All About Hydrangeas
For generations, these beloved shrubs have charmed with their big blooms and carefree nature
Perfection doesn't really exist in the plant world—or on any planet where living things thrive. But hydrangeas come pretty close. With long-lasting blue, violet, pink, white, or chartreuse blooms and an easygoing disposition, these reliable summer-flowering shrubs look right at home in a wide range of situations, from carefree cottage gardens to more formally manicured ones. When many other flowering shrubs and perennials have passed their peak, these deciduous beauties continue their season-long performance, with abundant, attention-grabbing flowers that dry to shades of linen for autumn and winter interest.
For all their versatility and showmanship, hydrangeas are not particularly picky about where you plant them. They'll happily grow in just about any landscape that offers well-drained soil, moisture, and some shade during the hottest part of the day. New varieties have even been bred to rebloom throughout the season. They've also shed troubles that plagued hydrangeas of previous generations, like floppy flowers. You can find types with colorful fall foliage and smaller stature, perfect for small yards. There are varieties that boast more sun tolerance and extra cold hardiness, too. So if you haven't explored the nursery lately and wonder if these old-fashioned garden favorites are right for you, this is the place to find out.
Shown: Bigleaf hydrangeas (shown) are found in gardens across the United States, but the iconic shrub actually hails from Japan. North America has its own native species, however; both oakleaf and smooth hydrangeas grow naturally in our eastern woodlands.
Where do They Grow? Hydrangeas hold their own in USDA Hardiness Zones 4 to 9. They do well in acidic as well as alkaline soils. Unlike many flowering shrubs, they tolerate both sun and shade.
When to buy? Like all shrubs, hydrangeas are best planted in spring or fall, when temperatures are mild. Summer planting is never ideal, but with plenty of water and some shade, the plant should power through.
How much care? After planting, maintenance is easy, calling for little more than watering and snipping spent flowers.
Are they Pet-Safe? Keep Fido and Fluffy away. All hydrangeas contain traces of cyanogenic glycosides, toxins that, if ingested, cause gastrointestinal upset in cats and dogs.
What do they cost? A 1-gallon pot goes for $20 to $30, depending on the variety.
Selling points: This group has two bloom shapes, round mopheads and flat lacecaps. Most flower in early summer on buds set the previous year, but everbloomers, like 'Endless Summer' (shown), flower repeatedly into fall.
Size: Up to 6 feet tall and up to 8 feet wide
Zones: 6 to 9
Selling points: Cold hardy and forgiving of dry shade, this tough North American native boasts white, sometimes pink, dome-like blooms starting in early summer and lasting into fall. 'Annabelle' is an old-school standby, while 'Incrediball' is less prone to flop.
Size: 3 to 5 feet tall and wide
Zones: 4 to 9
Selling points: Extra sun-loving, this sizable type is the only hydrangea you can train into a tree form. Most varieties, including 'Little Lime' (shown), boast cream-to-pink conical flowers that last into late summer.
Size: 10 to 22 feet tall and up to 8 feet wide
Zones: 4 to 8
Selling points: One of the best picks for deep shade, this southeastern native features cone-shaped blooms from mid- to late summer and hefty leaves that turn purple-red in autumn. 'Snow Queen' (shown) is especially bright in fall.
Size: 4 to 10 feet tall and up to 8 feet wide
Zones: 5 to 9
(Hydrangea anomala subsp. petiolaris)
Selling points: Although slow to start, this woody vine does fine in sun or shade and offers a multiseason show that's worth the wait, with white lacecap summer flowers, golden fall foliage, and russet-colored winter stems.
Size: Up to 50 feet tall
Zones: 4 to 9
Selling points: This underused, compact species produces delicate bunches of lacecap blooms from summer to autumn. Depending on soil pH, varieties such as 'Bluebird' (shown) flower blue or pink, and some even boast showy burgundy foliage in fall.
Size: 4 feet tall and wide
Zones: 6 to 9
Panicle hydrangeas naturally grow as shrubs, but a little pruning can turn them into trees, or standards, making room for more plantings at their feet. H. paniculata 'Grandiflora' (shown), commonly called PeeGee, takes on a dramatic tree form. Towering up to 22 feet, it boasts white summer flowers that mature to rose, while newer dwarfs, such as 'Limelight,' top out at 8 feet.
Any garden structure looks lovelier with a vine scampering up it. Place climbing hydrangea near entryways or seating areas where you'll enjoy its sweetly scented flowers. And give its aerial roots something sturdy to cling to, such as a masonry wall or a large tree trunk. Standout varieties include variegated 'Firefly' and its silvery-leaved cousin, 'Moonlight.'
Thanks to the many recently introduced dwarf varieties, it's easier than ever to make room for hydrangeas. If your yard has only a little space to spare, consider trying the 3-foot-tall-and-wide mophead 'Glowing Embers' (shown), the iconic pink or blue everbloomer 'Mini Penny,' or 'Little Honey,' a white-flowering oakleaf variety with chartreuse foliage.
Planted in pots, hydrangeas can bring beauty to patios or decks. Compact varieties, such as 'Penny Mac' (shown), work especially well and help ensure a full look. Just be sure your shrub has good drainage and plenty of water; potted plants dry out faster than ones in the ground.
Spot a good site. Although hydrangeas can handle full sun in colder climes, they typically prefer morning sun and afternoon shade. Select a sheltered area with fertile soil and ample room for the shrub to spread.
Prep the hole. Dig a hole that is the same depth as your hydrangea's nursery pot and two times as wide. Remove the plant from its container, gently loosen any circling roots, and plant at the same depth at which it was growing in its pot—no deeper.
Apply mulch. Spread an organic mulch, such as compost or shredded bark, around the base of the plant to maintain the cool, moist soil conditions in which hydrangea roots thrive. A 2-inch mulch layer is plenty.
Water regularly. After planting, give the shrub a long drink and continue to check the soil for dampness in the weeks ahead. The soil beneath the shrub should feel cool and moist to the touch but not wet; soggy soil leads to root rot.
Mature shrubs are easygoing and require minimal attention.
Go easy on the fertilizer. Overfeeding can burn roots, and too much nitrogen leads to more foliage than flowers. In early spring, sprinkle just a half cup of slow-release 10-10-10 granular plant food around the shrub's entire root zone, then apply a second dose in midsummer. Hydrangeas also benefit from an annual topdressing of well-rotted manure or compost, which supplies nutrients and improves the soil's moisture retention.
Ready your garden hose. Hydrangeas are heavy drinkers. Those planted in sandy, fast-draining soils or beneath water-hogging shade trees are especially prone to drying out in summer. During the growing season, regularly check the top 6 inches of soil for moisture and water deeply when it feels dry.
Beware of frosts. Bigleaf varieties can be fickle bloomers because their flower buds sometimes fall victim to late frosts. For winter protection, cover the shrub with evergreen boughs or surround it with an open cylinder of chicken wire filled with straw. Just be sure to promptly remove the covering once the threat of frost has passed. Or, better yet, plant panicle, smooth, or everblooming varieties, which all bud too late in spring to freeze.
Shown: Smooth hydrangea 'Annabelle' benefits from the shade of a tree. Lime-hued lady's mantle and violet bellflowers provide a nice contrast to its white blooms.
Not crazy for that pale blue your hydrangea flaunts each summer? Try deepening it or even changing it to pink. Bloom color for bigleaf and mountain hydrangeas depends in part on soil pH. Most varieties flower blue in very acidic soils (pH 5.5 and lower), purple or a mix of shades in less acidic soils, and pink in more alkaline soils (pH 6.5 and higher). Using soil amendments that tamper with pH can intensify a shrub's hue or change it altogether. Just be prepared to keep reapplying.
Why it works Hydrangeas require aluminum to produce blue flowers. Plants can easily extract metals from acidic soils, but under alkaline conditions, metals become insoluble and flowers bloom pink.
What to do For pink flowers, mix 1 tablespoon of hydrated lime into 1 gallon of water and pour under the shrub. To go from pink to blue, try a soil drench of 1 tablespoon of aluminum sulfate (sold as "soil acidifier") dissolved in 1 gallon of water. Apply either solution monthly in March, April, and May.
If you have one shrub, you can easily get more by using this simple method, called layering. In spring or early fall, select a low, flexible stem almost parallel to the ground. Leave foliage on only the top 12 inches of the branch and strip off the rest. Bury the leafless section several inches deep, leaving the top 12 inches of stem above ground. Use a rock to keep the buried section from popping up, and stake the portion above-ground so that it stands straight. After a year or so, give the branch a slight tug—if it resists, it's rooted. Snip the stem near the base of the mother plant. Then, to help prevent the rooted branch from going into shock, wait a few weeks before digging it up and transplanting.
An annual trim to remove spent flowers and trigger growth keeps shrubs tidy. But before you snip, know which hydrangea type you have. Pruning time hinges on when shrubs set their buds, and not all types are on the same schedule.
Prune old-wood bloomers as flowers fade. The flower buds of this group—which include bigleaf, oakleaf, mountain, and climbing varieties—are produced the previous summer. To avoid accidentally cutting off buds, prune these shrubs before buds start to form, snipping fading blooms just above a nearby leaf node.
Prune new-wood bloomers in late winter. The buds on panicle and smooth hydrangeas form and flower all in one summer, so there's a wider window for pruning. When shrubs are dormant, snip dried flowers just above a leaf node where you'd like two new stems to sprout, or cut back the whole shrub 2 feet from the ground.
All great plant combinations play on similarities and differences. Most of us think of hydrangeas in terms of flower color, but they also offer bold textures with their foliage, and round shapes with their mounding habit and big blooms. As you select neighbors for your shrub, opt for ones that repeat or contrast with some of these features. The following perennials do a little of both; match your shrub with one or more for a no-fail combo.
Ferns Most are fine-textured and vase-shaped, contrasting nicely with the hydrangea's bold, round curves. Two tried-and-true picks are silvery ghost fern or evergreen soft shield fern (shown).
Ornamental grasses Their airy leaves make a stunning counterpoint to the hydrangea's dense, mounding foliage. Consider pairing a hydrangea with Korean feather reed grass, which thrives in part shade and sports pinkish plumes in summer.
Hostas The teardrop leaves of this classic shade dweller echo those of every hydrangea except oakleaf, while their hot and cool hues create contrast. Try pairing a blue-flowering hydrangea, for instance, with a gold-leaved hosta, or a blue-leaved hosta with a shrub that blooms pink.
It doesn't always mean drought. If the plant's leaves are wilty and its feet are wet, you've likely caused root rot by overwatering. Leaves might also wilt in high heat or full sun. In this case, they'll recover overnight. But if it happens daily, a move to a shadier locale is in order.
They often signal a nutrient deficiency. If only new foliage is affected, the plant may need more iron. This condition is called chlorosis and often occurs where soils have a high pH. Amending the soil with chelated iron and mixing in some compost will correct the issue. If only older leaves are yellowing, however, try fertilizing. The shrub may need nitrogen.
It's a symptom of powdery mildew. It might look like a dusting of confectioners' sugar, but it's actually a fungal disease. Plants growing in sites with high humidity and poor air circulation are especially vulnerable. Transplanting or pruning back neighboring plants can help tilt conditions in your shrub's favor, as can removing any affected foliage in fall to prevent the disease from wintering over.
This has several causes. Pruning at the wrong time of year and mistakenly snipping off buds is a common culprit. But an extra-harsh winter or a planting site with too much shade are also possible causes.