Gardening in a Changing Climate

Abby Rose had been doodling her dream house for a year, so when she walked up to a listing for an affordable one-story in Traverse City, Michigan, she knew she was home before even seeing the inside. Native oaks and maples threw dappled shade in the front and back yards but left plenty of sunny expanses where Rose, 34, could create the gardens she had envisioned, complete with fruit trees and winding wood-chip paths among tidy beds of flowers and vegetables. "It was love at first sight," she recalls.

Before buying her own little patch of heaven in the fall of 2016, Rose had joined the Traverse City Community Garden to keep her hands in the earth. She'd grown up 200 miles northwest of the area, as the crow flies, watching her mom tend more than 100 raised garden beds on the Keweenaw (KEE-wen-aw) Peninsula, just a mile from Lake Superior at the top of Michigan's Upper Peninsula. Experimenting with her own patch of soil as an adult provided a way for her to connect with her mother, Vicki Weglarz, through their shared passion for gardening.

Weglarz has lost count of the number of times she's driven to the Lower Peninsula to help her daughter take care of her community garden plot as well as plant her new home garden. And during those trips throughout the seasons, Weglarz has noticed something about the region. "They still get their winters," she says. "But now they get more freezing rain replacing the snows I grew up with in that area. It's like, 'Nice try, winter, but….'"

It's not her imagination, says Jeff Andresen, Ph.D., climatologist for the state of Michigan. In the 35 years he has been tracking weather and climate in the Great Lakes region, he's seen its average temperatures increase by almost 2 degrees Fahrenheit.

At the same time, the region is getting more precipitation and experiencing more winters that are mild by Michigan standards, so there's more winter rain and freezing rain than ever before. "We still have those severe winters with extended cold and snow, but they're less frequent than in previous decades," Andresen says. "And we're seeing big swings from one year to the next."

The Traverse City area, where Rose lives, appears to have experienced some of the most dramatic temperature increases in the Great Lakes region, or anywhere, for that matter. In 2019, climate reporters at The Washington Post analyzed temperature data from the National Oceanic and Atmospheric Administration (NOAA) climate database and developed a map showing the base of the Grand Traverse Bay as one of the nation's "hot spots," where average temperatures have warmed 3.6 degrees F, twice the worldwide average.

Most of the warming in the area and elsewhere has occurred in the winter and spring seasons and at night, Andresen says, and the average minimum temperature in the Great Lakes region has warmed 5 to 10 degrees just in the last 30 years. The last frost in spring also comes earlier than it did three decades ago, and the first frost in fall comes later, making the growing season one to two weeks longer, depending on where in the region you are located.

Across the nation, similar trends have rippled through events like the annual Tulip Festival in Pella, Iowa. From 1936 to 2001, the dates felt as timeless as gospel: the second weekend of May. But after hosting a string of festivals with beds of empty stalks where blooms had come and gone, city leaders moved the event dates ahead a week. "The last three years we've had perfect tulips," Pella's Historical Director Val Van Kooten said in April this year. "Last year we had a trifecta: tulips at their peak, flowering trees, and beautiful weather."

Many growers and farmers have navigated tougher challenges. According to the U.S. Department of Agriculture, rising average temperatures are allowing aggressive invasive weeds to spread northward, and longer frost-free seasons have given an edge to insect pests in northern states by giving them more time to reproduce.

Extremes in precipitation are more common now, too. In the Northeast, heavier and more intense rains threaten to reduce yields, while in the Southwest, increased drought poses a challenge to nut, fruit, and vegetable producers. And in 2019, the nation's second wettest year on record, inland floods washed out topsoil and millions of acres of crops in the Midwest and Southern Plains.

In Kansas, Mike Neustrom has experienced nearly all these weather issues. He owns Prairie Lavender Farm in the north-central part of the state. For his first 14 years in business, harvest times always fell around Father's Day. "I could almost tell what time of year it was just by the harvest," he says.

Then in 2016, an early spring gave him his first harvest three weeks early. That year, he got six cuttings from plants that had previously produced two or three a season. He got extra cuttings the next year, too. But in 2018, his good fortune reversed when a few unseasonably warm days in January and early February brought his plants out of dormancy just in time for three sub-zero days in a row. "We had gone into that winter after a drought," he says. "I lost basically my whole crop that year and about half of my plants."

A longtime member of the United States Lavender Growers Association, Neustrom regularly fields questions from members about what to expect during a growing season. "We don't have a clue anymore," he said. "We can't even keep track from year to year. It keeps changing."

Back in Michigan, horticulturist Nikki Rothwell, Ph.D., has experienced similar uncertainties when working with apple and cherry farmers up and down the state's Fruit Belt, which runs the length of the Lower Peninsula along Lake Michigan. As the coordinator of the Northwest Michigan Horticultural Research Station, she has witnessed a cascade of losses in the past 15 years or so, including crops pummeled by hail, wilted by fungal diseases, devoured by invasive pests, and battered by powerful winds that bruise fruit and rip trees from the ground.

Another challenge: Apple and cherry blossoms in Michigan are starting to bloom anywhere from a week to a month earlier than they did just a decade or two ago, thanks to temperatures warming up earlier in spring. "Then if we get a frost or freeze event, we can have big crop losses,"Rothwell says. When the frozen flowers wither and fall off before they can get pollinated, no fruit will form. Plus the trees only bloom once a year so you don't get another shot until the following spring.

Problems associated with climate change, such as more prevalent pests and crop damage, are likely to increase, according to scientists with government and non-government agencies. In short, all the signs point to needing to get smarter about gardening in an era of added challenges and unpredictability.

Temperature Changes: How Hardiness Zones Have Shifted

How cold your region's winter gets often dictates which species will thrive there. Tropical plants, for example, can't tolerate sub-freezing temperatures. But plants from temperate regions of the world, such as apple and cherry trees, need a certain amount of chilling in order to resume growth and flower in spring. To figure out what will survive winters in a given location, many gardeners rely on the Plant Hardiness Zone Map, created by the U.S. Department of Agriculture.

The USDA published its first hardiness map in 1960, then updated it in 1990, and most recently in 2012. When looking at the current map next to its previous iteration, you might notice that your zone boundaries have shifted a little. On the older map, you might have been in zone 6b but now are in zone 7a, which is 5 degrees warmer in terms of minimum average temperatures. That matches general warming trends observed by climatologists and growers, but it's also because of the different methodologies the USDA used to create the two maps.

The 2012 map reflects a longer and more recent time period (the 30 years from 1976 through 2005). The 1990 map was based on temperature data from only the 13-year period of 1974 to 1986, which included unusually cool years in the 1970s sandwiched between warming periods. When all the numbers got averaged out, many areas of the U.S. ended up shifting into slightly warmer zones, compared to the 1990 map. Critics have questioned if using a larger set of data for the 2012 map has skewed the actual warming trends that various regions may be experiencing.

However, another government agency, NOAA's National Climate Data Center, also develops its own planting zone maps, based on consistent 30-year periods of climate data. In particular, its most current set of "climate normals" maps, produced in 2011, shows how planting zones have shifted northward and upward in elevation in many parts of the country since 1971, similar to the trends the USDA maps show.

Meanwhile, scientists are documenting weather and climate patterns that seem anything but normal. The 10 warmest years on record have occurred since 1998, and nine of the 10 have occurred since 2005. That makes now a good time to think through your approach to the climate-related challenges you may face as you nurture your own gardens and landscape.

Planting for Excessive Rain or Drought

From coast to coast, growers and climatologists have seen dramatic changes over the past 50 years inrainfall amounts. Northern parts of the U.S. are wetter now and expected to see even more precipitation in the years ahead while southern areas, particularly in the West, will become drier.

Missy Gable directs the University of California's Master Gardener Program, which trains volunteers to share research-based information with home gardeners; things like how to solve pest problems and when to start seeds. California just endured its longest drought ever recorded (from December 2011 until March 2019), so Gable and her team have been fielding a lot of questions about how to conserve water in a home landscape. Her advice for anyone living in a dry region or trying to cut back on watering: plant smart with help from your local extension service.

"You can have a beautiful, low-water landscape that's also very productive," Gable says. In her yard, for example, plants that have thrived have included rosemary, thyme, chives ("...so many chives"), basil, oregano, sage, parsley and cilantro.

Gable also plants in locations with dappled sunlight on the soil's surface, which enables her to keep the ground moist around 10 different perennial varieties and three grasses, as well as bl \ackberries and bush raspberries that get a good drink every week or so when she changes out the water in her 4-year-old son's kiddie pool.

On the opposite end of the country, Northeastern gardeners are facing a much soggier new normal. In fact, heavy rainfall in that region has increased 71 percent since 1958. It's a trend the Midwest has seen as well, by 37 percent.

"In New York, one of the most dramatic effects of climate change is that when it rains, it pours," says Jennie Cramer with Cornell University's Cooperative Extension program. "Now rainstorms here are fewer and farther between, and they're so hard you can't even be outside." Such forceful deluges can damage young seedlings, flatten crops, and quickly wash away soil.

Cramer's advice for gardeners everywhere: Shop locally for plants that can take whatever nature throws their way. "Small seed companies, regionally adapted nurseries and mom and pop businesses are springing up all over the country," she says. "And when you use seeds and plants from people breeding them in your region, they'll be better adapted for where you're growing."

You can also learn what's working locally in a seed exchange or plant swap group. While sharing extras of what you're growing, you can trade success stories with gardeners in your area who are dealing with the same climate-related growing challenges you are.

Native Plants For the Win

Sometimes, the best way to ensure resilience is to consider what worked in your region historically. At the Houston Arboretum and Nature Center, that lesson came the hard way after Hurricane Ike in 2008 and a severe drought in the summer of 2011 caused the loss of 50 percent of the large tree canopy on the 155-acre grounds, including massive old post oaks and glossy-green cedar elms.

"People here are very attached to trees," Conservation Director Emily Manderson says. "The first response we heard was, 'You need to replant the forest!'" But when the staff sat down to develop a recovery plan, they began with a look back. "Houston historically was at the convergence of three eco-regions," Manderson says. "The dominant ecosystem was tall grass prairie that went all the way up to Canada." But without bison herds roaming the land and fires every few years, trees had filled in where grasses had once been.

The arboretum staff also considered challenges climate scientists have predicted for the years ahead; in particular, stronger storms occurring more often in the region. "We realized we couldn't just replant the trees and have this happen again," she explains. "It was an opportunity to listen to nature."

The group decided to restore the arboretum's prairies and savannas with plants that historically grew in them. The day workers began mowing for a 5-acre savanna test plot, hawks showed up, riding the currents overhead in search of mice and rabbits. The team seeded native species late that fall, and new birds arrived all winter and the following spring.

"Once the savanna seed mix started to bloom in April and grasses began to seed out that summer, we saw a significant change in pollinators and other associated wildlife," Manderson says. "It was just teeming with life—dragonflies and butterflies and bees and birds."

The native plants, which often have extensive root systems, also play an important role in absorbing heavy rains and holding soil in place, abilities that homeowners all over the city have learned to value in the wake of Hurricane Harvey's catastrophic flooding. Now, customers snap up native grasses and prairie plants at the arboretum's plant sales each year.

"We're a story of hope," Manderson says. "If this was being done more and more at a residential scale, the cumulative effect could really have an impact." So when you are designing your landscape or figuring out what to plant in your garden, it's worth looking for native species that can stand up to your region's climate extremes better than non-native or rare plants, while also creating valuable habitat.

Supporting Pollinators

Warmer temperatures and wetter conditions are giving many insect pests a leg up by expanding the areas where they can survive. Meanwhile, the good guys like butterflies and several bee species have struggled. Many scientists suspect that a worldwide decline in insect pollinators in recent years has to do with a combination of factors related to the changing climate.

One problem: As warmer springs nudge plants to bloom earlier, they lose their sync with insect pollinators, which respond to a different set of natural cues, such as day length. "You may have a situation where the plants bloom but their pollinators haven't arrived yet," explains Cramer. "By the time the pollinators arrive, those flowers are no longer available for pollination."

How can you help? "The ultimate thing you can do is have diversity in the types of plants you have in your landscape," Cramer says. Getting the job done is easy: Check your garden every week to make sure something is always in bloom. Add new plants to fill any flower gaps you notice. You could also add a bee house to provide shelter for wild mason and orchard bees. These prolific pollinators get bonus points with gardeners because they are less aggressive and less likely to sting than honeybees.

And when you see any insect in your garden, "assume it's a helper bug until you see evidence it's not," says Cramer. Sometimes that evidence can be obvious, like holes chewed in leaves or suddenly wilted plants. But if you're not sure if you've caught a bad bug in the act, take a photo and reach out to your local cooperative extension office for help.

A Climate-Aware Approach to Gardening

The best way to adapt to climate change in your garden is to dig in with equal measures of pragmatism and optimism, experts say. In that spirit, look for tools you haven't needed before. In Europe, farmers have started using agricultural netting to protect acres of fruit crops from hail, wind, snow, strong rainfall, and insects. Now, farmers in Michigan's fruit belt are considering the same option, Rothwell says, noting that backyard growers could do something similar to protect their raspberries and strawberries.

Abby Rose plans to install a DIY irrigation system this summer to help her garden weather anticipated heat waves and summer dry spells. Next spring, she hopes to build a hoop house to shield her heirloom tomatoes from more frequent spring cold snaps.

She also plants with an eye for diversity like her mom, who still tends upward of 75 different varieties of herbs, vegetables, and flowers in the UP. Rose isn't to that level yet. But she has the vision. "Not everything in a garden is going to make it," she says. "That's OK, because you're not putting all your eggs in one basket."

Rose welcomed spring in Traverse City this year with plans and plants, including a tray of baby leeks on a sunny bedroom shelf. The sage outside her window was almost ready to harvest by early April, the same week her mom was stepping into backcountry skis to start salad greens in her hoop house. Because wherever there's soil and sun and rain and resilience, there's hope.

"The effects of climate change on gardening are complex," Rose says. "It's almost like this is the new abnormal, and there's no way to move but forward."