Hydrangeas are deservedly popular shrubs with long bloom periods and handsome foliage. As a result, growers have introduced hundreds of cultivars in a dazzling array of colors. There are over 70 species and roughly 1000 cultivars and hybrids in production worldwide, with more being added every year.
Selecting a plant you’ll be happy with for the long haul can be tricky. Most cultivars and hybrids available in the US fall within six types, or species. Not all types have the same needs, and some can fail to bloom after a hard winter. So, where to start?
Here’s what I learned when I started researching hydrangeas.
Why are hydrangeas so popular?
They’re gorgeous and substantive, for one thing. They’re easy to grow, they make lovely borders and foundation plantings, look at home in all kinds of settings, and their lush, full blooms last seemingly forever. Nostalgia plays a role too. Heirloom varieties have graced estates and country homes since colonial times, here, in Britain and in Asia, especially Japan. It’s no wonder we love them so much.
Pros
- Shade friendly
- Disease resistant
- Extremely long bloom period
- Excellent color range
- Conical, lacecap and mophead flowers
- Robust growth habit
- Low to moderate maintenance
- Usually quite hardy
- A size and form for every garden
- Excellent cut flower
- Some are fragrant
Cons
- Many older cultivars bloom only on old wood
- Bigleaf types not always hardy
- Some can grow too large
- Many require annual pruning
- Need watering during dry periods
- Deer browse magnets in winter
Hydrangea Species
Before we talk cultivars it helps to get familiar with the species, since each has unique characteristics. The most obvious characteristic is bloom form. The shape of the flower head, or inflorescence, is the first thing you notice. Inflorescences can be loose balls of primarily sepals, called a mophead; or tiny fertile florets edged with sepals, called a lacecap. The florets are usually fertile, making most lacecaps attractive to pollinators. Others include cone and panicle inflorescences, which like the mopheads may or may not contain fertile florets.
Confusingly, flower form alone is not a reliable indicator of the species. It’s best to consider other characteristics along with flower form, such as whether a cultivar blooms on new wood, or old wood only. Then there’s overall size, habit and foliage traits to factor in.
Here’s a handy chart showing the main types and their distinguishing characteristics. (A downloadable file is provided at the end of this article for your convenience.)
Six Common Types:
- Bigleaf – Mostly have ball-shaped mophead inflorescences
- Panicle – Triangular or conical-shaped mophead or lacecap
- Oakleaf – Bottlebrush/ conical lacecaps; foliage looks like an oak leaf
- Smooth – Can be either mophead or lacecap (straight species is a US native form; includes hybrids as well)
- Climbing – A vigorous vine with white lacecaps; native to Japan
- Mountain – Smaller with mophead inflorescences; from Japan
Lesser Known:
- Chinese – A fuzzy-leaved species from Asia with smaller lacecaps
- Two wild native species, radiata and cinerea, and their hybrids
Most cultivars at US nurseries are bigleaf, smooth, oakleaf and panicle types. There are only a few climbing cultivars, which need a sturdy wall or tree to climb. Mountain cultivars can be a little harder to find. I have a lovely mountain Preziosa which I stumbled upon at my local nursery. The lesser known ones will take some effort to locate, but there are plenty to choose from without them.
When hydrangeas fail to flower
A common complaint about older specimens, especially bigleaf (macrophylla) varieties, is that they often fail to flower after a hard winter. The reason is some species only bloom on “old wood” (the previous year’s growth). When a hard winter kills the stems to the ground, new growth doesn’t mature in time to support flowers. The result is an entire season without flowers.
This is mainly a problem with bigleaf cultivars introduced before 2004. Oakleaf and mountain hydrangeas only bloom on old wood, but they’re hardier, so bad winters seldom kill them. In any case, a non-blooming plant should flower just fine the following year, provided it doesn’t die back over the next winter and you don’t prune it in fall.
Unfortunately, several hard winters in a row can mean no blooms for years on end. The best solution is to plant macrophylla cultivars which bloom on old and new growth. Enter Endless Summer, the new strain that proved to be a game changer in this regard.
Photo courtesy of Nature Hills website
Endless Summer – A Breakthrough
The first bigleafs bred specifically to bloom on new wood were branded Endless Summer and introduced in 2004 by Bailey Nurseries in Minnesota. They took the hydrangea world by storm and are now supposedly the top-selling hydrangea series. Their claim to fame is a guarantee of reblooming flowers, since buds form on new growth and on old wood. No matter what the winter brings, it will bloom. This means all of us in colder regions can enjoy Endless Summer’s lineup of new colorful introductions without worrying if we’ll get flowers or not!
So far there are five Endless Summer cultivars: Original / Bailmer, Twist ’n’ Shout, BloomStruck, Summer Crush, and Blushing Bride. According to Bailey’s, a sixth, a blue lacecap called PopStar, will be released for sale through retailers in spring of 2023.
I don’t grow any of these, so I have no direct experience with them. If you have an Endless Summer cultivar, by all means leave a comment below about how well it does for you. I’m curious if they truly live up to the hype. Since they’ve become so popular, I’m guessing they do.
Hydrangea Color Range
Traditional hydrangeas bloom in shades of white, cream, pink, blue or lavender, flushed or suffused with pistachio green or dusty rose. Newer hybrids come in fuchsia, red, rich purples and even bicolors and tricolors. All will age into softer or deeper shades of pink, mauve, olive, pistachio or beige, finally turning brown once the frost hits them. Many make great cut flowers in fresh arrangements and some even dry well too, especially the mopheads.
Changing the Color
Only certain bigleaf and mountain cultivar colors can be manipulated by adjusting the soil’s ph. Many hydrangea colors cannot be changed, so make sure, if you have an existing hydrangea whose color you want to play with, you know what cultivar it is and that it’s ph sensitive.
Once you’ve determined the color can be adjusted, test your soil with a soil meter. A reading of 5.0 – 5.5 will yield blue flowers (sepals); 5.5 – 6.5 will yield pink to purple, or both blue and pink blooms on the same bush. It’s much easier to go from pink to blue than blue to pink, however. Even so, it may take some weeks to notice a shift. Full disclosure: I have never tried changing the color of a hydrangea, but if you have, we’d love to hear any tips you’d like to share!
- To get bluer sepals: Add aluminum sulfate which is a soil acidifier, or Hydrangea Blue, a liquid fertilizer made for this purpose. There are accounts of people using vinegar, or coffee grounds, but these substances are difficult to control and produce unreliable results; personally, I’d stick with something proven like a commercial mix.
- To get pinker sepals: Add garden lime at the rate directed on the package. Some people use crushed eggshells to achieve this, but the skeptic in me thinks this would take a while– and a lot of eggshells!
Siting
For best performance, site your hydrangeas in part shade or dappled shade, especially during the hottest part of the day, and make sure they get enough water. Hydrangeas are thirsty plants and really appreciate extra hydration during hot spells. If your plant shows signs of wilting whenever the sun shines on it, it’s stressed; consider moving it to a shadier spot. Certainly don’t let it dry out where it is, and keep it well mulched to help retain moisture.
Most hydrangeas are large enough that a single specimen is often all that’s needed to fill in a vacant spot, and the smaller ones easily fit into flowerbeds and foundation plantings. Massed in the rear of an ambitious border or hedged along a fence would also be spectacular. They can be mixed and matched for contrast or kept homogenous. They’re very versatile, so you decide!
Fertilizing
Fertilizing is not necessary if you’re getting plenty of blooms. But a spring feeding every two years of an all-purpose slow-release granular fertilizer, like Osmocote 10-10-10, or Vitax Hydrangea Feed 8-4-12 can be beneficial. (Only blue bigleaf and mountain cultivars need an acidic fertilizer like Espoma Holly-tone 4-3-4.) Don’t go overboard; less is more. If you’re getting lush foliage but few flowers, stop fertilizing altogether. It’s best to avoid quick-release liquid fertilizers with high nitrogen, as these can trigger lots of foliage growth at the expense of flowers and possibly burn the roots.
If you prefer not to use a commercial product, top-dress with a shovel-full of good compost in spring, then mulch and water well.
Pruning
Pruning will depend on the species. Generally, panicle and smooth types need the most pruning; those that bloom on old wood need the least. Deadheading in fall is not necessary, and in fact leaving the dried flower heads on over winter deters deer. However, snow can accumulate on the heads and cause minor breakage, so you be the judge. Dried heads also enliven the winter landscape.
I leave my flower heads on over winter, then deadhead and prune my Quick Fire panicles in early spring by half and the Little Limes by one third. Oakleaf Gatsby Pink doesn’t need pruning, but the Haas Halos get cut right to the ground. The two Preziosas only need deadheading in spring because they’re old-wood bloomers. I also have a Limelight on a standard, which I prune hard twice a summer.
While hydrangeas definitely benefit from pruning, if you forget it’s no big deal. But the fuller floral display and bushier growth is so worth it.
A Few Personal Favorites
Here are a few cultivars I’m confident recommending. There are many more well worth seeking out. Hydrangeas belong in every garden. With some of the smaller-sized introductions, I bet you can find room somewhere in your landscape for just one more!
Quick Fire — This beautiful panicle selection from Proven Winners is lovely all season. It opens a full month before other hydrangeas, with pure white, lightly fragrant panicles that age pink and finally rose. It has wonderful winter presence as well.
LIttle Quick Fire is a dwarf version that’s exactly the same as its parent, just more compact in growth. It blooms maybe a week later than Quick Fire. I have one next to larger Quick Fires for extra fullness.
Preziosa – A mountain cultivar that’s occasionally carried by local nurseries and available mail order. Well-behaved and a bit smaller, with a fantastic color range. I grew this cultivar previously in acidic soil with blooms in creams and pale blues to rich lavender. In my current garden (neutral soil) it opens creamy pistachio kissed with pink, turns bubblegum pink and ages into shades of rose and red. Handsome foliage tints burgundy-purple in fall. An amazing cultivar that is also well proportioned and sturdy.
Little Lime – A compact hydrangea derived from its big brother, Limelight, that cheerfully tolerates everything nature throws at it. Even with two or three prunings a summer it blooms heavily. Perky chartreuse-white flowers fade to soft pistachio-pink by October. Reliable and tough as nails; I highly recommend it if you’re looking for something easy to start with. It goes well with everything and is trouble-free and easy to find locally.
Limelight is similar to Little Lime but much larger, with huge panicles that are whiter than Little Lime and age to a richer pink. It’s available as a shrub or grafted onto a standard, which is what I have. It does require hard pruning to keep it within bounds. A second midsummer pruning yields white and pink blooms simultaneously, which are great for cutting and drying. The weight of the blooms can make it floppy if it’s in a lot of shade, so some sun is desirable. Ideal for a large space or expansive border.
Gatsby Pink – An oakleaf cultivar in the “Gatsby” series from Proven Winners that has spectacular fall foliage and exfoliating bark. Summer blooms are big bottlebrushy cones that turn a medium pink. This plant looks best in a naturalized or less formal spot; its habit can be somewhat gangly and it will eventually get quite large. (Deer love it.)
Gatsby Moon is a similar, gorgeous oakleaf sporting fat all-white blooms just packed with double white sepals that age green; several Gatsby cultivars have star-shaped double sepals too, all strikingly lovely, with beautiful wine red foliage in fall.
Haas Halo – A native lacecap that opens white aging to green. Its fertile florets are adored by bumblebees. A fast grower that needs aggressive seasonal pruning, the flat, umbel-shaped blooms can get the size of dinner plates. Its form provides good structure in the winter landscape. Because the “smooth” leaves tend to be dark and coarse, I plant variegated impatiens at its feet to complement the aging flower heads with an echo of pale green and white.
A word about climbing hydrangeas
The climbers are quite different from the rest of the hydrangea family in that they are vines, not shrubs. The inflorescences are white lacecaps only. A key advantage is that they will flower in full shade or in woodlands. While they often take a few years to establish, they’re aggressive growers that can ultimately reach 40 feet high if not kept in check. Like wisteria and trumpet vine, these plants are capable of damaging mortar joints or pulling down weak supports, so give yours something strong to climb and keep an eye on it.
I hope you’ve learned a few things about these wonderful shrubs. If you need some extra color late in the summer or by your deck, pool or patio, a few hydrangeas just might be the perfect choice.
Downloadable comparison chart
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