2013 ASHS Annual Conference

In the Great Plains region of the U.S., Eastern redcedar (Juniperus virginiana; ERC), an aggressive tree species, has been identified as a possible alternative to pine bark (PB) for nursery substrates. The objective of this study was to evaluate plant growth of eight species produced in an ERC- or PB-based substrate, both in production and after field planting. In June 2011, three substrate mixes consisting of: 1) 80% PB : 20% sand; 2) 80% ERC : 20% sand; and 3) 40% PB : 40% ERC : 20% sand were pre-plant incorporated with controlled-release fertilizer containing micronutrients. Dwarf maiden grass (Miscanthus sinensis ‘Little Kitten’), Knockout rose (Rosa ‘Radtkopink’), holly (Ilex glabra ‘Compacta’), and Allee lacebark elm (Ulmus parvifolia ‘Emer II’) were planted in trade 11.36 L containers. Sedum (Sedum telphium ‘Autumn Joy’), hosta (Hosta ‘Sum and Substance’) and daylily (Hemerocallis ‘Charles Johnston’) were grown in trade 3.81 L containers. Growth index (GI), caliper (lacebark elm only), foliar SPAD, pH and EC levels were measured during the production phase. In October 2011 plants were field planted. Plants were harvested 336 days after field planting (DAFP). Shoots and roots were separated for dry weight data. At the end of the production phase, no significant differences were observed for substrate pH and EC. Knockout rose had no significant difference in plant GI among the substrates. Maiden grass and holly plants grown in PB had greater GI than plants grown in ERC. Sedum and lacebark elm had greater GI in the PB : ERC mix. Knockout rose and holly grown in ERC had greater leaf greenness (SPAD). Substrate blend did not influence SPAD measurements of lacebark elm and blanket flower. Lacebark elm had greater caliper in PB : ERC mix. At 336 DAFP, the substrate did not influence GI, SPAD, and dry weights (shoot and root) of knockout rose, maiden grass, daylily, sedum, and lacebark elm. Holly and hosta grown in PB had greater GI and shoot dry weight, whereas root dry weight and SPAD were unaffected. Overall, container-grown plants produced in ERC were slightly smaller than plants grown in PB, however, these differences were overcome in one growing season in the field for most species.