Bigleaf hydrangea (Hydrangea macrophylla 'Nikko Blue')
The classic Hydrangea macrophylla 'Nikko Blue' offers large, showy mophead blooms that change color based on soil pH, thriving in part shade.
Scroll down to discover growing tips, care requirements, companion plants, and more
Complete Plant Information
Overview
The Hydrangea macrophylla ‘Nikko Blue’, commonly known as the Bigleaf hydrangea, is a premier choice for gardeners seeking reliable, voluminous summer color. This deciduous shrub is famed for its large, rounded flower clusters, which present a dynamic color display dependent entirely on soil chemistry. Cultivars like Hydrangea macrophylla ‘Nikko Blue’ offer the gardener the unique opportunity to manipulate flower color, achieving deep blues in acidic conditions or vibrant pinks when the soil is more alkaline.
Valued for its lush foliage and substantial presence, the Bigleaf hydrangea quickly establishes itself as a focal point in the landscape. It features large, serrated leaves that provide excellent coverage throughout the growing season. This cultivar blooms from July into August, often showing off its color earlier than many other varieties, bringing extended visual interest to shaded areas of the garden.
Growing to a manageable 4 to 6 feet tall and wide, Hydrangea macrophylla ‘Nikko Blue’ is versatile enough for borders, specimen planting, or foundation accents. While requiring medium water and medium maintenance, the payoff in showy blooms makes the effort worthwhile for anyone wanting classic, cottage-garden charm.
Fast Facts
- Plant Family: Hydrangeaceae
- Plant Type: Deciduous shrub
- Hardiness Zones: USDA Zones 6-9
- Size at Maturity:
- Height: 4-6 ft
- Spread: 4-6 ft
- Bloom Time: July to August
- Bloom Description: Blue in acid soil; Pink in alkaline soil
- Sun Exposure: Part shade
- Water Needs: Medium
- Maintenance Level: Medium
How to Grow
The ideal location for your Bigleaf hydrangea involves rich, well-drained soil, protected from the harshest afternoon sun. While Hydrangea macrophylla ‘Nikko Blue’ prefers part shade, it can manage full sun if the soil moisture is kept consistently high throughout the heat of summer. Plant in the cooler periods of early spring or autumn to allow the roots to establish before facing temperature extremes.
Consistent moisture is crucial; plan for medium watering, ensuring the soil never dries out completely. Soil pH management is key for color control. To encourage the true blue characteristic of Hydrangea macrophylla ‘Nikko Blue’, amend the soil with aluminum sulfate. Conversely, adding lime will neutralize acidity, resulting in pinker blooms. Remember to apply these soil treatments well in advance, typically in late autumn or early spring, before the growing season starts.
Pruning should be minimal. Since this is generally a rebloomer best known for its flower clusters, the best time to prune is immediately after flowering ceases. If pruning is necessary, cut back flowering stems only to a pair of healthy buds. In late winter or early spring, focus only on removing weak wood or stems damaged by winter cold.
For winter protection, especially as this shrub is hardy to Zone 6 but can suffer bud loss in Zone 5, applying a 3-inch layer of mulch using shredded bark, compost, or peat is highly recommended year-round. This insulation helps moderate soil temperatures and prevents freeze-thaw cycles from damaging dormant buds.
Landscape Uses
Bigleaf hydrangeas excel in various landscape roles due to their substantial presence and reliable summer color. They are perfect when grouped or massed together within a shrub border, creating a solid block of texture and bloom that anchors a garden bed. Hydrangea macrophylla ‘Nikko Blue’ also performs beautifully as a distinctive specimen or accent plant near patios, porches, or house foundations where their form can be appreciated up close.
Because of their preference for dappled light, these hydrangeas pair well with woodland perennials and shade-loving shrubs. Consider companion plantings such as hostas, astilbes, or ferns that share similar moisture and light requirements. A hedge made entirely of Bigleaf hydrangeas offers a softer, more colorful alternative to traditional evergreen hedges, especially during the summer months.
For a stunning effect, plant Hydrangea macrophylla ‘Nikko Blue’ near elements that retain moisture, like water features or beneath high canopy maples. Their large size also makes them excellent candidates for large container plantings, allowing you to easily move them to better light conditions or provide extra winter protection as needed.
Standout Features
Flower Qualities
- Showy
Noteworthy Characteristics
Hydrangea macrophylla, commonly called big leaf hydrangea, is a deciduous shrub with a rounded habit that, in the St. Louis area, typically grows 3-6’ tall and as wide unless damaged by harsh winters or pruned smaller. It generally features serrate, obovate to elliptic, dark green leaves (4-8” long) and large clusters of long-blooming summer flowers in either lacecap form or mophead form. ‘Nikko Blue’ is part of the hortensia or mophead group, featuring large sterile florets arranged in globular panicles. It typically grows 4-6’ tall and displays large, rounded, 4-5” clusters of pink or blue florets blooming for up to two months, often starting in June.
Tolerances
No specific tolerances were listed for this cultivar.
Potential Problems
Bigleaf hydrangeas like the Hydrangea macrophylla ‘Nikko Blue’ can be susceptible to a few common issues, including bacterial wilt, leaf spot, and mildew, which are often exacerbated by poor air circulation or overly humid conditions. Gardeners should also watch for occasional aphid infestations, especially on new, tender growth.
Preventative care is the best defense against fungal issues. Ensure proper spacing between plants to allow good airflow, and water at the base of the plant rather than wetting the foliage, particularly late in the day. Should aphids appear, a strong spray of water or insecticidal soap application is usually sufficient to manage the population on your Bigleaf hydrangea.
Frequently Asked Questions
What hardiness zones is Bigleaf hydrangea suitable for?
This popular Hydrangea macrophylla ‘Nikko Blue’ is best suited for USDA Hardiness Zones 6 through 9.
How large does Bigleaf hydrangea grow?
Hydrangea macrophylla ‘Nikko Blue’ typically matures to a height of 4 to 6 feet, with a similar spread of 4 to 6 feet, assuming conditions are favorable.
When does Hydrangea macrophylla ‘Nikko Blue’ bloom?
This shrub produces its showy blooms from July to August, with the resulting flower color being entirely dependent on soil pH—blue in acid soil and pink in alkaline soil.
What sun exposure does Bigleaf hydrangea need?
The ideal environment for Hydrangea macrophylla ‘Nikko Blue’ is part shade, though it can tolerate more sun if consistent, medium moisture levels are maintained.
Conclusion
The ability of Hydrangea macrophylla ‘Nikko Blue’ to deliver massive, long-lasting summer color, combined with its customizable flower hue, solidifies its status as a garden staple. For gardeners seeking reliable blue or pink mopheads, the Bigleaf hydrangea is an excellent choice for adding texture and focal points to partially shaded areas. Before planting, always confirm your soil pH and zone compatibility to ensure the most vibrant display from your new Hydrangea macrophylla ‘Nikko Blue’.
Companion Planting
When selecting partners for your Hydrangea macrophylla ‘Nikko Blue’, focus on plants that thrive in similar partial shade and rich, medium-moisture environments. Hostas provide excellent contrasting foliage texture, ranging from fine to broad, and their coloration complements the deep greens of the hydrangea leaves beautifully. Consider incorporating shade-loving woodland plants like Japanese Forest Grass (Hakonechloa macra) along the front edge of the border to create soft, flowing movement beneath the larger shrub structure.
For seasonal interest that extends beyond the hydrangea’s bloom time, look toward spring-blooming bulbs like snowdrops or early daffodils that will emerge before the Bigleaf hydrangea fully leafs out. Later in the season, incorporating plants like Coral Bells (Heuchera) adds varied leaf color, drawing attention to the area even when the mophead flowers are fading. Grouping plants with similar water needs simplifies irrigation management for this medium-water shrub.
Design Ideas for Color Control
Achieving the signature intense blue of Hydrangea macrophylla ‘Nikko Blue’ requires proactive soil management, making it a fun project for attentive gardeners. Dedicate a distinct planting bed specifically for blue conversion, ensuring the soil pH consistently measures below 6.0. Use aluminum sulfate spread around the drip line in early spring, watering it in thoroughly to begin affecting the soil composition well before bud set.
Conversely, if you prefer the rosy pinks, incorporate dolomitic lime into the soil during late fall or early spring. This raises the pH, binding up the available aluminum ions that are necessary for blue coloration. Design borders where the blue Hydrangea macrophylla ‘Nikko Blue’ is backed by white-flowering shade shrubs, like white rhododendrons or white Astilbes, to maximize the intensity of the blue hue through contrast.
