How Pennsylvania's Roadside Vegetation Law Supports Conservation

In July 2024, Governor Josh Shapiro signed House Bill 787 into law, an important step for ecological stewardship in Pennsylvania. The law directs the Pennsylvania Department of Transportation (PennDOT) to plant native vegetation along highways and prohibits the use of invasive plants. Representative Brett Miller (R-41) introduced the bill, which had strong bipartisan support. Ultimately, the bill had 20 co-sponsors, 13 Democrats and 7 Republicans. (For a complete list of co-sponsors, visit.)

How does House Bill 797 of 2024 benefit Pennsylvania ecology?

House Bill 797 directs PennDOT to plant vegetation native to Pennsylvania whenever feasible and prohibits the planting of USDA-defined invasive species and plants on Pennsylvania’s Noxious Weed List. The bill supports the value of biodiversity in our Commonwealth and acknowledges the threat that invasive species pose. In an email, Representative Brett Miller noted that this bill had an impact even before it was passed. Since the bill was six years in the making, PennDOT was aware of the discussions around it and began amending its practices in anticipation of the bill’s passage. State agencies, including the Department of Conservation and Natural Resources, the Pennsylvania Department of Agriculture, the Department of Environmental Protection, and the Governor’s Invasive Species Council, provided input and support of the bill as it moved through the process to final passage. House Bill 797 now enshrines and makes permanent PennDOT's practice of planting natives and prohibiting invasive non-native plants on Pennsylvania roadways.

What native plants are included in PennDOT's seed mixes?

PennDOT has developed seed mixes labeled broadly for conservation, as well as those labeled specifically for special situations, such as wetlands and slopes. The plant combinations are appropriately varied and contain a number of natives that are not commonly seen or available at garden centers. Here are two examples of the seed mixes:

Conservation Mix (Formula N): purpletop (Tridens flavus), little bluestem (Schizachyrium scoparium), Canada wildrye (Elymus canadensis), switchgrass (Panicum virgatum), Indiangrass (Sorghastrum nutans), roundseed panicgrass (Panicum sphaerocarpum), black-eyed Susan (Rudbeckia hirta), ox-eye sunflower (Heliopsis helianthoides), white avens (Geum canadense), common milkweed (Asclepias syriaca), partridge pea (Chamaecrista fasciculata), showy tick-trefoil (Desmodium canadense)

Wetland Mix: fox sedge (Carex vulpinoidea), riverbank wildrye (Elymus riparius), prairie cordgrass (Spartina pectinata), lurid sedge (Carex lurida), soft rush (Juncus effusus), blue vervain (Verbena hastata), swamp milkweed (Asclepias incarnata), sneezeweed (Helenium autumnale), Allegheny monkeyflower (Mimulus ringens), nodding bur marigold (Bidens cernua), seedbox (Ludwigia alternifolia), boneset (Eupatorium perfoliatum) northern blue flag (Iris versicolor), fowl bluegrass (Poa palustris), green bulrush (Scirpus atrovirens)

In these examples, as with all native plant seed mixes PennDOT uses, oat grass (Avena sativa) or cereal rye (Secale cereale) may be added as temporary cover crops to protect native seeds as they become established. The seeds are listed in order of prevalence in the mix.

When are non-native plants used?

In addition to seven mixes of native plant seeds, PennDOT uses a Residential Mix and a Clear Zone Mix, which contain more familiar, non-native turfgrasses. The Residential Mix contains perennial ryegrass (Lolium perenne), creeping red fescue or Chewings fescue (Festuca rubra or spp. commutata), and Kentucky bluegrass (Poa pratensis). The Clear Zone Mix contains a hard fescue mixture (Festuca longifolia) and creeping red fescue. Though these plants are not native to Pennsylvania, they are not invasive. According to a report furnished by PennDOT, in seeding projects between July 24, 2024, and July 15, 2026, native plant seed mixes were used in slightly more than half of the applications for permanent coverage, while the Clear Zone and Residential mixes were used in slightly under half of the applications. Reasons for using non-native grasses in the Residential mix take into account public expectations of how traditional turf grass should appear near homes. Clear Zone mixes are used in areas where tall native plants might obscure sight lines for drivers.

What positive future impact may the passage of House Bill 797 have?

At the heart of the law is the expectation that planting vegetation native to Pennsylvania will strengthen wildlife habitat and help restore local ecosystems. Because PennDOT maintains nearly 40,000 miles of roadway, its consistent use of native species will make these plants more visible, familiar, and acceptable to the public. Those of us who advocate for conservation in Pennsylvania hope that increased public exposure will encourage broader acceptance and, in time, make native plants more commonplace in residential and community landscapes as well. Further progress could come from PennDOT's monitoring of its conservation seed mixes and adjusting them for coverage and longevity, especially in challenging sites. Collaboration with conservation organizations, such as those who helped shape the bill, could also help the agency evaluate how well these plantings support pollinators and other native wildlife.