Start from the bottom with tree care

By Neil Sperry

McClatchy Newspapers

There’s a lot of odd information out there in our big world of shade trees.

A lot of trees are hurt by uninformed well-wishers, and gardeners often don’t realize that they’ve been the culprits until it’s too late — if at all.

Fact: 90 percent of any tree’s roots are in the top foot of soil. That’s obviously true for a mangled old pine hanging onto the barren top of a mountain, but it’s just as true for a 75-foot pecan growing in the deep, fertile soils along the Mississippi River. Sure, that big pecan has a tap root to anchor it, but the roots that do all the work of pulling out water and pumping up nutrients are near the soil’s surface, because that’s where nutrients accumulate, and that’s where the rain falls.

Your take-away from all of that: Don’t do major soil work in and around shade trees if it’s going to have serious consequences for those critical roots.

Most of all, don’t add more than an inch of fresh topsoil per year, and preferably none at all. Adding fill soil beneath a large tree is one of the best ways to guarantee that a tree will die a slow (three-five years) death. Oxygen will gradually be compacted out of its root zone.

If you’ve planted a new shade tree this spring, your care will need to ramp up considerably for the rest of this growing season.

The tree’s roots don’t yet extend out into the rest of the native soil, and that means it will dry out more quickly than the established plants around it.

You’ll need to water it by hand every two or three days for the first summer. Let a hose run slowly and soak its soil deeply.

It’s best to build a shallow water-retention berm with the soil left over from the tree’s planting. Fill the basin, and let it soak in completely.

I’m also confused by the “mulch volcanoes” you see pulled up around new trees after planting. Mulches certainly do allow water to soak into the soil instead of running off, and they certainly lessen the soil-to-air contact, and therefore the fast drying, but enough, already! A couple inches is plenty. You’ll see mounds that are 8 and 10 inches deep. They’re soaking up half the rainfall and irrigation, and they’re not letting it soak into the soil.

It’s normal to see roots expanding out of the soil as the tree grows. Remember that those roots are in that top foot of soil, so when roots grow and enlarge to 7 or 8 inches (or more) in diameter, it’s only natural that part of that growth will push them up and out of the ground.

So do you cover them or cut them? No and no! You figure ways to adapt them into your plantings, because by the time you have large roots, you probably also have heavy shade from the trees’ canopies, and that means you’ll be looking for shade-tolerant ground cover that will take the place of failing turfgrass.

As you’re making that choice, you can also find ground cover that will help conceal all those roots.