This spring was not a great one for hydrangeas all around the United States, and according to my guest this week, Lorraine Ballato, the problem can be traced back to the wild weather that occurred over the winter. Lorraine shares the reasons your hydrangeas may be struggling, the various degrees of hydrangea cold tolerance, and what options gardeners have to achieve better outcomes.
Lorraine is a horticulturist, garden writer, lecturer, photographer and trusted authority on hydrangeas who literally wrote the book on hydrangea care: “Success with Hydrangeas: A Gardener’s Guide.” She gardens in Connecticut, in zone 5b, and writes at LorraineBallato.com, which earned a silver medal for garden blogging from GardenComm.
Lorraine calls hydrangea the “Queen of the Divas” — because it’s demanding. It’s not like forsythia, which you can just stick in the ground and then walk away from, nor is it like a rhododendron, whose buds can shrug off 2-degree weather all winter, she says.
“Weather is an interesting challenge, and it’s not going to get easier,” Lorraine says. “It’s going to get more involved, I think. I think it’s going to be more challenging for us.”
But Lorraine is specifically talking about big-leaf Hydrangea, which is the most ubiquitous in the American landscape.
She is not referring to panicle or woodland Hydrangea. “Those are foolproof because they flower on new growth, and so no amount of crazy pruning deer browse, winter weather is going to affect those,” she says.
And even some old-wood blooms such as oakleaf Hydrangea or climbing hydrangea are very winter hardy.
Hydrangea macrophylla, known as bigleaf hydrangeas or mophead hydrangeas, are struggling due to weather. To some degree, some of the Hydrangea serratas (mountain hydrangeas) are also struggling.
One reason big-leaf hydrangeas are so popular is that they really light up the landscape.
“Most shrubs will give you a flower for two, three weeks, maybe four if you’re lucky, and then the flower is gone,” Lorraine says. “And so you don’t have anything else except the green bush or whatever the foliage looks like. Hydrangeas are different. They hold that flower the whole season and then the flower morphs into other colors as the season progresses. So you don’t get just a few, three weeks, you get two to three months or more if you’re lucky.”
Mophead hydrangeas have significant root hardiness, meaning the plants can survive during really cold winters. But the stems, while somewhat hardy, are not as resilient as the roots. If the stems or buds die over the winter, the roots will send up new stems in spring, but the plant won’t flower. That’s because most varieties of mophead hydrangea only bloom on old wood.
After a mild winter, or a “forgiving season,” as Lorraine puts it, hydrangeas will bloom much better. “So for example, 2022 was a fabulous year, and ’21 was over the top,” she says. “Every place, we had a mild winter, we had plentiful rain. We didn’t have extremes. We didn’t have temperature swings. All of those factors made for a fabulous Hydrangea season.”
But in 2023, things aren’t going too great for hydrangea growers.
Understanding Hydrangea Species and Traits
When selecting hydrangea plants for your garden, it is important to know the specific species you are getting. Is it Hydrangea macrophylla (bigleaf)? H. serrata (mountain)? H. quercifolia (oakleaf)? H. petiolaris (climbing)? H.paniculata (panicled)?
Knowing the scientific name of a plant takes the common name out of the equation, and this will help you find the best growing advice. In gardening, common names can often be used for several different species — species that each have different growing requirements. Research a plant based on its scientific name to ensure you are finding the right advice for your specific plant.
The other thing to understand about hydrangeas is which varieties only flower on old wood, and which can flower on new wood. Forsythia, azaleas and redbud are a few examples of plants that flower on old wood, and that is generally the case with H. macrophylla and H. serrata. (Endless Summer is an example of an H. macrophylla cultivar that can grow on both old and new wood.)
How Winter Cold Affected Hydrangeas
Much of the United States had extreme temperatures on the cold side around Christmas last year. It wasn’t just that it was cold, it was that the cold hit quickly and was sustained for a number of days. That doomed many plants.
It didn’t help that November was relatively warm. Hydrangeas tend to be one of the last plants to drop their leaves in fall, and when they still have leaves, they are still in the process of developing buds for next year’s flowers. Because of the warm weather, hydrangeas had not gone dormant yet when a cold snap hit in November. For Lorraine, her hydrangeas all had their leaves before the cold snap, and overnight all of the leaves were curled up, brown and crinkled on the ground.
Temperatures rebounded in December up until Christmas when extreme cold hit. Hydrangea stems can’t hold onto buds once temperatures go below 26º — and in parts of the country, the temperature was 0º or as low as -5º.
Temperatures warmed up again, and Connecticut had its warmest January on record, Lorraine notes.
“The plants start to say, ‘Oh, it might be time to wake up,’” she says. “And so you start to see some changes in them. Well, guess what happens in February? Bingo. Down go the temperatures again. So to say that the plants are confused is an understatement.”
If any buds made it through November and February, the wild swings of March did them in. There were days in Connecticut where the temperature was 55º during the day and 25º at night and as high as 65º during the day and 20º the same night.
“You get those swings, and that plant cannot tolerate that,” Lorraine says.
Gardeners with rebloomers thought they were lucky — but not so fast. When their hydrangeas broke dormancy and had little “broccoli heads” showing what should have become blooms, a freeze occurred on May 18. That was the latest freeze date on record for Connecticut.
“Whatever was developed and whatever had emerged, whatever had broken dormancy got frozen,” Lorraine says. “So, there was no way out of this.”
Either any one of these weather events or the cumulative effect of all of them prevented many hydrangeas from blooming this year.
How Hydrangea Growers Can Mitigate and Overcome Weather Extremes
We can’t change the weather, but there are some things we can do to mitigate it or overcome its effects.
Choosing rebloomers is a big way gardeners can enjoy hydrangeas without the heartache.
Lorraine is a fan of H. serrata Tuff Stuff, a lacecap Hydrangea. “It’s a fabulous plant,” she says. “We’ve loved it. It’s performed really well.”
However, Lorraine’s Tuff Stuff did not go unscathed. The side that was exposed to the wind and weather has no life on the stems while the side that was protected by the planks of a raised garden bed has flowers on all of the stems.
It’s not just the temperature but the desiccating wind that makes the difference, she points out. If a hydrangea is not already protected by a raised bed, building, fence, foliage or other windbreak, you could set up burlap on stakes around it. You could dig the plant up in fall and relocate it to a more sheltered spot or plant something tall around it like an azalea, rhododendron or spruce that will grow fast.
Gardeners may also want to swap struggling hydrangeas for other hydrangea varieties with better hardiness.
“Maybe it’s time you trade up,” Lorraine says. “You get rid of some of the dogs.”
H. macrophylla Lady in Red is one that Lorraine calls “bulletproof” and a feast for pollinators. “She has bloomed for me every single year for the last 20-plus years,” Lorraine says. “She got hit with the tornado in 2019. About six weeks ago, we had a 60-foot tree come down and knocked off one side of her, and she is still putting out flowers this year from the very beginning of the season. She’s absolutely indestructible.”
Lady in Red is one of the parents of an Endless Summer Hydrangea you may have heard of named Twist-n-Shout. Lady in Red was patented, but the patent expired last year, which means it may become more readily available as more nurseries can grow it.
New to the marketplace and recommended by Lorraine is Blue Enchantress, a mophead hydrangea. Lorraine also likes anything in the Let’s Dance series, particularly Can Do!, a rebloomer that is a cross of H. macrophylla and H. serrata. And new in the Endless Summer series is Pop Star, which Lorraine has four of, each growing in a different place. “They all have flowers on them, every single one,” she says.
Enjoy More Blooms Sooner on Rebloomers
Reblooming Hydrangeas have “apical dominance,” which means that the tip of the stem uses plant hormones to control what happens on the rest of the stem, Lorraine explains. When the flower dies or is cut off, the hormones in the rest of the stem are released, allowing more flowers to grow down the stem.
If you have a rebloomer and are wondering whether a stem is alive or dead, scratch the stem with your fingernail. If you see brown, cut off the stem. If you see green, it’s alive, and you should snip off just the tip of the stem.
“You want to release that hormone so that it will allow those flowers to emerge along the length of the stem,” Lorraine says.
Rebloomers will flower down the stem eventually anyway, but you can accelerate the emergence of flowers by deadheading.
Lorraine also advises fertilizing at the same time that you deadhead, and she recommends rose food or any fertilizer that’s formulated for shrubs. She stays away from balanced fertilizers, like a 10-10-10, that include nutrients hydrangeas don’t need and will contribute to pollution and nutrient runoff.
Cutting the Tips of Hydrangeas That Only Flower on Old Wood
When you cut the tip of a plant that flowers on old wood, nothing will happen. At least not immediately. It will not stimulate the plant to flower down the stem that season. What it will do is cause the tip of the stem to branch in two. Those two new tips could each flower the following year.
The time to cut these types of hydrangeas depends on where you live. If you are in zone 5 like Lorraine, aim for between July 1 and July 10. Old-wood hydrangeas will begin to set their flower buds when days get shorter, after June 21, and when nights are consistently below 60°. Once those criteria are met, it will take six to eight weeks for buds to form.
“Those buds, as we know, have to make it through the whole winter until we see next spring,” Lorraine says.
If you haven’t already listened to my conversation with Lorraine Ballato on hydrangea cold tolerance, you can do so now by scrolling to the top of the page and clicking the Play icon in the green bar under the page title.
How are your hydrangeas performing this year? Let us know in the comments below.
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“Will Your Bigleaf Hydrangeas Bloom This Summer” article by Lorraine Ballato
“Success with Hydrangeas: A Gardener’s Guide” book by Lorraine Ballato
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