SHA Preferred Plant List
- Why revise the PPL?
We wanted to streamline the PPL to remove erroneous species which should not be planted (invasive) and species which are rarely/never planted. Specific cultivars were removed as well as we prefer to have Maryland native straight species proposed, which provide a more beneficial food source for pollinators. The species listed in the revised PPL are SHA's preferred species for installation within our right-of-way and/or parcels. Cultivars or alternative species can still be accepted but reviewed project-by project with justification as outlined in the selection criteria section.
- Selection Criteria:
The first and foremost priority for plantings within SHA right-of-way is to specify straight species Maryland natives. This is especially true for reforestation or TMDL plantings. There are specific design considerations where the specification of cultivars might be more suitable for the specific location. Some examples include prominent locations with high visibility, areas where cultivars would be more suitable for the existing conditions and design intent, cultivars that have better resistance to pathogens, plants with ornamental fruit that require male and female varieties, and species that only have desirable cultivars (i.e. ginkgo). Native cultivars of species listed on the PPL are preferred. Non-native species are only to be used when matching existing surrounding vegetation or some specific design criteria and should never be a species that is considered 'aggressive' or invasive.
- The Highway Clear Zone (CZ):
The Highway Clear Zone is defined by the AASHTO Roadside Design Guide: the unobstructed, traversable area provided beyond the edge of the traveled way for the recovery of errant vehicles. The clear zone includes the shoulder, curb and gutter, bike lanes, and auxiliary lanes unless the auxiliary lane functions as a through lane. Required clear zone distance is not the same for all roadways, as clear zone distance is based on traffic volumes, speeds, and roadside geometry. Roadside geometry may include foreslopes, backslopes, and/or drainage channels. Plants species that are not considered ‘fixed objects’ (i.e most shrubs and perennials) are ok to plant in the clear zone, where appropriate.
- Note:
Maryland Native species were determined from the USDA Plants Database.
For any projects which are within the zone of influence for any airport regulations, refer to the Maryland Aviation Administration (MAA) Approved Plantings List to see if SHA PPL species are appropriate.