Flowering bulbs are known to naturalize in grassy areas like meadows and pastures (Bryan, 2002; Leeds, 2000). Although many plant species are described as bulbs or geophytes, their storage structures may be botanically characterized as corms, rhizomes, or tubers (Hessayon, 1996). Examples of true bulbs include Hyacinthus (hyacinth), Muscari (grape hyacinth), and Narcissus (daffodil) spp. (De Hertogh and Le Nard, 1993). Crocus (crocus) and Gladiolus (gladiola) spp. produce corms, and tubers and rhizomes are found in Anemone (windflower) and Eranthis (winter aconite) spp. (De Hertogh and Le Nard, 1993). To simplify this discussion here, the term “bulb” will be used to discuss all of these plants, including those with true bulbs, corms, tubers, and rhizomes.
Bulbs that naturalize in grassy areas must be vigorous enough to compete with the grass, and grass systems must be managed in a way to not damage the bulbs (i.e., postponing mowing or grazing until foliage has had time to senesce) (Hessayon, 1996). More than 16 million hectares of managed turfgrass are cultivated in the United States and represent lawns, golf courses, parks, roadsides, cemeteries, and athletic playing fields (Milesi et al., 2005). Both temperate (cool-season) and tropical (warm-season) grasses are used in turf situations and they vary considerably in their growth phases, with cool-season grasses growing most in spring and fall and warm-season grasses experiencing peak growth in the summer.
In the transition zone, warm-season turfgrasses can experience low-temperature induced dormancy for up to 6 months of the year (Patton, 2012). Two previous studies (Mirabile et al., 2016; Richardson et al., 2015) demonstrated that some flowering bulbs can persist in zoysiagrass (Zoysia japonica Steud.) and bermudagrass (Cynodon dactylon) in transition zone environments, providing color and biodiversity to dormant turfgrass situations. However, both studies examined a small number of bulb entries, and neither study documented how these plants might affect other organisms in the system, such as beneficial pollinating insects. In highly managed turfgrass systems, many flowering bulbs may be unable to withstand basic lawn cultural practices such as mowing or weed control.
Pollinator decline has been widely documented in recent years and has been associated with habitat and biodiversity loss, wide-spread planting of monocultures, pesticide usage, pollinator pests and diseases, and climate change (Biesmeijer et al., 2006; Goulson et al., 2015; Potts et al., 2010). Pollinator health is enhanced when diverse floral resources are available throughout the seasons when pollinators are active (Abrol, 2011; Goulson et al., 2015; Wackers and van Rijn, 2012). Significant expanses of managed turfgrasses, such as roadsides, cemeteries, and lawns, represent land areas that might be designed and managed to support pollinating insects (Hopwood, 2008; Ries et al., 2001). Historically, seed mixtures for lawns and pastures contained clover and other legumes (Tyson, 1941), which were included to provide nitrogen to the grass plants through symbiotic nitrogen fixation (Sincik and Acikgoz, 2007). However, a secondary benefit of those species was the abundant floral habitat provided to pollinating insects (Larson et al., 2014). With the advancement of the synthetic herbicide and fertilizer industry, flowering plants are often eliminated from turfgrass systems, consequently removing floral resources for pollinators.
Some flowering bulbs, such as crocus and grape hyacinth, have been documented to provide forage resources for honey bees in early spring (Steinkraus, 2010), but information on pollinator preference over a wide range of bulbs is limited. Identifying bulb species that could both add color to dormant warm-season turfgrasses and supply nutrition to pollinators, could fill two roles in many turfgrass ecosystems. If bulbs do not interfere with the majority of turfgrass cultural practices, they could provide additional ecosystem services of lawns and encourage home and business owners to establish pollinator-friendly habitats. The objectives of the current study were to investigate a large number of early-spring flowering bulbs for persistence in warm-season turfgrasses and determine if flowers produced by early-spring bulbs provide appropriate pollen and nectar resources for pollinating insects.
Abrol, D.P. 2011 Pollination biology: Biodiversity conservation and agricultural production. Springer, New York, NY
Anderson, R.G. 2004 Spring flowering bulbs for Kentucky gardens. Kent. Coop. Ext. Serv. Bul. HortFacts 52-04
Biesmeijer, J.C., Edwards, M., Kleukers, R., Kunin, W.E., Ohlemuller, R., Peeters, T., Potts, S.G., Reemer, M., Roberts, S.P.M., Shaffers, A.P., Settele, J. & Thomas, C.D. 2006 Parallel declines in pollinators and insect-pollinated plants in Britain and the Netherlands Science 313 351 354
Bryan, J.E. 2002 Bulbs. Timber Press, Portland, OR
Canale, A., Benelli, G. & Benvenuti, S. 2014 First record of insect pollinators visiting Muscari comosum (L.) Miller (Liliaceae-Hyacinthaceae), an ancient Mediterranean food plant Plant Biosyst. 148 889 894
Carta, A., Flamini, G., Cioni, P.L., Pistelli, L. & Peruzzi, L. 2015 Flower bouquet variation in four species of Crocus ser. Verni J. Chem. Ecol. 41 105 110
Christians, N.E., Patton, A.J. & Law, Q.D. 2017 Fundamentals of turfgrass management. 5th ed. Wiley, Hoboken, NJ
Cornell University 2007 Best 15 bulb & perennial combinations. Department of Horticulture, Ithaca. <http://www.hort.cornell.edu/combos/FeaturedCombos/Best15Combos/index.html>
Dana, M.N. 2001 Flowering bulbs. Purd. Univ. Coop. Ext. Serv. HO-86-W
De Hertogh, A.A. & Le Nard, M. 1993 Botanical aspects of flower bulbs, p. 7-20. In: De Hertogh and Le Nard (eds.). The physiology of flower bulbs. Elsevier, Amsterdam, Netherlands
Goulson, D., Nicholls, E., Botias, C. & Rotheray, E.L. 2015 Bee declines driven by combined stress from parasites, pesticides, and lack of flowers Science 347 6229 1255957, doi: 10.1126/science
Hessayon, D.G. 1996 The bulb expert. Transworld Publishers, London
Hodges, D. 1952 The pollen loads of the honey bee: A guide to their identification by colour and form. Intl. Bee Res. Assn., London, England
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
Leeds, R. 2000 The plantfinder’s guide to early bulbs. ASHS Press, Alexandria, VA
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
Mirabile, M., Bretzel, F., Gaetani, M. & Lulli, F. 2016 Improving aesthetic and diversity of bermudagrass lawn in its dormancy period Urban For. Urban Green. 18 190 197
Payero, J. 2017 Introduction to growing degree days. Clem. Coop. Ext. AC-09
Potts, S.G., Biesmeijer, J.C., Kremen, C., Neumann, P., Schweiger, O. & Kunin, W.E. 2010 Global pollinator declines: Trends, impacts, and drivers Trends Ecol. Evol. 25 345 353
Richardson, M.D., McCalla, J., Buxton, T. & Lulli, F. 2015 Incorporating early spring bulbs into dormant warm-season turfgrasses HortTechnology 25 228 232
Ries, L., Debinski, D.M. & Wieland, M.L. 2001 Conservation value of roadside prairie restoration to butterfly communities Conserv. Biol. 15 401 411
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. Plan. 38 1861 1877
Totland, Ø. & Matthews, I. 1998 Determination of pollinator activity and flower preference in the early spring blooming Crocus vernus Acta Oecol. 19 155 165
Tyson, J. 1941 Growing beautiful lawns. Mich. Agr. Expt. Sta. Res. Bul. 224
Wackers, F.L. & van Rijn, P.C.J. 2012 Pick and mix: Selecting flowering plants to meet the requirements of target biological control insects, p. 139–165. In: G.M. Gurr, S.D. Wratten, W.E. Snyder, and D.M.Y. Read (eds.). Biodiversity and insect pests: Key issues for sustainable management. Wiley, Chichester, England
Wisdom, M.M. 2018 Systems to attract and feed pollinators in warm-season lawns. Univ. of Arkansas, Fayetteville, MS Thesis. 2975. <https://scholarworks.uark.edu/etd/2975>