Companion planting involves strategically placing different plant species near one another to enhance growth and visual appeal. For hydrangeas, selecting appropriate companions is beneficial because they can conceal the often-bare lower stems of mature shrubs. This layering technique creates a more cohesive and lush garden bed while ensuring all plants share similar needs to thrive.
Understanding Hydrangea Growing Conditions
Successful companion planting requires matching the environmental needs of the hydrangea with neighboring plants. Hydrangeas perform best in partial shade, ideally receiving morning sun followed by protection from intense afternoon heat. Bigleaf and smooth hydrangeas are typically the most shade-tolerant varieties, while panicle hydrangeas tolerate more sun.
Compatible plants must also accommodate the soil composition. Hydrangeas require soil rich in organic matter and consistently moist, but it must also be well-draining to prevent root rot. Most varieties prefer a slightly acidic to neutral soil pH, generally ranging from 5.2 to 6.2. The pH level is significant for Bigleaf Hydrangeas (Hydrangea macrophylla) because it dictates the availability of aluminum, which turns the flowers blue in acidic soil and pink in alkaline conditions.
Groundcovers and Edging Plants
Low-growing groundcovers and edging plants address the visual gap beneath the hydrangea canopy by carpeting the space with contrasting foliage and texture. Hostas (Hosta spp.) are a choice companion, sharing the preference for moist, shady conditions and slightly acidic soil. Smaller varieties, such as ‘Blue Mouse Ears’ or ‘Mighty Mouse,’ create tidy, mounding forms that offer a bold, broad-leaf contrast to the rounded hydrangea foliage.
Japanese Forest Grass (Hakonechloa macra) is an excellent option, as it flourishes in partial shade. Its arching, cascading habit, reaching 12 to 18 inches in height, introduces a fine, flowing texture that offsets the solid structure of the shrub. The variegated cultivar ‘Aureola’ provides a bright, chartreuse-gold color that lightens shady areas beneath the hydrangeas.
Creeping groundcovers like Ajuga (Ajuga reptans) form a dense, low mat that helps suppress weeds and retain soil moisture. Cultivars like ‘Black Scallop’ or ‘Burgundy Glow’ feature dark, glossy, purple-tinged foliage that adds rich color to the base of the planting. Low-growing ferns, such as the Japanese Painted Fern (Athyrium niponicum), contribute a delicate, lacy texture and silvery fronds that contrast with the large, green leaves of the hydrangea.
Perennials and Small Shrubs for Contrast
Mid-level perennials and small shrubs create the next layer of planting, adding vertical interest and extending the garden’s season of appeal. Astilbe (Astilbe spp.) is favored for its similar cultural needs, thriving in dappled shade and moist soil. Its feathery, plume-like flowers rise on spiky stems, providing a striking textural counterpoint to the large, rounded hydrangea flower heads.
Bleeding Heart (Dicentra spectabilis) is a classic shade garden plant that blooms in late spring before the hydrangeas reach their peak. The unique, heart-shaped flowers and delicate, finely cut foliage offer a romantic aesthetic. This perennial often goes dormant in summer, and the developing hydrangea canopy provides screening for the resulting gap.
Small, broadleaf evergreen shrubs like Azaleas and Rhododendrons (Rhododendron spp.) are companions for hydrangeas, sharing an affinity for acidic soil and partial shade. They typically bloom in the spring, offering vibrant color before the hydrangeas flower in summer. Boxwood (Buxus spp.) provides reliable, year-round structure with its dense, evergreen foliage. Varieties such as ‘Green Velvet’ or ‘North Star’ maintain a compact, formal shape, creating a dependable green backdrop that highlights the seasonal blooms.