Like many homeowners, you may worry about tree roots wreaking havoc on the foundation, but the root system of river birch (Betula nigra) will not damage your home. The roots seek out water from any underground source, including crevices and cracks. As long as you have a solid, well-built foundation, you shouldn't have any problems; the roots will simply travel in another direction for hydration.
Myth Versus Fact
According to the North Dakota State University Extension Service, river birches can stand 7 feet from homes and still not ruin basement walls. If river birch grows next to your house, you're more likely to have roof damage from branches swaying in the wind than foundation damage. If you have a leaky basement and notice cracks, seal the fissures, as soon as possible, to avoid attracting roots. Thirsty roots could aggravate pre-existing damage. For added reassurance, dig a trench next to the foundation and install a plastic root barrier.
River birch roots grow near the surface of the ground and are not strong enough to lift up concrete substructures. However, planting river birches next to buildings will shorten the span of the root system and possibly compromise the health of the tree. Keeping river birch 30 feet from your house will encourage a healthy root system but don't move a river birch just because it's not in the ideal spot. Transplanting any tree can compromise its health; you don't want to risk losing a valuable landscape specimen, like a river birch.
Pruning and Insects
Mature river birches require little care but prune the branches if they jeopardise your roof or windows. Pruning in the winter or spring can cause weeping and oozing so don't cut back limbs until autumn, if possible. The tree resists the bronze birch borer and leaf spots, but some pests can cause aesthetic damage. Aphids and sawflies come out in the spring and cause leaf loss, but they do not compromise the long-term health of river birches. If the defoliation is extensive, a slow-release fertiliser will encourage recovery.
A 3-inch deep layer of shredded bark or leaves around the trunk will help the tree retain moisture. During periods of drought in the spring and summer, water river birch once a week. Turn on a slow-running hose near the tree trunk for up to three hours in the absence of sufficient rainfall. In the fall and winter, avoid watering the tree to prepare the foliage and root system for the cold season.
- North Dakota State University Extension: Questions on Birch
- University of Washington Botanic Gardens: Gardening Answers Knowledgebase
- North Carolina State University Cooperative Extension: "River Birch Pests No Big Problem"; Charlotte Glen; May 2009
- Northeastern Area Forest Service: "How to Grow and Maintain a Healthy Birch Tree"; Steven Katovich, et al.; February 1997