Remedy for a Tree Stealing Light

All trees use sunlight to manufacture food by the process of photosynthesis.

Trees need sunlight to grow, and in most cases, are able to get all they need. Some trees, however, get so big that they leave other smaller trees in the shade, affecting their growth and health. Pruning a tree that is stealing sunlight remedies the situation by creating more area for the sunlight to get through, which benefits other nearby trees.

Woodland Competition

Trees use sunlight for photosynthesis, the process by which they make their own food. A single tree standing alone in the middle of a lawn or field is free to make use of all the elements it needs to survive, including sunlight, rain and nutrients in the soil. Standing close to other trees, however, a large tree can appropriate more than its share of sunlight, forcing the others to compete for these elements. This is evident in stands of trees whose foliage is concentrated primarily in their uppermost branches. Such trees grow long and lanky from having to compete for sunlight, which in some cases significantly compromises the health of some or all of them. Good forestry practices involve thinning such stands of trees, which opens up more area between those that are left standing.

Urban Sprawl

A large tree with a dense, wide canopy casts shade over a broader stretch of ground than does a scrawny tree. Maintaining a lawn or trying to grow other plants under such a tree becomes challenging and in some cases nearly impossible. Proper pruning of large trees removes unwanted branches and allows more sunlight to reach the ground, improving the survival odds for grass, flowering plants and shrubs.

Pruning Process

Crown thinning involves removing preselected branches, allowing for improved air and light penetration. Roughly one-fourth of a healthy branch is removed, as are all dead, damaged, deformed or diseased branches. Weaker V-shaped branches are removed as well as branches that cross over or rub other branches. No more than one-quarter of a healthy tree's branches should be removed at any one time; and if more pruning is necessary, it should be done over a succession of years. Crown raising removes roughly a quarter of the lowermost branches, while crown reduction is used for trees that have grown too tall for the space they occupy. If keeping a large tree pruned doesn't remedy the situation, it may be necessary to cut it down and replace it with a smaller variety that won't pose a threat to surrounding vegetation.

Considerations

Anything that compromises the health of trees, including light deprivation, can weaken them and make them more susceptible to diseases and insect infestations. Sickly trees are also the first to fall during storms and high winds, causing damage to nearby buildings and to other vegetation and wildlife habitats. Regular pruning and thinning benefits not only the trees selected for the process but others around them, as sickly trees can pass on any problems to their healthier neighbors.

References

• University of Minnesota Extension; Pruning Trees and Shrubs; Zins and Brown; 2002
• U.S. Department of Agriculture: How to Prune Trees
• International Society of Arboriculture; Pruning Mature Trees; 2004