Hydrangea macrophylla Blue Sky

Hydrangea macrophylla 'Blue Sky' is a medium-sized variety with relatively flat inflorescences, quite different from the usual large heads of this variety. Its summer flowering lasts for several months, usually from July to September. Its flowers are among the bluest there are, provided it is planted in acidic soil. It will fade or turn pink in more alkaline soil, as it cannot assimilate aluminum. This beautiful, easy-to-grow bush will thrive in neutral to acidic soil. Choose partially shaded areas, either alone or in the centre of a mixed bed.

Hydrangea macrophylla is a deciduous bush. It is native to Japan where its beauty has been appreciated for centuries and mentioned in poems dating back to the 8th century! Festivals are even dedicated to this bush. Hydrangeas belong to the Hydrangeaceae family, which they have given their name to, and which includes other widely distributed ornamental genera, such as Deutzia, Philadelphus, or Carpenteria. Among H. macrophylla, there are round-headed varieties and flat-headed varieties.

'Blue Sky' is a remarkable variety for its almost unreal blue inflorescences. From July to September, it produces almost flat panicles of lace-cap flowers, composed of small fertile flowers tightly packed in the centre and surrounded by sterile florets with 4 overlapping petals. In acidic soil, they take on an absolutely sublime blue colour, which is rare in the plant kingdom. These remarkable inflorescences measure over 15cm (6in) in diameter. They are enhanced by the medium to dark green foliage (the depth of colour depending on sun exposure).

This bush has a fairly compact habit, reaching about 1.3 to 1.5m (4 to 5ft) in all directions. Its habit is rather regular and it eventually forms a dense rounded mass of vegetation. Its large ovate and acuminate leaves (pointed at the tip) cover the branches well. It can tolerate full sun, preferably with some shade to avoid excesses, or it can be exposed to the east to benefit from the morning sun that is not too intense. It will also thrive in partial shade. The important thing is that it can find moisture in the soil. It may be necessary to provide regular watering, especially in summer. Dry air is also not desirable; it will thrive more in humid oceanic climates or under the shade of large trees that will provide the cool environment it loves.

Like all Hydrangea macrophylla, this bush is not strictly an ericaceous plant. It prefers neutral to acidic soils, while tolerating some limestone. However, its flowering will only fully shine in acidic soil; it will turn pink in slightly alkaline soil. This bush is quite hardy (-20°C (-4°F) or below, although severe frosts can damage the tips of the branches. However, they easily regrow after pruning in spring). It can also be grown in a large container due to its compact mature size. In this case, make sure to water it regularly and not let the substrate dry out. Easy to grow, it can live for a very long time.

'Blue Sky' evokes emotion with its surprisingly blue colour and delicate flowers. You can plant it alone in the light shade of large trees, but it will also be stunning when planted in mixed beds with plants that prefer acidic soil. Choose plants that match its romantic charm and staggered flowering to create a gentle scene throughout the seasons. With its pink and then white star-shaped flowers early in the season, Magnolia stellata 'Royal Star' will kick off the charming flowering, followed by Rhododendron yakushimanum 'Silberwolke', a compact variety with purplish buds opening into magnificent pale-pink flowers that then turn white. The lesser-known Styrax japonica 'Evening Light' will complement 'Blue Sky' with its hundreds of white drooping flowers contrasting with its violet foliage. And to accompany the blue inflorescences of 'Blue Sky', the long creamy-white spikes of Clethra barbinervis 'Great Star' will be perfect, while in autumn, the flamboyant red and yellow colours of its foliage will provide a show in itself.