Hardy 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.    Surely there is one (or two) that will work in your landscape. 

Species and Cultivars

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

Smooth hydrangea Annabelle
Annabelle Hydrangea

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.  

Cultivar

Height (Width)

Comments

Annabelle

3-5 (4-6)

Large white snowball flowers

Bella Anna

5 (5)

Pink flowers

Incrediball

5 (6)

Large white snowball flowers

Invincibelle Ruby

3 (2-3)

Pink to ruby red flowers

Invincible Spirit II

3-4 (3-4)

Pink flowers that fade to green

White Dome

5 (4)

White lacecap flower

Pink blossom of Hydrangea Endless Summer
Hydrangea Endless Summer

Mophead Hydrangea (Hydrangea macrophylla)

The mophead or big leaf 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.   

 

Cultivar

Height (Width)

Comments

BloomStruck

3-4 (4)

Pink, blue, or purple

Blushing Bride

6 (6)

White flowers that age with pink blush

Endless Summer

3-4 (4)

Blue, purple, or pink flowers

Let’s Dance Moonlight

2-3 (2-3)

Pink or blue mophead

Twist and Shout

5 (5)

Pale pink or blue lacecap flowers

Panicle hydrangea plant in front of ISU Campanile
Panicle Hydrangea Quick Fire

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 in this species including ‘Grandiflora’ or PeeGee.  Once again the flowers are so large they often weigh down the branches.  Panicle hydrangeas are a vigorous growers and can be pruned as small trees.  Panicle hydrangeas perform best in moist, well-drained soils in full sun to partial shade.

Cultivar

Height (Width)

Comments

Grandiflora

12-18 (8)

Large white flowers that fade to pink or green

Limelight

8 (6)

Greenish white flowers that blush pink

Little Lime

3-5 (3-5)

Lime green flowers age to pink

Little Quick Fire

3-5 (5)

Creamy white flowers that turn a deep pink

Pink Diamond

8-10 (8-10)

White flowers turn pinkish

Pinky Winky

8 (8)

White flowers that fade to pink

Quick Fire

6-8 (6-8)

Creamy white flowers that turn a deep pink

Tardiva

8-10 (6)

Large, open white flowers

Vanilla Strawberry

6-8 (5)

Flowers change from vanilla white to strawberry red

White Diamonds

5 (5)

Open white flowers

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.  

Cultivar

Height (width)

Comments

Gatsby Star

6-8 (8)

Double greenish white star-shaped flowers

Snowflake

6 (8-10)

Double flowers that fade to rosy pink

Vaughn’s Lillie

4 (5)

Large flower heads

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.   

For more on pruning hydrangeas, see the Horticulture and Home Pest Newsletter article from March 23, 2017

Blossom of a blue Macrophylla hydrangea
Blue Hydrangea macrophylla

blossoms of hydrangea Vanilla strawberry
Panicle Hydrangea Vanilla Strawberry

 

Bloom of panicle hydrangea limelight
Panicle Hydrangea Limelight

Authors: 

Links to this article are strongly encouraged, and this article may be republished without further permission if published as written and if credit is given to the author, Horticulture and Home Pest News, and Iowa State University Extension and Outreach. If this article is to be used in any other manner, permission from the author is required. This article was originally published on August 24, 2018. The information contained within may not be the most current and accurate depending on when it is accessed.