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Bigleaf Hydrangea (Hydrangea macrophylla)

Hydrangea macrophylla is a perennial, deciduous plant and a woody, multi-stemmed shrub, although sources differ and some describe the wild form as a subshrub.

LightIt is suited to partial sun through shade and can also grow in full sun; in hot or low-rainfall conditions, direct sunlight during the hottest part of the day is best avoided.
WaterIt needs regular watering and prefers soil that keeps the root zone moist while draining well; it does not tolerate dry roots, although briefly wetter conditions are acceptable.
HumidityIt is generally reported to prefer high humidity and to need little air movement.
TemperatureSources differ on cold limits, with the limited available information placing the minimum at about -10 °C. It is generally described as frost hardy. A single source also reports a USDA hardiness-zone range, without a con
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Overview

Hydrangea macrophylla is a perennial, deciduous plant and a woody, multi-stemmed shrub, although sources differ and some describe the wild form as a subshrub.

Origin and habitat

Hydrangea macrophylla is native to Japan, although sources differ, with some accounts also specifying the Volcano Islands. Its habitats include sunny coastal areas and coastal woodlands in Japan, and it is also widely grown in gardens, parks, and other cultivated horticultural settings. It is reported to be cultivable in a variety of climates and is widely grown as an ornamental plant in temperate regions.

Characteristics

Sources differ on mature size, reporting a height of about 100–300 cm and a spread of about 91–250 cm. It grows quickly and has opposite, simple leaves that are usually ovate to elliptic, with pointed tips and serrated margins. The large inflorescences of wild forms are usually relatively flat corymbose or cymose clusters, generally with small fertile flowers in the center and large, conspicuous sterile decorative flowers around them; cultivated forms commonly include flat lacecap and nearly spherical mophead inflorescences, with flowers in white, pink, red, blue, or purple, and the color of some cultivars can shift from pink toward blue depending on soil acidity and aluminum availability. Sources differ on flowering duration: flowering is mainly from late spring through summer, with some accounts extending it into autumn or even early winter; the fruit is reported to be a nearly spherical capsule.

Light

It is suited to partial sun through shade and can also grow in full sun; in hot or low-rainfall conditions, direct sunlight during the hottest part of the day is best avoided.

Watering

It needs regular watering and prefers soil that keeps the root zone moist while draining well; it does not tolerate dry roots, although briefly wetter conditions are acceptable.

Humidity and airflow

It is generally reported to prefer high humidity and to need little air movement.

Temperature and dormancy

Sources differ on cold limits, with the limited available information placing the minimum at about -10 °C. It is generally described as frost hardy. A single source also reports a USDA hardiness-zone range, without a confirmed numerical range here.

Growing medium and mounting

It adapts to various soils, including clay, sandy soil, and ordinary soil, while preferring well-drained loam and a root zone that does not become overly dry. It can grow from strongly acidic to alkaline soils, though shallow calcareous soil may cause chlorosis, and soil acidity and aluminum availability can affect flower color in some cultivars.

Feeding

Fertilizers or organic materials can alter soil acidity and aluminum availability and thereby adjust flower color in some cultivars.

Propagation

It can be propagated by stem cuttings and layering. Taiwanese agricultural information recommends taking previous-season stems before early-spring budding for cuttings, while Japanese information also describes propagation by cuttings during the rainy season.

Common problems

It is reported to be particularly susceptible to disease caused by honey fungus, and white-tailed deer are reported to cause feeding problems. An overly dry root zone can impair growth, shallow calcareous soil can cause chlorosis, and missing the appropriate pruning period can affect the next flowering cycle. Tender spring shoots are sensitive to frost, while shade during the hottest part of the day is advisable in hot or low-rainfall areas. Mature plants can withstand some cold, but sources differ substantially in their descriptions of cold tolerance.

Identification

Large opposite serrated leaves and large inflorescences are conspicuous identifying features; horticultural forms commonly have spherical mophead inflorescences or lacecap inflorescences edged with large decorative flowers, and many cultivars have flower colors influenced by soil acidity and aluminum availability.

Photos

Hydrangea macrophylla
📷 belvedere04 · CC BY 4.0 · source
Hydrangea macrophylla
📷 Tony Rebelo, some rights reserved (CC BY-SA), uploaded by To · CC BY-SA · source

Sources