I can be a garden critic so when I say that hydrangeas are one of my favorite shrubs for the landscape, I mean it.
Hydrangeas offer a long flowering period, beginning in mid-summer and for most, finishing in fall. Depending on the species, flowers come in tones of pink, crimson, green, white, purple, and blue. Flower color can vary with soil conditions in two species while others change naturally as they age. The flowers eventually dry and remain on the plants, providing structure and texture through the winter.
There’s a lot of online information on hydrangeas so I can understand if the subject is a lot to chew on. Let me help.
There are 6 species of Hydrangea that are widely cultivated throughout the world and all of them thrive in western Pennsylvania gardens. Each species offers numerous cultivars which adds variety in flower color, flower structure, growth habit, and overall size. New cultivars are released just about every year which gives the gardener an ever-growing number of choices.
Let’s talk about them in detail.
King of Hydrangeas: The Bigleaf Hydrangea (Hydrangea macrophylla)
This species is what most envision when they think “hydrangea.” Bigleaf hydrangea, regularly sold in floral shops and featured most in garden magazines, is organized into two groups: mopheads and lacecaps.
Mopheads (also called hortensias) have large clusters of flowers or florets, that form in a rounded shape. Most of these florets are sterile and offer no pollen or nectar but if you look closely at the overall floral structure, you’ll usually see a smaller number of fertile ones underneath. Many botanists suggest the sterile florets simply act as beacons to pollinators.
Lacecap flowers are arranged differently, hosting a ring of showy, sterile florets around a larger group of tiny, fertile ones. Lacecaps tend to be more modest than mopheads but offer more nectar and pollen to pollinators. Mopheads are more popular to gardeners because they are considered showier, but my favorite Bigleaf hydrangea is Proven Winners’ lacecap cultivar “Let’s Dance Starlight.”
Bigleaf hydrangeas are the most particular when it comes to growing conditions. They require part sun for optimal growth as they tend to yellow or crisp in full sun and struggle to flower in heavy shade. They demand rich, moist, well-drained soil and dislike any extremes. Once established, they require little care, but you didn’t think those gorgeous flowers would come without a little planning, did you?
Flowers & Pruning: Bigleaf Hydrangea
Pruning hydrangeas is a longer conversation for this species. Bigleaf hydrangeas flower on “old wood” which means flowers are produced on the prior year’s stems. If your hydrangea is flowering this year, for example, that means its flowers are growing off last year’s stems.
Hard cold snaps, repeated deer browsing, and heavy shade can inhibit flowering in this hydrangea but the human urge to prune is the usual cause. The only time pruning is appropriate, if it’s necessary for size mitigation, is immediately after flowering (late summer) so the plant has time to develop next year’s flower buds.
The flowers of Bigleaf hydrangea vary in shades of pink, purple, and blue depending on the presence of aluminum in the soil. The absorption of aluminum is regulated by soil pH. Because the soils in our region are usually mildly acidic, flowers tend to take on hues of purple. If you want your hydrangea to produce blue flowers, you can apply aluminum sulfate to lower the soil pH. For pink flowers, you can apply lime to raise the soil pH and make it more alkaline. These products are found at most nurseries and are best applied a few weeks before flowers develop. Note that a handful of cultivars are not sensitive to pH so they don’t change color.
Most Bigleaf hydrangeas average between 3-5 feet high/wide but some are smaller, such as Proven Winners Cityline® series. They make excellent foundation plants since they seldom get large enough to block windows or impede foot traffic.
Like the king in chess, the king of Hydrangeas must be placed carefully for it…but it is the king of the group, nevertheless.
Best of Two Worlds: Mountain Hydrangea (Hydrangea serrata)
True to its name, this species originates from mountainous areas of Japan. Naturally, this hydrangea has greater cold hardiness compared to the closely related Bigleaf hydrangea which means its ability to flower is less likely to be compromised by intense cold snaps. Proven Winners offers several cultivars including Tuff Stuff™, Tiny Tuff Stuff™, and Tuff Stuff Ah-Ha™.
Like Bigleaf hydrangeas, flower color varies with the pH of the soil. Similarly, part sun and rich, moist, well-drained soil is best. The flowers on this species are, to my knowledge, all lacecaps.
The Regal Native: The Smooth Hydrangea (Hydrangea arborescens)
This species is often called the “Annabelle Hydrangea” though “Annabelle” is just one of many cultivars. The Smooth hydrangea is native throughout the mid-Atlantic and the Southeast, including Pennsylvania. It’s a regal plant, worthy of the most formal of gardens, yet fits right at home in the informal native garden. This one is my favorite.
Flowers emerge green and turn white though newer cultivars have introduced pink flowers in this species. Like the Bigleaf hydrangea, flowers come in mophead and lacecap forms, with lacecap flowers attracting more pollinator activity.
As this is a woodland plant, part sun to part shade is best. Plants in sunnier locations need consistent moisture so they don’t burn. This plant flowers on old and new wood, so pruning mishaps are seldom detrimental. The hollow stems are attractive overwintering sites for pollinators and so I give them a light trim in mid-spring (instead of fall) when the plant begins to wake up.
Smooth hydrangeas come in large, medium, and small sizes. Proven Winners Incrediball® and Lime Rickey® are larger plants while Invincibelle Wee White® is one of the smallest.
When plants are young, their heavy flowers sometimes cause the stems to bow, so don’t be too judgmental when you see a floppy plant in a nursery container. Stems get sturdier with age, with some cultivars proving better than others, of course. A second trim in early summer can reduce floppiness and increase compact growth.
Despite its delicate appearance, this zone 3 plant is tough and is a great plant for the beginner and professional alike.
Tough and Beautiful: Panicle Hydrangea (Hydrangea paniculata)
If you’re looking for a “tough as nails” Hydrangea, this is your candidate. If you haven’t had success with the other hydrangeas, try this one.
Panicle hydrangeas are cold hardy like the Smooth Hydrangea but will also grow well in full sun and heat. Once established, this hydrangea can even tolerate brief dry spells.
Panicle hydrangeas have panicle or cone-shaped floral structures that produce hundreds of florets. These florets change colors as they age. Proven Winners’ cultivar “Limelight” starts out green, changes to white, and then acquires tones of pink in the fall. Fire Light® unfolds white and changes to crimson.
This species is available in dwarf forms such as Little Lime® and Bobo®, intermediate sizes such as Pink Winky® and Quick Fire®, and large cultivars such as “Pee Gee” and “Tardiva.” Because the wood is strong, you can buy “tree form” hydrangeas where the intermediate and larger varieties are trained to grow like small trees. You can find these in our tree section.
Panicle hydrangeas are forgiving of pruning mishaps, but they are best pruned in mid-spring when they begin to wake up. Pruning out small scraggily stems can help the plant focus resources on developing larger flowers on thicker stems. Leave the dried flowers on through the winter for textural interest.
Queen of Hydrangeas: Oakleaf Hydrangea (Hydrangea quercifolia)
The elegance of the Oakleaf hydrangea is incomparable. The large floral structures are shaped like the Panicle hydrangea but the small, fertile florets underneath the showy florets tend to be more pronounced, a boon for pollinators. Flowers also change from white to pink/crimson in late summer and fall.
Like chess, the queen has a few more abilities than the king. The foliage on this species is by far the most beautiful (it lives up to its name “oak leaf”). The leaves are leathery with interesting form and texture. The fall color is also the best, turning hues of red and purple and persisting long after many other plants have defoliated. On larger mature specimens, the exfoliating cinnamon-colored bark adds interest to the winter landscape.
The Oakleaf hydrangea is more sun tolerant and shade tolerant than the Bigleaf Hydrangea making it more versatile. Like all hydrangeas though, make sure this one is given a good start with rich, moist, well-drained soil. Keep pruning to a minimum, but if it’s needed, do so in summer after flowers begin to fade. As with the Bigleaf hydrangeas, they flower on “old wood” so pruning in fall or early spring may cost you a year’s worth of flowers. Rather than relying on pruning for size control, plant dwarf cultivars if you’re limited on space.
Like the other species, I leave the dried flowers on the plant for winter interest. This species is native to the Southeast but still makes an excellent addition to the native or pollinator garden for us. Next time you’re in, check out the cultivar ‘Ruby Slippers’ in our display beds along the garden center store.
Master of the Vine Arts: The Climbing Hydrangea (Hydrangea anomala subsp. petiolaris)
Yes, there is a vining hydrangea! Preferring part shade to shade, the Climbing hydrangea is a great plant to use as a vertical specimen or accent in the landscape. It’s an excellent choice for narrow garden beds where height is needed but space is a limiting factor. This species sports massive white lacecap flowers in early to mid-summer and beautiful dark-green foliage the rest of the year. Cultivars of this species are also available in green/gold and green/white variegation.
Climbing hydrangeas produce “feet” that adhere to structures as some vines tend to do. While great for a trellis or arbor, it’s perfect to plant on a bare wall. The vine will not damage brick or other material, but aerial roots would have to be scraped off if you decided to remove it. Climbing hydrangeas don’t start producing flowers till they are around 3-5 years old so be patient. We have two young specimens planted in the display beds in front of the garden center store.
Like Bigleaf and Oakleaf hydrangeas, if pruning is necessary for size control, prune after flowering as they flower on old wood. If it’s not necessary, don’t prune at all.
There’s Room in the Garden for At Least One!
Be sure to check out Proven Winners’ stellar guides and FAQs on hydrangeas!
I think every garden should have at least one hydrangea! Whether you have full sun, shade, a tiny yard, or any other limiting factor, there’s a hydrangea that will work for you.
Because we believe hydrangeas are among the finest garden shrubs, we usually have 20 or more different cultivars in stock by midsummer. Summer is a great time to shop for hydrangeas as that’s when they begin flowering. Come on in and check out our selection!
As always in summertime, don’t forget to water your plants!