Cool-Season Turfgrass Germination and Morphological Development Comparisons at Adjusted Osmotic Potentials

One of the major factors limiting seed germination and seedling development in a low-input, low-maintenance environment is soil moisture availability, yet little is known about the germination response of cool-season turfgrasses to differing osmotic potentials. Controlled-environment studies were conducted to identify germination characteristics of cool-season turfgrass species experiencing water-restricted conditions. At osmotic potentials between 0.0 and -1.6 MPa, perennial ryegrass (Lolium perenne L.) germinated more and had greater radicle lengths than tall fescue [Schedonorus arundinaceus (Schreb.) Dumort], hard fescue (Festuca brevipila Tracey), strong creeping red fescue (F. rubra ssp. rubra L.), Chewings fescue [Festuca rubra L. ssp. fallax (Thuill.) Nyman], and Kentucky bluegrass (Poa pratensis L.). Under higher osmotic potentials of 0.0 to -0.8 MPa, strong creeping red fescue had the greatest plumule lengths, but only perennial ryegrass was able to maintain significant plumule length at an osmotic potential of -1.2 MPa. Generally speaking and with some deviation between species, decreasing water potential between 0 and -0.7 MPa serves primarily to delay germination while decreasing water potential between -0.7 and -1.6 serves primarily to prevent germination. Based on germination occurrences and initial radicle and plumule length development at decreasing osmotic potentials, utilizing perennial ryegrass in turfgrass seed mixtures may enhance establishment under low soil moisture conditions.