The Landscape Below Ground
This 24-chapter manual contains the proceedings of an International Workshop in Tree Root Development in Urban Soils presented by The Morton Arboretum in Lyle, Illinois. (©1994, 222 pp., softcover, Developed in partnership with the USDA Forest Service)
It has been said that 80 percent of all landscape tree problems start below ground. Yet the below ground parts of the tree are the most difficult, and often the most expensive to study. Study often requires the destruction of the specimens. Despite these challenges, our base of knowledge continues to grow, due in great part to the scientists who participated in the Landscape Below Ground workshop.
Concerns about root system development of landscape trees should begin at propagation. Containerised plants often develop circling roots that can lead to serious problems when they are planted out in the landscape. Use of properly designed containers, and proper treatment of the root ball at planting time, can help to prevent circling roots.
Transplanting is an unnatural process. Over 90 percent of the root system can be lost. During the time that the root system is regenerating, water stress can develop very quickly. The time required for the tree to establish on its new site is affected by many factors, and may take years in northern climates. Severing roots during the transplanting process can lead to girdling roots.
Experienced horticulturists will sometimes spend more on preparing the planting site than on the plant. Alkalinity, deicing salts, and oxygen depleted rooting environments create unseen stresses for trees. These stresses particularly affect the growth of trees in planters. The challenge is to provide a suitable site that is also economical.
Providing specially designed root space under pavements has been successful on some sites, but sometimes roots growing under pavements are considered a nuisance. Physical and chemical barriers are being developed, but sometimes installing them around existing trees can cause major root damage. A study on root damage from trenching produced some unexpected results.
Soil compaction and resulting poor aeration is one of the biggest problems faced in the landscape. Measuring compaction and aeration can also be a challenge. Incorporation of light-weight aggregates before plants are installed can provide long-term benefits, but remedial action is often the only choice. A variety of equipment is available for this job.
The most current information available on all of these subjects is included in these proceedings.