Feed Shade Trees for Long Life
A mature tree not only increases the value of your home but also offers shade during these hot days of summer, thus reducing the cost of air-conditioning. Trees also provide branches for hanging swings and places for birds to nest and perch.
However, your surrounding lawn does not provide the best conditions for keeping mature shade trees healthy. Soil compaction is often a problem, as foot traffic, riding mowers and often other vehicles compact the soil surrounding the roots.
Fertilizing the lawn does not feed trees. Turf grasses are heavy feeders on nutrients, leaving little to nothing for the deeper roots of trees. Apply an excess of fertilizer under shade trees, and you are likely making the turf susceptible to diseases.
Fertilizer tree spikes don’t help much, either, as research shows they fertilize primarily the surrounding grasses. Deep-root feeder probes often go too deep as they’re designed to prevent the fertilizer solution from bubbling to the surface.
There is a better way.
In the early 1980s, the University of Maryland installed a water feature in the center of the campus mall. During its construction, heavy equipment compacted the soil beneath the canopy of willow oaks lining the mall. Within one year, the trees went into severe decline, with large branches dying.
To save the trees, I augered hundreds of four-inch diameter holes 10 inches to a foot deep at two-inch intervals. We packed the holes tightly with LeafGro. Next spring, the trees were producing lush new growth on many of the dying branches. By mid summer, we could see that the treatment had made a difference.
The University repeated my treatment every seven to eight years. Thirty years later, the trees are still thriving.
The treatment was so successful that I was invited to the University of Virginia in Charlottesville, where the construction of a new library had damaged mature southern red oaks. Since the red oaks were widely scattered, I varied the system by using a trencher and dug four-inch-wide and 12-inch-deep trenches in a wagon wheel fashion around each tree. The trenches started 10 feet from each trunk and extended beyond the drip line of the branches. Mixed in equal proportions with composted yard debris, soil from each trench was used to fill them to grade. All of the treated trees resumed normal growth within two years.
Just prior to presenting my research finding at the National Arborist Association, I named the process “vertical mulching.” Many arborists from across the country have since used it successfully.
Within a year after moving to Deale, I vertically mulched two large cherry bark oak trees that were declining in vigor. Using a six-inch power auger, I drilled holes 10 to 12 inches deep at three-foot intervals, then filled them with LeafGro. I have repeated the treatment every seven to eight years.
This year I vertically mulched using Bloom with fantastic results. My 150- to 200-year-old cherry bark oak trees are not only covered with dark green leaves but also with longer new growth than ever before. The lawn beneath the canopy of branches is better than ever, though I have not applied a drop of fertilizer in more than 10 years. Because it is cut tall and let fall, the grass clippings surrounding each hole filled with Bloom have fertilized the soil between the holes. The lawn in the shade of the trees is a uniform green and growing just as fast as the grasses near the augered holes.
I continue to be awed by the plant-growth responses I am observing from different uses of Bloom — the superior soil conditioner produced at Blue Plains Wastewater Treatment Facility from Class A biosolids.
Ask The Bay Gardener your questions at [email protected]. Please include your name and address.