Hydrangeas for Iowa

Hydrangeas are popular shrubs for the home landscape.  Their large, elegant flowers charm homeowners and visitors alike throughout the summer months.  In the past decade, there has been an explosion of new cultivars with varying flower colors and shapes. With all this variety there is likely a hydrangea (or two) that will work in your landscape. 

Several hydrangea species can be grown in Iowa.  Two species (Smooth Hydrangea and Panicle Hydrangea) are easy-to-grow, reliable performers.  The others can be a bit more challenging. 

Smooth Hydrangea  |  Panicle Hydrangea  |  Bigleaf Hydrangea  |  Oakleaf Hydrangea  |  Climbing Hydrangea  |  More Information

Smooth Hydrangea (Hydrangea arborescens)

One of the most durable and reliable of the hydrangeas is smooth hydrangea (Hydrangea aborescens).  This 3- to 5-foot shrub flowers freely from June to September.  The flowers are rounded and change from an apple green to creamy white during the summer.   Flowers are also showy in the fall as they fade to tan and persist into the winter.  ‘Annabelle’ is one of the most popular cultivars and is noted for its large (almost 1-foot-diameter) flower heads.  This cultivar can be spotted from a great distance.  The flowers are often so heavy they weigh the stems to the ground giving the shrub a “weeping effect”.  For plenty of flowers and dense, dark green leaves, plant smooth hydrangea in partial sun to partial shade.  Smooth hydrangea is tolerant of many soil types but thrives in moist, well-drained soils.  This is one of the cold hardiest of the hydrangeas surviving well into Minnesota.  

Cultivars of Smooth Hydrangea

Panicle Hydrangea (Hydrangea paniculata)  

The panicle hydrangea (Hydrangea paniculata) blooms later than the smooth hydrangea, often not flowering until July.  But the 6- to 12-inch-long, cone-shaped, creamy white flowers are equally persistent.  As the flowers age, they often fade to pink.  This is the largest of the shrub-type hydrangeas, sometimes reaching 15 feet or more in height.  There are many wonderful cultivars of this species including ‘Grandiflora’ or PeeGee.  Once again the flowers are so large they often weigh down the branches.  Panicle hydrangeas are vigorous growers and can be pruned as small trees.  Panicle hydrangeas perform best in moist, well-drained soils in full sun to partial shade.

Cultivars of Panicle Hydrangea

Bigleaf Hydrangea (Hydrangea macrophylla)

The mophead or bigleaf hydrangea (Hydrangea macrophylla) has the colorful blooms that are commonly sold in florist shops and supermarkets as a cut flower.  It is the only hydrangea species where the flower color depends on soil pH – blue in acidic soils and pink in alkaline soils.  In Iowa, most mophead hydrangeas are purplish-pink due to our slightly alkaline soils.   Many of the newer introductions bloom on new growth, in addition to the previous season’s growth.  Despite their improved flowering habit, some cultivars are finicky and bloom erratically. When purchasing plants, check the label for cold hardiness recommendations as there are several cultivars that are not hardy in zone 5 for Iowa.   

Cultivars of Bigleaf Hydrangea

Oakleaf Hydrangea (Hydrangea quercifolia)

One of the most interesting hydrangea species is the Oakleaf hydrangea (Hydrangea quercifolia).  The coarse leaves are 3 to 8 inches long and shaped like oak leaves (hence the common name).  The foliage is also noted for its attractive, red-burgundy fall color.  This 3- to 5-foot shrub has showy, cone-shaped, creamy white flowers in June and July.  Like the panicle hydrangea, its flowers often develop pinkish undertones as they mature.  The oakleaf hydrangea is considered hardy to USDA Hardiness Zone 5.  It should perform well in protected sites in southern Iowa, but may not survive in northern areas of the state.  It prefers partial shade in fertile, moist, well-drained soils in areas protected from harsh winter winds.  Several cultivars are available.  

Cultivars of Oakleaf Hydrangea

Climbing Hydrangea (Hydrangea anomala subsp. petiolaris)

Not all hydrangeas are shrubs.  One such example is the climbing hydrangea (Hydrangea anomala subsp. petiolaris).  It clings easily to tree bark and various structures and can climb to 50 feet.  The white flowers appear in 6-to 10-inch-diameter, flat-topped corymbs in early July and persist for several weeks.  The glossy dark green leaves provide the perfect backdrop to show off the blossoms.  Another interesting feature of this plant is its exfoliating brown shaggy bark which is rather striking in the winter landscape.  Climbing hydrangea thrives in partial shade in a moist, fertile, well-drained soil.  Plants are slow to establish, taking a few years before vigorous growth begins.  Support will also be needed as the plants become established and to direct growth.  Japanese beetles may partially defoliate plants in some years.  Climbing hydrangea is hardy to USDA Hardiness Zone 4.  

Another added bonus to most hydrangea flowers is that they make excellent cut and dried flowers.  You can bring the blossoms inside to brighten the indoor landscape.   

More Information

For more on pruning hydrangeas, see this article: Pruning Hydrangeas