Previously we looked at three key ways to 'read' the health of a mature tree:
last year’s new growth, basal root flare, and evenness of new growth to recognize problems in a tree’s root/mycorrhizal system.
Here are 3 more ways to understand the health of young and mature trees.
· Is the center of the tree’s canopy slowing in growth or even dying? If we stand back and look at the profile of the tree (in either summer or winter) are the centre branches smaller, and the density of the crown ‘thinner’ compared to the rest of the branch density. If this is the case, then the rest of the canopy can be healthy, but it tells us that the roots are stressed, and the tree has stopped vertical extension growth and is allowing the center of the tree to die. This often happens when there has previously been an extended period of drought. Ensuring an even water supply is critical.
· Another observation to check is to compare the silhouette of a canopy in leaf with another one of the same species (it must be the same species). If it is thinner - less leaf mass - then again, the root/mycorrhizal system is failing or under stress, probably due to water shortage once more or to heat exhaustion.
· Finally, recent construction (within the last 10 years) near or around a mature tree’s root/mycorrhizal system will have an impact over time. The loss of root uptake ability for air, nutrients and water to be assimilated from the soil, ‘starves’ the tree of these essential elements for life. Compaction of the tree’s soil mass can have a similar effect and can occur simply by too many people walking around the tree’s base.
In each of the above cases, regularly watering the soil under and around the canopy is essential if the tree is to attempt to survive and mitigate the human impact. However, if for example, construction has changed the water table (lowered, typically, but also if it is raised or water is trapped and is saturating the soil mass), then long term solutions must be found.
