Insights into standards for nursery-grown tree stock

Root to shoot balance in nursery tree stock is an important quality characteristic and contributing factor to tree form, growth and planting success in the landscape. Yet specifying root to shoot balance criteria and standards has been problematic owing to a lack of critical information on biological variation among species, nursery production practices and the role of climatic influences on shoot morphology and growth. Our research addressed this knowledge gap through a field-based survey of nursery tree production throughout Australia, capturing information on 159 species and varieties and nearly 14,000 trees. Our findings revealed large natural variation in root to shoot balance across the wide range of containerised trees sold in Australian nurseries. Species differences were well captured by a simple classification into winter deciduous and evergreen categorical types. This rich data set, specific to nursery grown trees in Australia, provides insights into potential improvements in quality assessment criteria and standards for nursery-grown tree stock for landscape use.