Effects of media porosity and container size on overwintering and growth of ornamental grasses

Five ornamental grasses (little bluestem [Schizachyrium scoparium (Michx.) Nash], prairie dropseed [Sporobolus heterolepis (A. Gray) A. Gray], feather reedgrass [Calamagrostis xacutiflora (Schrad.) DC. 'Karl Foerster'], flamegrass (Miscanthus Anderss. 'Purpurascens'), and variegated Japanese silvergrass (Miscanthus sinensis Anderss. 'Variegatus')} were propagated by transplanting plugs or field divisions into 480-mL (10-cm round), 2.7-L (no. 1), and 6.2-L (no. 2) nursery containers with media ratios (v/v) of 0:1, 1:1, 2:1, 3:1, 1:0 rice hulls to sand, resulting in aeration porosities in 2.7-L containers of 5%, 12%, 22%, 28%, and 41%, respectively. Planting dates were between 28 Oct and 10 Nov. 1997; 30 Apr. and 7 May 1998; and 23-28 Oct. 1998 and 1-10 May 1999. Plants were covered with plastic and straw from the second week in November until the second week in April. Winter survival was evaluated 6 weeks after uncovering and for finished dates every 2 weeks thereafter. Species had a significant effect on overwintering survival, but container size and media did not. Sporobolus heterolepis and M. sinensis 'Variegatus' had significantly lower overwintering survival than the other species. Container size significantly influenced growth; the 6.2-L containers had the highest values for all growth parameters. Growth response to media was a weak (nonsignificant) quadratic response, indicating for these species no clear trend for the best media aeration porosity.