HYDRANGEAS: SHRUBS FOR ALL SEASONS

Flowers are beautiful, but they are gone in an instant. Fall color is fantastic, but it’s gone when the leaves fall. Garden lovers – and landscape professionals – are always on a quest for the grail: plants with four seasons of interest. Hydrangeas may not be the perfect four season plant, but they come darn close.

The problem is that when you say “hydrangea” most people think of the colorful flowers of the mophead-type hydrangea such as Hydrangea macrophylla, a species that does not perform reliably in Northern Illinois. An exciting new introduction, Endless Summer®, may be the first in a line of more hardy forms of this plant but for the most part there are four hydrangea species best suited to Midwestern landscapes.

Climbing hydrangea (Hydrangea anomala spp. petiolaris) is an extremely ornamental woody plant. It takes about five years to mature but it is well worth the wait. Do not make the mistake of installing the young containerized plant next to a delicate wood or wrought iron trellis. The flowers may look delicate but the plant can reach 30 feet or more, with a powerful grip that can damage wood or brick structures. The same vigor that makes this vine a potential danger to structures makes it a dramatic feature in the landscape.

Care of the climbing hydrangea -- after the initial coddling until it becomes established -- is minimal. Pruning is only necessary for cosmetic reasons, and pests and diseases are not usually a problem. Plant in sun, part shade or shade; keep the soil moist and during hot weather, periodically moisten the tree, wall or garden structure that supports the vine. Climbing hydrangea has lacy white fragrant flowers, yellow fall color and peeling bark; it is hardy to zone 4.

Smooth hydrangea, also called hills-of-snow-hydrangea (H. arborescens) is one of the most familiar forms of hydrangea. It is one of two species native to North America, originating in the hills of Appalachia. It is often used in “Grandma’s Gardens,” cottage gardens and gardens that focus on old-fashioned plants. The snowball shaped flowers of this plant are sometimes confused with those of the snowball viburnum but, apart from the name and the fact that both have round white flowers, a visual comparison of the two make the differences clear. The flowers on the smooth hydrangea are exceptionally large – up to a foot in diameter – in creamy white to green. Because of the size of the flowers, the shrub can sometimes appear large and floppy.

The cultivar ‘Annabelle’ is preferable to the species and is readily available. The massive mostly sterile flower clusters bloom in late spring to mid summer. For best flowering and form, cut back each winter to less than a foot above the ground. New cultivars have been introduced in recent years – a few of those are listed in the sidebar. Smooth hydrangea is considered reliably hardy to zone 4, performing best in zone 5 but able to survive, with winter protection and with the expectancy of some frost damage, up to zone 3 and possibly zone 2.

The panicle hydrangea is more often found in cultivar form than in the species. The “PeeGee” hydrangea (Hydrangea paniculata ‘Grandiflora’), probably the most common cultivar, derives its common name from the abbreviation of its botanical name – “Pee” for paniculata and “Gee” for ‘Grandiflora’. This plant is valued for its huge, conical flowers, which bloom on new growth in mid to late summer and can grow as large as 12-18 inches long by 6-12 inches wide. The distinctive flowers, which change from white to cream tinted with pink to burgundy, are popular not only in the landscape but also in arrangements of fresh and dried flowers.

Shrub form PeeGee hydrangeas are often integrated into mixed borders, while the tree form makes an attractive but unusual specimen. For larger flowers, cut back PeeGee hydrangeas almost to the ground in late winter or early spring, thinning branches at the same time. Plant in moist, well drained soil in full sun.

The common name of the oakleaf hydrangea (H. quercifolia) refers to its large dark green leaves that have 3 to 7 lobes and resemble red oak leaves. Oakleaf hydrangea has distinctive peeling bark, attractive purple-to-bronze fall color and large white flowers that bloom in June and July. In the Chicago area, flower buds may be at risk during a severe winter. When planted in full sun, the flowers will turn pink, rose, to maroon in fall. In excessive shade, there may be no bloom at all. This is one of the two species of hydrangea native to North America, originating in the Piedmont area of the Southeast.

This top-rated shrub continues to grow in popularity, and new cultivars are becoming more readily available (see sidebar). This shrub has a spreading habit and may reach up to 12 feet in height, with an equal spread. It naturalizes well in wooded sites is hardy to zone 5 with the possibility of some winter dieback. Oakleaf hydrangea prefers evenly moist, well-drained soil and periodic fertilization. It tolerates alkaline soil but may have problems in heavy clay.

While these are the plants we know as hydrangeas, in fact this genus has been around for millions of years. Fossil records of hydrangeas have been found in Alaska and in the Pacific Northwest dating from a period 40-70 million years ago, as well as more recent fossils (from 25-40 million years ago and from 12-25 million years ago from Colorado through the Pacific Northwest, and from 12-25 million years ago in China.1

Today hydrangeas can primarily be found growing in their native form in eastern Asia, but also in eastern North America and along the western coast of Central and South America.



Hydrangea Hybrids and Cultivars: New and Newer

There have been many improved varieties of hydrangeas introduced over the years including the well-known Hydrangea arborescens ‘Annabelle’ and ‘Grandiflora’, H. paniculata ‘Floribunda’, ‘Grandiflora’ (the famous PeeGee hydrangea) and the late-blooming ‘Tardiva’, and H. quercifolia ‘Snow Queen’ and ‘Snowflake’.

The following list includes new and recent hybrids and cultivars that are hardy to at least zone 5. With the exception of Endless Summer®, most hybrids and cultivars of H. macrophylla are not reliably hardy in the Chicago area.

Hydrangea anomala ssp. petiolaris ‘Miranda’ – Climbing plant with white flowers and irregular yellow-gold variegation.
H. anomala ssp. petiolaris ‘Skyland Giant’ – 12-inch lacy white flowerheads, yellow fall color and peeling cinnamon-colored bark.
H. arborescens ‘Hayes Starburst’ – Compact form with double sterile florets above flowerhead.
H. arborescens ‘Riven Lace’ – Creamy white sterile flowers, upright habit. Needs soil that is consistently moist but well-drained.
H. arborescens White Dome® (PP14168) - Similar to ‘Annabelle’ but with dome-shaped white flowers in a lacecap form. Shade tolerant.
H. arborescens ssp. radiata ‘Samantha’ – Green-white sterile florets turn lime-white with age.
H. macrophylla Endless Summer® (PPAF) – Reliably hardy mophead-type hydrangea. Flowers pink in this area, blue in more acidic soils.
H. paniculata ‘Dharuma’ – Dwarf Japanese form with white flowers turning pink in late summer.
H. paniculata ‘Kyushu’ – The large white panicle flowers bloom mid-summer.
H. paniculata Limelight™ (PP12874) – Similar to the PeeGee hydrangea, the green flowers change to near white and then to pink. Award-winning.
H. paniculata ‘Little Lamb’ (PP15395) – Very hardy, fairly compact white-flowering form.
H. paniculata ‘Mehanii’ – Dwarf rounded habit, white panicle flowers, yellow-bronze fall color.
H. paniculata ‘Pink Diamond’ – Large white to pink flowers bloom in mid-summer. Purple bronze fall color.
H. paniculata Pinky Winky™ (PP16166) – Hardy, heavy-blooming pink and white flowers.
H. paniculata Quick Fire® (PP16812) – Blooms very early, flowers turn a vivid dark pink as they age.
H. paniculata The Swan™ (PP13606) – Exceptionally large white flowers.
H. paniculata ‘Unique’ – White flowers turn pink with age; bronze fall color.
H. paniculata ‘White Lace’ – Small, compact form with large white flowers, blooms in summer.
H. paniculata ‘White Moth’ – Large white flowers fade to pink over a very long blooming season.
H. quercifolia ‘Alice’ – A Dirr selection with large white flowers and burgundy red fall foliage.
H. quercifolia ‘Alison’ – Another Dirr selection with exceptionally good burgundy red fall color.
H. quercifolia ‘Pee Wee’ – A dwarf form with long lasting burgundy red fall color.
H. quercifolia ‘Sikes Dwarf’ – Dwarf upright, arching form with white flowers and burgundy red fall foliage.
H. quercifolia ‘Vaughn’s Lillie’ (PP12982) – Heavy-blooming compact form with large creamy white flowers, purple-red fall color. Part shade.

1 Hydrangeas: A Gardener’s Guide by Toni Lawson-Hall and Brian Rothera, 1995, 2000, Timber Press, Portland, OR

This article is adapted from previously published articles I wrote for THE LANDSCAPE CONTRACTOR magazine.