Root and Shoot Responses of ‘Miss Kim’ Lilac to Container Type and Environment

Abstract

Growth and quality of ‘Miss Kim’ lilac produced in two container types (plastic and fabric) and in above ground (AG) versus below ground (BG) systems were compared. Plants were overwintered in place for 2 or 3 years with no additional protection, except in a combined AGBG treatment where pots were AG during the growing season then placed in BG socket pots for winter. Survival and shoot biomass were equal in both container types within the AG or BG systems. The AG systems reduced top and root dry weights compared to BG systems; however, survival and plant quality were not adversely affected except in a bag in pot (BIP) system. Root distribution and morphology, but not mass, were affected by container type, with more small-diameter roots distributed uniformly throughout the substrate in fabric AG containers. Containers inserted into BG sockets (as in pot in pot growing systems) were insulated from lethal high and low root zone temperatures (RZT). These treatments produced the greatest amount of root and shoot growth and are suitable for container production systems in northern areas. Plants reached the same size whether in plastic or fabric liner pots within the BG system. The BG environment, however, did not alleviate root circling and matting. Growth was reduced in AGBG containers as well as AG containers, indicating that winter root mortality was not the only limiting factor. Roots in AGBG experienced the same winter RZT as BG treatments, yet the top and root dry weights were reduced by 41 and 60 percent respectively, in comparison to BG. Environmental stress in AG containers during the growing season may limit growth more than commonly realized.