The 2009 ASHS Annual Conference

Pine bark is the primary potting component for nursery containers in Ohio and other Upper Midwest states.  Most pine bark comes from lumber or paper mills in southern states.  Due to the recent energy crisis, availability of pine bark has declined while the cost to import pine bark from southern states has risen dramatically.  The objective of this research was to determine if locally grown switchgrass (Panicum virgatum) could be harvested and used as an alternative to pine bark in nursery containers.  Switchgrass was processed through a hammermill with a 2.5 cm screen prior to use.  Switchgrass was blended with either 0%, 30%, or 50% sphagnum peat moss by volume.  Roses (Rosa ‘ChewMayTime’) from 5.7 cm wide cells were potted into 15 cm tall and wide plastic containers with one of the three substrates.  Switchgrass with 0% peat moss had low water holding capacity (36%) compared to that amended with 30% or 50% (45% and 53%, respectively).  Substrate pH of switchgrass with 0% peat moss was 6 or greater throughout the experiment.  Amendment with peat moss at 30% or 50% reduced pH to between 4.0 and 4.5 throughout the experiment.  Despite differences in substrate physical properties and pH, substrate type caused no differences in root or shoot growth over the course of the experiment (8 weeks).