Growth is a natural occurrence which, in the garden, is part of the design process which knowingly adheres to this activity.

Growth in plants consists of a two-way dimension; trunk and branches have an upward direction whereas roots have a downward orientation.

This is simplicity itself as the root acts as an anchor in ‘holding’ the ‘top growth’ in place during windy weather.

Its other function is to allow water and nutrients to be taken from the soil and carried upward through the trunk into the branches and foliage. The top growth comprises the trunk, branches, foliage, flower and seed or fruit, which relies on the water and nutrients from the soil in order to fulfil its purpose and, indeed, survival.

Top growth is upward and also spreading, which indicates the need to understand each plant type’s character and habit and its relationship with its neighbours. Over-planting is mostly a waste of time, money and labour as it creates the need for a more constant maintenance programme in order to create the most favourable conditions for each plant to give of its best. When too many plants are in proximity numerous problems arise — pest and disease problems spread quicker, faster growing species dominate weaker species. There is also the unseen problem of roots from neighbouring plants invading each other’s root zone, which make transplanting or thinning out a delicate operation, invariably damaging the uptake of water and nutrients of plants wishing to be retained.

The root zone, as a rule of thumb, has a similar spread to the drip tip of the canopy of the tree/plant, which can itself create problems. The above-ground activity of a plant can be seen whereas the profile of the root system is below ground and ‘unseen’; unknown being a factor in root damage to walls, tanks and structures. Dry stack walls are heavily impacted by root penetration as they are not bonded together, with the result that as roots grow and displace the soil, the expansion ‘pushes’ against the wall. The end result is commonly the wall’s collapse.

This is especially true on Bermuda stone retaining walls with a weak joint between blocks. It allows root penetration; thereafter, the root follows the joint line. Roots will travel the easiest route to find moisture and will find cracks or weak points in a structure and penetrate, creating a destructive force which remains unknown until the tank dries up or a wall subsides.

Planting vigorous growing plants near footpaths and driveways should also be cause for concern, especially if the planting hole is not large enough to accommodate expansion of the root system as it grows outward and downward. Shallow soil depth increases the risk of surface growing roots which can ‘lift’ asphalt, pavers etc and thus become a trip hazard.

As we have been in a drought situation for the month of May and earlier, the appearance of foliage — especially on larger trees — has been slow. With a good downpour things will change, with vigorous growth being the order of the day. Top growth means root activity as well as the appearance of foliage. It is therefore important to consider these principles when designing in general and, for existing plantings, carrying out exploratory trenching if there is a potential for root damage near structures, paths and roads.

Root pruning should be carried out professionally with skilled labour, as the roots are the life blood of the plant during its lifetime; poor or incorrect pruning could have a devastating effect on future growth. Remember, roots will travel to water and reach it via the quickest way, be it along wall joints (see picture) or through cracks in walls. This is especially common in Bermuda stone, which is generally soft.