Turf lawns are estimated to cover roughly 2% of the continental United States (Milesi et al., 2005), mostly in highly urban areas. Although management of lawns varies by function and individual manager, it is typically characterized by three primary cultural practices: mowing, fertilizing, and irrigation (Turgeon, 1999). These practices are intended to favor turf species and, when applied in tandem with proper establishment techniques, result in stands of uniform turf. Despite lawns being currently managed as uniform monocultures, they are often host to flowering plants that provide foraging resources for bees and other pollinators. A recent insect survey of park lawns hosting dandelion (Taraxacum officinale F.H. Wigg.) and white clover (Trifolium repens L.) conducted in Lexington, Kentucky (Larson et al., 2014), found 37 associated bee species. These plant species are typically considered weeds in the United States and are sometimes eliminated through the use of broadleaf herbicides. However, lawns managed intentionally for forb abundance and richness would likely have a beneficial impact to local foraging bee communities. Previous research has suggested a strong positive relationship between forb community richness and pollinator community richness that likely extends to lawn communities as well (Ebeling et al., 2008; Potts et al., 2003). Such management goals would necessitate the reduction of other lawn inputs and would further the goal of increased sustainability. Mowing often correlates negatively with plant species richness in lawns (Bertoncini et al., 2012; Garbuzov et al., 2014; Lerman et al., 2018; Shwartz et al., 2013; Smith and Fellowes, 2015), and managing floral lawns could lead to less-intensive mowing regimes. The inclusion of legumes such as white clover has shown to enhance turf nitrogen uptake through nitrogen fixation (McCurdy et al., 2014; Sincik and Acikgoz, 2007), and would potentially reduce fertilizer inputs into lawns.
At the other extreme of flowering lawns, researchers as the University of Reading in the United Kingdom have abandoned the use of turfgrasses altogether, and have been developing species lists and management practice guidelines for purely floral lawns (Smith and Fellowes, 2015) that have been found to have benefits to flower-visiting insects (Smith et al., 2014). These lawns may provide benefits to flower-visiting insects, but they are not meant to be areas of high human traffic and recreation. Human traffic on monocultures of white clover was found to reduce green cover up to 14 times faster when compared with hybrid bermudagrass [Cynodon transvaalensis Burtt- Davy 3 C. dactylon (L.) Pers.], suggesting the importance in turfgrasses for maintaining long-term cover in variable traffic conditions (Brosnan et al., 2014). Another potential challenge of these nonturfgrass plantings is the reliance on precultivation and installation, which can be costly on a large scale, and the potential need for more specialized care. In addition, there is still a strong cultural connection with turf lawns (Harris et al., 2013), and an intermediate flowering lawn that combines turfgrass and floral species may have broader and more practical appeal, especially for recreational use. For these reasons, grass–forb mixes established from seed are an important area of focus for future research. This type of floral-enhanced lawn should provide quick groundcover, reduce lawn maintenance, save money, and provide typical lawn functions such as recreation.
Although floral lawns hold great promise in improving biodiversity in urban areas, guidelines for establishing usable forbs in a lawn are needed to encourage adoption. The main objective of this study was to identify a turfgrass species that would allow for better success in the introduction of flowers not typically thought of as turf weeds. An ideal turfgrass species would maintain groundcover, but also allow for establishment and bloom of its forb companions. Some effort has been made into developing seeding strategies for white clover into established lawns to benefit pollinators and soil nitrogen (McCurdy et al., 2013; Sparks et al., 2015). White clover is an established agronomic crop that is widely associated with pasture agriculture, and is well adapted to the grazing systems under which it evolved (Leffel and Gibson, 1973). Pasture systems and lawns are similar in many ways, (e.g., compaction and cutting by animals or humans) and it is no surprise that white clover does well in both environments. So although white clover is a viable option for improving lawn floral abundance, more forb options are needed to improve the diversity and conservation value of turfgrass lawns.
To understand more fully how turfgrass species influence other forbs, we selected four common turfgrass species used in home lawns in the northern United States to mix with a species of clover: Kura clover (Trifolium ambiguum M. Bieb.). Kura clover is a rhizomatous perennial plant originating from eastern Europe/western Asia and has been investigated as a cold-tolerant forage plant for pasture cattle in the United States. Kura clover is not commonly cultivated across the United States, but it can be found growing infrequently in seminatural areas. Kura clover is known for its slow establishment period and sensitivity to grass competition (Hill and Mulcahy, 1995; Seguin et al., 1999) when used under pasture conditions. Kura clover’s agronomic properties, such as high seed germination rates and grazing tolerance, combined with its sensitivity to competition make it an ideal model species for isolating how competitive pressure from different turf species might affect the establishment and bloom of flowering plants not typically associated with turfgrass lawns.
We predicted that slow-establishing and nonrhizomatous turf species would favor Kura clover establishment and bloom, whereas fast-establishing and rhizomatous species would disfavor Kura establishment and bloom. Our primary goal was to identify turfgrass species that can be seeded at their recommended rates while minimizing turfgrass species-specific competitive effects. Identifying turfgrass species more amenable to forb species additions is important to subsequent studies aimed at identifying other limiting factors in forb establishment, such as germination and mowing tolerance. This is the first of a series of studies that aims to provide foraging resources for pollinating insects in turf lawns.
Beauregard, M.S., Seguin, P., Sheaffer, C.C. & Graham, P.H. 2003 Characterization and evaluation of North American Trifolium ambiguum-nodulating rhizobia Biol. Fert. Soils 38 311 318
Bertin, C., Paul, R.N., Duke, S.O. & Weston, L.A. 2003 Laboratory assessment of the allelopathic effects of fine leaf fescues J. Chem. Ecol. 29 1919 1937
Bertin, C., Senesac, A.F., Rossi, F.S., DiTommaso, A. & Weston, L.A. 2009 Evaluation of selected fine-leaf fescue cultivars for their turfgrass quality and weed suppressive ability in field settings HortTechnology 19 660 668
Bertoncini, A.P., Machon, N., Pavoine, S. & Muratet, A. 2012 Local gardening practices shape urban lawn floristic communities Landsc. Urban Plan. 105 53 61
Brosnan, J.T., Dickson, K.H., Sorochan, J.C., Thoms, A.W. & Stier, J.C. 2014 Large crabgrass, white clover, and hybrid bermudagrass athletic field playing quality in response to simulated traffic Crop Sci. 54 1838
Christians, N.E., Patton, A.J. & Law, Q.D. 2017 Fundamentals of turfgrass Management. 5th ed. Wiley, Hoboken, NJ
DeBels, B.T., Griffith, S.E., Kreuser, W.C., Melby, E.S. & Soldat, D.J. 2012 Evaluation of mowing height and fertilizer application rate on quality and weed abundance of five home lawn grasses Weed Technol. 26 826 831
Ebeling, A., Klein, A.-M., Schumacher, J., Weisser, W.W. & Tscharntke, T. 2008 How does plant richness affect pollinator richness and temporal stability of flower visits? Oikos 117 1808 1815
Froud-Williams, R.J., Chancellor, R.J. & Drennan, D.S.H. 1983 Influence of cultivation regime upon buried weed seeds in arable cropping systems Appl. Ecol. 20 199 208
Garbuzov, M., Fensome, K.A. & Ratnieks, F.L.W. 2014 Public approval plus more wildlife: Twin benefits of reduced mowing of amenity grass in a suburban public park in Saltdean, UK Insect Conserv. Divers.
Harris, E.M., Martin, D.G., Polsky, C., Denhardt, L. & Nehring, A. 2013 Beyond “lawn people”: The role of emotions in suburban yard management practices Prof. Geogr. 65 345 361
Hill, M.J. & Mulcahy, C. 1995 Seedling vigour and rhizome development in Trifolium ambiguum M. Bieb. (Caucasian Clover) as affected by density of companion grasses, fertility, drought and defoliation in the first year Austral. J. Agr. Res. 46 807 819
Laberge, G., Mabood, F. & Seguin, P. 2005 Kura clover early growth is comparable to that of white clover when not nitrogen limited J. Plant Nutr. 28 447 457
Larson, J.L., Kesheimer, A.J. & Potter, D.A. 2014 Pollinator assemblages on dandelions and white clover in urban and suburban lawns J. Insect Conserv. 18 863 873
Laskey, B.C. & Wakefield, R.C. 1978 Competitive effects of several grass species and weeds on the establishment of birdsfoot trefoil Agron. J. 70 146 148
Leffel, R.C. & Gibson, P.B. 1973 White clover, p. 167–176. In: Forages: The science of grassland agriculture
Lerman, S.B., Contosta, A.R., Milam, J. & Bang, C. 2018 To mow or to mow less: Lawn mowing frequency affects bee abundance and diversity in suburban yards Biol. Conserv. 221 160 174
McCurdy, J.D., McElroy, J.S., Guertal, E.A. & Hall, F. 2013 White clover (Trifolium repens) establishment within dormant bermudagrass turf: Cultural considerations, establishment timing, seeding rate, and cool-season companion grass species HortScience 48 1556 1561
McCurdy, J.D., McElroy, J.S., Guertal, E.A. & Wood, C.W. 2014 White clover inclusion within a bermudagrass lawn: Effects of supplemental nitrogen on botanical composition and nitrogen cycling Crop Sci. 54 1796 1803
Milesi, C., Running, S.W., Elvidge, C.D., Dietz, J.B., Tuttle, B.T. & Nemani. R.R. 2005 Mapping and modeling the biogeochemical cycling of turf grasses in the United States Environ. Manage. 36 426 438
Morris, K.N. 2016 2005 National Kentucky bluegrass test 2006–10 data final report. NTEP No. 11-10. 2011
Potts, S.G., Vulliamy, B., Dafni, A., Ne’eman, G. & Willmer, P. 2003 Linking bees and flowers: How do floral communities structure pollinator communities? Ecology 84 2628 2642
Seguin, P., Sheaffer, C.C., Ehlke, N.J., Russelle, M.P. & Graham, P.H. 2001 Nitrogen fertilization and rhizobial inoculation effects on Kura clover growth Agron. J. 93 1262 1268
Shwartz, A., Muratet, A., Simon, L. & Julliard, R. 2013 Local and management variables outweigh landscape effects in enhancing the diversity of different taxa in a big metropolis Biol. Conserv. 157 285 292
Sincik, M. & Acikgoz, E. 2007 Effects of white clover inclusion on turf characteristics, nitrogen fixation, and nitrogen transfer from white clover to grass species in turf mixtures Commun. Soil Sci. Plant Anal. 38 1861 1877
Smith, L.S., Broyles, M.E.J., Larzleer, H.K. & Fellowes, M.D.E. 2014 Adding ecological value to the urban lawnscape: Insect abundance and diversity in grass-free lawns Biodivers. Conserv. 24 47 62
Sparks, B., Munshaw, G., Williams, D., Barrett, M., Drive, V. & Woosley, P. 2015 Preplant cultivation techniques and planting date effects on white clover establishment into an existing cool-season turfgrass sward HortScience 50 615 620
Springer, T.L. 1996 Allelopathic effects on germination and seedling growth of clover by endophyte-free and -infected tall fescue Crop Sci. 36 1639 1642
Turgeon, A.J. 1999 Turfgrass management. 5th ed. Prentice Hall, Upper Saddle River, NJ
Vandevender, J. 2003 Kura clover planting guide. Natural Resource Conservation Service Plant Materials Center, Alderson, WV