Hydrangea

The North American species H. arborescens is not particularly attractive and is usually seen only in scientific collections. However, the various forms and named varieties which have been developed from the species, the so-called ball hydrangeas, have long been grown in Finland.

The best-known of these varieties, ’Grandifolia’, was found in the wild in Ohio in the year 1900; it has ball-shaped double blossoms about 10-18 cm in diameter. ‘Annabelle’ is another variety of wild origin, having been found near a town in the state of Illinois called Anna. This variety has showy inflorescences which can be over 20 cm in diameter.

These ball-hydrangeas are generally considered rather winter-tender. At Mustila, they grow more or less as perennials, the tops freezing each winter. This is not a problem regarding flowering since the flowers form on the new growth each year. In gardens and parks hydrangeas are usually cut down to ground level every year. A reasonable number of branches guarantees large blossoms.

The naming of these various tree hydrangea varieties has become rather confused though ‘Annabelle’, with its enormous blossoms, is usually easily distinguishable.

The Mustila hydrangea was ”discovered” among old plantings in the Arboretum in the 1980s, named and selected for FinE-elite plant propagation based on its abundant flowering, beautiful habit and winter hardiness. In appearance it resembles the wild Pee Gee hydrangea, H. paniculata. The erect, conical, white flower corymbs resemble lace. The large sterile outer flowers surround sparser small central fertile flowers. Flowering takes place in September, when few other shrubs are in flower, and the dried inflorescences remain on the shrubs, decorating them throughout the winter.

The Mustila hydrangea, like other hydrangea species, has a naturally attractive habit and needs no trimming, although it is often recommended in gardening books.

Pee gee hydrangea is the shrub that all the familiar autumn hydrangeas have been developed from. Reaching 4 metres in height, shrubby or sometimes tree-like, this species has creamy-white flowers in conical clusters. In addition to the small fertile flowers they also have a showy border of sterile flowers with large sepals instead of reproductive organs.

Some of the varieties developed from pee gee hydrangea have a large number of sterile flowers in the outer ring, while some have only these sterile flowers, and they are unable to produce seed. The variety ‘Grandifolia’ is one of these. In past decades it was among the most popular garden shrubs in Finland. Mustila’s own namesake variety (H. paniculata ‘Mustila’) closely resembles in outward appearance the natural pee gee hydrangea.

In addition to the ‘Mustila’ variety, there are also true young pee gee hydrangeas growing at the Arboretum, from natural seed collected on Hokkaida and the Kurile Islands. In recent years about 40 pee gee varieties have been planted to discover which of them are best suited to Finnish conditions. The species is a valuable addition to Finnish gardens, flowering as it does in late summer and autumn when very few other shrubs are in flower.