Hydrangeas, known as “Hortensie” in German, are popular garden shrubs celebrated for their diverse and abundant blooms. They offer vibrant color and visual interest from late spring through fall.
Understanding Hydrangea Varieties
Hydrangeas encompass several distinct types, each with unique characteristics influencing their appearance and care.
Bigleaf Hydrangea (Hydrangea macrophylla)
Bigleaf hydrangeas are recognized for their large, showy flower heads, appearing as “mopheads” (globe-shaped clusters) or “lacecaps” (flat blooms with a central ring of small flowers). These shrubs typically grow 6 to 10 feet tall and wide.
Panicle Hydrangea (Hydrangea paniculata)
Panicle hydrangeas, often called “PeeGee” hydrangeas, have cone-shaped or pyramidal flower clusters. Blooms typically start white or lime-green, transitioning to pink or reddish hues as they mature, especially in cooler temperatures. Some varieties reach up to 8 feet tall.
Smooth Hydrangea (Hydrangea arborescens)
Smooth hydrangeas, including popular cultivars like ‘Annabelle’, produce large, rounded flower heads, typically white, with pink varieties also available. These native North American shrubs generally reach 3 to 5 feet tall and wide. Their blooms can measure up to 12 inches across.
Oakleaf Hydrangea (Hydrangea quercifolia)
Oakleaf hydrangeas have deeply lobed, oak-like leaves that turn red, bronze, or purple in fall. They feature elongated, cone-shaped white flowers that age to pink, and exfoliating bark.
Mountain Hydrangea (Hydrangea serrata)
Mountain hydrangeas are similar to bigleaf hydrangeas, often with lacecap-style flowers. They are more compact and cold-tolerant than macrophylla varieties. Bloom color can range, influenced by soil pH, like bigleaf types.
Climbing Hydrangea (Hydrangea anomala petiolaris)
Climbing hydrangeas are deciduous vines that ascend structures using aerial roots. They produce flat, lacecap-like white flowers in early summer and have exfoliating bark once established. These climbers can exceed 50 feet.
General Hydrangea Care Fundamentals
Successful hydrangea cultivation relies on understanding universal care principles for healthy growth and abundant flowering.
Hydrangeas prefer partial shade, especially in regions with intense afternoon sun. In northern climates or coastal areas, some varieties tolerate more direct sun, but protection from harsh midday sun is beneficial. Placing them on the eastern side of a building provides morning sun exposure while shielding them from intense afternoon heat.
Hydrangeas require well-draining soil to prevent root rot from soggy conditions. Enriching soil with organic matter, like compost, improves drainage in clay and moisture retention in sandy soils. While soil pH influences bloom color in some types, healthy soil structure aids nutrient uptake and root development.
Hydrangeas need consistent moisture, especially during dry periods and establishment. Water deeply one to two times weekly during the growing season, ensuring water reaches the root system. Early morning watering allows foliage to dry, reducing fungal risk.
Plant hydrangeas in fall or early spring, allowing roots to establish before temperature extremes. Dig a hole twice as wide as the root ball, no deeper, ensuring the plant sits at its nursery pot level. Water thoroughly after planting to settle the soil.
Fertilization supports growth and flowering, but excess nitrogen can hinder blooms. A balanced fertilizer or one with higher phosphorus is recommended. Apply in spring as new growth emerges, around the drip line of branches for effective nutrient distribution.
Tailored Care for Hydrangea Varieties
Specific care, particularly pruning and bloom color, varies among hydrangea types. Adapting practices to each variety ensures optimal health and flowering.
Hydrangeas bloom on either “old wood” (stems from the previous year) or “new wood” (current season’s growth). This distinction dictates pruning time.
Bigleaf Hydrangea (Hydrangea macrophylla)
Bigleaf hydrangeas bloom on old wood. Prune shortly after summer flowering to avoid removing next year’s buds. Remove spent flowers, dead, or weak stems, cutting back to a strong leaf set or bud. Late-season pruning can stimulate growth vulnerable to winter damage.
Bloom color for many Hydrangea macrophylla varieties is influenced by soil pH. Acidic soils (pH below 5.5) produce blue flowers, while alkaline soils (pH above 6.0) yield pink blooms. Neutral conditions may result in purple or mixed colors. Amend soil with aluminum sulfate for blue flowers, or lime for pink. White varieties are unaffected by soil pH.
Panicle Hydrangea (Hydrangea paniculata)
Panicle hydrangeas bloom on new wood. Prune them in late winter or early spring while dormant, cutting stems back by about one-third to encourage sturdy new growth. This type is cold-tolerant, thriving in many USDA Hardiness Zones, and some tolerate full sun.
Smooth Hydrangea (Hydrangea arborescens)
Smooth hydrangeas also bloom on new wood. Prune them in late winter or early spring before new growth. Some gardeners cut plants back significantly, even to 6-12 inches, to encourage strong stems that support large blooms and prevent flopping. They are adaptable and hardy in USDA Zones 3-9.
Oakleaf Hydrangea (Hydrangea quercifolia)
Oakleaf hydrangeas bloom on old wood and need minimal pruning. Prune immediately after flowering to shape or remove dead/damaged wood. Excessive pruning reduces next season’s blooms. This variety is hardy in USDA Zones 5-9 and more drought-tolerant once established.
Mountain Hydrangea (Hydrangea serrata)
Mountain hydrangeas bloom on old wood, similar to bigleaf varieties. Prune right after flowering to preserve next year’s buds. They are smaller and more cold-tolerant than Hydrangea macrophylla, suiting a broader range of climates.
Climbing Hydrangea (Hydrangea anomala petiolaris)
Climbing hydrangeas bloom on old wood. They establish slowly but become strong climbers. Prune in summer, immediately after flowering, to manage size and shape. Remove overly long shoots to maintain form on structures. Hard pruning is tolerated but may reduce flowering for a couple of seasons.
Troubleshooting Common Hydrangea Issues
Even with proper care, hydrangeas can experience issues. Promptly addressing these problems helps maintain plant health and ensures continued blooming.
Lack of blooms often stems from incorrect pruning, especially for old wood varieties. Late spring frosts can damage developing flower buds. Too much shade inhibits flower production, as hydrangeas need adequate light. Over-fertilization, particularly with high-nitrogen fertilizers, promotes leafy growth at the expense of flowers.
Wilting indicates insufficient or excessive watering. Dry soil causes leaves to droop as the plant struggles to maintain turgor. Soggy soil from poor drainage leads to root rot, also manifesting as wilting due to damaged roots. Heat stress or too much afternoon sun can also cause temporary wilting, even in well-watered plants.
Yellowing leaves (chlorosis) indicate nutrient deficiencies, particularly iron, often tied to soil pH imbalances. High soil pH (alkaline) makes iron unavailable, leading to yellowing between leaf veins. Poor drainage also contributes. Proper soil pH, drainage, and balanced fertilization resolve this.
Hydrangeas are robust but can encounter pests and diseases. Aphids and spider mites appear on new growth; manage them with a strong water stream or horticultural oil for severe infestations. Fungal issues like powdery mildew and leaf spot are common in humid conditions or with poor air circulation. Adequate spacing and avoiding overhead watering prevent these diseases.
Winter Protection Strategies
Protecting hydrangeas in winter is important for survival, especially for less hardy varieties or in colder climates. Proper preparation ensures a healthy return and abundant blooms in spring.
Before winter, ensure hydrangeas are well-hydrated. Deep watering in fall, especially before ground freeze, helps roots retain moisture. Stop fertilization in late summer or early fall, as late new growth is vulnerable to frost damage.
Apply a thick mulch layer around the plant’s base for root and crown insulation. A 6-12 inch layer of organic material (shredded leaves, straw, wood chips) regulates soil temperature and prevents freeze-thaw heaving. Apply in late fall after ground freeze, remove in spring.
For bigleaf hydrangeas and other old wood varieties, protect flower buds from freezing temperatures for next year’s blooms. In cold zones (USDA Zone 6 and below), wrap plants loosely with burlap or create a cage filled with leaves/straw for insulation against cold winds and extreme temperatures.
Container-grown hydrangeas need special winter attention. Potted plants are more susceptible to root freezing due to less insulation. Move them to a sheltered location like an unheated garage, shed, or near the house, where temperatures stay cool but above freezing. Even dormant, water container hydrangeas occasionally (about once a month) to prevent roots from drying.