I just spent two weeks in the Pacific Northwest. Since our daughter and her family live there, we visit frequently, but typically at Thanksgiving or in mid-winter. This time we managed to arrive in July. What a treat! With blue skies, light breezes, and puffy white clouds, the weather was (mostly) perfect. All that rain during the fall, winter, and spring results in stunning summer gardens, with emerald green lawns and towering trees. And the flowers! Yes, the rhodies and azaleas were done, but the hydrangeas were in full bloom. Everywhere we looked, we saw huge flower clusters of bright pink, magenta, white, and most noticeably, pure sky blue.
There are many types of hydrangea—around 70 species plus countless cultivars. While most originated in eastern Asia, a few are native to North America. Here are some of the ones we saw in the Puget Sound area.
Most familiar are the Mopheads, Hydrangea macrophylla. Also known as Bigleaf Hydrangeas, they have large, heart-shaped leaves with coarsely toothed edges. These are actually my least favorite. The big, round flowers are impressive, but lack the delicacy of other hydrangea types. They remind me of the big, green bushes covered with polka-dot flowers I drew as a child.
While most species have white flowers, the blooms of Mopheads come in a variety of colors—white, pink, rose, burgundy, lavender, and blue.
Color is often affected by a combination of soil pH and the presence or absence of aluminum ions. While I admit to having a “thing” about true-blue flowers, the blue Mopheads somehow look unnatural. If I hadn’t seen them growing on the plant, I would have guessed that the flower colors had been photoshopped. (This photo is one of the more demure cultivars, but imagine it in an intense sky blue!)
On the other hand, Lacecap Hydrangeas are a subspecies, Hydrangea macrophylla normalis, that I absolutely adore. Large sterile flowers surround a cluster of closed buds—the fertile flowers—with a resulting lacy appearance, giving them their name.
Then there are Mountain Hydrangeas, another subspecies (H. m. serrata). Smaller and more compact than others of this species, Mountain Hydrangeas have flowers similar to those of the Lacecaps. While all of the macrophylla hydrangeas are hardy to USDA zones 5 or 6, these are a bit hardier than the others and therefore more likely to succeed in cold winter areas such as Colorado. Even then, they’ll need ample water and a shady, sheltered spot.
Panicle Hydrangeas (H. paniculata) has pointed flowers, as if you rolled a lacecap into a cone, and smaller, thinner leaves with prominent veins. While H. macrophylla is a large shrub, reaching 5 or more feet in height (although some dwarfed cultivars are available), H. paniculata can be even larger, sometimes passing ten feet in height, and may be pruned into small trees. This is an even hardier species, growing in zones 3 to 7. Also, unlike the rest of the hydrangeas, they prefer a bit of sun during the day.
Oakleaf Hydrangeas, H. quercifolia, are easily identified by their large, oak-shaped leaves. The flowers are a smaller version of lacecap. Native to the southeastern U.S., they prefer somewhat hotter summers than the mopheads, and can handle drier conditions—but not saturated soil. Oakleafs are the only hydrangea with showy fall foliage, in shades of red and burgundy. They’re hardy to about zone 4.
You would think that hydrangeas would grow well in Colorado, as for the most part the plants are sufficiently hardy to withstand our climate. However, it turns out that most hydrangea types bloom on old wood—last season’s growth—and our drying winter winds and sudden, wild temperature fluctuations often result in significant die-back. What’s the point of growing a hydrangea if it never has flowers?
If you’re set on growing hydrangeas in Colorado, you could try one of the “ever-blooming” H. macrophylla cultivars. These bloom on both old and new growth, so you may get some flowers even if you lose a lot of branches over the winter.
Probably the best bet for determined Colorado gardeners is another native to the eastern U.S. Smooth Hydrangeas, H. arborescens, shown at right, are hardy in zones 3 through 9! Even better, Smooth Hydrangeas produce their green-becoming-white flowers on new wood. Winter die-back doesn’t faze them. You can even treat them as perennials, cutting them to the ground in late winter. Just make sure you have plenty of room, as the plants are a hefty six by six feet.
For me, instead of struggling to grow a shrub ill-suited to our climate, I prefer to view hydrangeas where they thrive, and western Washington certainly qualifies!