INFLUENCE OF MOWING ON LEAF AND TILLER ORIENTATION OF TURFGRASSES

Annual bluegrass (Poa annua L.) is a major grass weed on athletic fields. Since mowing modifies interspecies competitive ability, a program was initiated to determine if any morphological adaptations to mowing occur which might enable Kentucky bluegrass (Poa pratensis L.) to compete more successfully with annual bluegrass. Changes in leaf and tiller orientation of 11 Kentucky bluegrass cultivars and annual bluegrass in response to mowing or not mowing were measured. The mowing treatment consisted of clipping the grasses at 2, 3, 4 or 5 cm. For the 12 grasses there was a significant increase in leaf angle at the 2- and 3-cm mowing height. The increase was not consistent for all grasses and mowing treatments. Leaf angle was not related to the ability of the cultivars to compete with annual bluegrass. The grasses became more prostrate when mowed. While Kentucky bluegrass cultivars with the most prostrate growth habit have been shown to be more competitive with annual bluegrass, growth habit does not appear to be sufficiently important to be the main criterion for choosing Kentucky bluegrass cultivars for use in regularly irrigated, close clipped athletic fields.