Crabapple and lilac growth and root-zone temperatures in Northern Nursery production systems

Abstract

Crabapple (Malus 'Donald Wyman') and common lilac (Syringa vulgaris 'Monge') were grown from liners to marketable size in five production systems: field-grown, plastic container, pot-in-pot (PiP), bag-in-pot (BiP), and above-ground system (AGS). The objectives were to compare growth in modified container systems, which could potentially eliminate overwintering requirements in northern production nurseries and to compare the effects on tree root growth during landscape establishment. There were no significant differences in crabapple root or shoot mass after two seasons except PiP dry root weights exceeded field-grown trees. For lilacs, there were significant differences in growth and shoot dry weight with field-grown and PiP plants being largest. PiP root-zone temperatures (RZTs) were similar to field-grown RZTs. Container, BiP, and AGS systems all exceeded lethal high and low RZT thresholds, resulting in root damage. Five trees from each treatment were transplanted into a low-maintenance landscape and dug up 3 years later. There were no significant differences in top growth, but the effects of the production systems were evident in the root architecture. BiP and field-grown trees had fewest root defects and the greatest number of roots extending into the landscape soil.