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  • Writer's pictureMartin Ford

Three Important Ways To Understand a Large Tree's Health

When stepping back and surveying a tree, we often feel it is too large and so don’t feel

able to ‘read’ or understand its health.  Here are 3 principal observations you can rely on – there are more, and they are for another blog but notice these first and then add. Each of these 3 tell us whether the roots/mycorrhizal system is active – that is the key health factor for trees to live full lives. The first 2 we look for during winter dormancy.

Firstly, identify last year’s extension growth – did the tree add a lot of new shoots and did they grow long (6” or more)? If they did not, then the root system is not very active and the lack of new growth shows us this without having to dig up the roots.

Secondly, if basal flare where the tree’s trunk enters the soil has the beginnings of the major anchoring roots spreading away from the trunk in all directions then the tree is stable and vigorous. If, however, a side of the tree enters the soil almost vertically then the roots have not grown on that side and this can be for several reasons. This means the tree is dependent on the remaining roots for both support and to find the nutrients/water needed to be healthy.

Thirdly, in the spring and summer, as new leaves/needles emerge, watch to see if they have even colour and growth. Variations in size and the leaves’ natural colour indicate some form of stress and interruption to the growth cycle. It could be temporary but generally it means some sort of root stress/death, and how the tree responds to this occurrence needs to be noted during the coming years.

Last year's extension growth

Basal root flare

Uneven leaf colour/growth


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