FEATURE
The pitfalls of
TREE PIT SOILS Tim O’Hare has advised on the soil design and specification of tree planting systems for over 25 years. In that time, he has also investigated numerous failed planting schemes and has noticed a re-occurring theme of problems relating to inhospitable rooting environments within tree pits. He explains the soil-related causes for many of these tree failures and offers some solutions to an all-too-common problem Why do so many trees that leave the nursery in a healthy state end up failing in the first few years after planting? Common causes Poor soil conditions within the tree planting pit will prevent basic root function. This in turn leads to a lack of water uptake and a rapid decline of the tree when it comes into the growing season. The most common factor responsible for this is the development of anaerobic conditions within the pit. Far lesser problems, certainly during the tree’s establishment period, are low fertility, lack of water, the wrong pH or ground contamination. If anaerobism can be avoided, the tree has a fighting chance of survival.
FROM HEALTHY NURSERY TREES....
Anaerobism Anaerobism is the term attributed to a ‘low oxygen’ environment. In soils this is an immediate and major problem that can cause plant failure. Without oxygen, plant roots simply cannot take up water (or plant nutrients within the water), which induces a ‘drought condition’, even though there may be ample water in the soil.
... TO DEAD PLANTED TREES
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Pro Landscaper | December 2023
There are three main causes for inducing anaerobic soil conditions: • Lack of drainage • Soil compaction • Topsoil that is placed too deep
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