Comparing the Missouri Gravel Bed and a Wood Chip Production Method for Tree Growth

Tree root defects from current nursery production practices influence short- and long-term tree performance and survivability. The Missouri Gravel Bed (MGB) system, a production method using gravel as a substrate, has been used to prevent many of these defects from occurring. MGB production involves planting bare root stock into a bed of gravel with frequent drip irrigation in order to produce a root system with relatively few defects. MGB production methods have also been purported to allow for summer transplanting of many species, as opposed to traditional dormant transplanting.Because gravel has low water- and nutrient-holding capacity, biochar (5% by volume) was incorporated into one plot as a possible means of improving both water- and nutrient-holding capacity over gravel alone. Wood chip mulch was also investigated as a growing substrate in place of the gravel in a growing system. In 2015, three species, Quercus bicolor (swamp white oak), Taxodium distichum (baldcypress), and Tilia cordata (littleleaf linden), were studied in pea gravel (PG), biochar-amended pea gravel (BC), and wood chip mulch bed (MB) growing environments. Very few differences occurred over the growing season with above- or belowground parameters indicating that the minimal-to-no-cost, more readily available substrate of wood chip mulch should be considered in these growing systems.

Effects of Tree Production Method and Transplanting on Root Hydraulic Conductance1

The objective of this study was to investigate the post-transplant, root specific hydraulic conductance (KS) of two oak species (Quercus bicolor Willd. and Quercus rubra L.). Q. bicolor and Q. rubra trees responded differently to transplanting across the differing types of production methods. Overall, higher post-transplant fine root KS resulted in a larger leaf area after transplanting. Container-grown (CG) trees had the highest root KS immediately after transplanting compared to balled-and-burlapped (BNB), in-ground fabric (IGF), and bare-root (BR) trees, but KS in CG trees was largely reduced at the end of the first growing season after transplanting. Post-transplant variations of fine root KS also differed between the two tree species. Fine root KS remained similar in BNB and IGF Q. bicolor trees after transplanting, but increased with time after transplanting in Q. rubra trees. The increase in KS was especially greater in BNB and BR Q. rubra trees than IGF Q. rubra. Index words: transplanting, root hydraulic conductance, tree production method, Quercus bicolor, Quercus rubra, oak. Species used in this study: Swamp white oak (Quercus bicolor Willd.); northern red oak (Quercus rubra L.).

The Effects of Planting Depth on Windthrow, Stability, and Growth for Four Tree Species in Containers

Establishing the effects of planting depth on tree stability and growth is critical in understanding the role nursery production plays in planting depth issues at the landscape level. In this study, bare root Whitespire birch (Betula platyphylla var. japonica ‘Whitespire’), green ash (Fraxinus pennsylvanica), Snowdrift crabapple (Malus × ‘Snowdrift’), and bicolor oak (Quercus bicolor) were grown for 17 weeks in a container production setting with four levels of substrate over the first main-order root: 0, 5, 10, and 15 cm. Birch demonstrated the greatest instability of all species, leaning significantly more when planted at 0 cm than at 15 cm. In ash and crabapple, there were no significant differences in either the number of trees leaning or the amount of lean in all treatments throughout the study. Oak stems bent excessively, invalidating lean measurements. Stem caliper increase was significantly greater in ash planted 0 and 5 cm deep than 10 and 15 cm deep. There was no significant difference in stem caliper increase between planting depths in other species. Birch planted 0 and 5 cm deep had greater root volume increase than those planted 10 and 15 cm deep. Root volume increase in ash, crabapple, and oak did not differ significantly between treatments. Infrequent windthrow events were observed, but appeared random and apparently unrelated to planting depth. The perceived benefit of planting trees deep in containers to improve stability was observed in only one species (birch) at one depth (15 cm) and was at the expense of significantly reduced root volume increase.