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Climate-Ready Detectives Select Plants for the Future

Articles: Climate-Ready Detectives Select Plants for the Future

Spring 2024 

Amid the tumult of rapidly shifting climate conditions, gardeners at every level are asking, “What can I plant now?” From drought to wildfires, floods, and frosts—weather events throughout the Pacific region are increasing in severity, frequency, and unpredictability, creating vivid ripple effects for our plants.

Here public garden curators, nursery professionals, extension agents, and designers from the Pacific region share their perspectives.

All gardening is local: the power of the microclimate

Whether you realize it or not, you may have just landed in a new hardiness zone. Gardeners and horticulture professionals rely on US Department of Agriculture (USDA) hardiness zones as one factor in determining what will grow well where. Zones tell you the coldest temperature limit to expect (on average). In November 2023, USDA overhauled and updated its hardiness zone map in collaboration between its Agricultural Research Service and Oregon State University’s PRISM Climate Group (Agriculture Research Service 2023a). Since the last map edition in 2012, the US warmed by 2.5°F (1.4°C), moving more than half of the country up by a 5°F half-zone. The latest map also adds two new zones, 12 and 13.

Cold hardiness is only one of the variables gardeners need to consider in selecting plants, especially if your region doesn’t experience freezing. Even if a plant matches your zone, its soil, moisture, or heat needs may not align. For gardeners, trying to surf along with the conditions each plant evolved for is complicated.

Many gardeners will rejoice at being able to overwinter some previously borderline annuals, but some plants require cold temperatures, too. Peonies, tulips, and many fruits needing a minimum number of “chilling hours” to bloom or fruit successfully may become less suited to your warmer zone.

Then there is moisture. Much of the West is classified as “summer dry,” receiving negligible summer rain, while some regions, notably Western Oregon, Washington, and British Columbia are also “winter wet”—a combination that many plants considered drought-tolerant cannot tolerate.

Understanding the microclimates of your garden makes all the difference to the success of your plantings, from temperature, rainfall, and soil properties. High elevations tend to have better drainage in the soil, but also experience higher winds. On the other hand, the base of a hill can form a frost pocket, where both the cold air and the rain linger in plantings. House or retaining walls can help trap sun and warm air, helping the soil warm (and dry out) faster.

Every plant has opinions on each of these conditions, which repay our attention thousandfold.

While each of the experts we interviewed offers a unique outlook, distinct throughlines emerged in creating and stewarding climate-ready landscapes.

Know your conditions and pair the right plant to your place—it’s more important than ever.

Plan for environmental vitality, not just beauty or function in design and care. The key attribute? Diversity of species.

Be ready to adapt to new weather, new pests, new plants, and new growing patterns

What the experts say:

Here’s what our experts had to say, with takeaways you can use in evaluating your own plantings.

PUBLIC GARDEN CURATOR

Ray Larson, curator of living collections, University of Washington Botanical Gardens, Seattle, Washington

After “maybe the best crape myrtle bloom here ever” in 2023, Larson is considering all his options in plant selection, which includes looking at magnolias (Magnolia) and crape myrtles (Lagerstroemia) adapted to the Southeast, as well as Northwest California and Southern Oregon plants from high elevations that can take cold and heat, and some hardier conifers that are adapted across a great range. He may add more incense-cedars (Calocedrus) or western hemlocks (Tsuga heterophylla) from hotter areas.

Takeaway:

Experiment smartly. “That old adage that says it’s good to spend a year, go through the seasons, is true, but hard to stick to.” To enable his experimental impulses, he said, “I like to buy things and put in a container to see what’s going on.”

“I see a lot of experimentation in our future,” he added.

The University of Washington Arboretum's Pacific Connections garden highlights plants from five countries including New Zealand. Credit: Erica Browne Grivas

EXTENSION AGENT

Brooke Edmunds, extension agent, Oregon State University, and Master Gardener lead in Marion and Polk counties, Oregon

“I get a lot of people saying ‘I’m going to make a big investment. Tell me what I can plant,’” said Edmunds. “That’s hard. We don’t have a crystal ball. Especially here in the West. We’ve had heat waves, drought, and excessive water. It’s a tough time for a lot of plants out there.”

“I know folks are doing research studies,” she added, “but we are chasing it a little bit because things are changing so fast.”

Takeaway:

“Gardeners need to keep learning and being curious. If a plant is struggling start acting like a detective,” Edmunds said. “Is it something with the soil, is it not in quite the right spot? Is it getting enough sunlight? We all have to adapt.”

Show the planet some love by watering wisely. Credit: Erica Browne Grivas

DESIGNER

Sue Goetz, CPH and ecoPRO-certified garden designer, Seattle, Washington

Goetz said, “I observe plants in their spaces—everywhere I go, at home and abroad, checking on how the Viburnum davidii is doing at the local fast-food place, and scoping out neglected slopes, roadside or freeway plantings after a heat spell to see what is thriving.”

Takeaway:

For Goetz, there’s no substitute for local observation. “The elusive plant manual for what is happening to our climate doesn’t really exist—it is constantly evolving and changing. I take pictures and make notes—of plants doing well and possibly why—if I can observe or know how it has been cared for. I have a notebook of scribbled lists of plants by type and condition I have gathered for years.”

Extended frost event caused Seattle nursery to remove its tender plants to a warehouse. Credit: Erica Browne Grivas

PUBLIC GARDEN PROFESSIONAL

Douglas Justice, associate director of horticulture and collections, University of British Columbia Botanical Garden, Vancouver, British Columbia

“We are looking south because as we travel along the Pacific Coast the summers are traditionally longer and warmer, so those that are native to Southern Washington, Oregon, and California are becoming the plants we need to at least try.”

Vancouver tends toward “cool mediterranean,” he said, but they are looking toward plants adapted to “warm mediterranean” conditions, always planting in sites with appropriate drainage during its soggy winters.

Takeaway:

Water your established plants, especially trees.

“We have seen some pretty crazy extremes [of weather] and the frequency of these events has gotten greater,” said Justice. “This puts an enormous amount of pressure on plantings that we normally would take for granted.”

“If I’m advising people on what to plant, my greatest advice would be to make sure that people understand how valuable trees are. Trees are going to save our asses in 50 years.” If you have to choose between cleaning your car and watering your trees, “trees are more valuable than clean cars.”

Phlomis, a Mediterranean shrub and California poppy coexist happily in summer-dry Seattle, author's garden. Credit: Erica Browne Grivas

NURSERY PROFESSIONAL

Alec Charais, chief marketing and product development officer, Bailey Nurseries, nationwide grower with locations in Oregon, Washington, Illinois, Georgia, and Minnesota

“At Bailey Innovations, we are always thinking about this, and many of the breeding projects that are in process are designed for not only today’s needs, but anticipating what the needs of the next decade and beyond will be, too,” said Charais.

Bailey has been expanding options in the drought-tolerant chastetree genus (Vitex), like Queen Bee chastetree (Vitex agnuscastus ‘Bailtexthree’), a selection that is both dense in growth and compact in size and inviting to pollinators. Bailey has also developed plants with greater heat tolerance, helpful both in transport and the garden, like Little Hottie panicle hydrangea (Hydrangea paniculata ‘Bailpanone’) from First Editions.

Takeaway:

Good breeding takes time, research, and testing. Find the best plants for your garden’s needs, ideally ones that can adapt to the ever-changing climate like those that have lower water needs, can stand up to extreme temperatures, and provide food sources for pollinators.

Covering the ground with plants retains moisture, nourishing the soil biome and increases diversity. Credit: Erica Browne Grivas

NURSERY PROFESSIONAL

Sean Hogan, owner of Cistus Nursery, Sauvie Island outside Portland, Oregon

Hogan is both an avid plant collector and a confessed climate geek. He searches the world for plants that thrive in similar conditions to the Northwest.

If you enjoy growing rare plants new to your region, he recommends becoming an amateur meteorologist when it comes to your location, asking “With what frequency do we leave our zone, how long does it last, and for us especially in the Northwest, how long does it stay below freezing?”

Takeaway:

“Go outside and look,” he said. “The first clue is, look at what you are thinking of growing; how are these things performing in your neighborhood?” He suggests harnessing local expertise by joining local gardening groups and taking classes.

In terms of cultivation, he sees self-sustaining landscapes as the goal. “The days of adding poop are over—let’s look at multilayered groundcovers” to retain moisture and soil health.

Cistus nursery collects a plant palette from around the world. Credit: Erica Browne Grivas

DESIGNER

Michael Yun, RLA, principal, Knot Studio, Portland, Oregon

Yun is especially concerned for the trees. “Those are going to be the most impacted and the slowest to respond. They are enduring more impacts from extreme weather. In Portland we just had a major ice event in January on the heels of heat event in the summer, and we lost a lot of Douglas firs.”

“The climate impacts we have to design for are highly varied,” he said. “We’re not just planting for a warmer climate.” Yun predicted the increased weather extremes will likely transform the plant palette over time, but noted we can’t say exactly how or when.

There could be an understandable tendency to focus on the plants with the toughest constitutions, reliable performers, but that can create unintended monocultures fostering pests, diseases, and loss of biodiversity.

“I’m a designer who leans on a lot of native plants because ecological function is really important for the work we are doing. It tends to focus on native plants that are hardier. But what we would hope is we would continue to have a diverse range of species in our plant palettes.”

“There is both the joy and pleasure that comes with growing a wide range of species that stimulates the imagination, and the nuance of how many roles and niches are fulfilled by individual species in an ecosystem.”

Takeaway:

Observe, don’t rush.

“Let’s let nature do the work and continue being sensitive and curious about the variety we have around us, and maybe watch the world a little more. Gardeners have the opportunity to do their own experiments. Herbaceous plants especially give you a lot of data and you can make adjustments as needed.”

Support local plant communities and nurseries.

“People sometimes conflate the idea that if it’s the same species they can buy it anywhere,” but locally sourced plants supported by regional mycorrhizae will perform the best.  His local native plant nursery, Bosky Dell, grows and digs the plants on site, and he believes that local mycorrhizae give his plantings a boost in establishing.

Unexpected weather events can catch gardeners and plants off guard. Credit: Erica Browne Grivas

PUBLIC GARDEN CURATOR

Kathy Musial, living collections curator, The Huntington Library, Art Museum, and Botanical Gardens, San Marino, California

For Musial, some things haven’t changed. She picks climate-appropriate plants through “trial and error. That’s part of what we do as gardeners and at the botanic gardens.”

She places a great emphasis on watering. “As for advice to gardeners, my advice has always been about learning how to water your garden correctly. Too much emphasis is placed on plant selection. Certain obvious groups aren’t going to work (like alpines), but by and large a good proportion of plants offered by nurseries tolerate a lot of adverse conditions as long as they are watered and cared for correctly for their first year in the ground.”

Takeaway:

She recommends hand-watering new plantings for the first 6–12 months, especially through the summer, and, once established, watering deeply and less frequently—perhaps every one to two weeks to encourage root development, but not watering during winter rains.  “I water my garden every two weeks. Most people overwater,” she said.

Plants native to your area will establish more easily - here a Ribes sanguineum blooms early in the Seattle area, offering nectar to hummingbirds. Credit: Erica Browne Grivas

NURSERY PROFESSIONAL

Aimee Damman, director of marketing and communications, Swansons Nursery, Seattle, Washington

Swansons chooses plants that will succeed locally, but also prints custom signage describing how a plant may perform in the Northwest—which may differ from the grower’s tag. The nursery also focuses on teaching gardeners how to foster a resilient landscape within new weather patterns.

“Our summers can have extended periods of heat with no rain, so we aim to educate customers on watering techniques that allow their plants to become healthy and established in their landscape,” Damann said. “We also educate our customers about water-wise options, being sure to inform customers that all plants need some additional water, especially until they are established.” 

Takeaway:

Look to natives for a lower-input landscape. “We offer a large selection of Washington native plants that generally thrive with less care when they are planted in the correct conditions, because they have adapted to our specific climate.”

Learn more with our ‘What Climate is This?‘ series

This article was sponsored by:

Resources

Ray Larson, University of Washington Botanic Gardens, Seattle, Washington X

Brooke Edmunds, Oregon State University Extension Service, Corvallis, Oregon

Sue Goetz, The Creative Gardener, Seattle, Washington

Douglas Justice, University of British Columbia Botanical Garden, Vancouver, British Columbia

Alec Charais, Bailey Nurseries, nationwide grower.

Sean Hogan, Cistus Nursery, Sauvie Island, Oregon X

Michael Yun, Knot Studio, Portland, Oregon

Kathy Musial, The Huntington Library, Art Museum, and Botanical Gardens, San Marino, California

Aimee Damman, Swansons Nursery, Seattle, Washington

Bosky Dell Natives

Agricultural Research Service, US Department of Agriculture. 2023a. USDA Plant Hardiness Zone Map.

Agricultural Research Service, US Department of Agriculture. 2023b. “USDA Unveils Updated Plant Hardiness Zone Map.” Press release, November 15, 2023.

Oregon State University. 2023. “New plant hardiness map, used by gardeners nationwide and based on OSU climate data, unveiled.” Press release, November 15, 2023.

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