Source File:


Marion County is responsible for managing an average of 28 feet of roadside vegetation along ~1200 miles of roads. This network of vegetation crosses every ecosystem in the county and has the potential to provide ecological connectivity across the county's increasingly fragmented landscape. When state highways and city streets are included, the network only increases in its scale and density.

In its current condition, this network of vegetation is often a maintenance liability and frequently serves as a pathway for invasive plant species. Maintenance has traditionally consisted of controlling the vegetation by brushing, mowing, and herbicide spraying. Traffic safety, site distance maintenance, and noxious weed control have been the top priorities, though special treatments have also been included for threatened plant species and private management agreements.

While there are serious problems to address in the vegetation network, there is also a great deal of potential for it to provide positive functions with lower maintenance requirements. If we can replace, even partially, the non-native species with appropriate native species, then we will have corridors for transporting genetic information (via seed and pollen distribution) between isolated ecosystems and provide a contiguous habitat for plants and wildlife. By selecting native plants with appropriate growth habits, we can reduce the maintenance requirements and provide an aesthetically pleasing landscape that reflects the local character of the landscape.

These corridors will increase biodiversity and native plant populations, while reducing the chance that rare native plants will become threatened or endangered. Frequently, remnant native plant populations are found in the roadsides. If these populations can be deliberately increased and supplemented then we will begin to tap the potential of this network.

There are obvious limitations to these paths of connectivity. These are thin stretches of vegetation, often running through areas with regular disturbances regimes and passing areas with invasive plant populations. Once we begin to establish native plants in areas where they are most likely to succeed, however, we will have anchor points to work from. Through careful management, active cooperation with landowners, and coordinated efforts other transportation agencies, our chances of success are even greater.

Native Seed Test Plantings - Tests and Cost Estimates Marion County tested a number of native grass/forb seed mixes during the year 2000 in order to determine which species and combinations work best for erosion control, slope stabilization, noxious weed control, and roadside site distance concerns. Following are some initial test mixes that were hydroseeded onto the indicated sites.

New seed mixes were developed for year 2001 construction projects. These new mixes were drawn from year 2000 test results and from the recent recommendations made to Marion County for native seed selection. (Refer to source file to view chart plus photos of reseeding efforts.)