Establishing flower strips near agricultural fields with minimal weed management.

Vegetation along field margins is an important component of agroecosystem biodiversity but also harbors problematic weeds. Establishing flower strips along these margins is a well-established method of increasing biodiversity and promoting ecosystem services. Key knowledge gaps are related to interactions between seeded plants and existing weeds. We conducted a two-site field experiment in 2022 and 2023 in NY State, USA to test how seed mix composition (monocots plus dicots vs. dicots only) and seeding density (four rates) modify flower strip establishment under weedy conditions. Measurements included seedbank density and diversity, aboveground density and diversity, biomass, cover, canopy height, density of plants in the flowering stage, and abundance of bees, ladybeetles, and spiders. We found that weeds emerging from the soil seedbank hampered flower strip establishment at both sites. The aboveground density of seeded species was highest when monocots plus dicots were seeded at the highest tested rates. Although seeded plants occurred at lower densities than non-seeded plants, they were larger than non-seeded plants in 2023. Mean seeded plant size (g per individual) in September 2023 was 6–54 g and mean non-seeded plant size was below 1 g in all treatments. The number of seeded dicots in the flowering stage tended to increase with seeding rate in 2023. Flower strips affected bee abundance, especially in sweep-net samples from August 2023 (P = 0.01). At the Ithaca site, control treatments averaged 0.0–0.3 bees while flower strip treatments averaged 1.3–4.7 bees. Overall, these results highlight the potential for flower strips to enhance biodiversity even under weedy conditions. They also suggest that farmers seeking to establish flower strips in weedy fields should use high densities of competitive species. • Weeds hamper establishment of flower strips in agroecosystems. • Our study demonstrated strong competitive interactions between weeds and flowers. • An increased seeding density was more useful than adding monocot seeds to the mix. • Flower strips were ecologically beneficial even in weedy areas. [ABSTRACT FROM AUTHOR]