Smooth Hydrangea, Shrub Hydrangea

The Smooth Hydrangeas are also commercially available as wild Hydrangeas. The wild species is native to the Appalachian Mountains, a north-south mountain range in the eastern United States. It is also found in the Delaware River valley. However, the wild Smooth Hydrangea is not cultivated as a garden plant. We only sell selected varieties that have particularly large, sterile inflorescences and that are suitable for gardens.

The Smooth Hydrangea is an upright shrub that grows up to 78.74 inches high with numerous basal shoots. The twigs are remarkably thin and have an ocher yellow bark which later turns red to dark brown. Snowball Hydrangeas spread underground through short runners, so old shrubs can take up a lot of space over the years.

The light green, opposite leaves are ovate to elliptical and pointed at the end. They can be 3.14 inches to 5.90 inches long and have a matte surface. The plants shed their leaves at the end of the season, which means that the fall colors do not form.

From a botanical point of view, the large, flat flower panicles are called umbrella panicles. They appear from the end of June to September at the ends of the new shoots and consist of numerous sterile single flowers that are initially greenish-white, which later turn into creamy white. As they fade, they take on a lime green hue and can be used as decorations even when they dry out. The ‘Annabelle’ variety is still one of the most blooming and large-flowered selections. It is not uncommon to see flowers of up to 9.84 inches in diameter.

Since the flowers are usually sterile, ‘Annabelle’ and most of the other varieties do not grow fruit.

Smooth Hydrangeas grow in sunny to shaded locations, which should be protected from wind and if possible, from rain as well. A larger tree is ideal as a shade, which also reduces the impact of very heavy rainfall. In heavy rain, the flowers quickly become so heavy that the flower stalks buckle and the whole shrub literally falls apart. Usually, however, it will straighten up on its own after a while. As with all Hydrangeas the soil should be loose and sufficiently moist with lowest possible lime content along with being rich in humus. A pH-value between 5.5 and 6 is ideal.

Smooth Hydrangeas are among the most frost hardy Hydrangeas and can withstand cold winters without any problems. Therefore, unlike the more sensitive Mophead Hydrangeas, it is not necessary to plant Smooth Hydrangeas as early as spring. Planting in fall is also no problem for them. Prepare the soil thoroughly using deciduous humus or sand if required. Since Smooth Hydrangeas, like all Hydrangeas, have a high water requirement, a slightly shaded location is better than one in full sun. In any case, the freshly planted shrubs should be kept properly damp for the first few weeks. Mulch the soil with a layer of leaves or, bark mulch after scattering a few handfuls of horn shavings around the root.

Unlike the Mophead Hydrangea, in which only the old inflorescences are removed, the Smooth Hydrangeas can be cut back to just above the ground at the end of February. They then sprout particularly vigorously and form large inflorescences. Avoid strong pruning in very windy locations. The long new shoots are not very stable and the flower heads droop after rain showers. If pruning is less rigorous, the flowers remain a little smaller and the entire branch structure is more stable.

Provided that you know which Hydrangeas are growing in the garden, you can’t go awfully wrong when it comes to pruning. In our video, we show you how to prune the different species.

The flowering shrubs are usually integrated individually or in groups in perennial plantings in sunny to partially shaded locations. Smooth Hydrangeas go very well with large-leaved ornamental perennials such as Rodgersia, Astilbes, Monkshood, Globe Thistles (echinops), High Sedum and ornamental grasses. In addition, the low shrubs cut a fine figure as lush flower hedges.

• “Grandiflora”: Another classic along with ‘Annabelle’— it is a bit more vigorous and stable, but has smaller flowers
• “Pink Annabelle”: As the name suggests, it is an ‘Annabelle’-type variety with light pink flower balls. It is also sold under the name ‘Invincible spirit’
• ‘Strong Annabelle’: It grows more compact, has slightly smaller flower balls than the real ‘Annabelle’ and is therefore considered more stable
• ‘Incrediball’: the variety with the largest inflorescences to date. They form a beautiful hemisphere and can reach up to 11.81 inches in diameter. In terms of color, they hardly differ from ‘Annabelle’ but are a little whiter during the main flowering period

All smooth Hydrangeas are easy to propagate in early summer by half-woody cuttings. It is also possible to propagate with hardwood cuttings in winter, and new plants can even be obtained by dividing — in other words, cutting off the runners in fall or spring.

The Smooth Hydrangeas suffer less from incurable viral infections than the Mophead Hydrangeas. Leaf spot diseases and powdery mildew occur occasionally. The most common pests include scallop insects and vine weevils.