Monday, June 18, 2007

Killing them softly with their mulch?


Is the City of Madison Parks Division killing its trees with all that mulch? It's something we wonder about as we bike around the city and notice what seems to be an unusual number of dead or dying trees, along with the mounds of bark mulch piled up around so many of the trees in the parks (serving primarily, it seems, as protection against those huge, powerful mowers that the overworked Parks employees use to try to keep up with the fast-growing grass). We're not experts, and it may just be a coincidence. We're just wondering.

One thing's for sure: They seem to be violating their own Mulch Guidelines (emphasis added).
Newly planted street trees are mulched at the time of planting. Mulch settles and breaks down over time, therefore, adding a little mulch each spring or fall is beneficial. Please remember that mulch should NOT be heaped next to the trunk of the tree. A small gap should be left between the trunk and the mulch.

Benefits of Mulch

• Retention of soil moisture
• Weed and grass control
• Protection of the trunk from mowing equipment
• Erosion control as mulch breaks the impact of rain
• Improved soil structure (better aeration, temperature and moisture conditions)
• Improved appearance.
It's hard to see much of a gap between this mulch pile and the trunk. The mound more closely resembles the dread "mulch volcano," albeit a volcano with a little crater in it, than the preferred doughnut model, with the tree untouched in the center of the hole. Why all the mulch? I suspect it's nothing more insidious than a bureaucracy which sets up a program that then is carried out over-eagerly by zealous staff until it turns into a caricature of itself. They seem to have lost sight of what they are doing, and why they are doing it.

The hazards to trees of mulch mounded up too closely to trees have been well-documented: It can actually cut the amount of water reaching the roots. It can create a hospitable environment for fungi and other pests to attack the tree. And recently T wondered about another danger: species mixing. Putting different species into intimate contact with each other that don't naturally have contact in nature seems unwise -- as we learned with animal feed and mad cow disease. Do we know where the bark mulch comes from and where it's been? What's the effect of piling it up against a completely different tree, one that naturally thrives in the midst of its own mini-ecology that does not include heaps of bark mulch?

Again, just wondering is all.

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