May 1, 2012

Nurturing mature trees


Folks love trees, for good reason. They’re beautiful. They provide shade and habitat. They cool the planet. And they’re fantastic carbon sinks. (These last two points mean trees help enormously to reduce the effects of climate change).

As a consequence, we in the landscape industry have an opportunity — several actually. We can make some money, do some good by saving some trees, and make people happy. 

Construction crews, including landscapers, frequently re-grade and compact the soil around trees, constricting their root systems. In addition, we customarily remove every scrap of fallen leaves and debris and grow grass right up to the base of a tree, depriving it of vital nutrients.

There’s lots of hope though!  People are starting to realize the value of trees to their properties and to our parks. Even though personal debt loads are at an all time high and municipal budgets are being slashed, people are finding the cash to save their trees.

Greg Hill is the owner of Maple Hill Tree Services in Streetsville, Ont. I had a long chat with him recently about the work he is doing to restore tree health. “Our approach is an organic one,” he says, “where we work to reverse the soil compaction and add organic matter back into the soil.

“When a new park is created, grading and storm water collection is a major concern, and rightfully so. But all too often it is at the expense of trees that the park was designed around. The problem usually starts with the compaction of the soils over the trees’ root systems, which prevents the movement of water and oxygen through the soil, down to the roots. Without these two basic elements, the tree roots cannot function and, in time, will die. In addition, the new grading is designed to swiftly drain rainwater in the park toward the storm drains.

“The impact is rarely obvious immediately,” Hill says. “Most trees have built up resources of carbohydrates, like money in the bank, which they will use for growth and the restoration of their root system. The root system may still be performing some of its function but not to full capacity, so the tree starts to deplete its stored resources to manage its survival. As the root system declines and the resources are depleted, slowly over time, the tree starts to shut branches down. In many cases, if nothing is done, the tree will continue to decline in this fashion until other contributing factors like disease or insects finish the job.”

Maple Hill uses a combination of methods to restore soils to their natural condition: radial trenching, soil fracturing, soil aeration, injectable mycorrhizae, the addition of organic material and, of course, watering. Mycorrhizae are beneficial fungi which have a symbiotic relationship with tree roots. Mycorrhizae also need healthy soil conditions to survive.

Hill says, “The main component in this process is organic material, which we supply through our Renewable Resource Division. That’s where we compost the wood chips and log material that comes back to our yard through our daily arboriculture operations. We only use material which is disease free. It is most important that the mulch is composted for multiple years, as it will contain elements and natural nutrients in a form that is readily available for the roots to absorb. This mulch is added to the surface and injected into the soil. An added benefit of a healthy layer of mulch over a root system is that it cools the roots in the summer, insulates in the winter, and retains moisture year round.

“It is imperative this mulch be composted. Research has proven that spreading fresh wood chips over a root system can be detrimental as they can deplete nitrogen from the soil for the decomposition process and harbour disease and insects. Besides this, they have no nutrient value,” he says.

“One of the problems we often come up against as consulting arborists when we are involved with tree preservation on construction sites, is that developers, builders and machinery operators sincerely do not realize they have caused damage to the trees on their properties. In all fairness to them, the trees looked healthy enough when the project was completed so they have a difficult time understanding the concerns of the arborist. These trees often don’t start to show signs and symptoms of the construction damage for three to five years, and some times more, after the damage was done.”

Maple Hill has had great luck stopping the decline of beautiful, old trees in parks in southern Ontario, and even restoring their health. This means there are examples of success stories that can be shown to parks managers and homeowners, to convince them to invest in the health of their trees.

My chat with Greg Hill gives me hope that we can do the right thing, i.e., save the trees and save our heritage. As a businessman, I see opportunity here. As an environmentalist, I see our future!
Sean James is owner of an Ontario-based environmentally-conscious landscape design/build/maintenance company. In addition, he is an eco-consultant and a popular speaker.