Hydrangea bushes loaded with their big white spheres of flowers are a common sight here in the Midwest. You often see them planted around houses in the older sections of town, towering over the hostas and flopping onto the lawn after a rainfall.

They are so common that, even though I love hydrangeas, I was surprised to find them in the florist’s cooler one day in June. “Where did you get the hydrangeas?” I asked, expecting to hear that one of the designers had cut them from her garden. “California – and they weren’t cheap,” the floral buyer replied.
A few days later, another florist visited my farm and exclaimed over the hydrangeas planted up against my house, which were in the stage of turning from white to green. He wanted to buy them all. (I have a policy against selling any flowers planted around the house, so I declined.)

Flower-growing friends in Missouri and Virginia experienced the same demand this summer. Hydrangeas are hot. Florists can’t get enough of them, despite the fact that they are one of the most common landscaping shrubs throughout most of the United States. They’re common because they are easy to grow, which means hydrangeas are a crop that many flower growers might want to consider.

They aren’t foolproof, however. The most common mistakes in growing hydrangeas are choosing the wrong variety, planting them in the wrong site, and pruning them at the wrong time. If you’re a novice to the world of hydrangeas, here are the basic facts that will prevent you from making those mistakes.

The genus Hydrangea includes 80 species, but just a handful are of importance to the cut flower grower. The main types are H. arborescens, H. paniculata and H. macrophylla. All produce panicles, either rounded or pyramidal, of fertile and sterile flowers. The fertile flowers are small, while the sterile flowers are larger and showier with petal-like sepals. It is the combinations of sterile and fertile flowers that determine the look of the panicle, whether it is airy or solid.

H. macrophylla
Hydrangea macrophylla cultivars are divided into two types – hortensias and lacecaps. Hortensias, also called mopheads, have solid spheres of flowers in shades of white, pink or blue. Lacecaps are flattened domes of fertile flowers surrounded by sterile flowers for a pinwheel appearance. Color in the pink and blue cultivars (not the white ones) is tied to the pH of the soil. Acidic soil (below pH 5.5) will produce blue flowers and soil with a pH higher than 5.5 will produce pink flowers. Some cultivars are better suited to pink flowers and some to blue flowers, so it’s important to choose a pink cultivar if your soil is alkaline, and vice versa.

Most macrophyllas are hardy in Zones 6 to 9, and they are most successful in the South, Northwest, and in coastal areas. The single most important thing to understand about them is that they flower on the previous year’s stems. That means they are setting next year’s buds in August and September, so if they are cut after July or if they are killed by cold winter weather or late spring frosts, there will be no blooms next year. That leads to problems for Southern growers many years when warm temperatures in late winter cause the buds to swell and leaves to emerge in early March. Then a frost, even as mild as 28° F, can shrivel the buds and destroy that year’s flowers. Growers in areas with spring temperature fluctuations should plant macrophyllas on the north side of building or fence, so that they don’t warm up too early in spring.

Blooming is a hit and miss affair in the North and Midwest. But there’s hope for us. Two recently discovered plants may expand the range of H. macrophylla into colder climates.

The first is a variety that was found flowering profusely in the garden of University of Georgia coach Vincent Dooley in 1996, a year when every other hydrangea in Athens, Georgia, was killed by a late frost. Research has shown this variety, called ‘Dooley’, to be hardy to -11 degrees. Flower buds also are set along the entire stem, so if the end bud is killed, the lower buds will still open. ‘Dooley’ is available in wholesale quantities from Spring Meadow Nursery (616-846-4729; www.pottedliners.com) or in smaller quantities from Hydrangeas Plus (866-433-7896; www.hydrangeasplus.com).

Hydrangea fans are even more excited about a cultivar called ‘Endless Summer’ that is being propagated now and will be introduced in spring 2004. It was found flowering in the St. Paul, Minnesota, test site of Bailey Nursery, where winter temperatures can go to -30°F. Michael Dirr, the University of Georgia expert in woody plants, has tested ‘Endless Summer’ and says he is convinced that it is perpetual flowering, that is, that it forms buds all season on new growth.

‘Endless Summer’ will be rated hardy to Zone 4. “We have been working with it here in the Twin Cities since 1987 and our original plants are all still alive.” said Debbie Lonnee of Bailey Nursery. “It will, though, die down very hard – in most winters,basically to the crown. My suggestion to consumers will be, if they buy one in mid to late summer, to cover it once the ground freezes with hay or straw – much as you would newly planted perennials.”

H. paniculata
Meanwhile, breeders have been working to develop attractive cultivars of the hardy Hydrangea paniculata, which can be grown in Zones 4 through 9. The old standby in the species, dating back to 1867, is ‘Grandiflora’, commonly known as Pee Gee (the initials of paniculata Grandiflora). Many nurseries now refer to all paniculata hydrangeas as “Pee Gees” or P.G. It produces large cone-shaped clusters of white sterile flowers that eventually turn pinkish and then brown. In habit, it tends to be floppy, sprawling on the ground after a rain. It can also be purchased in tree form, which solves the problem of drooping on the ground but also costs a lot more. Pee Gee hydrangea trees are often seen in the landscape in the Northeast. For a stunning photo of tree form H. paniculata, visit the website of Virginia cut flower grower Bob Wollam: www.wollamgardens.com.

Recent improvements to the species include new colors, forms and habit.
• ‘Limelight’ is a new selection from the Netherlands with lime green flowers, a color that is currently popular with floral designers.
• ‘The Swan’ is a new plant from Belgium. It’s unlike any other hydrangea, with massive sepals the size of your hand.
• ‘Pink Diamond’ comes from Belgium. Its large but delicate flowers are held upright on the plant . They emerge a pure white in midsummer and gradually transform to a rich pink
• ‘Unique’ has white flowers on stiff stems that do not droop.The individual florets are larger and not jammed so close together. The look is cleaner and more refined. Individual flowers heads are 16 inches long and 10 inches wide.
• ‘Kyushu’ produces flower heads that are a balance of fertile and sterile flowers, so more airy in appearance. It is similar in form to ‘Tardiva’ but blooms a month earlier, beginning in July. It also holds its flowers up neatly.
The plants listed above are available from many garden centers,wholesale from Sherman Nursery (see ad at left), or from Spring Meadow, listed above.
H. paniculata flowers on new wood, so it is not affected by cold winters. New shoots emerge from the ground each spring and form buds that develop into flowers in mid to late summer. A hard pruning in early spring will result in larger flowers. Harvesting flowers in fall, when most are still blooming well, will not affect next year’s flowering.

H. arborescens
These are the snowball types that start green, open to pure white and turn green again as they age. The old-fashioned variety with the floppy habit is ‘Grandiflora.’ A newer cultivar that is somewhat more tidy is ‘Annabelle.’ It blooms earlier and has larger flower heads – up to 12 inches across – than ‘Grandiflora.’
H. arborescens is hardy in zones 4 to 9, though some growers in zone 3 report that theycan survive winters when grown in a site protected from the wind. They can be grown in full sun in the north, but they prefer protection from the afternoon sun in the south. They also can be grown in dappled shade, though they won’t get as big. They do not do well in windy spots, as the big leaves get dessicated easily. Mine do fine on the north side of buildings, protected from the wind, and with only bright light.

H. arborescens blooms on new wood, which means that they can be cut to the ground in fall or winter, or winterkilled above ground, and they will still bloom on their new growth the next summer. If they haven’t been cut the previous year, they can be pruned in late winter. Cut them to the ground to rehabilitate old plants or to get the largest flower heads. To get more heads, but smaller ones, prune sparingly, leaving 18-24 inches of old stems on the plant.

Harvest and post-harvest
Many growers have problems keeping hydrangea flowers from wilting. They should be cut when half the flowers in the inflorescence are open. Ray Gray of Sunset Flowers of New Zealand, in Oregon City, Oregon, wrote about harvesting hydrangeas in the July issue of The Cut Flower Quarterly, newsletter of the Association of Specialty Cut Flower Growers. Ray says he cuts only early in the day, he dips the stems in a jelly jar of Quick Dip and then puts them immediately into buckets of hydration solution. The hydrangeas are stored overnight in the cooler before being shipped. Old-fashioned recipes call for the stems to be dipped into boiling water or boiling vinegar, foliage removed, and stored overnight in deep, cold water.

For drying, wait until the flowers are beginning to dry on the plant. They should have a papery look. Then stand the stems in buckets without water to dry.