The Hortensia Garden

A sea of flowers! In the summer months the Hortensia Garden in the Hortus Haren is in full bloom and overwhelms the visitor with a selection of the most beautiful Hydrangea cultivars.


There are more than 70 species of Hydrangea, most of which come from East Asia. H. macrophylla, the “farmer’s hydrangea” in the most well-known sort. For centuries it has been a beloved garden plant and hundreds of cultivars have been developed, with mophead or lacecap flowers and tints ranging from blue to purple, red, pink and white.

The Hortensia Garden also contains many cultivars of the species Hydrangea serrata, the mountain hydrangea. The serrata has a more delicate manner of growth than does the macrophylla. The two species hybridize easily, however, also in the wild. A noteworthy example of such a hybrid is Hydrangea ‘Preziosa’.


A remarkable property of both sorts of hydrangea is that the flower color can vary depending on the availability of aluminum ions in the soil, which in turn depends on the acidity of the soil. In acidic soil with sufficient aluminum, flowers will be blue, whereas these same flowers will be pink or red in a more alkaline soil. Just to keep things interesting, not all hydrangeas react this way; some cultivars—white ones, in particular—don’t change color.


The hydrangea blooms in one of three ways: ball (mophead), lacecap, or cone-shaped panicle. In each case, the flower clusters consist of the showy, sterile flowers (whose bright display attracts bees and other pollinators) and smaller, less noticeable but fertile flowers containing stamens and pistils. Mophead flowers have relatively few fertile flowers and those there are hard to see. Lacecaps, on the other hand, owe their beauty to the heart of fertile flowers surrounded by a ring a sterile flowers.

A species that blooms with plumes, or cone-shaped panicles is Hydrangea paniculata, the plume hydrangea, and in the wild it can even grow into a small tree. The oakleaf hydrangea (Hydrangea quercifolia), native to the United States, also forms flower plumes. The color of the flowers varies from white to light pink, but the most striking feature of the plant in the large leaves that turn an intense dark red in the fall.

The hydrangeas begin to bloom at the end of June and throughout the summer the garden is a sea of color. The fall brings its own beauty as the flowers—and some of the leaves—slowly change color.


In the wild most hydrangeas grow in open woodlands or on the edge of forests. In the Hydrangea Garden, trees have been planted to provide the filtered sunlight conditions preferred by the hydrangeas. A variety of perennials have been planted to complement the hydrangeas, and hyacinths and other woodland flowers carpet the garden in the spring.

Additional Hydrangea Species in the Garden:

Hydrangea anomala subsp. petiolaris, climbing plant or ground cover;

Hydrangea aspera, velvet hydrangea, so-called because of the hairs on the leaves and twigs;

Hydrangea heteromalla, can grow to a small tree;

Hydrangea involucrata, a low-growing species, native to Japan.