Dune sedge is a perennial, creeping sedge with slow-growing rhizomes, which forms a dense leafy cover 20–25 cm tall if not mowed. It tolerates moderate traffic and a variety of soil types and climates, including the hot summers in the Central Valley of California. Like most sedges (Carex sp.), it grows well in partial shade, but with sufficient water will perform well in full sun (Greenlee, 2000). It can be mowed regularly as a turf or mowed one to several times per year at height of 8–10 cm. Unmowed, it makes an attractive natural deep green meadow and remains green year-round, performing similar to fine-leaf fescues (Festuca sp.).
Broadcast seeding of dune sedge is not practical because the seed is difficult to collect in large enough amounts, it is slow to emerge in field conditions, and establishment is sporadic due to weed competition (Amme, 2008). Therefore, it is typically established by transplanting plugs or plants grown in small pots 6–12 inches apart (Greenlee, 2000), and plants spread by rhizomes. Closer spacing of transplants is cost-prohibitive for larger plantings, and wider spacing exacerbates weed competition for 1 year or more.
Weed control is essential in weedy sites for 1 year to reduce the weed seed bank (Anderson, 2001). Weeds should be controlled in the fall or winter before planting using broad-spectrum herbicides, and/or preemergent herbicides can be used immediately following planting. Nonchemical preplant strategies include weed flaming, sheet mulching, or soil solarization. Although susceptible to weed competition during establishment, dune sedge is very competitive once established and subsequent weed control is often minimal.
A turf demonstration trial was established in Sacramento County in 2010, in which four turf species were each compared at irrigation regimes of 40%, 60%, and 80% reference evapotranspiration [ETo (Ingels, 2011)]. Dune sedge was fairly drought tolerant, performing well at 60% ETo, whereas clustered field sedge (Carex praegracilis) exhibited browning and severe stunting at this level. The sedges and several other species were planted as plugs or from small pots. All weeds were controlled in the year before planting, but where transplants were used weed seedling growth was substantial, requiring three to four periods of extensive hand weeding until full establishment of the turf.
In a New Zealand study, eight postemergent herbicides were evaluated for weed control and plant phytotoxicity after spraying over forest plants, including weeping brown sedge [Carex flagellifera (Harrington and Schmitz, 2007)]. Only glyphosate, a nonselective herbicide, and amitrole, which controls annual grasses and broadleaf and aquatic weeds, caused substantial phytotoxicity to the weeping brown sedge. Aminopyralid, clopyralid, fluazifop, haloxyfop, metsulfuron, and terbuthylazine caused little or no phytotoxicity. In another New Zealand study, clethodim, clopyralid, dicamba, fluazifop, haloxyfop, and triclopyr were not phytotoxic to the weed species oval sedge (Carex ovalis) or the native species (Carex gaudichaudiana), but glyphosate killed 100% of these plants (Champion, 1998).
In a study conducted in Illinois, the postemergent herbicide sethoxydim was used for treatment of canary grass (Phalaris arundinacea) without interfering with the growth of a native sedge/meadow seed mix (Simpson, 2009).
Interest in alternative turf species such as dune sedge is increasing, but little information is available on the efficacy and crop safety of common weed control tactics during the critical establishment period. Therefore, three trials were conducted in newly transplanted dune sedge to evaluate weed control efficacy and crop response. The purpose of this project was to test several weed control methods in a dune sedge planting and evaluate the phytotoxicity of herbicides on the transplants. We had a special interest in testing reduced-risk postemergent herbicides because of local interest in reducing the use of synthetic herbicides.
Anderson, J. 2001 Using transplants to establish native grasses, sedges, rushes and forbs (plug planting), p. 69–70. In: P.R. Robins, R. Bresnick Holmes, and K. Laddish (eds.). Bring farm edges back to life: Landowner conservation handbook. Yolo County Resource Conservation District, Woodland, CA
Champion, P.D. 1998 Selective control of weeds in New Zealand wetlands. Proc. 51st N.Z. Plant Protection Conf. 1998:251–254
Greenlee, J. 2000 Sedge lawns for every landscape, p. 31–35. In: S. Daniels (ed.). Easy lawns: Low maintenance native grasses for gardens everywhere. Storey Books, North Adams, MA