Staff at the Brooklyn Botanic Garden were cutting grass in February, something they don’t normally start doing until much later.
At the Queens Botanical Garden, gardener Colin Kirk pulled weeds throughout the winter. He opened vents to lower greenhouse temperatures—in January.
And at the Wave Hill Public Garden and Cultural Center in The Bronx, scilla sardensis, or glory of the snow, started blooming in March, when April is typical. Witch hazel began blooming in January, also two months early.
These are just some of the changes the gardeners and foresters who work at New York City’s parks and botanic gardens are noticing as the effects of climate change take hold.
These green spaces — coming alive with color and about to take on many more visitors in springtime — serve as a laboratory for what happens when temperatures climb and rain falls in buckets.
Though parks serve a different purpose than botanic gardens, which can be more like museums for plants, staff at both kinds of places around the city are tracking the changes and figuring out how to adjust.
“For everything new that comes, there’s a learning curve here,” said Rowan Blaik, vice president of horticulture at the Brooklyn Botanic Garden. “We know we will adapt. It’s a question of pace.”
New disease-carrying bugs, patterns in weather and other ecosystem shifts may force the phasing-out of some plant species. Others, however, may flourish.
“We’re staring down the barrel of some existential questions in horticulture overall,” said Melissa Finley, curator of woody plants at the New York Botanical Garden in The Bronx.
The winter that just ended was on average warmer than others in New York City since 1900, with snow only falling on the first day of February — the latest first snowfall since 1869. Overall, this winter is, so far, the least snowy one ever.
Since the ground didn’t freeze this year, many plants that normally go dormant continued to grow, which meant weeding and grass cutting at city gardens and parks continued through much of the winter.
Cathy Deutsch, the director of horticulture at Wave Hill, also said that the lack of snow may harm the plants.
“Snow cover provides insulation for the plants, and so they are somewhat protected from those dramatic fluctuations in temperature, but we had no snow cover this year,” Deutsch said.
Staff in all five boroughs spoke of plants — crocuses, deadnettles and daffodils — appearing up to a month earlier than normal.
While the unexpected blooms may have elicited delight or curiosity for some visitors, ever-earlier growing seasons could dramatically impact the spring spectacle.
When cherry trees and magnolias bloom while there’s still a chance of a cold snap, the buds risk freezing if temperatures then drop. If that happens, visitors who relish gazing at the blossoms in spring may be disappointed to miss out on the flowers.
Bees and Bugs, Too
Early blooms can upset an entire ecosystem, as pollinators have evolved alongside native plants to meet one another’s needs for survival.
“When suddenly we are having plants blooming a few days or a few weeks before pollinators are around, then that’s an issue,” said Blaik of Brooklyn Botanic Garden.
For instance, bees may come out earlier if temperatures are warmer and find themselves without food if plants have already bloomed; the same is true for migratory birds.
“It’s sort of like dominoes,” said A.J. Logan, a gardener at Prospect Park Alliance. “All those relationships fall apart if one of them is gone, or if that plant, say, blooms early, and the pollinator is still hibernating, and there’s like a mismatch in timing.”
Mild winters also mean pests stay active, from the emerald ash borer that destroys ash trees to a type of roundworm that carries a disease affecting beech trees.
“We rely on long periods of cold weather to kill off a lot of the insects that are lying dormant to help kind of create regulation for the spring and in the summertime,” said Puiyan Taglianetti, visitor services and education manager at Staten Island’s Snug Harbor Cultural Center and Botanical Garden. “But with such a mild winter, we then have to expect there to be an increase in insect activity on the ground.”
The staff at Snug Harbor has had to pluck aphids from the plants. Kristy King, director of natural areas management at the Parks Department, said her staff members have been picking ticks off their legs through the winter months.
High temperatures can stress native plants, like birches and maples, as well as flowers that are northeast staples, like lilacs and peonies.
But some non-native species used to warmer weather, like crepe myrtles and Japanese camellias, may thrive.
“Even within the five boroughs of New York City, the conditions between the Bronx and Staten Island are quite different,” King said. “We’re in a really unique location … to see things start to establish and see things start to move northward.”
Part of the northern range of the eastern redbud — a tree that sprouts purple-pink flowers in the spring — is in Staten Island, but may begin to do well in The Bronx or northern Queens, she said. On the other hand, the sugar maple’s southernmost range may shift northward, which may mean the city loses those trees as the climate changes.
Finley, of the New York Botanical Garden, is looking forward to seeing some of those positive changes, as she’s thinking about how far into the future a species might be able to thrive.
“Part of me is excited to try more southern oak species, for example, to see if … the changes in climate have shifted just enough for an oak that normally grows in the south to grow up here,” Finley said.
Changing temperatures also mean that invasive plants can compete with native plants. Logan pointed out the ground coverage of herby, invasive plants like garlic mustard and lesser celandine in Prospect Park.
“Weeds and invasive species are more aggressive because they can sustain [in] extreme temperatures,” Logan said. “The invasive ones have all the best strategies for their survival, like putting out a lot of seed. They leaf out first, and they drop their leaves last, so they’re taking more nutrients and sun than everyone else.”
Logan and his colleagues have suppressed weeds by laying down cardboard, spreading leaves and mulch on top and letting the pile decompose. Then, they can plant desired plants in that pile. It’s a strategy he predicts will have to be employed even more in the future.
Weathering the Storm
As the planet warms, New York City will experience more intense rainfall and more storms. Already, gardeners and foresters have had to deal with alternating dry periods and downpours.
When he’s looking to buy plants, Colin Kirk of the Queens Botanical Garden has been eyeing those like New England aster, echinacea and evening primrose that are likely to withstand the whiplash.
“You really need tough plants that can kind of simultaneously survive these kinds of drought-like conditions, and then also receive a deluge of water within like one or two days,” Kirk said.
When there’s a downpour that soaks the soil, the roots of some trees, like tulips and cherries, can’t hold on — and that can cause the trees to tip over.
And when heavy rain comes after a drought, the soil becomes hydrophobic, meaning it can’t absorb the water.
Rain “will just hit it [the soil] and wash off, which causes a lot of erosion,” said Wave Hill’s Deutsch, who has seen roots exposed on the surface after a top layer of soil washes away.
And more frequent storms also leads to more time restoring woodland areas that get destroyed.
King didn’t expect to spend so much of her 15-year career at the Parks Department cleaning up downed trees and ravaged areas after storms. She’s noticed the increase in frequency over the years, from Hurricane Sandy in 2012 to Isaias in 2020.
“Storm response has been significant,” King said. When she plans for restoring an area, she said she looks for plants that are part of “intact communities,” which are “by nature more resilient than, say, a random assemblage.”
When Logan started as a gardener at Prospect Park five years ago, he worked on a project to restore degraded areas of the park after Hurricane Sandy. He planted lots of oaks, sweet gum and tulip trees.
“It’s the diversity of the ecology that will strengthen the planting,” he said, adding that oaks are a keystone species that benefit birds, insects and fungi.