Large-Flowered Panicle Hydrangea

Like most Hydrangeas, the Panicle Hydrangea (Hydrangea paniculata) is native to East Asia. Its wild form is native to the temperate climate zone of East Asia from Russia to China, as well as almost all of the Japanese main islands. It grows in partially shaded locations in deciduous or riparian forests in fresh to moist soils, reaching heights of up to thirty foot. The Panicle Hydrangea became known in Europe around 1830 when it was discovered and first described by the German doctor and naturalist Philipp Franz von Siebold during a long stay in Japan. The wild species is difficult to find in garden centers. The large-flowered garden variety ‘Grandiflora’ is the most common in this country.

The Panicle Hydrangea has a shrub-like and upright growth habit with numerous forked branches. The bark of the young shoots is light gray to ocher, while it is darker on the older branches. The old main shoots have a gray-brown bark which peels in paper-thin pieces. Depending on the variety and location, Panicle Hydrangeas in the garden usually reach a height of 6.5 to 13 ft and a width of up to 10 ft. Annual growth is 9.85 inches and often more than double that after hard pruning.

The Panicle Hydrangea is deciduous with opposite leaves, sometimes there are even three leaves on one leaf node in a whorled arrangement. The leaves are ovate and 2.75 to 5.90 inches long. The matt green surface is remarkably coarse, the bottom has a gray-green color. They develop green-yellow fall foliage in drier, relatively low-nutrient locations.

The broad cone-shaped panicles of the ‘Grandiflora’ variety are 7.87 to 9.84 inches long and appear at the ends of the new shoots from July to September. They consist of numerous creamy white sterile florets. The flowering shoots are ideal as cut flowers for vases. They turn pale pink when they fade and are still very attractive when they have dried out – either as a wintery flower bed decoration or as a dried bouquet.

The ‘Grandiflora’ variety does not produce fruit or seeds.

The idea spot for Panicle Hydrangeas is a wind-sheltered location with full sun to partial shade, as wind can cause the long flowering shoots to break when in bloom. The soil should be sandy to slightly loamy, fresh to moist, rich in humus and not too low in nutrients. Unlike most other Hydrangeas, the Panicle Hydrangea is able to tolerate short periods of dryness relatively well. The pH should be in the acidic to neutral range. Panicle Hydrangeas are not quite as lime-sensitive as Bigleaf Hydrangeas.

Panicle Hydrangeas are usually sold in pots and can be planted all year round, because, unlike Bigleaf Hydrangeas, they are completely frost-hardy. Sandy soils that are less rich in nutrients should be improved with mature compost before the flowering shrubs are planted. Make sure they have plenty of water after planting and mulch the soil with fall foliage or bark mulch. It is advisable to sprinkle a few handfuls of horn shavings around the plants before mulching. Locations in the root area of larger trees are not ideal for Panicle Hydrangeas, as the flowering shrubs do not tolerate root pressure well. In poorer soils, the shrubs should be provided with compost every spring after pruning. Panicle Hydrangeas do not need winter protection.

Just like Buddleja, Panicle Hydrangeas bloom on new wood. Therefore, heavy pruning the old flowering shoots at the end of February results in longer new shoots with particularly large panicles. However, severe pruning is only recommended for Hydrangeas in nutrient-poor soils in wind-sheltered spots, otherwise the flowering shoots break off easily during strong thunderstorms in summer. Depending on the location, leave at least one to two pairs of nodes, but no more than half, on last year’s flowering shoot. Flowering shoots that are weaker or too compact can be completely removed.

Panicle Hydrangeas are suitable as specimen plants in perennial beds. They go very well with Larkspur and other taller flowering shrubs. The summer bloomers also look good planted in small groups with Rhododendrons, which often look a little sad in midsummer. A little known fact: you can also create great flowering hedges with Panicle Hydrangeas. They can also be combined with other summer bloomers that are not too competitive, such as Hibiscus (Hibiscus syriacus). Smaller varieties are also suitable for large tubs on the patio.

Besides the ‘Grandiflora’ variety mentioned here, there are a number of other interesting garden varieties of the Panicle Hydrangea.

All Panicle Hydrangeas are relatively easy to propagate – either from semi-hardwood cuttings in early summer or from hardwood cuttings in winter. You can, for example, use the old flowering shoots as your base material; these are removed during pruning in late winter anyway. Cut a few pieces that are about as long as a pencil or pair of scissors, and put them in a sheltered, partially shaded spot in humus-rich, moist, sufficiently loose garden soil immediately after pruning.

Panicle Hydrangeas are somewhat susceptible to powdery mildew and leaf spot diseases. Moreover, the flowering shrubs sometimes become infested with aphids and vine weevils.