HORTSCIENCE 45(3):393–400. 2010. [Tripsacum dactyloides (L.) L.] was as effec- tive as any of the tree species studied at mechanically stabilizing soil and that switch- Relative Rooting Depths of Native grass was significantly more effective. Beard (1989) reported that bermudagrass [Cynodon Grasses and Amenity Grasses with dactylon (L.) Pers.] was the most deeply rooted of the commonly used turfgrasses with Potential for Use on Roadsides a depth of more than 2.5 m under mowed conditions. Fairway wheatgrass [Agropyron cristatum (L.) Gaertn.] and tall fescue were in New England the most deeply rooted of the cool-season Rebecca Nelson Brown1, Cynthia Percivalle, Sophia Narkiewicz, grasses. In a study of 16 tall fescue cultivars and Samantha DeCuollo and lines, Kim et al. (1999) found that all entries rooted to 60-cm depth, and five entries Department of Plant Sciences, University of Rhode Island, 210 Woodward rooted to 75-cm depth. There was no differ- Hall, Kingston, RI 02881 ence in rooting depth between tall forage types and lower-growing turf or dwarf types Additional index words. Festuca rubra, Sorghastrum nutans, Panicum virgatum, Andropogon when plants were clipped. Sprague (1933) gerardii, Festuca brevipila, Elymus canadensis, Elymus virginicus, Elymus villosus, Elymus found that almost all the roots of kentucky hystrix, Panicum amarum, Pucciniellia distans, Festuca arundinacea, Lolium perenne, Agro- bluegrass and multiple species of bentgrass stis perennans, Schizachyrium scoparium, Deschampsia cespitosa, Muhlenbergia schreberi, (Agrostis spp.) occurred in the top 10 cm of Eragrostis spectabilis, Bouteloua courtipendula, Koeleria macrantha, Sporobolous cryptan- the soil profile, whereas hard fescue had drous, Bromus inermis a more even root distribution and that weekly mowing at lawn height versus annual mow- Abstract. Erosion is a significant problem on highway embankments in Rhode Island. At ing did not affect rooting depth in mowing- present, a mixture of red fescue (Festuca rubra L.), perennial ryegrass (Lolium perenne tolerant species. Stuckey (1941) found that L.), and kentucky bluegrass (Poa pratensis L.) is planted to stabilize the soil. However, roots of perennial ryegrass and several other only the red fescue survives long term on slopes. Red fescue is shallow-rooted, leading to species were annual, whereas those of ken- sod sloughing after heavy rains. The objective of this study was to compare the rooting tucky bluegrass were perennial. Weaver depth, plant height, and adaptation to roadside conditions of 16 native grasses and five (1968) reported that roots of the common amenity grasses with red fescue to identify species that could be used to reduce sod prairie grasses were perennial. Weaver sloughing. Research was conducted from May 2006 through Aug. 2009 in the greenhouse (1968) extensively studied the root growth at the University of Rhode Island in Kingston and on the shoulder of state Route 4 in of native prairie grasses and midwestern North Kingstown, RI. The cool-season grasses smooth brome (Bromus inermis Leyss. ssp. range and pasture grasses in the first half inermis), Pumpelly’s brome [Bromus inermis Leyss. ssp. pumpellianus (Scribn.) Wag- of the 20th century, including some of the non], Canadian wildrye (Elymus canadensis L.), Virginia wildrye (Elymus virginicus L.), grasses in this study. However, the deep soils silky wildrye (Elymus villosus Muhl. ex Wild.), eastern bottlebrush (Elymus hystrix L.), of the midwestern prairie are very different perennial ryegrass, and tall fescue (Festuca arundinacea L.) and the warm-season grasses from the soils of the eastern seaboard little bluestem [Schizachyrium scoparium (Michx.) Nash] and purple lovegrass [Era- (Sprague, 1933). Studies of grass rooting grostis spectabilis (Pursh.) Steud.] were similar in height to red fescue while rooting depth in eastern soils have focused on the significantly more deeply. Of these 10 species, little bluestem, purple lovegrass, and tall podzolic agricultural soils and typical turf- fescue showed the best survival on the roadside. grass species (Sprague, 1933; Stuckey, 1941). Little is known about the rooting patterns of eastern ecotypes of the prairie Slopes in highway right-of-ways in Rhode rocks. The topsoil ranges from medium- grasses studied by Weaver (1968) or about Island and much of New England are com- textured silt to sand (Wright and Sautter, the rooting patterns of the eastern native grass monly seeded with a grass–legume mixture, 1988). Red fescue is shallow-rooted with most species not found in the prairie. which is predominantly red fescue (RIDOT, of the root mass confined to the topsoil layer The objective of this study was to identify 2004). Red fescue is preferred for roadside use (Beard, 1989). When root growth is concen- alternative grass species that root more because it is drought-tolerant and thrives on trated in a shallow mat with a sharp boundary deeply than red fescue without producing acidic, infertile soil. Roadside embankments in the soil profile, slope failure is likely to significantly more top growth. Particular are generally constructed of subsoil and occur beneath the mat (Simon and Collison, emphasis was placed on grasses native to gravel, over which 2 to 6 inches (5 to 15 cm) 2002). This sloughing of the sod and topsoil southern New England because national of topsoil is spread as a distinct layer (RIDOT, layer is precisely the type of slope failure that highway policy strongly encourages the use 2004). The subsoils are very stony with occurs along roadsides in Rhode Island, par- of native vegetation in highway right-of- coarse-textured loamy sand between the ticularly when the turf cover at the top of the ways (Clinton, 1999). bank has been rutted by vehicles (C. Franco, personal communication). A more even distri- Materials and Methods Received for publication 1 Oct. 2009. Accepted for bution of root mass with depth provides better publication 14 Jan. 2010. slope stabilization (Simon and Collison, 2002). Plant materials. Twenty-two grass spe- This research was funded by a grant from the Gray and Sotir (1996) report that estab- cies were included in this study. Specific Rhode Island Department of Transportation. Seed lished grasses reduce surface erosion by 90% details, including seed sources and native was donated by Calvin Ernst of Ernst Conservation or more over bare ground. They also report status, are presented in Table 1. Two of the Seeds, Martin van der Grinten of the Big Flats Plant that roots effectively increase the shear grasses used, perennial ryegrass (Lolium Materials Center, and the National Plant Germ- strength of soil, decreasing the likelihood perenne L.) and red fescue, are components plasm Repository. that the soil will slip, and that fine roots are of the seeding mixes currently used on We thank Carl Sawyer for technical assistance, Jessica Gilbert and Peter Fish for assistance with more effective than thick roots at binding roadsides in New England. Red fescue is root washing, and David Brown for assistance with soil. In a study of the effectiveness of native to New England (USDA-NRCS, the figures. different vegetation types at preventing slip 2009), although the seed normally used on 1To whom reprint requests should be addressed; events on stream banks, Simon and Collison roadsides is a cultivated type from Canada. e-mail [email protected]. (2002) reported that eastern gamma grass Tall fescue and smooth brome have been HORTSCIENCE VOL. 45(3) MARCH 2010 393 Table 1. Grass species used in the rooting depth studies and the roadside trials, including native status, type of photosynthesis, and seed sources. Common name Species Typez Statusy Accession Sourcex Big bluestem Andropogon gerardii C4 Native New England ecotype BFPMC Autumn bentgrass Agrostis perennans C3 Native Commercial ECS Smooth brome Bromus inermis ssp. inermis C3 Introduced Commercial ECS Pumpelly’s brome Bromus inermis ssp. pumpellianus C3 Native PI accessions 196321, 655132, 19749, W-6 19743, and 372670 Hairgrass Deschampsia cespitosa C3 Native and introduced PI 241051 and commercial W-6, ECS Eastern bottlebrush Elymus hystrix C3 Native PI 531615 W-6 Canadian wildrye Elymus canadensis C3 Native Iowa ecotype BFPMC Virginia wildrye Elymus virginicus C3 Native Pennsylvania ecotype BFPMC Silky wildrye Elymus villosus C3 Native PI 531703 W-6 Tall fescue Festuca arundinacea C3 Introduced Cultivars Rebel and Bladerunner ASS Hard fescue Festuca brevipila C3 Introduced Cultivar Durar BFPMC Red fescue Festuca rubra C3 Native and introduced Common creeping red ASS Indiangrass Sorghastrum nutans C4 Native PI 591811 and cultivar NE54 PGRCU, ECS Little bluestem Schizachyrium scoparium C4 Native Connecticut ecotype, cultivar Aldous ECS Panic grass Panicum amarum C4 Native Cultivar Atlantic BFPMC Switchgrass Panicum virgatum C4 Native PI 414069 and cultivar Cave-in-Rock PGRCU, ECS Nimblewill Muhlenbergia schreberi C4 Native Commercial ECS Alkaligrass Puccinellia distans C3 Introduced PI 443386, cultivar Fults W-6, ECS Perennial ryegrass Lolium perenne C3 Introduced Cultivars Palmer IV and Line Drive ASS Purple lovegrass Eragrostis spectabilis C4 Native RI ecotype, FL ecotype Roadside, ECS Sideoats grama Bouteloua curtipendula C4 Native Commercial ECS Sand dropseed Sporobolus cryptandrous C4 Native Commercial ECS Prairie junegrass Koeleria macrantha C3 Native and introduced Cultivar Barleria Barenbrug zC4 grasses are commonly known as ‘‘warm-season’’ and C3 grasses as ‘‘cool-season.’’ yStatus refers to whether the species is