Hydrangeas 101


Hydrangeas are the ornamental darlings of the woody plant world. Long popular with gardeners, some hydrangeas were sold in the Midwest before the Civil War. Like many plants, they have come in and out of vogue. Today, hydrangeas are experiencing an extraordinary revival.

The genus Hydrangea includes flowering shrubs, small trees and climbers. Shrubs vary in size from dwarf specimens to enormous bushes. The two species native to North America are smooth hydrangea (H. arborescens) and oakleaf hydrangea (H. quercifolia). In the past decade, breeders have been busy creating dozens of new varieties with noteworthy attributes.

Hydrangeas tout big beefy blossoms that are generally cream-colored, but some flaunt shades of blue, lime green, violet, pink, strawberry or a mixture of tints. They are a welcome addition to shrub borders, foundation plantings, perennial beds, cottage gardens, and more.

Depending on their flower shape, hydrangeas are called lacecap, mophead or panicle. Their wonderful fresh flowers are lovely in arrangements and, left on the plant, the dried blossoms offer winter interest in the landscape.

Extreme winter cold can be a challenge for some hydrangeas. Panicle and smooth hydrangeas produce flowers on the current season’s growth. For example, in March and beyond, the plants form flower buds on new woody stems—they should always produce flowers despite winter freezes. Other hydrangeas form flower buds on last year’s growth. As the temperatures dip in winter, their buds may freeze, which results in no flowers the following spring.

H. paniculata (Panicle Hydrangea)

H. paniculata    
(Panicle Hydrangea)

Panicle hydrangeas are considered the most cold hardy of the species. They are sought after for their cream-colored cone-shaped flowers that dazzle the garden in summer. Although some cultivars can reach a height and width up to 15 feet, a more typical size is 6 to 8 feet tall and wide. There are many new compact cultivars, such as ‘Little Lime’, ‘Bobo’ and ‘Little Quickfire,’ which are short in stature and useful in small spaces. And a bonus—the flower color changes from green, cream to strawberry pink in late summer.

If you currently have a panicle hydrangea that is too large for its space, you can cut stems back by about one-third or so, preferably before the leaves emerge in early spring. Panicle hydrangeas prefer loamy, moist, well-drained soil in sun to part shade.


H. serrata (Mountain Hydrangea)

H. serrata    
(Mountain Hydrangea)

Mountain hydrangeas hail from Japan and Korea and produce lacecap flowers in shades of blue or pink. Plants tend to be tender in the Chicago area, which means that flower buds that formed last year could freeze over winter. However, breeders have created some newer cultivars that will bloom on old and new growth. Site plants in part shade in soils that are moist, but well-drained. Plants will tolerate full sun if grown with consistently moist soil.


H. arborescens (Smooth Hydrangea)

H. arborescens    
(Smooth Hydrangea)

Smooth hydrangea is a native in southern Illinois. 'Annabelle' is a cultivar that features much larger flowers than the species. It is a deciduous shrub with a rounded habit that typically grows 3 to 5 feet tall.  Breeders have worked with ‘Annabelle’ to create plants with stronger upright stems, bigger flowers and flowers in different shades of pink. Plant smooth hydrangeas in a spot that has dappled sunlight to light shade with consistently moist soil. Although the shrub often dies back to the ground in northern climates, this won’t affect flowering as the flower buds develop on new growth in spring. Easily grown in average moist, well-drained soils in part shade. Tolerates full sun if grown with consistent moisture.


H. macrophylla (Bigleaf Hydrangea)

H. macrophylla    
(Bigleaf Hydrangea)

Bigleaf hydrangeas offer flowers in blue, pink, mauve and bicolors. In alkaline soils, common to northeastern Illinois, flowers will be pink. A fertilizer for acid-loving plants will help turn the flowers blue to purple. The subtle variations in color, even within the same flower, create fascinating effects. Newer cultivars can perform well in the Midwest, but some may suffer from considerable branch dieback during freezing weather. Success is possible with winter protection and regular applications of compost. Most varieties tolerate full sun in the North, but benefit from afternoon shade.


H. quercifolia (Oakleaf Hydrangea)

H. quercifolia    
(Oakleaf Hydrangea)

Oakleaf hydrangea has a long history in Illinois. The Grove Nursery, in what is now Glenview, offered oakleaf hydrangea in its 1856-57 catalog. This shrub, which is native to the southeast United States, is valued for its four-season interest. Great flowers, good fall color in shades of red, purple and bronze, cinnamon-brown peeling bark and handsome foliage from summer through autumn make it a valuable plant for the home garden. Plants tend to be 4 to 6 feet tall and do best in a shrub border with some shade.


H. anomala ssp. petiolaris (Climbing Hydrangea)

H. anomala ssp. petiolaris    
(Climbing Hydrangea)

A woody vine with flat, fragrant flowers that open in late June, climbing hydrangea is a vigorous perennial that clings to almost any surface. It requires a sturdy structure and will cover trees, walls, rocks, and pergolas. Although it’s slow to establish, vines can reach 30 to 40 feet tall with time. Plant it in a spot that has rich, well-drained, moist soil and full sun to light shade.


See the Garden’s evaluation of panicle hydrangeas.

Nina Koziol is a garden writer and horticulturist who lives and gardens in Palos Park, Illinois.