Trees in the hardscape require long-term aeration
By Wayne Smith
ISA Certified Arborist
Where the Pinellas Trail intersects Main Street in Dunedin, a venerable oak tree stands watch, arching its giant limbs above the trail. Its roots lie buried under asphalt paving and a strip mall's concrete foundation.
In October, the City of Dunedin invested in its landmark tree. It installed W.A.N.E. 3000 Tree Feeder units, which allow the tree's roots to breathe and to get water and nutrients, although they lie beneath asphalt.
Paving around a tree was once a death sentence. Some trees succumbed swiftly, others lingered, but premature death was inevitable. For trees to live, their roots must breathe. They must take in oxygen and expel carbon dioxide. Paving deprives the roots of this critical exchange of gases at the interface of the soil surface.
I invented the tree feeder units, called W.A.N.E. for Water-Air-Nutrient-Exchange, in 1971. They were the first aeration devices aimed at keeping trees alive in the urban hardscape.
Each unit has a cylindrical housing that is inserted through the pavement and into the soil below. Its perforated lid, which sits flush with the pavement, allows air and water to enter the soil and carbon dioxide to be expelled. Slow-release fertilizer inside the filter provides nutrients to the roots. The number of units installed around the circumference depends upon the tree’s size and condition. The perforated lids can be pulled off the units periodically to remove any accumulated debris, which maximizes the amount of oxygen getting through to the tree’s roots. Nutrients can be added, as well.
The W.A.N.E. units provide portals to a tree’s root system. The avenue opened for entry of oxygen and release of carbon dioxide is fundamental to the tree’s survival. The water and nutrients transmitted through the units provide additional benefit.
The Georgia Dome, the Capitol Mall, and Central Florida theme parks all use W.A.N.E. Tree Systems. When installed as part of a comprehensive tree preservation program, the W.A.N.E. unit is an effective aeration device. If a tree’s roots have been butchered through twelve months of careless construction, popping in some W.A.N.E. units at the end will not effect a miracle cure. But in the hands of a competent arborist, who has developed, implemented and supervised a tree preservation program throughout the construction process, the unit will keep healthy trees healthy.
In downtown Clearwater, off South Fort Harrison, a grand oak tree sits in the middle of a parking lot outside the Pinellas County Utilities building. Even with the W.A.N.E. system, this tree lives in a very harsh environment. Yet it’s live crown ratio remains good – although its roots have buried under pavement for almost 30 years. Clearwater's City Forester at the time, Chris Coles, was an early advocate of the W.A.N.E. units, and the city began installing them to service the root systems of its valuable, historic trees.
Without a system to aerate it, that grand oak tree would have died. Similar live oaks two blocks away were paved over and given no aeration. Respiration diminished and toxins accumulated. The oaks exhausted their stored-up energy, roots died back, portions of the trees died back, and photosynthesis diminished, further decreasing respiration. The bleak cycle of decline played out for years. For each tree, it was a slow death.
Within blocks of each other, all these live oaks had the same potential to live. But one got an aeration system and the others did not. That is the difference.
Unlike its more costly alternatives, the W.A.N.E. Tree System continues to function for decades. Its more costly alternatives cause tree roots to mass at the surface. Turfblock and tree grates present trip hazards. Sediment accretes in porous pavements with time and they become impervious – no longer providing mediums for exchange of oxygen and carbon dioxide at the soil’s surface.
During the Dunedin installation, I trained the city’s employees in the techniques required to lay out, install and service W.A.N.E. units. Proper technique is necessary for an effective result; yet, it can be taught in one session. I will trains employees of any Florida municipality that wishes to install these aeration devices.
For private installations, a W.A.N.E. Tree Systems crew will travel to any location in the state of Florida.
Urban sprawl is something we’re living with now. Within the urban areas, green spaces are shrinking. To offset the lack of green space available for healthy tree roots, effective aeration has become essential to the preservation of urban trees.
It has been thirty-five years since the W.A.N.E. unit was developed and it remains the industry standard, the most effective aeration device on the market. I believe it is use is now more important than ever if we are to save our urban forests. It allows roots to breathe, which gives trees a fighting chance.
Wayne Smith is an ISA certified arborist who has been working to preserve urban trees for 49 years. He has been a member of ISA, Florida Chapter, since its inception.
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