Flowering time (month)
Ornamental or utility value
The Hydrangea paniculata, like almost all hydrangeas, originates from East Asia. Their wild form is native in the temperate climate zone of East Asia from Russia to China as well as on almost all Japanese main islands. It grows in semi-shade locations in deciduous and alluvial forests on fresh to moist soils and reaches heights of up to nine metres. The panicle hydrangea became known in Europe around 1830, when the German doctor and natural scientist Philipp Franz von Siebold discovered it during a stay of several years in Japan and described it for the first time. The game species is hardly available in specialist garden shops in the United States. The most widespread garden in this country is the large-flowered garden form ‘Grandiflora’.
The Rispenhortensie grows shrubby and upright with numerous forked branches. The bark of the younger shoots is light grey to ochre brown, that of the older branches somewhat darker. The old main shoots carry a grey-brown bark, which detaches in paper-thin pieces. In the garden, panicle hydrangeas are usually two to four metres high and up to three metres wide, depending on the variety and location. The annual growth is 25 centimetres, often more than double after strong pruning.
The deciduous leaves of the Rispenhortensie are mostly opposite, sometimes there are three leaves on a node (leaf node) in a lively arrangement. The leaves are ovate and 7 to 15 centimetres long. The matt green surface is strikingly rough, the underside shows a grey-green hue. In drier, rather nutrient-poor locations, a green-yellow autumn colour is formed.
The broad conical panicles of the ‘Grandiflora’ variety are 20 to 25 centimetres long and appear at the ends of the new shoots from July to September. They are composed of numerous sterile, cream-white individual flowers. The flower shoots are very suitable for the vase cut. They turn pale pink when they wither and remain attractive for a long time even when dried – either as a winter bed decoration or as a dry bouquet.
The variety ‘Grandiflora’ does not grow fruit and seeds.
Location and soil
The ideal place for Rispenhortensien is sunny to absunig and wind-protected, since the long flowering shoots are somewhat windbreak-prone at the bloom-time. The soil should be sandy to slightly loamy, fresh to moist, rich in humus and not too low in nutrients. The Rispenhortensie tolerates relatively well in contrast to most other hydrangeas however also shorter dry-periods relatively. The pH value should be in the acid to neutral range. Rispenhortensias are not quite as sensitive to calcification as farmer’s hydrangeas.
Planting and care
Rispenhortensias are usually offered in pots and can then be planted all year round because, unlike farmer’s hydrangeas, they are absolutely frost hardy. You should improve nutrient-poor sandy soils with ripe compost before planting the flowering shrubs. After planting, ensure a good water supply and mulch the soil with autumn leaves or bark mulch. Before mulching, it is advisable to sprinkle a handful of horn shavings around the plants. Locations in the root area of larger trees are not ideal for panicle hortensias, as the flowering shrubs hardly tolerate root pressure. On poorer soils, the shrubs should be provided with compost every spring after pruning. A winter protection is not necessary with Rispenhortensien.
Rispenhortensias bloom just like, for example, the summer lilac on the new wood. Therefore, a strong pruning of the old flowering shoots at the end of February leads to the formation of long new shoots with particularly large flower panicles. However, very strong pruning is only recommended on poorer soils in wind-protected areas with soils that are not too rich in nutrients, as otherwise the flowering shoots can easily break off in strong summer thunderstorms. Leave at least one to two pairs of eyes, but not more than half, of last year’s flowering shoots standing, depending on the location. Weaker or too dense old flower shoots are cut out completely.
Video: Cut hydrangeas correctly
You can’t do much wrong with hydrangea pruning, provided you know which hydrangea grows in the garden. In our video we show you which species are cut and how.
In this video we show you how to cut hydrangeas correctly. Credit: Alexander Buggisch / Producer Dirk Peters
Rispenhortensias are suitable for individual placement in a shrub bed. Here, for example, they can be combined very well with knight spurs and other higher flowering perennials. The summer bloomers are also well suited as small groups in rhododendron plantations, which often appear somewhat dull in midsummer. Something hardly anyone knows: even great summer flower hedges can be designed with panicle hortensias. Here they can also be combined with other, not too competitive summer bloomers such as hibiscus (Hibiscus syriacus). Smaller varieties are also suitable for large tubs on the terrace.
In addition to the variety ‘Grandiflora’ presented here, there are a number of other interesting garden forms of the Rispenhortensie.
The flowers of the variety ‘Diamant Rouge’ (left) turn bright pinkish red when faded. Unique’ (right) forms fertile flowers in addition to pure show flowers
Kyushu’: The selection of the Japanese wild form bears large, cream-yellow inflorescences which contain fertile flowers in addition to the sterile show flowers. It is not quite as splendid optically, but first choice for the natural garden, since its fragrant flowers are true insect magnets. ‘Unique’: The flower candles, up to 25 centimetres long, contain one-third fertile flowers. The sterile show flowers are initially creamy white and turn bright pink at the end of September when withered. ‘Diamant Rouge’: The still relatively new dwarf form grows only 1.5 metres high and turns its creamy white sterile inflorescences strawberry red at the end of September. ‘Limelight’: This variety flowers lime green and when withered the creamy yellow inflorescences turn pink. With a growth height of 2.5 metres it belongs to the more compact Rispenhortensien.
Pinky Winky’: This is the first two-tone variety, as the creamy white individual flowers do not all turn reddish at the same time as they fade, but gradually from bottom to top. The upright growing cultivation with a height of two meters is also suitable for plant pots.
All Rispenhortensien can be reproduced relatively easily – either by slightly woody cuttings in early summer or by cuttings in winter. For this purpose, for example, the old flower shoots can be used as starting material, which are removed anyway during pruning in late winter. Cut a few pieces, about the length of pencils or scissors, and immediately after cutting, place them in a sheltered, semi-shady place in humus-rich, moist and sufficiently loose garden soil.
Hydrangeas can easily be propagated by cuttings. In this video we show you how to do it.Credit: our store/ Alexander Buggisch / Producer Dieke van Dieken
Diseases and pests
Rispenhortensias are somewhat susceptible to powdery mildew and leaf spot diseases. In addition, the flowering shrubs are sometimes infested by aphids and saplings.
Panicle hortensia in the our store-Shop
I am Don Burke, one of the authors at My Garden Guide. I am a horticulturist that cultivates, grows, and cares for plants, ranging from shrubs and fruits to flowers. I do it in my own garden and in my nursery. I show you how to take care of your garden and how to perform garden landscaping in an easy way, step by step.I am originally from Sydney and I wrote in local magazines. Later on, I have decided, more than two decades ago, to create my own blog. My area of specialization is related to orchid care, succulent care, and the study of the substrate and the soil. Therefore, you will see many articles dedicated to these disciplines. I also provide advice about how to improve the landscape design of your garden.