Give Landscape Plants Proper Space

To develop properly, all plants need enough space for adequate light and air movement. Proper spacing is important for two basic reasons: (1) to be economical to get the maximum effect for a minimum number of plants, and (2) to allow plants to develop fully without crowding each other, the house, or other objects. To determine the proper spacing for landscape plants, you need to know how tall and wide the plants grow, particularly in the case of trees and larger shrubs. Spacing in hedges is another matter, and is a separate consideration.

Spacing becomes easy of you know the ultimate width of a plant, and are placing several of the same type together. Since you know that the spread in one direction will be half of the total, and you are planting several plants of the same kind, you plant them about the same distance apart as their ultimate width. If you want to form a screen with some intermingling of the branches they should be planted slightly closer.

When you don’t know the width of a plant but do know the height, consider that many plants, particularly shrubs, will grow as wide as they grow tall. If you know that a plant grows somewhere between five and 10 feet tall, and are not able to get more exact information, simply space the plants midway between these figures, or about seven or eight feet apart. Remember that local soil types and culture of the plants may also influence their ultimate height and width.

Not all plants fit this generalization. Very low plants, such as groundcover junipers, spread considerably more than their heights, so that a plant growing no more than 10 inches tall may have an ultimate spread of 10 feet. Upright plants become a reverse exception, and some growing 10 or more feet tall have a width of only a few feet. Therefore, it becomes important to know or find the dimensions of a plant of unusual form before planting.

Spacing hedge plants is another matter. They must be spaced close together to give a full, dense screen. Plants for a low hedge (three to four feet high) should be spaced about 18 inches apart. Tall hedges (up to eight feet) will need to be spaced about four feet apart.

Ground cover plants with a low, spreading habit, may have different spacings, depending on how fast a complete cover is wanted. Cost may be a factor in determining spacing of ground cover plants. Remember that 100 plants at a six-inch spacing will cover about 25 square feet, at a 12-inch spacing they will cover about 100 square feet, and at a 24-inch spacing they will cover about 400 square feet.

Proper spacing of trees is necessary to allow them to develop their best form. Sometimes, however, close spacing is used to give a clump or naturalistic wooded effect. When trees are placed very close together, as for a clump effect, they are in competition with each other. Good care is essential or in time, one or two may become dominant, crowding out the remaining trees in the clump.

Trees, expecially large shade trees, should be placed well away from the home to avoid later pruning problems. Strong-wooded trees, such as oak, might be planted as close as 20 feet from a house, but soft wooded trees, such as silver maple, should be planted at a greater distance in case branches break off during a storm. Very large shade trees should be planted about 50 feet from each other.

Trees of medium size, such as red maple or golden rain tree, should be spaced at about 35 feet apart. Small trees, such as dogwood, redbud, hawthorn or flowering crab, may be planted 15 to 20 feet apart, and eight to ten feet from the house when used as an accent or part of a corner planting.

• © 1985, International Society of Arboriculture. All rights reserved.