Spacing Proper spacing is the most frequently ignored principle of forest management that I see cruising timber in this region. It takes only about 15 years for trees to fully occupy an area, so thinning is needed about every decade or two. Planting trees in a field is like growing 10 puppies in a box with a supply of enough food for one adult size dog. For a while they all grow well and are healthy and happy. After a while they grow larger and start to fight over the available food.
Smaller ones get sick and die.
You can fill in the details - you know what will happen. People don't seem to realize that trees go through the same thing as the puppies in the box. If you plant trees you have a responsibility to care for them. Careful and regular thinning is the first step. Crowded trees will have narrow sparse crowns that don't support good growth.