Hydrangeas are popular deciduous shrubs valued for their large, showy blooms. Correct placement relative to the house is crucial, extending beyond aesthetics to affect the plant’s health and the structural integrity of the home. Considering the mature size before planting prevents future issues like restricted airflow and moisture damage against siding. The ideal distance is determined by practical and biological factors.
Determining the Minimum Required Distance
The primary guide for proper hydrangea placement is the plant’s mature width. A general rule for foundation plantings is to position the plant’s center at a distance equal to half its expected mature spread, plus an additional 1 to 2 feet. For instance, a shrub with an 8-foot spread should be planted 5 to 6 feet from the wall. This buffer distance allows air to circulate freely around the plant and the structure.
The extra space is also necessary for practical home upkeep, ensuring access for painting, window cleaning, or foundation inspections. Planting large shrubs closer than 3 feet is discouraged, as it restricts growth and complicates maintenance. For smaller or dwarf varieties, a minimum distance of 3 feet from the foundation is a practical starting point.
Factors Based on Mature Size and Cultivar
Required planting distance varies significantly due to the vast differences in hydrangea species and cultivars. Always check the plant tag for the specific mature width, ignoring the plant’s current size. Standard Hydrangea macrophylla (Bigleaf) varieties typically spread 6 to 8 feet, requiring a setback of 4 to 5 feet. Smooth hydrangeas (Hydrangea arborescens) also grow to about 5 feet wide.
The largest types, such as many panicle (Hydrangea paniculata) and oakleaf hydrangeas (Hydrangea quercifolia), can spread 10 feet or more, necessitating a planting distance of 6 feet or greater. Conversely, newer dwarf cultivars, often spreading only 3 to 4 feet wide, can be planted closer, potentially 3 feet from the house.
Avoiding Structural and Moisture Risks
Planting a hydrangea too close introduces moisture and maintenance issues. The dense foliage traps moisture against the siding and foundation, creating high humidity. This moisture accelerates the deterioration of exterior paint, siding, and wooden trim, and may compromise basement waterproofing. Constant dampness against a structure encourages wood-boring insects, mold, and mildew on the house itself.
The lack of air circulation negatively affects the hydrangea’s health. Poor airflow prevents leaves from drying quickly after rain, increasing susceptibility to fungal diseases like powdery mildew.
The roofline and eaves create a “rain shadow” where the soil receives less natural water. Planting too close forces the hydrangea to rely entirely on manual watering. If placed directly beneath a downspout, it can be subjected to excessive flooding, both detrimental to root health.
Hydrangeas possess a fibrous, non-aggressive root system that poses no threat to modern concrete foundations. The actual risks are related to the foliage and moisture retention, not root intrusion. The setback distance ensures the plant’s canopy does not touch the structure, allowing the wall to dry out naturally and providing space for the plant to achieve its full shape.