Abstract

The efficacy of non-chemical weed control during plug establishment of a wildflower meadow on glyphosate-killed turf grass was studied. Each field sub-block (not-tilled or twice-tilled to 15 cm (6 in) depth) on killed grass received the following sub-plot soil cover treatments: no cover, woven polypropylene weed fabric, double shredded hardwood/softwood mulch at 7.5 cm (3 in) depth, or fabric covered by mulch. Each 3 × 3 m (10 × 10 ft) subplot was planted in late spring with 100 plugs on 30 cm (1 ft) centers at the following frequency: Baptisia australis (10), Coreopsis lanceolata (20), Solidago speciosa (10), Panicum virgatum (20), and Schizachyrium scoparium (40). Tillage of the killed grass not only failed to benefit wildflower establishment, but increased weed shoot biomass during the second growing season. Greater wildflower shoot dry weights at 120 days after transplanting with mulch (with or without underlying fabric) than with fabric alone or no cover was associated with greater soil moisture, reduced soil temperature range, and reduced weed cover and shoot biomass. Weed fabric compared to no cover failed to affect wildflower shoot dry weights during either growing season but decreased weed growth during the second growing season. Fabric under mulch compared to mulch alone generally failed to affect wildflower growth and had no effect on weed growth during either growing season. During the second growing season, weed shoot dry weights remained low in mulched plots and remained high in non-mulched plots. Regardless of cover, wildflower shoots underwent considerable dry weight gain, while weed shoot dry weights generally remained constant or declined during the second growing season compared to the first. We conclude that, at least under our experimental conditions, applying a 7.5 cm (3 in) layer of wood chip mulch directly over glyphosate-killed turf was the most efficaceous and cost effective method of establishing a wildflower meadow using wildflower plugs. Neither placing weed fabric under the mulch nor twice-tilling the killed turf before mulch application benefitted wildflower shoot growth.