Root damage and root plate lifting: what the standards and agencies describe

This page describes what published sources say about one structural condition in trees. It gives no verdict on any tree and is not an assessment. The sources come from the United States and the United Kingdom. The parent page, structural defects in trees, compares the conditions that have pages here.

What the sources describe

The US Forest Service brochure says trees with root problems may blow over in wind storms and may even fall without warning in summer under the weight of their leaves. It names severing or paving over roots, raising or lowering the soil grade near the tree, parking or driving vehicles over the roots, and extensive root decay. It lists soil mounding, twig dieback, dead wood in the crown and off-colour or smaller leaves as symptoms often associated with root problems, and says that because most defective roots are underground, aboveground symptoms may be the best warning. Its list of reasons to act names a tree leaning with fresh root exposure, soil movement or mounding at the base, more than half the roots under the crown cut or crushed, and advanced decay in the root flares or buttress roots.

The University of Florida extension publication describes main support roots as the anchorage that holds a tree upright and says defects in them are hard to see. It lists a gradual loss, dieback or thinning of the crown, cavities or swelling in the root collar, fungal conks or mushrooms around the base, and visibly pruned or broken root stubs as indicators. It says a buried root system from deep planting or a rise in soil grade can lead to root dieback, that most trees should have a well-defined root flare at least partly visible, and that circling or girdling roots can cause stem compression, dieback in the crown, and decay or structural weakness at the base.

The Illinois Extension article lists shallow roots, damaged and decayed roots and restricted root space, and names stem girdling roots and root collars buried by soil and mulch as other issues. It says the effects may appear suddenly or take years to show, and that a sparse crown or an isolated section of the canopy can often be traced to the roots.

Root plate and soil movement

The National Tree Safety Group guidance defines the root plate as the mass of woody structural and fine roots that spread out from the base of the tree and give it physical support. It lists root plate lifting and severe root damage among the signs that might indicate a structural defect, although not necessarily a hazardous one. The ISA Trees Are Good leaflet says cracks or separations in the soil may indicate soil heaving from excessive movement of the roots, especially if the tree is leaning, and names root loss under its item on human-caused defects. The University of Georgia field report describes buttress roots and the fungi that can weaken roots; see Ganoderma conks and brittle cinder fungus, both described at the lower trunk and roots.

Where the sources add a caution

Roots are mostly out of sight, which is why each source lists what shows above ground. The National Tree Safety Group guidance defines a defect as a condition that predisposes a tree or part of it to structural failure and says not every unusual feature is one. The US Forest Service brochure says a defect matters where a target, such as a person or property, is within striking distance of the tree.

Who looks at this

For the methods and the credentials, see tree risk assessment methods and consulting arborist credentials. For how roots work, see tree biology.

Root damage and root plate lifting: what the standards and agencies describe

What the sources describe

Root plate and soil movement

Where the sources add a caution

Who looks at this

Sources