The downside of managing urban trees is that sometimes trees have to come down. So you might have chipped up the branches to use them as mulch (just like dyed mulch, it's not good to use fresh chips as garden mulch because it slows plant growth down). You might use the rest for firewood—hopefully someone can use the trunk as lumber. But what will you do about the stump?
In Clarks Summit, we have a shade tree commissioner who is rightly concerned about blighting a community by leaving big stumps in the right-of-way. We wrote our tree ordinance to require all street trees to be cut to one inch above the grade.
Relatively speaking, a one-inch high stump is not much of an eyesore. But many tree guys routinely leave six-inch-high stumps, and this is a different story. (Beyond laziness, these tree guys don't want ground contact to dull their chains. But one inch is enough clearance).
So what can you do about the wood left in the ground? I have an arboricultural solution, but first let's think about what the industry will sell you: stump-grinding. Even with a machine, stump-grinding is a labor-intensive process that turns the stump into small chips which are often heaped up back in the remaining hole in the ground. It is not a place to plant anything, so it is just a different eyesore. Here, the best option is to remove all the chips, bring in soil, tamp it, and plant a different tree or plant grass. If the stump was large, the resulting lawn grade will look awkward, so planting a new tree is probably the best look. In a landscape setting, unless the new planting has to go exactly where the stump is, if the stump is cut low enough, new plants and mulch will completely hide the old stump.
The arboricultural solution is to add water. You read that right. When arborists prune trees properly, they attempt to prevent the accumulation of decay-enhancing water on the remaining wood. So with a stump, if we want to enhance decay, we should cut the stump to encourage the accumulation of water.
In one photo, you can see that I cut a depression into the stump. If the depression is filled with mulch, the stump will stay wet. Look at the other photo. The center of the stump was already rotten when the tree was cut down. This is because a combination of improper pruning and the type of tree (silver maple) encouraged decay to move down the tree. But in every type of tree, the weakest defense against decay is vertical. In that rotten stump, the decay traveled down from eight feet away.
So if every stump was cut with a decay-enhancing depression, we would have fewer stumps quicker.
Joshua Arp is an ISA-certified municipal specialist, Clarks Summit's municipal arborist and an operator of an organic lawn and landscape maintenance business. Reach him at firstname.lastname@example.org.