photo of a rain garden planted with native vegetation
Example of a rain garden planted with native vegetation.

This page introduces sources for the selection of plants for stormwater BMPs, salt tolerance, green roofs, and trees. An excellent resource applicable to a wide variety of vegetated BMPs, including bioretention BMPs, is Plants for stormwater design by Shaw and Schmidt (2003).

check it out image
See this new page on plants for swales.
Information: Information on plants for green roofs has been updated. This updated information is summarized below. See green roofs or trees.

Sources for stormwater BMP plant material selection

The following agencies provide up to date information on plant material selection for vegetated stormwater BMPs .

There are two specific situations in which these above sources should not be used: high salt concentrations (in spray and soil) and green roofs. Recommendations on salt tolerant and green roof plant material selection are given below.

Seeding and seed mixes

Salt tolerance

Locations where salt tolerance is a concern include roadsides receiving frequent winter snowmelt spray, vegetated swales or basins where snowmelt runoff infiltrates the soil, and water bodies receiving relatively large volumes of snowmelt. This discussion is limited to selection of vegetation for constructed stormwater BMPs and vegetated areas receiving runoff from high use transportation routes and parking lots, wet and dry infiltration basins associated with regional ponding, county and state roadway swales and filter strips, and winter road snow dumping areas.

Salt tolerance is not a concern for stormwater BMPs such as rain gardens and infiltration swales in low to moderate use local streets and catchments with little or no salt-laden snowmelt runoff.

Salt tolerance is common to many plants of coastal marshy areas. These species are reliable on the east and west coast in their indigenous ranges. Some of these species are very widespread. The populations found in the Midwest are not necessarily salt tolerant. For inland areas the availability of naturally occurring populations of salt tolerant species is limited.

Salt tolerance has been shown in some of the dry grassland species of the west. The range of these species may include Minnesota. The local populations may exhibit salt tolerance and are recommended.

Salt tolerance has also been shown in some of the aggressive and invasive species found in the Midwest. These species, although amenable to the high salt areas are not recommended because of the stress that may be introduced to native plant communities. Depending on the species, their seeds may travel fairly far by wind or water and are not recommended for rural or urban areas, even if native plant communities are not adjacent.

Stormwater BMPs with high salt concentrations will be susceptible to invasion by exotic and invasive species due to multiple stressors from the salt, along with sedimentation and high phosphorus concentrations and petroleum products. Common buckthorn, one of the aggressive Midwest exotic species of saturated soils, has high salt tolerance. Box elder, a native of lowlands, but often a colonizer in disturbed sites also has high tolerance. Reed-canary grass has moderate tolerance, and purple loosestrife has high tolerance.

The table below lists species and plant seed mixes which should be reliable in soils with high salt concentrations. The tolerance to salt spray may vary, and is shown in parentheses if known. The plant materials listed do not include highly aggressive and invasive species.

Salt tolerance ratings can vary across the country and between investigators, depending on the ways the data are collected and the ratings categories selected. Rating systems are not standardized between various investigators for different plant types (trees, shrubs, herbs) and uses (agriculture, horticulture). The sources sited here were used to represent as best as possible recent research, regional evaluations, and results from specialized salinity testing laboratories.

Note that information on salt tolerance for Minnesota plants warrant some interpretation. Much of the salt tolerance information published nationally is oriented toward agriculture rather than stormwater BMPs. The first table below attempts to interpret data from the literature for applicability to Minnesota. The second table below provides sources for seed mixes.

Cold climate plant materials of the upper midwest with known salt tolerance, listed from wet to dry soil moisture
Link to this table

Plant Material Soil Moisture Salt Tolerance in Soil Growth Form Notes on Use
American elm (Ulmus Americana) Always Wet/Frequently Saturated Medium/Low1 Tree
Green ash (Fraxinus pennsylvanica) Always Wet Medium1 Tree
Canada wild rye (Elymus canadensis) Frequently Saturated Medium Herbaceous-grass
Meadow foxtail (Alopecurus pratensis) Frequently Saturated Low Herbaceous-grass
Karl Foerster reed grass (Calamogrostis acutifolia ‘Karl Foerster’) Frequently Saturated/ Mostly Drained High Herbaceous-grass This is a cultivar for landscaping
White ash (Fraxinus Americana) Frequently Saturated/ Mostly Drained High1 Tree
Poplars (Populus spp.) Frequently Saturated/ Mostly Drained Medium1 Tree Including aspen, cottonwood, black and silver-leaved poplar; fast growing; also provide good streambank stabilization; highly tolerant to salt spray
Hackberry (Celtis occidentalis) Frequently Saturated/Mostly Drained Medium Tree
Jack pine (Pinus banksiana) Mostly Drained High1 Tree
Smooth sumac (Rhus glabra) Mostly Drained Medium Shrub Colonizes and spreads in high sun
Staghorn sumac (Rhus typhina) Mostly Drained High Shrub
Cutleaf sumac (Rhus trilobata) Mostly Drained High Shrub
Rugosa rose (Rosa rugosa) Mostly Drained Low Shrub
Perennial ryegrass (Lolium perenne) Mostly Drained Medium Herbaceous - grass
Blue grama grass (Bouteloua hirsuta) Mostly Drained High Herbaceous - grass Selections being made for strongly salt-tolerant varieties; see University of Minnesota for latest
Little bluestem (Schizachyrium scoparium) Mostly Drained High Herbaceous - grass
Alkali grass (Puccinella distans) Mostly Drained High Herbaceous - grass
Tall wheatgrass (Agropyron elongatum) Mostly Drained High Herbaceous - grass
Western wheat grass (Elytrigia smithii) Mostly Drained High Herbaceous - grass
Seed Mix: MNDOT urban prairie Mostly Drained High Herbaceous - grass
Seed Mix: MNDOT western tall grass prairie U M Herbaceous - grass

1trees with some tolerance to spray


Recommended salt tolerant mixes
Link to this table

DESCRIPTION: Combination native and turf mix. Reaches a height of approximately 18 inches. For use inurban areas where conditions may be saline, droughty & generally poor soils. Oats to be substituted for Winter Wheat in spring plantings at a ratio of 1 to 1. RATE: 60 lbs/acre (67.2 kg/ha)
Common Name Scientific Name # Pounds Percentage
Grama Sideoats Bouteloua Curtipendula 4.80 8.00%
Grama Blue Bouteloua Graciis 3.60 6.00%
Prairie Clover Purple Dalea Purpureum 1.20 2.00%
Wildrye Canada Elymus Canadensis 2.40 4.00%
Wheat Grass Slender Elymus Trachycaulus 3.60 6.00%
Rye Grass Annual Lolium Talicum 4.80 8.00%
Wheat Winter Talicum Aestivum 15.60 26.00%
Bluegrass Canada PCA Compressa 7.20 12.00
Grass Alkali Puccinella Distans 9.60 16.00%
Bluestem Little Schizachyrium Scoparium 6.00 10.00%
Dropseed Sand Sporobolus Cryptandrus 1.20 2.00%X
Totals 60.00 100.00%
Pounds of cover crop to be bagged seperately (Tech Memo 04-09-ENV-02 78.00
Mixture 10B (western Tall Grass Prairie): Grasses are PLS Forbs & introduced are bulk, yellow tag when available. DESCRIPTION: Native mix. Reaches a height of 36 to 48 inches. For use in western Minnesota. Oats to be substituted for Winter Wheat in spring plantings at a ratio of 1 to 1. RATE: 30 lbs/acre (33 kg/ha)
Common Name Scientific Name # Pounds Percentage
Bluestem Big Andropogon Gerardi 1.80 6.00%
Grama Sideoats Bouteloua Curtipendula 2.40 8.00%
Wildrye Canada Elymus Canadensis 1.80 6.00%
Wheat Grass Slender Elymus Trachycaulus 1.20 4.00%
Wheat Grass Western Elytrigia SmithA 0.60 2.00%
Rye Grass Annual Lolium Talicum 3.00 10.00%
Wheat Winter Talicum Aestivum 10.20 34.00%
Forbes F-1 or F-2 N/A 1.50 5.00%
Switchgrass Wild Type Panicum Virgatum 0.30 1.00%
Bluestem Little Schizachyrium Scoparium 3.00 10.00%
Indian Grass Sorghastrum Nutans 3.00 10.00%
Needle Grass Green Stipa Viridula 1.20 4.00%
Totals 30.00 100.00%
Pounds of cover crop to be bagged seperately (Tech Memo 04-09-ENV-02 51.00


Forbs

Little information is available on the salt tolerance of native forbs (herbaceous plants that are not grasses). The following genus or species may have moderate salt tolerance (Tober et al.).

  • blanket flower (Gaillardia)
  • yarrow (Achillea millefolium)
  • yellow coneflower (Ratibida pinnata)
  • fringed sagewort (Artemisia frigida)
  • purple prairie clover (Dalea purpurea)
  • primrose (Primula vulgaris)
  • stiff sunflower (Helianthus pauciflorus)
  • Maximilian sunflower (Helianthus maximiliani)
  • Lewis flax (Linum lewisii)
  • Canada milkvetch (Astragalus canadensis)
  • two-grooved milkvetch (Astragalus bisulcatus)
  • scarlet globemallow (Sphaeralcea coccinea)

Recommended readings related to salt tolerance for herbaceous plants.

Intolerant species

photo of a green roof
Photo of a green roof

Some common Midwest species are known to be intolerant of high salt soil concentrations. Avoid planting these species or seed mixes when salt is expected to be a stressor.

  • Grey dogwood (Cornus racemosa)
  • Red-osier dogwood (Cornus stolonifera)
  • Silver maple (Acer saccharinum)
  • Sugar maple (Acer saccharum)
  • Basswood (Tilia Americana)

Green roofs

Information: Information on plants for green roofs has been updated. This updated information is shown in the tables below.

The green roof BMP has the most specialized circumstances for plant materials and thus requires a very different list of materials compared to on-the-ground BMPs. More than any other BMP, it is unwise to proceed on selecting green roof plant materials without full knowledge of the entire green roof structural design system. This has to do with the very constrained growing conditions for this highly engineered BMP. Note that the following discussion relates to plant selection for green roofs and is not a design sheet for green roof BMPs.

The first consideration on plant material selection is the basic green roof design type. Extensive green roofs (EGRs) have been commonly using xeriscape types of plantings in a shallow, draughty growing medium. These types of plantings are more appropriate for urban rooftops (See the table below for planting recommendations). Intensive green roofs (IGR) include earth-bermed structures and tend to be heavier and reliant on richer, deeper substrates and may also have shrubs and trees. As such, the plant materials for extensive and intensive green roof systems are not usually the same. For example, the selections for an earth-berm IGR planting may be quite different from an EGR system. It should be noted that plant species and diversity can affect ecological function


Non-native succulent species appropriate for extensive green roofs in Minnesota. Note: Many species of sedums grow well on green roofs in Minnesota. The list below shows some of the most common species. Many other Sedum species can also perform well.
Link to this table

Scientific name Common name Plant height (inches) Approximate bloom time Flower color Sun exposure Winter interest
Allium schoenoprasum Chives 10 Spring White Full sun to partial shade Dormant
Sedum album Stonecrop 6 Summer White Full sun Red
Sedum hybridum 'Immergrünchen' Stonecrop 6 Summer Yellow Full sun Orange/bronze
Sedum kamtschaticum var. floriferum'Weihenstephaner Gold' Russian Stonecrop 5 Summer Yellow Full sun Red
Sedum kamtschaticum Russian Stonecrop 6 Summer Yellow Full sun Red
Sedum reflexum 'Blue Spruce' Stonecrop 8 Summer Yellow Full sun Blue-green
Sedum rupestre 'Angelina' Golden Stonecrop 5 Summer Yellow Full sun Coral/orange-red
Sedum sexangulare Stonecrop 4 Summer Yellow Full sun to shade Red
Sedum spurium 'Dragon's Blood' Two Row Stonecrop 4 Summer Red Sun Red

Native species that have been grown successfully on extensive green roofs in Minnesota
Link to this table

Scientific name Common name Plant height (feet) Approximate bloom time Flower color Sun exposure Found to require irrigation in some projects or studies Found to survive with little or no irrigation in some studies or projects
Allium cernuum Nodding Wild Onion 1 to 1.5 July-August Pink Full sun to part shade X3,4
Allium stellatum Prairie Wild Onion 1 to 2 July-August Pink Full sun to part shade
Andropogon gerardii Big Bluestem 2 to 6 n/a n/a Full sun to part shade X1,2,*
Anemone patens Pasque flower 0.5 April-May Purple Full Sun to Part Shade
Antennaria neglecta Field pussytoes 0.5 April-June White Full Sun to Part Shade
Antennaria plantaginafolia Pussytoes 1 April-June White Full sun to part shade
Aquilegia canadensis Columbine 2 to 3 May-July Red/Yellow Full sun to part shade
Asclepias verticillata Milkweed 1 to 1.5 June-August White Full sun to part shade
Aster ericoides Heath aster 1 to 3 July-October White Full sun to part shade
Aster laevis Smooth aster 1 to 3 August-October Blue-violet Full sun to part shade X4
Aster lateriflorus Calico aster 2 August-October White Full sun to part shade
Aster macrophyllus Large-Leaved aster 1 to 2 August-October Lilac Full sun to part shade
Aster novae-angliae New England Aster 3 to 5 August-October Red-violet Full sun to part shade
Aster oolentangiensis Shyblue aster 3 August-October Blue Full sun to part shade
Aster sericeus Silky aster 1 September-October Purple Full sun to part shade
Bouteloua curtipendula Side-Oats Grama 1 to 3 n/a n/a Full sun X1,*
Bouteloua gracilis Blue Grama Harebell 0.5 to 1 n/a n/a Full sun X1,5,*
Campanula rotundifolia Harebell 1 to 1.5 June-September Blue Full sun to part shade
Carex pensylvanica Pennsylvania sedge 0.5 n/a n/a Full sun to full shade
Carex vulpinoidea Brown Fox Sedge 1 to 3 n/a n/a Full sun to part shade
Chamaecrista fasciculata Partridge Pea 2 to 3 July-September Yellow Full sun to part shade
Coreopsis palmata Bird's Foot Coreopsis 2 June-August Yellow Full sun to part shade
Dalea purpurea Purple Prairie Clover 1 to 2 June-July Yellow Full sun X4 X1
Fragaria vesca Wild strawberry 0.5 May-June White Full sun to part shade
Fragaria virginiana Wild strawberry 0.5 White Full sun to part shade X4 X1,*
Geranium maculatum Wild geranium 1 April-June Pink Full sun to full shade
Geum triflorum Prairie smoke 0.5 April-June Red Full sun to part shade X1,*
Heuchera richardsonii Alumroot 1 May-June Greenish white Full sun to full shade
Koeleria pyramidata June grass 2 n/a n/a Full sun to part shade X4 X1,2,3
Liatris aspera Rough Blazing Star 1.5 to 4 August-September Rose, lavender Full sun to part shade X4
Liatris cylindracea Cylindric Blazing Star 1 July-October Purple Full sun to part shade
Penstemon grandiflorus Large-Flowered Beard Tongue 2 May-June Purple Full sun to part shade
Phlox divaricata Woodland Phlox 0.5 to 1.5 April-June Blue Part shade to full shade
Polemonium reptans jacob's Ladder 1 April-June Blue Full sun to full shade
Ruellia humilis Wild Petunia 1 June-August Purple Full sun
Schizachyrium scoparium Little Bluestem 3 n/a n/a Full sun to part shade X4
Solidago nemoralis Gray Goldenrod 0.5 to 2 August-October Yellow Full sun
Solidago ptarmicoides Upland White Aster 1 July-August White Full sun
Sporobolus heterolepis Prairie Dropseed 2 to 4 n/a n/a Full sun to part shade X4 X1
Thalictrum dioicum Early Meadow-Rue 1 to 2 May Greenish yellow Full sun to part shade
Tradescantia bracteata Bracted Spiderwort 1 May-July Purple Full sun
Tradescantia occidentalis Western Spiderwort 2 May-July Blue Full sun
Tradescantia ohiensis Ohio Spiderwort 3 May-July Blue Full sun to part shade X3,4
Viola pedatifida Bearded Birdfoot Violet 0.5 April-June Purple Full sun to part shade

1Based on trial green roofs at Chicago Botanical Garden, Richard Hawke, Personal Communication
2Based on Kevin Carroll, personal communication, 2013.
3Based on research at Michigan State University, Rowe in Sutton et al 2012b
4Based on research at Michigan State University, Monterusso et al 2005. In this study, plants were irrigated the first growing season, and irrigation was then abruptly stopped July 10 of the second growing season, during an unusually warm and dry summer; plants were not irrigated at all during the third growing season.
5Based on observations at Phillips Eco-Enterprise green roof, The Kestrel Design Group personal communication, 2013.
*Goes dormant or turns brown with little or no irrigation in drought but rebounds when water is available again.
Secondly, the plant material selection, through biological processes and nutrient cycling, may effect whether the BMP exacerbates or mitigates the function of nutrient storage. Research to date comparing EGRs and control (nongreen) roofs shows that green roofs are a poor BMP for nutrient storage and removal from precipitation. In evidence from both southern and northern climates, total phosphorus concentrations are higher in runoff leaving a green roof compared to control roofs, although the mass loading is the same as the control (Moran et al., 2004). Nitrogen losses from a green roof do not differ significantly from control roofs. So for nutrient loading and design of removal systems, other BMP tools should be located ‘further down the runoff path’ from the rooftop BMP to trap runoff from green roofs. It is unclear how the IGRs function for nutrient storage.

Extensive green roofs are definitely a reliable BMP for reducing peak runoff rates. This has been demonstrated in several controlled studies in both southern and northern climates. Intensive green roofs provide the same function. It is not clear if the plant material plays a significant role in this or whether it is related to the design of the planting medium and underlying roof runoff system. To date it has always been assumed that the overall design should support plant materials that are tolerant of drought conditions and not prolonged saturated soil.

There is plenty of opportunity for experimentation on green roof plant material. Most controlled experiments have been limited in the kinds of plant material tested. The Genus Sedum has been widely used in extensive green roof plantings. It is unknown whether plantings dominated by other and widely different plant groups will yield the same results. As such, the function of a green roof as a stormwater BMP may vary: nutrient storage may not be an issue with some plant materials. Until further case studies and experiments are conducted on the nutrient storage function of this BMP, it is wise to assume that all plant material selections will yield added nutrient runoff, particularly if the plants are fertilized. Thus, the green roof system should be designed in series with other BMPs which are expected to function in this respect.

The variety of choices of EGR plant material for warm and cold climates is generally limited in the following ways:

  • Water and nutrients from precipitation
  • Substrate - often at least partially synthetic and droughty
  • Limited organic matter build up – isolated from organic debris, leaf build-up, sedimentladen runof
  • Shallow rooting zone – less than one foot

Plant selection is restricted to materials which will be successful in very shallow substrates, perhaps 6 inches, up to 12 inches deep. Long-lived, perennial drought tolerant species commonly display deep taproot growth or deep fibrous root systems. This is the main reason that the Genus Sedum is so commonly relied upon. In contrast, many of the prairie forbs and grasses valued for infiltration BMPs may not be appropriate for green roofs.

The plant material selection for any one specific green roof is also dependent on the substrate content and depth. Intensive and extensive systems were already defined, and will significantly effect the substrate choices. The plant material selections provided here have been limited to those for EGRs. Even within an extensive system, in which the substrate is in general droughty, the specific design of each system will significantly effect plant productivity. Experiments in which the same plant material was grown on several different substrates demonstrates the importance of this. As such, one of the main criteria for selecting EGR plants is the substrate design. And often, this is limited by the structural integrity of the building, particularly for retrofit designs.</p>

For EGRs, irrespective of the specific design, one general consideration applies to establishing plant material. The material will usually be introduced as young plants, and to reduce transplant shock and provide an enriched environment for further growth, an organic substrate such as compost should be used as the immediate transplant medium.

Tree information

The information below provides links to several tables listing characteristics of tree species that are suitable as stormwater Best Management Practices. The list of trees does not include all trees suitable for stormwater management, but the list encompasses the most common trees used.

Green Infrastructure: Trees can be an important tool for retention and detention of stormwater runoff. Trees provide additional benefits, including cleaner air, reduction of heat island effects, carbon sequestration, reduced noise pollution, reduced pavement maintenance needs, and cooler cars in shaded parking lots.
Information: To view all the information contained in the tables listed below as a single Excel file, click here: File:Tree species table.xlsx
  • General information: table containing the following information for a list of trees
    • native or non-native
    • street tree or landscape only
    • deciduous, coniferous, or deciduous coniferous
    • sun requirements
    • position in forest structure (e.g. understory, etc.)
    • relative growth rate to maturity
  • Morphology: table summarizing tree height, canopy diameter, relative tree size, and relative growth rate
  • Tolerance to stresses: table providing the following information
    • Minimum zone hardiness
    • Tolerance to urban stresses
    • Tolerance to soil texture conditions
    • Salt tolerance
    • Stress tolerance
  • pH and mositure ranges: table providing information on acceptable pH and moisture ranges for different tree species
  • Tolerance to inundation: table providing information on tree tolerance to inundation with water. Note that information exists for a limited number of tree species.
  • Additional benefits of trees: table providing a list of non-stormwater benefits for several tree species
  • Notes: table providing additional information for select species, such as susceptibility to specific stresses, preferred choice of cultivar, etc.
  • Suitable for CU structural soil: table providing a list of tree species suitable for use with Cornell University (CU) structural soil


References for salt tolerance

References for green roof plant material selection

  • Bengtsson, L. 2004. Hydrological Response of Sedum-Moss Roof. American Geophysical Union. Fall Meeting 2004. abstract #H41A-0285.
  • DeNardo, J.C., A.R. Jarrett, H.B. Manbeck, D.J. Beattie, and R.D. Berghage. 2003. Stormwater Detention and Retention Abilities of Green Roofs. World Water and Environmental Resources Congress. 2003. Paul Bizier, Paul DeBarry - Editors, June 23–26, 2003, Philadelphia, Pennsylvania, USA.
  • Federal Energy Management Program. September 2004. Green Roofs. DOE/EE-0298.
  • Moran, Amy, Bill Hunt, Greg Jennings. 2004. Greenroof Research of Stormwater Runoff Quantity and Quality in North Carolina. NCSU Water Quality Group Newsletter August 2004.
  • Shooting Star Native Seeds. 2005. Mn/DOT 2005 Seed Mixes.
  • Uhl, M, Schiedt, L, Mann, G, Henneberg, M. 2003. Long-term study of rainfall runoff from green roofs. Wasser und Boden. Vol. 55, no. 3, pp. 28-36. Mar. 2003.

This page was last modified on 11 October 2018, at 09:33.

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