To achieve the proper spacing when planting white pine trees, you must consider several factors, including the cultivar, the intended use of the trees and the conditions at the growing site. White pines are fast-growing trees with soft needles and a blue-green color. These long-lived trees survive from 200 to an estimated 450 years.
Spacing of trees depends upon the planned use for the trees. You may plant white pines as ornamentals, as part of a windbreak, to form a screen or for lumber. How you plant the trees affects their shape and growth habit. In stands, white pines tend to branch only along the upper portion of their trunks; trees grown with space around them or in the open create branches further down their trunks.
As a general rule, leave 6 feet between white pine trees. The University of Wisconsin Extension recommends planting 600 to 1,000 trees per acre for timber. A spacing of 6 feet by 6 feet equals approximately 1,200 trees per acre, while an 8-by-8-foot spacing equals approximately 700 trees per acre. For windbreaks, plant white pines in a double or triple row, leaving 8 to 15 feet between the rows.
In some cases, spacing will be affected by the cultivar you select. Cultivars of white pine vary in their form from rounded to upright. Some have drooping branches. 'Compacta' is a slow-growing version. Keep in mind that white pine trees rarely grow in homogenous stands, and a mixture of trees that preserves the plant diversity in an area is better for wildlife.
White pines are not good for foundation plantings because of the height and spread of the mature trees, which reach 20 to 40 feet wide and 50 to 80 feet tall, with a maximum potential height in excess of 150 feet. White pines make a poor choice for urban locations, as the trees do not tolerate salts or air pollutants well.
White pine trees are deep-rooted and perform well on sandy, loam, sandy-loam and clay-loam soils. White pines outperform nearby hardwoods on sands. The trees grow in excess of 2 feet per year, on average. Under canopy, growth may be limited to 6 inches per year, but unimpeded, the trees can grow more than 4 feet per year and will reach a larger diameter.
Plant your trees in the spring, while they are dormant. Select a site that provides full sun and a moist, well-drained soil. While some white pines tolerate poorly drained soils, Eastern white pines are intolerant of drought, standing water and wet soil. You must prepare the soil by turning it, and remove nearby plant competition to give white pines a proper start.