Planting shrubs near a home requires careful consideration to ensure the long-term health of the plant and the structural integrity of the building. Planting too close is a common mistake that can lead to costly problems, including damage to siding and foundation issues. The most important factor in determining the appropriate planting location is the shrub’s ultimate mature size, not its current size. Ignoring the eventual width and height a plant will reach can result in overcrowding, blocked access, and moisture-related complications for the structure. Planning placement accurately based on mature dimensions prevents future maintenance issues and the need for expensive relocation or removal.
Determining Distance Based on Mature Size
The foundational principle for positioning any shrub near a structure centers on its mature width, or ultimate spread. A simple rule of thumb is to plant the shrub’s trunk at a distance that is at least half of its mature width. For example, a shrub that grows 6 feet wide should be planted a minimum of 3 feet away from the side of the house. This distance ensures the foliage can fully develop without physically touching the exterior wall at maturity.
To determine the mature size, consult the plant’s nursery tag, research the specific cultivar, or check local extension publications. If the spread is not specified, the mature height can serve as a proxy for the width, as many shrubs grow nearly as wide as they grow tall. Basing the planting distance on the mature size accounts for the plant’s full growth potential. Planning for the shrub’s adult dimensions, rather than its size at the time of purchase, prevents the need for extensive corrective pruning or replanting later.
Specific Distance Guidelines for Different Shrub Sizes
Applying the principle of planting at least half the mature width away provides a general guideline, but specific minimum distances offer a practical framework for various shrub categories. For small shrubs, which typically mature to a width of 3 feet or less, the planting distance should be a minimum of 1.5 to 2 feet from the house foundation. These varieties include dwarf boxwoods or compact spireas, and this spacing allows for a small air gap even when the plant is fully grown.
Medium shrubs, which mature between 4 and 6 feet wide, require a greater setback to prevent them from pressing against the siding. Planting the center of a medium shrub, such as a rhododendron or standard holly, approximately 3 to 4 feet away from the structure is recommended. This distance ensures that the spread on the house side will still leave a small, necessary clearance.
For large shrubs and small ornamental trees that can reach an ultimate spread of 8 feet or more, the planting distance should be increased to 5 to 8 feet from the house. This range accommodates the larger radius and provides an ample buffer against the structure. Columnar or narrow shrubs can be spaced based on their narrowest dimension, but it is wise to add a small buffer of at least 6 to 12 inches beyond the calculated half-width to account for any unexpected spread.
Preventing Structural and Moisture Damage
Placing shrubs too close to the home introduces significant risks related to moisture retention, which is the biggest issue arising from improper spacing. Dense foliage pressed against the exterior wall prevents airflow, trapping moisture from rain or humidity against the siding. This constant dampness accelerates the deterioration of exterior cladding, leading to rot, peeling paint, and the potential for mold and mildew growth on the structure itself.
The moist, shaded environment created by overgrown shrubs also attracts pests that can damage the home. Termites are attracted to the moisture and the plant’s cellulose material, gaining an easy path to the house structure if they infest the roots or dead wood of a close-planted shrub. Dense bushes also provide shelter for rodents and other insects, acting as protected habitats that allow them to move closer to potential entry points in the foundation or walls.
While root intrusion into a modern, intact foundation is rare for most common landscape shrubs, aggressive varieties or those planted too close to older foundations can still present issues. Large shrubs may exert physical pressure on the foundation over time, particularly if the soil moisture fluctuates wildly, causing expansion and contraction. Ensuring that the planting hole is located well outside the foundation’s perimeter helps mitigate any potential risk of root systems interfering with the building’s structural integrity.
Considerations for Ongoing Maintenance and Airflow
Adequate spacing is necessary for long-term plant health and homeowner convenience. Providing a generous gap between the shrub and the wall ensures enough room for essential maintenance tasks, such as cleaning the gutters, inspecting the foundation, or repainting the siding. If the mature plant is touching the house, accessing the area behind it for necessary pruning or inspection becomes a difficult chore.
The space between the foliage and the home is also important for maintaining proper airflow around the plant. When air circulation is restricted, moisture can linger on the leaf surfaces, creating a favorable environment for the development and spread of fungal diseases like powdery mildew or leaf spot. Good airflow helps the leaves dry quickly after rain or irrigation, significantly reducing the chances of these common plant pathogens taking hold. Additionally, planting too close can cause the side of the shrub nearest the house to receive uneven light exposure, leading to lopsided growth.