Effect of Container Size on Tree Establishment and Anchorage

2011 | Dr. Edward Gilman, University of Florida

Wind causes tree overturning which damages trees, adjacent buildings, and associated structures. Tens of thousands of trees (maybe more) overturned in hurricanes in the southeast United States between 1989 and 2004 (Duryea et al. 2007). In many cases the original nursery root ball was clearly evident as young trees lay horizontal on the ground. Trees were poorly rooted into landscape soil, even when planted 10 or more years earlier. Periphery of root balls was defined by roots deflected by the container wall or branched where roots were cut when transplanted from a field nursery. Causes of root failure in wind are poorly documented for non-coniferous shade trees. Container production has become increasingly popular in the past 50 years in the warmest parts of North America and is increasingly used in northern climates. Trees planted in containers typically have root defects such as circling, kinked, or diving roots. If left untreated, these defects can lead to tree instability when planted in the urban landscape.  The literature indicates that root systems set main structural roots early in their life, perhaps in the first 3 to 5 years. If trees are still in a container at this time, all structural roots may be deflected by the container wall reducing the number of straight roots that grow into the landscape soil. Straight roots have been associated with stable trees when planted from small liner pots in reforestation efforts; bent roots lead to anchorage problems. There is little data on landscape sized trees.

Study Results
Acer rubrum L ‘Florida Flame’ were grown in #3 containers of eight types, then shifted to #15 containers, then finally into #45 containers. Half the trees were root pruned by removing periphery 3 cm of root ball at each shift to larger containers. In addition to and simultaneous with being shifted into successively larger containers, some trees from each container size were planted directly into soil. Type of container and root pruning had no impact on trunk diameter, tree height, or root cross-sectional area on trees planted into soil from any container size. Type of container influenced architecture of planted root systems evaluated when all trees were five-years old with limited impact on anchorage. Container type only impacted anchorage of trees planted from #45 containers, and impact was small. In contrast, shaving root balls during production substantially reduced imprint left by all containers evaluated when trees were five-years-old. Shaving during production also improved anchorage by 20%-25% compared to not root pruning. More roots grew on north than the south side of tree in the nursery and landscape. Bending stress increased with trunk angle and its square while winching trunks to five degrees tilt.

Year: 2011

Funding Duration: 1-3 years

Grant Program: John Z. Duling

Grant Title: Effect of Container Size on Tree Establishment and Anchorage

Researcher: Ed Gilman

Key words: Bending Stress; Container Production; Root-soil Plate; Straight Roots

Peer Reviewed Publications from Grant:

• Gilman, E., M. Paz and C. Harchick (2016). Effect of Container Type and Root Pruning on Growth and Anchorage after Planting Acer Rubrum L. Into Landscape Soil. Arboriculture & Urban Forestry 42(2): 73-83.
• Gilman, Edward F., Miesbauer, Jason, Harchick, Chris, and Beeson, Richard C. 2013. Impact of Tree Size and Container Volume at Planting, Mulch, and Irrigation on Acer rubrum L. Growth and Anchorage. Arboriculture & Urban Forestry 39(4): 173–181. View the Publication >

General Audience/Trade Publications:

Presentations:

For more information on this project, contact the researcher via TREE Fund at treefund@treefund.org.