The effect of container size and aeration conditions on growth of roots and canopy of woody plants

Studies were made on the effect of container size on the growth of Ficus retusa, Pistacia lentisucus and Dodonea viscosa. The larger the container, the larger was the plant. The ratio of plant weight to unit of container-volume decreased with increasing size, whereas the ratio of plant weight to unit surface area remained more or less constant with changing size of container.Aeration of 10-liter containers using 3 methods to increase the surface area of the mixture by 60% while reducing the volume by 40%, increased growth by as much as 165%. Especially enhanced growth was achieved when the structure of the root system was not changed by aeration devices. Root growth was enhanced most in the lower section of the containers. The ratio root-weight: container-volume increased up to 340%, whereas the ratio root-weight: mix-surface area increased by only 100% at the most.These results, and others, indicate that most of the thin roots (or root activity) of woody plants grown in containers are concentrated in the periphery of the container, whereas the roots in the center serve mainly as connectors between the main and peripheral roots.It is suggested that the root system in the containers changed the ratio between the 3 soil phases by decreasing the gaseous phase, mainly in the upper part of the container, and that this phenomenon is a major contributor to the low efficiency of the container-volume usage. Correction can be best achieved by increasing the outer surface of the mixture rather than by using a better aerated mixture.