Call The Mulch Police!!!
Improper mulching and edging, unfortunately, is an all too common practice in the landscape industry. Excessive mineral soil and organic material placed at the base of trees and shrubs year after year can be detrimental to plant health. These "mulch volcanoes" can be spotted a mile away towering a foot or more above ground level. These volcanoes are created by improper planting and/or improper edging.
When planting a tree, it is extremely important not to bury the root flare. A skilled arborist or horticulturist knows how to do this. But even a tree planted at the proper depth can quickly have it's root flare buried by poor edging practices.
In an effort to save time and money, uneducated and/or unscrupulous contractors will bury tree trunks with soil that is dug up during the edging process. The excess soil is then hidden from view with a thick layer of organic matter. This saves the contractor lots of time because he doesn't have to haul the soil away. Tree trunks look like telephone poles when their flares become buried.
Excessive organic material and soil piled up against a tree trunk year after year can effect tree health negatively. Roots will develop in the volcano, possibly girdling buttress roots or in extreme cases, girdling the entire trunk. Also, bark can be rotted away because of the constant moisture which is held against the trunk. It's like wearing a wet sock all day, every day.
If you have a landscape full of volcanic trees, stop what you have been doing. Make sure the flare at the base of the trunk is exposed. And always remember these simple words: wide, not high.