Subscribe to our Got Nature? Newsletter

Got Nature? Blog

Purdue Landscape Report: I think white pines are beautiful trees, especially at maturity, and they have the added advantage that they are one of the few conifers that don’t try to kill you with their needles. Besides working with the foliage, have you ever had to “rescue” a child who climbed too high in a spike-infested deathtrap of an evergreen? Did you develop the rashes to prove it? Not with a white pine!

My kids haven’t had the chance to climb a mature white pine. Many seem to decline at about 15-20ft. We have been describing this issue as white pine decline, but it isn’t entirely easy to explain. There are a number of factors that influence overall plant health and that can contribute to plant decline, but let’s focus on white pines here. White pine decline is typically attributed to root stress that can be caused by or exacerbated by high soil pH (chemically unavailable nutrients), heavy soil texture (clays), compaction, and excessive soil moisture.

Anything that affects the roots can affect the overall health of the tree, so if the roots are compromised and they cannot uptake water or nutrients, the tree will decline due to lack of nutrients or even lack of water. Needles on an affected tree will turn yellow and eventually brown and fall off prematurely (Figure 1). A symptom of white pine decline includes stems that have shriveled or desiccated bark because roots are not functioning properly and cannot pull in enough water (Figure 2).

---

Question: Can tree roots cause damage to a home’s foundation? I have a 3’ in diameter pin oak tree that is within 10 feet of my house. A certified arborist took a look at it and said that he would like to use an Air Knife to expose the roots near the foundation (a walkout basement) to determine if the roots are causing damage and/or need to be pruned, or whether the tree needs to be removed since it is situated too close to the house. Before I spend $500 for them to use the Air Knife, I wondered if you thought it would be worthwhile or not necessary.

Answer: Tree roots can damage a house foundation, with an invitation to do so. Tree roots are very opportunistic and will only grow and penetrate where it is easiest to grow such as friable soils and mulch. Typically, when roots encounter solid, impervious surfaces such as pipes, sidewalks, curbs and foundations, they are redirected laterally or up and over. However, if there is a breach or a crack nearby, they can and will exploit those voids in search of moisture. Such as sewer pipes aren’t damaged by the roots, they are just very capable of finding those leaks and moving into the moist and often nutrient-rich pipe.

Roots normally grow horizontally and not very far beneath the soil surface. Sometimes when roots encounter the looser backfill soil near the foundation, they can abruptly start growing down. You may be able to locate these roots, if they exist, by excavating a foot or two down within a few feet of the foundation. If you find a suspect root, cut it off. Unfortunately, in some cases excavation down to the base of the foundation may be necessary. This may have to be done anyway to repair and stabilize it. Cutting the roots should prevent future problems, especially if a root barrier is installed to prevent re-growth.

Resources
Surface Root Syndrome, The Education Store, Purdue Extension resource center
The Nature of Teaching: Trees of the Midwest, The Education Store
Tree Appraisal and the Value of Trees, The Education Store
Construction and Trees: Guidelines for Protection, The Education Store

Lindsey Purcell, Urban Forestry Specialist
Purdue University, Department of Forestry and Natural Resources

---