Urban Forestry — Abstract of Paper


The Influence of Treeshelters and Irrigation on Shoot and Root Growth of Three California Oak Species
Douglas McCreary,¹ Laurence R. Costello,² Jerry Tecklin,³ Katherine Jones,² and David Labadie³


Treeshelters are individual seedling protectors that can accelerate height growth of native California oaks. There is concern, however, that this growth may occur at the expense of the roots, resulting in poor long-term field performance. This study could detect no differences between protected and unprotected seedlings in shoot weight, root weight or shoot/root ratios after 4 1/2 years, suggesting that shelters do not adversely affect balances between seedling shoots and roots. Shelters did, however, stimulate height growth and reduce initial stem diameter growth, resulting in tall narrow plants that might not be able to stand upright without staking if shelters are removed too early. This study also evaluated the effects of irrigation levels on growth of three oak species—blue oak (Quercus douglasii), valley oak (Q. lobata) and coast live oak (Q. agrifolia). There were no significant differences among irrigation levels, suggesting that, in environments similar to the study site or in areas with fertile deep soils, supplemental irrigation after initial establishment is not necessary. Finally, the extremely rapid growth of both the valley oak and coast live oak in this study indicates that these species show promise for planting in urban landscapes.