Rooting habits of trees and the impact thereof on building structures.

The stability of a tree and its capacity to extract moisture and nutrients from the soil necessitate the development of an effective and sturdy root system.  The conformation and spread of a root system is genetically defined, but is also adaptive to site conditions.  In addition, time is a factor, as older trees can develop extensive root systems in search of water and nutrients.

In South Africa there are many different climates with particular soil types that can influence the development of root systems.  A major problem arises where specific trees are planted too close to structures or installations which can be damaged by root systems.  Building foundations, paved areas, sewerage pipes and irrigation pipes are all vulnerable when a root system penetrates to deep or too wide.

Many of these occurrences are not visible immediately, but are only noticed when a real problem manifests with cracking walls or pipes. At this stage, the tree is already established and it becomes an issue to remove the tree.  The answer to this dilemma is planning with foresight and good species selection for a specific site.

Expert advice must be taken in respect to appropriate climate and soils; intelligent design that embrace site spaces and structures; good planting and establishment techniques as well as on-going maintenance and care of trees.  Through improved knowledge and planning, property owners and estate managers will be better able to ensure correct placement and location of trees, in order to avoid costly damage to infrastructure in the future.

Relocation of trees

Relocating established trees or shrubs from one location to another is one method of changing your landscape and saving money at the same time.  When moving a large specimen to accommodate a new building layout or to preserve the tree in a different locale, great care should be taken throughout the process.

A number of factors conspire to make tree relocation a challenging task.  Large trees are tremendously heavy and this can make them exceedingly difficult to transport.  Moving large trees requires specialised equipment and expertise; crane trucks are used to transport and manoeuvre trees and the operation of this machinery can be both expensive and labour-intensive.  In some cases this means that relocating trees is not feasible. Not only are trees large and difficult to move, they also need to be handled carefully to avoid damaging the stem and root ball.  The tree’s root system, apart from anchoring the tree in the ground, is the primary pathway along which nutrients and water enter the tree and as a result, damage to the root ball can have a catastrophic effect on the health of the tree.

Tree mortality during relocation represents a very real threat which can however be mitigated by following the guidelines set out above and by moving the tree during winter when it is in a semi-dormant states.  Trees relocated during autumn and winter recover faster and are less susceptible to mortality than trees relocated during summer and spring.  By planting during the colder months the tree’s root system is allowed to settle without having to supply the same quantity of nutrients and water demanded during the growing season.

Although there are a myriad of factors which contribute to successful tree relocation, ultimately the fundamentals remain unchanged.  Root ball preparation and post-planting care determine the success of one’s planting operation.  Experience shows that some tree species are far more sensitive to change than others.  Trees with adventitious roots generally recover from relocation and transplanting operations more readily than trees with tap roots.  Whilst there are notable exceptions to this rule, on average a 95-100% success rate is achieved when transplanting trees with adventitious roots and 80 -90% success rate for select trees with tap roots.  It is also worth mentioning that for transplants conducted during spring and summer, success rates can fall by as much as 25% from the aforementioned figures.  However, it is not only the techniques employed and care taken during planting, but the period immediately after planting that determines the success of the endeavour.   During and immediately after planting, trees should be viewed like patients in a high care ward; regular deep watering and bracing the tree by means of guying is in most instances an imperative in the months that follow planting.