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Root systems

Roots keep trees steady and, well, rooted, as well as providing them with water and minerals. However, as they continually grow, tree roots can cause damage to light surfaces such as paths or boundary walls. Also, not through direct action but by drying out clay subsoil beneath house foundations, they can cause subsidence. This is the most common cause of damage to house foundations.

The species most likely to cause direct damage to paths are those with an abundance of surface roots, such as ash, cherry, birch and pine but damage can be caused by most species. Those which produce suckers from the roots, like English elm, may cause additional problems.

There is a popular misconception that the roots of a large tree growing under typical British conditions will penetrate to a depth of several metres. People refer to these as “tap roots” or “anchor roots”.

Under most conditions of soil and climate in Britain, this picture is far from the truth. Tree roots need to obtain water, nutrients and oxygen from the soil. These are usually most readily available near to the surface and carbon dioxide produced by the roots disperses more readily there. As a consequence, most roots are normally found in the upper two feet or less.

On poorly-drained clay soils in areas with a moderate or high rainfall, all the roots of a large tree may be in the upper foot or less.

Roots will sometimes penetrate to a depth of four or five metres, particularly in drier parts of Britain but this is the exception rather than the rule. Even in these cases, the majority of roots are likely to be in the upper foot.

All roots contribute to the moisture supply and stability of the tree and there is no meaningful distinction between what are often called “feeder roots” and “support roots”. The uptake of moisture and nutrients takes place mainly through very fine hair-like roots at the ends of the smallest woody roots. Many of these fine roots may die in the autumn and grow again the following spring. These could be called “feeder roots” but would not include any roots more than 1mm in diameter.

 

If you would like to report the condition of a tree to the council, please use this online form.