Dwarf White Clover Supports Pollinators, Augments Nitrogen in Clover–Turfgrass Lawns, and Suppresses Root-Feeding Grubs in Monoculture but Not in Mixed Swards

Abstract

The runoff or leaching of nitrogen fertilizers from monoculture turfgrass lawns contri-butes to water pollution, and such lawns are susceptible to insect pests and provide few resources for pollinators. One approach to creating more sustainable lawns is to incorporate white clover (Trifolium repens L.), a nitrogen-fixing legume, into grass seed mixtures or existing turfgrass swards. “Dutch” white clover (DWC), a ubiquitous landrace, forms non-uniform clumps when intermixed with turfgrasses, thus it is often considered to be a lawn weed. Recently, several dwarf varieties of white clover have been selected for their small leaf size and low growth habit, allowing them to tolerate low mowing heights and blend better with grasses. To date, there have been no studies published on the entomological aspects of dwarf clover in pure stands or intermixed with turfgrass. We established field plots with combinations of DWC, two cultivars of dwarf clover, and tall fescue (Schedonorus arundinaceus (Schreb.) Dumort.) in monoculture or mixed swards, and compared the invertebrate communities therein. Predatory arthropods and earthworm numbers were similar in all plot types. The clover monocultures were resistant to white grubs, but the grub densities in the clover–tall fescue dicultures were similar to those found in the pure tall fescue swards. Dwarf clovers and DWC were similarly attractive to bees and supported similar bee assemblages. The tall fescue foliar N content was elevated 17–27% in the dicultures with clovers.

Temporal Occurrence, Abundance, and Biodiversity of Bees on Weed-Infested Turfgrass

“…As floral resources are dwindling in landscapes, weedy turfgrass lawns can supplement foraging bees with pollen and nectar, and these resources should be conserved. Although current and past studies showed the value of weedy areas in turfgrass lawns [35], homeowners and lawn maintenance managers still strive for well-maintained, manicured turfgrass lawns. Raising awareness of weedy turfgrass may encourage more pollinator-benefitting practices within urban and suburban areas in the future.…”

“…On centipedegrass and bahiagrass, a 14 d mowing gap allowed enough time for the emergence of new spikelets to be available for foraging bees [11,12]. White clover is known to disappear from grassy weed areas over several years [34]; thus, reseeding with white clover is recommended [35]. Bombus, Apis, and Lasioglossum bees dominated the bee community on weeds in turfgrass.…”

Sugar feeding by invasive mosquito species on ornamental and wild plants

“…While most plant species were identified in 1–2 samples, two genera occurred at higher frequencies (in > 12 samples): Prunus and Trifolium . Prunus represents a group of trees and shrubs that are cultivated for their fruits and decorative qualities and Trifolium are extremely common in lawns and along roadsides in the United States and produces a substantial amount of nectar in florets that are assumedly shallow enough for a mosquito’s proboscis to reach 44 , 45 . In a study by Kicel et al 46 , 1-octen-3-ol was determined as a major constituent in the scent profile of Trifolium repens ’ stems and leaves.…”

Sugar feeding by invasive mosquito species on ornamental and wild plants

“…albopictus mosquitoes. This plant is extremely common in lawns and along roadsides in the United States and produces a substantial amount of nectar that gathers at the bottom of tube-shaped florets that are assumedly shallow enough for a mosquito's proboscis to reach [51,52]. It was identified from some plant DNA samples using both barcodes, providing robust evidence that local invasive mosquitoes were using it as a sugar source.…”