Gardeners should consider the effects of a steadily warming climate when they make plant choices this year, experts say.
“Climate change is very gradual, but we’re definitely seeing plant choices change a little bit,” said Chris Kennedy, owner of Kennedy’s Country Gardens in Scituate. Eastern Massachusetts is included in the plant hardiness Zone 6b, but the number is expected to rise. That means some common plants that flourish here now will need to go north to survive, while plants such as the Southern Magnolia Grandiflora will ultimately do well here.
But this spring, many traditional choices will still hold up against the chances of more 90-degree-plus summer days, heavier rains, and flooding that climate change brings.
For sunny sites
For suburban gardeners planting in a sunny location, Kennedy suggested popular choices such as lavender, an old-fashioned favorite with a pleasant fragrance and blue flowers, and catmint, an aromatic member of the mint family “that’s really stunning and looks good when the flowers [are] not in bloom” given its grayish-blue foliage. Other choices include sun-loving Stonecrop sedum, a low-spreading plant with thick, succulent leaves, and the allium family of long-lived bulbs, including the “onion” variety that produces round, blue flowers.
For shady locations
For gardens on a shady site, Kennedy recommended shade-tolerant plants such as the hosta, which is “long-lived and easy to grow,” though some gardeners may find deer nibbling its leaves. The lungwort variety produces blue or purple flowers and stunning foliage with an itchy surface that repels deer. Hydrangea is another shade garden choice. Hydrangea arborescens, a wide-branched plant with blossoms in a variety of colors, is also drought tolerant, Kennedy said, a climate-change bonus. Another choice, Hydrangea paniculata, is adaptable and easy to grow.
On the coast
Gardeners in coastal areas should consider plants that tolerate wind and salt, Kennedy said. “The salty wind hurts evergreen plants,” he said, causing them to drop their leaves. Plants that do well by the ocean and stay green in the winter include rhododendron, boxwood, azaleas, hydrangea, and catmint. Ornamental grasses work well, he said, as does Rosa rugosa (“beach roses”), though they are “thorny and tough to maintain.” Among traditional roses, ‘Apricot Drift’ has flowers with a peachy color and does well on the coast.
Container gardens require more work, Kennedy said. “Mother Nature does not water them enough. You have to plan on watering more.”
His recommendations for containers in a sunny location included edibles such as tomatoes, herbs, basil, and blueberry. Among ornamentals, he suggested plants that attract butterflies, bees, and hummingbirds with bright-colored flowers such as lantana, verbena, butterfly weed, and milkweeds. “The milkweed family is good for butterflies,” he said.
Plant ‘for the conditions you have’
Kristen Nicholson, co-owner of Blue Stem Native, a Norwell nursery that sells only native plants, recently held a program on the effects of climate change. Environmentalists have pointed out that regional native species have adapted to all the changes that have occurred — so far.
“The key to success in the face of climate change is planting for the conditions you have and not for those you like,” Nicholson said. “Put in plants that can handle the conditions you already have, and the plants will survive and thrive. Sun and moisture are always the key things to think about.”
For a suburban garden, she recommended butterfly weed or rose milkweed in view of the threat climate change poses to biodiversity: These plants attract pollinators, such as butterflies, and other insects. Milkweed, Nicholson said, is ideal for monarch butterfly reproduction. She also recommended Monarda fistulosa, also known as bee balm, a summer bloomer with red to lavender flowers, and Monarda punctata, called spotted bee balm, for sunny and dry conditions and sandy soil.
“For shade gardens,” she said, “asters are an incredible plant” that blossoms from late summer into fall. Among the varieties she favors is the big-leafed aster, Eurybia macrophylla, as “a great hosta replacement.” Other shade garden choices include red columbine; anemone varieties that blossom in spring and summer; and the Penstemon variety called ‘Hairy Beardtongue.’
For a coastal garden, Nicholson recommended plants that can handle high salinity in soils, such as seaside goldenrod, cousin to the plant seen along country roadsides. “You see it growing right on the dunes,” she said. Other choices for the coastal area’s poor soils include wild strawberry, butterfly weed, sundial lupine (a sun plant with dark-blue flower spikes), and a native cactus called Eastern prickly pear. In shady conditions, calico aster will do well.
“Containers are wonderful for more aggressive plants that you don’t want to take over your area,” Nicholson said. Her choices for container gardens include mints such as the wild bergamot and spotted bee balm. Low-bush blueberry will grow in partial shade. She recommended mint family varieties with narrow leaves, noting that these nourish insects threatened by climate change.
Climate change is also a factor if you’re thinking of planting a tree on your property, said Dan Herms of Davey Tree Expert Co.
“The climate is changing faster than the lifespan of a tree,” Herms said.
He advises planting oaks and other trees able to flourish in warmer parts of the New England hardiness zone. Some well-loved trees, such as birch, need a colder climate, he said, and climate change will send them farther north.