Hydrangeas brighten up summer?
by: Sara Raab

Of the summer-blooming shrubs, few are as bold as the hydrangeas. Just when the lilacs are past their glory, and the sweet fragrance of the mockorange has faded from memory until next year, the fat heads of hydrangea blossoms are about to burst open.

All hydrangeas carry their flowers in large clusters that are either spherical, conical or disc-shaped, depending on the species. The clusters are comprised of masses of tiny fertile flowers surrounded by or mixed in with the showier sterile flowers.

One of the hardiest hydrangea species is the lovely smooth hydrangea (Hydrangea arborescens) which is commonly  grown in the home landscape. This extremely versatile plant has huge, creamy-white globe-shaped flower clusters lasting from late June to September.

One of the best features of this shrub and most hydrangeas is its ability to thrive in both full sun and partial shade, actually preferring the shadier location.

The named selections of smooth hydrangea have huge flower heads that can reach up to twelve inches across.  'Annabelle' is valued for its symmetrically formed and extremely large flower clusters, while 'Grandiflora' (also known as the Hills-of-Snow hydrangea) is the most commonly available.

Both of these cultivars are occasionally guilty of allowing the massive flower heads to weigh down the stems until they are indelicately resting on the ground. You can try to stake up the outer stems or take the opportunity to make a flower arrangement.

The key to maintaining this plant is to provide one annual pruning in late winter, by cutting the plant to the ground.  The fast growth rate of this shrub brings it back to height quickly each season, and since the flowers are produced only on the current season's growth the display is not affected.

The panicle hydrangea (H. paniculata) is another very hardy summer-blooming hydrangea; this one begins its show in the heat of August. Named for is cone-shaped flower heads, the panicle hydrangea is a large shrub reaching fifteen feet in height or more.

We are quite fond of the cultivar 'Unique' which can be seen in both the Herb and Sunken gardens at Olbrich Gardens. 'Tardiva' blooms a bit later, with the creamy white flowers fading to pink as they age, eventually deepening to rose with the cooler temperatures of autumn. 

The most widely known cultivar of the panicle hydrangea is 'Grandiflora', also known as the PeeGee hydrangea.  This plant is often pruned into a tree form which can be quite graceful. There are some beautiful old specimens of PeeGee hydrangea in Forest Hills Cemetery on the west side of Madison.

The flower heads produced on both the smooth and panicle hydrangeas are highly valued as dried specimens. Used extensively in floral crafts because they are so long-lasting, hydrangea is used in wreaths, ornaments, and dried arrangements. We even used some to decorate the Holiday Tree at Olbrich Gardens last December!

You can easily dry the clusters off your own plants by snipping the stem and hanging the cut clusters upside down for a few weeks. Or if you're lazy like me, just arrange them fresh in an empty vase and leave them -- your fresh arrangement will turn into a dried one in no time.

One of the most beautiful hydrangeas is not a shrub at all, but a climbing vine that bears gorgeous white disc-shaped flowers in late June and early July. Climbing hydrangea (H. petiolaris) clings tenaciously to any sturdy structure with the help of aerial roots and will climb to an almost unlimited height. Though slow to establish, once your new plant is settled it will easily clamber up stone and brick walls as well as the bark of old trees.

An interesting feature of this vine is its three-dimensional branching structure. Unlike other vines such as Boston ivy or Virginia creeper which grow flat against walls, climbing hydrangea produces short lateral branches that grow perpendicular to the surface on which it is growing. This outward growth gives substance and texture to the vine as a whole, especially when in bloom.

Throughout the winter months the cinnamon colored bark that is concealed all summer is revealed, providing much-appreciated color and texture in the winter landscape. 

Being extremely shade tolerant like its kin, the climbing hydrangea is particularly well-suited to a location on the north or east side of a wall or tree. Just remember that this is a large, woody vine that requires a sturdy structure on  which to grow and it is not recommended for planting on wooden structures.

The oakleaf hydrangea (H. quercifolia) is well worth consideration despite being on the northernmost fringe of hardiness here in southern Wisconsin. Another shade-tolerant five foot shrub, this hydrangea is a standout for its foliage.


As the name suggests, each leaf is deeply lobed like that of an oak tree. Dark green throughout the summer, in the fall this shrub turns a rich scarlet-purple, and through the winter the exfoliating bark is displayed like that of the climbing hydrangea. 

After last winter's mild temperatures, the three groups of oakleaf hydrangea that we have at Olbrich Gardens are all displaying the buds that will soon form into large white panicles of flowers.  However, after a normal winter we would not expect to be so lucky. In fact, we have decided to grow this plant for its foliage alone and if conditions allow for flowers to develop, all the better.