Two of the most common garden questions that the Extension office gets in the spring are; "Why is my garden not producing the way it used to?" and "Would a soil test help me determine why my garden is not producing?"
In many cases the reason for the smaller production of these local gardens is competition from trees. Small annual vegetable plants cannot compete for water and nutrients with a large, aggressive tree. Generally, most of the feeder roots from a tree grow horizontally and will be in the top 1 to 3 feet of soil. Green ash, for example, have a rooting dept of 1 to 4 feet and have a root spread equal to the height of the tree. Colorado blue spruce has a similar rooting depth, although their root spread is less. Cottonwood trees, which in many cases are very large, can have a root spread of more than the height of the tree.
If trees are a problem there are not any easy solutions. The garden or trees can be moved, a barrier can be built in the soil between the trees and the garden, or a raised bed can be built. If a raised bed is built, a barrier needs to be built in the base of the bed to prevent the tree roots from coming into the raised area.
Many mature yards do not have enough open space to move a vegetable garden and most homeowners are reluctant to take down large trees that they have spent years getting established. Information on building barriers is available at the Extension office. The barrier option is not cheap or easy, but can be effective.
Vegetables also need to be grown in an area that receives full sun. Shade from trees or buildings can reduce vegetable production.
Mike Rose is the North Dakota State University Extension service agent for Ward County.