After Construction Planting Problems

There is scientific proof that trees planted on blacktop in mulch can grow better, for a short time, than trees planted directly into soil following construction.

A construction site contains soil that is about as bad as it can get. First, the soil has been compacted by the heavy equipment necessary to build a solid structure. Plant root systems need air to live. Ideally, good soil is about 50 percent solid particles, 25 percent air and 25 percent water. We can’t compress all of the air out of the soil and expect plants to survive.

Second, the dirt dug up from 10 feet down in order to lay the foundation or basement – what I like to call gumbo - is now on top of the compressed topsoil. Gumbo usually cannot support plant life.

In addition to poor soil, paint solvents and other waste from construction make the site inhospitable to plants.

To make certain that your carefully designed landscape doesn’t have to be re-planted, you must invest some time and money in preparing the soil.

Starting with your lawn, consider adding about two to six inches of topsoil before sodding or seeding, and incorporate it 4 to 10 inches deep. This is not mandatory, but it will help get your new lawn off to a much healthier start.

When planting shrubs and trees, dig a wide, but shallow hole. Holes dug too deep will prevent proper drainage and the plant will literally drown. Don’t break up the soil under the plant since the weight of large trees will cause the plant to sink on loosened soil; again, there is danger of drowning.

Realize that most roots grow fairly close to the surface of the ground, spreading out widely away from the plant. The hole should be at least 12 inches wider, all the way around, than the ball of the plant, and can be as much as seven or eight times larger. For the tree’s best interest, the hole really can’t be too wide.

Remove any rocks larger than golf balls and break up some of the larger clods of soil. Stop short of pulverizing, however. If you break up the soil too much, it will compact more quickly and you’ll soon be back to no air in your soil. Particles ranging from no smaller than the size of a pea to about as big as a golf ball should prevent the soil from becoming cement—like after you soak it. Variety in particle size is good. Remove and dispose of one-fourth to one-third of the soil remaining in the hole. Then add some good topsoil, peat, compost, etc, to the hole and mix it in thoroughly with the soil still to be dug from the hole. At this point, you can also add some fertilizer, although some experts now believe that planting time is not the best time to add it.

Since cut roots can’t really absorb it, much of the nitrogen portion of the fertilizer will leech out through the soil before the plant can use it. The phosphorous and potassium portions will persist, however. If you’re afraid you won’t have time later, add a well-balanced fertilizer now. (Remember, though, the best time to fertilize established plants is in the autumn, especially if you only have time to fertilize once a year.)

You have now added airspace, organic matter and nutrients to the soil, giving your new plants the best possible start. The rest is up to the plant.