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Friday - April 10, 2009

From: Ozark, AL
Region: Southeast
Topic: Grasses or Grass-like
Title: Tree without extensive root system in Ozark, AL
Answered by: Barbara Medford

QUESTION:

I would like to plant a tree (in full sun next to a brick house wall) that doesn't have an extensive root system. I have concerns about the roots and the water/septic lines, as well as the concrete house foundation and walkways. Do you have any suggestions?

ANSWER:

Rule 1: Trees have extensive root systems. That has been developed by Nature over millions of years so that the trees can (a) obtain moisture and nutrition from as wide an area as possible and (b) stand up.

Rule 2: There's not much we can do about Rule 1. We don't have the capability to grow "designer trees" that don't have roots, seeds, nuts, or drop their leaves and make a mess.

We're not trying to be funny (well, maybe a little), but those are just the facts. You have more than one problem with a tree being planted. Water and septic lines are vulnerable to woody plants, of which trees are the largest specimens, because of those extensive roots. We have addressed the problem of trees/woody plants and foundations, paving and septic systems in several previous answers. Rather than repeat all that information, we invite you to read these answers to help you make a decision:

Pavement near existing trees.

Concrete patio around a tree.

An excerpt from a question about trees and septic lines:

"You don't want any woody plants close to your lateral lines, as in trees and shrubs. They are the ones that send roots out far beyond their driplines, sneaking up on you. But you don't want to leave that area completely bare, because you know it wouldn't stay bare, it would get weedy and unless it was mowed, some of those "weeds" would grow up to be woody plants. We don't know how your lateral lines are situated, but you do need to be aware of them if you plant a tree in that area. If the area is too near the lateral lines, you may have to reconsider what you plant there."

Excerpt from a question about distance of tree from foundations, other hard surface:

"We wish we knew how to explain to a tree that it should not invade foundations, buckle sidewalks or pop roots up in the garden, but that's just the way trees are. Most of their roots are within 6 to 12 inches from the soil surface, and they are relentless in their search for water, oxygen and nutrients.

"As to the exact distance either should be planted from foundations or sidewalks, that becomes a matter of personal judgment. Soil subsidence around foundations is more often the result of the soil becoming too dry. It is true that tree roots will range out from their trunk as much as twice the diameter of the tree crown in search of moisture but this is usually not a prime factor in foundation damage.

"In general terms regarding the planting of trees near structures, the ground area at the outside edge of the canopy, referred to as the dripline, is especially important. The tree obtains most of its surface water here, and conducts an important exchange of air and other gasses. The most critical area lies within 6 to 10 feet of the trunk. Paving should be kept out of the dripline and no closer than 15 feet from the tree trunk."

Without knowing the amount of space you have available, it's difficult for us to make any firm recommendations. It should be emphasized that the bigger the tree above the ground, height, width, whatever, the bigger the root system is going to be below the ground. We will make a few recommendations for small trees and shrubs that are native to Alabama, but whether or not they will adapt to the space you have without doing damage to structures or killing the tree will be up to you to decide. Follow each plant link to the page on that individual plant, and learn the expected dimensions of the mature tree or shrub to help you determine whether it is a viable candidate for your space. And speaking of the lateral lines, the best plants over lateral lines are native grasses, with their fibrous roots which will help conduct moisture to the surface, hold the soil in place, but not interfere with the water and septic lines. Just in case this is applicable in your case, we will also recommend some grasses native to Alabama.

Small trees and shrubs native to Alabama

Cercis canadensis (eastern redbud)

Chionanthus virginicus (white fringetree)

Frangula caroliniana (Carolina buckthorn)

Halesia diptera (two-wing silverbell)

Hamamelis virginiana (American witchhazel)

Malus angustifolia (southern crabapple)

Prunus mexicana (Mexican plum)

Vaccinium arboreum (farkleberry)

Grasses native to Alabama

Bouteloua curtipendula (sideoats grama)

Chasmanthium latifolium (Inland sea oats)