Hydrangea

Hydrangea macrophylla · bigleaf hydrangea · lacecap hydrangea · mophead hydrangea · hortensia

At a Glance

Overview

Hydrangea macrophylla is a species of flowering plant in the family Hydrangeaceae, native and endemic to Japan. It is a deciduous shrub growing to 3 m (10 ft) tall by 2.5 m (8 ft) or more broad with large heads of pink or blue flowers in summer and autumn. The species is currently treated as monotypic, with no subspecies or varieties. Common names include bigleaf hydrangea, lacecap hydrangea, mophead hydrangea, and hortensia. It is widely cultivated in many parts of the world in many climates.

Botanical Description

The term macrophylla means 'large- or long-leaved'. The opposite leaves can grow to 15 cm (6 in) in length, are simple, membranous, orbicular to elliptic and acuminate, and generally serrated. The natural inflorescence is a corymb with all flowers placed in a plane, featuring numerous central, small, fertile pentamerous flowers and a few peripheral, large, tetramerous sterile flowers. The small flowers have five small greenish sepals and five small petals. Flowering occurs from early summer until early winter. In cultivation, numerous variants exist; most cultivars (over 500) feature large, sterile or mostly sterile tetramerous flowers forming a hemisphere or sphere, known as mophead or hortensia hydrangeas. A smaller cultivar group (over 20) retains the natural flat flowerhead structure with small central flowers surrounded by large sterile flowers, known as lacecap hydrangeas.

Origin and Habitat

Hydrangea macrophylla is endemic to Japan, occurring in coastal habitats from Honshu southwards. Natural wild plants have lacecap flowerheads. A closely related species, Hydrangea serrata, was historically treated as a variety of H. macrophylla but is now recognised as separate. The species is naturalised in China, Korea, Siberia, New Zealand and the Americas, and has become invasive in the Azores and Madeira archipelagos.

Cultivation

Hydrangea macrophylla is widely cultivated in many parts of the world across various climates. It prefers positions in full sun or partial shade. The species is not to be confused with H. aspera 'Macrophylla'.

Care and Maintenance

Prune after flowering. The flower colour of cultivars is affected by soil pH; acidic soil (pH below 7) typically produces blue flowers, while alkaline soil (pH above 7) produces pink or red flowers. This colour change is caused by aluminium ion uptake affecting flower pigments.

Uses

Amacha is a Japanese beverage made from fermented leaves of Hydrangea macrophylla var. thunbergii. Hydrangeae Dulcis Folium, a drug made from fermented and dried leaves of H. macrophylla var. thunbergii, has possible antiallergic, antimicrobial, and hepatoprotective properties. The plant is included in the Tasmanian Fire Service's list of low flammability plants. Leaf extracts are being investigated for antimalarial activity and hydrangeic acid for anti-diabetic properties.

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Cultivars and Varieties

Quick Care Summary

Facts sourced from Wikipedia / Hydrangea macrophylla (https://en.wikipedia.org/wiki/Hydrangea_macrophylla)