Hydrangea involucrata - Bracted Hydrangea

The Hydrangea involucrata, sometimes called involucrata 'azisa', is very different from the large-leaved hydrangeas (macrophylla) of our grandmothers. It rarely exceeds 1m (3 ft 4 in) in height, has a distinctly spreading habit, and blooms abundantly for almost 4 months if faded flowers are removed. Its flowering is as unusual as it is rustic: large rounded flower buds that resemble peonies open into flat, airy inflorescences, with a deep lavender colour in the centre and white on the periphery, a colour that is independent of the soil that hosts the bush. They bloom on original foliage, dark green, embossed and soft to the touch. Unlike many hydrangeas, it tolerates slightly chalky soils but requires a shaded exposure.

The Hydrangea involucrata or dwarf hydrangea, from the Hydrangeaceae family, is native to the high-altitude wet forests of Japan and Taiwan. It is distinguished by its small size but also by the fact that its flowering occurs on the current year's growth and not on one-year-old wood like Hydrangea macrophylla. This means that even if the stems are destroyed by severe, even late frost, the plant will develop new shoots from the base and its flowering will not be affected. The bush is hardy to about -18°C (-0.4 °F).

The plant forms a small bush, wider than tall, about 90 cm (35.4 in) to 1 m (3 ft 4 in) in height and 1.50 m (4 ft 11 in) in spread. The characteristic flower buds of this hydrangea are rounded, the size of peony buds. The beautiful plate-like flower heads of the Hydrangea involucrata, 12 to 15 cm (4.7 to 5.9 in) wide, bloom in large numbers from July to October, more or less early depending on the climate. They are composed of numerous small fertile flowers in blue-mauve buds, gathered in a central disk, surrounded by a few much larger sterile florets, pure white, carried by long peduncles. They are often visited by butterflies. The foliage, a beautiful dark green, covered with numerous short hairs, falls in autumn. It consists of oval leaves measuring about 8-10cm (3.1-3.9 in) long by 6-8cm (2.4-3.1 in) wide, finely toothed along the edges, strongly veined and with a wavy appearance.

The Hydrangea involucrata requires a cool environment, plant it in partial shade or not too dense shade, in a place protected from cold, dry winds, in a soil that remains moist, not too compact, slightly acidic, neutral, or even slightly chalky. This rustic variety, which blooms while others are already almost faded, extends the flowering period of hydrangeas. Plant it at the edge of woodlands, at the back of a flower bed, under tall trees, or near a shaded wall of the house. It can be accompanied by ferns, hostas, Japanese knotweed, Thalictrums.