A Comparison of “Air Root Pruning” and Conventional Plastic Containers for Cultivation of Two Palm Species

As monocotyledonous plants, palms have an adventitious, uniform root system usually branching to few orders.  Palm roots often branch when pruned, however, making a compact network.  In nursery production, some containers have various types of air holes cut into the side walls, which are purported to increase root production by “air pruning.”  We evaluated the effect of seven plastic containers (two without holes [standard], one with slit-like holes, two with line-like holes, and two with round holes) on the growth of two palms: kentia (Howea forsteriana) and king (Archontophoenix cunninghamiana). Container volume varied from 10196 cm³ to 29102 cm³ and significantly affected new leaf production: palms growing in larger containers produced more leaves.  King palms grew the largest stems in standard containers. Kentia palms showed no difference in stem caliper when grown in a standard container or one with line-like holes. The container with slit-like holes produced king palms of the poorest quality and size, likely because potting media was more readily flushed through the openings of this type of pot during irrigation. By contrast, containers with round holes produced kentia palms with the smallest stem caliper size. In summary, containers with air holes in the side walls did not increase palm leaf production or stem caliper size but larger containers did increase these growth parameters.