Hydrangea Hangover: February Cold Snap Damages Colorful Flower Islandwide

Nantucket’s hydrangeas might not be as colorful as usual this year. A warm January followed by a deep freeze in February has left many of the plants badly damaged, and some are even dead. As winters grow warmer, this may become a more common problem for the island—and it’s not just hydrangeas that are affected.

According to island landscaper Steven Collette, this past January was much warmer than average, leaving the hydrangeas in a state of flux. Plants often rely on temperature cues to regulate their behavior, leafing when it is warm and dying off when it is cold. The warm January meant that the hydrangeas got confusing signals. This was followed by a sudden extremely cold night in February, with temperatures dipping well below zero. Unprepared for the dramatic change in temperature, many of the hydrangeas experienced what Collette termed “catastrophic damage.”

“That led to this half-dead, half-alive look we’re seeing all over the island,” he said.

With extensive losses across the island, Collette thinks the reduction in blossoms will be very noticeable, particularly at first. “If I was making a rough estimate, my best estimate would be a 50 percent reduction [in flowers] on average across the island for the first bloom,” Collette said.

“There won’t be very many flowers,” Craig Beni, owner of Surfing Hydrangea Nursery, agreed.

These losses will be mostly seen in hydrangea macrophylla, most notably the iconic deep-blue Endless Summer cultivar that dominates downtown. Hydrangea macrophylla is responsible for most of the island’s blue and pink hydrangea blossoms. Other varieties, including those responsible for most of the white hydrangea flowers on-island, will be less affected.

Some hydrangea macrophylla, especially those highly exposed to the elements and those facing North, are completely dead, but others will begin to recover once the weather gets warmer this summer.

“I think what we’re seeing is hopefully not too many plants have outright died but there’s definitely a lot of stem dieoff,” Beni said. “I think most plants later this summer will actually be big and green but with very limited flowers.”

The recovery will continue over the next one to two seasons, and flower levels should return to normal—that is if the events of last winter don’t repeat. Warmer, more temperate winters and earlier springs are becoming common across New England due to climate change, which could mean fewer hydrangea flowers is the new normal for Nantucket.

“One year is annoying for a gardener, but the worry for an ecologist is this being more of a pattern than an anomaly,” said Dr. Sarah Bois, the Director of Research and Education at the Linda Loring Nature Foundation. “I’ve observed it…a couple of different times. That gives insight that it might turn into a pattern.”

Of course, the damage to the hydrangeas was caused by a harsh frost, not just a mild winter, but Bois says that, counterintuitively, climate change will increase such frosts as well.

“One of the more common predictions for our region is that there is going to be more danger of these frost events,” she said. “It’s not uniform. You can have earlier springs coupled with frosts.”

While the average temperature will likely increase on Nantucket as a result of climate change, Bois says that variation will increase as well. A warm January doesn’t necessarily imply a warm February. As the effects of climate change become more pronounced, extremes increase and variation goes up. Some scientists have termed this “Global Weirding.”

And it’s not just the hydrangeas that are affected.

“Some plants can withstand a frost…but then there’s a lot of other plants that in the normal spring will leaf out a little bit later. So those are the ones that don’t have the physiology to withstand a late frost,” Bois said. As an example, she cited cinnamon fern, some of which took significant damage from a recent spring frost after leafing early. “The fronds were just unfolding and they were all top-killed,” she said.

Collette has also noticed damage to ornamental grasses, among other plants.

“These kinds of extremes are definitely going to have lasting effects,” Collette said. “The plants are having to adapt.”

Beni is less concerned, at least when it comes to hydrangeas. “Of all the things we might panic about, I don’t think hydrangea flowers are the biggest one.”

But hydrangea flowers are only a small part of a much bigger problem. When plants grow earlier in the season, even if they aren’t killed by a late frost, they might still struggle. Pollinators like bumblebees often rely on different environmental cues than temperature, Bois says, and might not be around to pollinate plants that grow too early.

“We don’t understand fully the consequences of this,” she said.

While far from the most harmful repercussion of climate change, reduced hydrangea blossoming is not just a cosmetic issue; it’s also a commercial one. Landscapers like Collette have been monitoring the damage since it was first noticed early this spring, aware of the impact it could have on their business.

“Our only saving grace is that it has affected everyone,” Collette said. “Everybody’s hydrangeas kind of look the same”

If your hydrangeas have been affected, Collette recommends making sure they have enough water, removing the dead plant material, and perhaps most importantly, making sure you set your expectations appropriately for the number of flowers you are going to see.

“There’s really nothing else we can do,” he said.