Cover Story/Special Report: Weathering change

By Olivia Grider and Carolyn Mason

Washington D.C.’s cherry blossoms peak an average of seven days earlier than they did 30 years ago. Crepe myrtles thrive in Philadelphia and magnolias bloom in Manhattan, while in upstate New York warm January temperatures cause maple trees to produce syrup too early, reducing output by 40 percent.

These and other aberrant occurrences fuel the already heated debate about the effects of climate change on gardens and landscapes. While it’s generally accepted that average overall temperatures have warmed slightly, the cause, effects and predictions are the subject of international discussions and frenzied media coverage. Underneath the many layers of this emotionally charged issue are both obstacles and opportunities for landscapers. And weeding the facts from the hype is vital for the success of any business dependent on the whims of Mother Nature.

In compiling this report, Total Landscape Care conducted extensive interviews with landscapers and experts intimately involved in the ongoing climate change controversy and commissioned two extensive reader surveys. Results reflected the underlying uncertainty about the validity of more extreme climate change assertions as well as some general concern regarding bizarre weather patterns. One survey, for example, indicated more than 62 percent of respondents were concerned about changing average temperatures. At the same time, most surveyed landscapers have not experienced significant climate challenges in their business.

Our research indicates that no matter where your business is located, your weather-related struggles stem from fierce or erratic conditions such as drought, radical temperature swings, excessive heat and inconsistent growing seasons rather than the gradual creep of warmer average temperatures.

Mother Nature has always been unpredictable and until accurate weather prediction models are perfected, she will continue to confound experts, turn predictions upside down and embarrass meteorologists. In the meantime, opportunities abound for savvy landscapers who adjust their business models to reflect current trends.

Plant hardiness zone shifts stir controversy

Tony Avent, horticulturist and owner of Plant Delights Nursery in Raleigh, North Carolina, is known for his humorous tagline: “I consider every plant hardy until I’ve killed it three times myself.” However, like most landscapers, he depends on the United States Department of Agriculture Plant Hardiness Zone Map to guide his plant selection decisions. In fact, he’s a consultant for the much anticipated, soon to be released, new USDA map and is looking forward to the updated version. He’s also getting ready for questions and confusion from his clients when the “extreme green” media hype erupts over the new map’s expected warmer zone shifts.

“There’s going to be a huge hoopla with this new map. Get ready. If last year’s media coverage over the National Arbor Day Foundation’s updated plant hardiness map is any indication of the level of interest in all things green; then zone changes in what’s considered the bible of hardiness maps will further fuel the fury,” Avent says.

When the National Arbor Day Foundation released its updated plant hardiness map last year, headlines in the general media touted, “apples in Anchorage” and “magnolias in Manhattan,” to illustrate dramatic zone shifts from the USDA’s 1990 map. Most stories implied that the changes heralded a new era for landscapers who would now be able to offer their customers a wider variety of plants. Many writers linked the changes to evidence of global warming, even going as far as to declare zone shifts “the canary in the coal mine.”

If the new USDA map also shows warmer zone shifts, the media will most likely come to the same conclusions it did last year. No matter what your feelings are about the cause of global warming or its long-range implications, this controversy is an opportunity to help your clients sift through the hype.

Mapping changes
The USDA’s map was last updated in 1990. Today, the map frustrates many in the industry who feel it doesn’t reflect recent warming temperatures since it was, in fact, based on temperatures from the unusually cold 1970s and ’80s. Those record cold temperatures resulted in data that led to a conservative range of zones, critics said – good for more sustainable planting but considered unduly restrictive against warmer zoned plants and trees.

When the government still hadn’t published a new map by 2006, the National Arbor Day Foundation decided to generate its own hardiness zone map, releasing it last December. “One of the reasons we created the map was because the USDA map was out of date and we didn’t want to wait for their ‘coming soon’ version,” says Woody Nelson, vice president of communications for the National Arbor Day Foundation. He says the organization was spurred to action by demand from members who were reporting warmer-climate trees thriving in their areas and some trees that had been healthy for decades suffering heat stress. The group also felt these changes linked directly to global warming. “The new Arbor Day map is consistent with the consensus of climate scientists that global warming is underway,” the Foundation’s Web site says.

With the release of the Arbor Day map, the mainstream media focused on areas such as Washington, D.C., suburbs located in Zone 6 on the USDA map, but now classified as Zone 7 on the new map. The online map shows small portions of Arizona, Nevada and California lost a zone, and small pockets of the Midwest and Rockies gained two zones.

When looking at the Arbor Day map shown alongside the 1990 USDA map, more than 87 percent of respondents to a Total Landscape Care reader survey said they agreed with the Arbor Day changes. But most indicated a desire for more detailed information to help them sort through the often conflicting reports.

Shift happens
Plant hardiness zones have been shifting based on temperature fluctuations ever since Boston’s Arnold Arboretum printed the first map in 1937 using temperatures documented from 1895-1935. Henry T. Skinner created the government’s first official hardiness map in 1960 when he was director of the U.S. National Arboretum in Washington, D.C.; he adjusted it again in 1965.

The next update came in 1990 and added Canada and Mexico, along with new plants and weather changes. Many of the hardiness zone plant classifications lost some landscape plants and added new ones. Interestingly, the new Arbor Day map shows zone patterns much like the original 1960 USDA map, which used data from the warmer temperatures recorded in the 50s. “Temperatures cycle every 20 years from warm to cold and back again,” explains Avent, “and the maps based on average low temperatures reflect those cycles.” In fact, he goes a step further and says that the warming trend we see now will eventually give way to a colder one.

Controversy surrounds the USDA’s decision to use 30 years of low temperature data from the National Oceanic and Atmospheric Administration instead of the 13- and 15-year spans used for previous updates. Because the National Arbor Day map used 15 years from the same source, Nelson says the Arbor Day zones more accurately reflect the warming trend seen in the most recent 15 years. “Frankly, I’m puzzled by the USDA’s decision to use 30 years of data for their new map,” he says. But he’s certain that even with 30 years’ worth of data, there will be noticeable zone changes.

Kim Kaplan, spokeswoman for the Agricultural Research Service, defends the decision to use 30 years of data, saying it’s better science. “The longer time period balances the difference between weather and climate,” she says. “The new zone map will be interactive and will reflect elevation, slope and wind exposure – all factors making it more precise than before.”

Other features, such as GPS-compatibility, will show details down to heat islands (isolated higher-temperature zones, usually found in dense urban areas) that haven’t been featured previously. Eventually, the agency hopes to zero in on individual ZIP codes. Kaplan says that the delay in the map’s release is attributed to it being “a more complex, computer-savvy model that took longer to develop than we expected.” She reiterates what most landscapers say – that the map is one of many tools used to determine the best plants for specific areas.

Tara Dillard, a professional gardener and horticultural author from Atlanta is extremely interested in what USDA’s new map will show. Like most landscapers surveyed, she’s noticed some warmer-zone plants thriving in her area that never did before and some native ones that are not doing so well.

This is a well-documented phenomenon (see sidebars on Pages 44 & 45) noticed by those in the green business. “I don’t think there’s any question that it’s getting warmer,” Avent says. “We can grow plants now that we couldn’t in the ’80s.” Avent says what’s really changed is how politicized everything related to climate and weather has become. “Everybody has an agenda, especially the mainstream media. The key for landscapers is to cut through the agenda and use the available science to make better decisions.” According to Avent and others on the USDA’s steering committee, the new map is worth the wait. “Landscapers will absolutely be blown away by the scope of detailed information in this map,” he says.

The verdict is still out on the maps but the message is clear. The more scientific data you have, the better armed you are to create sustainable landscapes for your clients.

Managing mother nature
Erratic weather may lure landscapers into risky business moves. But those who observe the trends with a critical eye can focus on opportunities and continue making smart decisions.

When the National Arbor Day Foundation released its latest cold hardiness map in 2006, it created a stir by showing much of the country had warmed (based on average lows) since 1990. The mainstream media heralded longer growing seasons combined with expanded plant selection as a boon for landscapers. But is it?

While they acknowledge there are some opportunities to try new plants and perform more work, landscapers and plant specialists urged conservatism and caution. Warmer average lows, they noted, don’t rule out occasional extreme lows. All it takes is one cold snap to wreck a garden planted for a warmer zone, points out David Ellis, director of communications for the American Horticultural Society.

“Plants don’t read cold hardiness maps,” says Scott Jamieson, chief executive of The Care of Trees, a company with branches in several major U.S. cities. Plants don’t care about average temperatures; “if it gets to 26 below, it’s toast,” he warns clients about some of their choices. Even if data suggests temperatures are warming, Jamieson says he still advises clients to stick with plants that have existed in their area a long time.

A Total Landscape Care reader survey reflects Jamieson’s attitude. While 87.1 percent of respondents agreed with the temperature trend the Arbor Day map shows for their area, only 14.7 percent said they’re steering clients toward plants that didn’t grow well in their locations in the past.

Some of those surveyed for said average temperatures either weren’t changing in their area (24.9 percent) or the changes weren’t affecting their business (38.1 percent). “We haven’t looked at the climate and said, ‘We’ve got to change the way we do business,'” says Phil Steinhauer, co-founder of Designscapes Colorado in Denver.

However, 65 percent of surveyed readers said rapid temperature fluctuations have become more common in their areas during the past five years, and 68 percent of those say this trend has affected their business. Likewise, 64 percent have noted more erratic weather patterns compared to five years ago, and 75 percent of them say it has affected their business.

For landscapers being affected by warmer average temperatures, deciding whether to use less-cold-hardy plants isn’t the only dilemma. Plants that traditionally grew well in their respective zones are now struggling because of changes in average temperatures, say more than a quarter of survey respondents. And because higher average low temperatures in many areas are evidenced by earlier springs and later falls, extended seasons are taking a toll on some landscapers’ maintenance schedules and forcing them to weigh the risks and benefits of shifting planting times.

Landscapers, botanists and horticulturalists say many of the weather-related problems they’ve experienced during the past five to seven years aren’t reflected in maps based on average low temperatures. Instead, they cite dramatic temperature swings, inconsistent seasons, less gradual fall-to-winter and winter-to-spring transitions and drought as the real culprits.

Jim Martin, president of the Professional Landcare Network, which formed in 2005 from the merger of the Associated Landscape Contractors of America and the Professional Lawn Care Association of America, says the gist of comments from landscapers across the country has been the same: Weather patterns have become more severe and erratic. “What was predictable before has become radically less predictable,” says Martin, who has been in the landscaping business 30 years as owner of James Martin Associates in Vernon Hills, Illinois.

Picking plants and waiving warranties
Mainstream media reports of crepe myrtles in Philadelphia, magnolias in Manhattan and palm trees in Knoxville, Tennessee, are accurate. But they seldom point out these plants could be living on borrowed time. When the U.S. Department of Agriculture publishes its new map, similar articles are likely to hit newsstands, prompting customers in some areas to ask for warmer-zone plants.

Joanne Kostecky, owner of Joanne Kostecky Garden Design in Allentown, Pennsylvania, and immediate past president of the American Nursery & Landscape Association, says some landscaping companies will jump on the bandwagon and give clients what they want, but she thinks doing so is shortsighted and irresponsible. Planting with transition-zone plants is more suited for gardeners who understand the risks, Kostecky says. “I’m not going to follow that lead,” she says. “Your average homeowner looks to you for professional advice. It’s up to the landscaper to steer them toward plant materials that are hardy and sustainable.”

Martin says it’s ethical to plant something unproven if a client insists after you’ve explained the risks. “Tell them,” he says, “this is a marginally successful plant here. You might get two, five or 10 years out of it.” Martin’s company planted some marginally hardy plants in the past, but, with the exception of microclimates, has returned to the 1990 USDA hardiness zone guidelines.

Jamieson says it’s important to make sure clients understand that how a certain plant grows in one region isn’t necessarily how it will grow in another. A Southern magnolia, for instance, might survive in Chicago but it will likely never attain the grandeur of those in Southern states.

Not offering warranties for marginal plants and others that aren’t thriving under recent weather conditions is a good way to protect your profits and make clients think twice about insisting on inappropriate plants. Mariani Landscape in Lake Bluff, Illinois, is waiving warranties for roses, azaleas and rhododendron, says client representative Ed Furner. During the past six years, some winters have been exceptionally warm in Lake Bluff, but others have been colder than usual, he says. Extended periods of below-zero temperatures have cost the company thousands of dollars in plant-replacement expenses and are threatening the survival of even tried-and-true species. As a solution, the firm is considering treating the area as a colder, rather than warmer, zone.

Kostecky is taking a similar stance. In addition to buying hardy plants suited for Zone 6, where her company is located according to the 1990 USDA map, she scours nurseries and botanic gardens in colder zones where plants are used to weather extremes.

At the same time, experts agree that closing the door to less-cold-hardy plants would be a mistake. Kostecky is keeping her eye on three warmer-zone plants that have been thriving in her area. “Of course I’ll be open to using them in my business if they continue to do well,” she says.

Furner says it’s up to landscapers to test new plant material with an eye toward extending plant lists. His company has a nursery and experiments with plants there. As plants from warmer regions have proven themselves, Steinhauer has been growing a lot of plants he ruled out in the past. “The nurseries here in Colorado are pushing the zone limit to the warmer, more tolerant things,” he says.

Ellis with the American Horticultural Society says every region needs to look at what thrives, what doesn’t and adjust accordingly. He points out that several hardiness Zone 8-11 plants have been thriving for years at the organization’s headquarters in Alexandria, Virginia, which is near the border between Zones 6 and 7 of the 1990 USDA map and in Zone 7 of the Arbor Day map.

It’s a trend that 20.4 percent of surveyed respondents support, saying they’ve noticed plants that didn’t grow well in their area in the past thriving now due to differences in average temperatures. (For more on which plants are staking new ground, see sidebar on Page 44.)

Nipped in the bud
Much of the debate on climate change has centered on overall changes in average temperatures. But those averages don’t paint a complete picture for every area. “A few years ago we had an average January,” relates Andrew Blanchford, president of Blanchford Landscape Contractors in Bozeman, Montana. “The first two weeks were mostly 10 degrees to 30 degrees below zero and the second two weeks were in the 50s and 60s. That may be average, but it’s not normal. Temperature swings like that hurt plants.” Blanchford says he’s seen temperature fluctuations the entire 15 years he’s been in the area, but they’ve been more frequent and extreme in the past five years.

In January, Portland, Maine, experienced a few days of 70-degree temperatures, an event unheard of in recent memory, says Ted Carter, owner of Carter Design Group. Then temperatures plunged and plants already suffering due to warmer summer temperatures were further stressed. “It’s the weather extremes that are really difficult to deal with,” Carter says.

Martin says transitions from fall to winter and winter to spring have also changed in some areas, becoming periods of temperature spikes and troughs. Plants are leafing earlier in his region because of earlier warm temperatures, but the area also had an uncharacteristic April snowstorm this year.

Gradual cooling is particularly important in fall because it’s necessary for plants to enter dormancy and for their buds to harden in preparation for winter.

Blanchford says his area has had 75- to 80-degree temperatures in mid-October followed suddenly by freezing ones. When this happens, buds – which are responsible for the next year’s growth – are still soft and can be damaged. Sometimes an entire plant dies, but more often a portion of a tree is lost or a plant doesn’t flower in the spring, Blanchford says. Buds are often nipped in the upper portions of trees because residual ground heat keeps the lower portions warmer. In winter, single-day temperature swings of 50 to 60 degrees are harming even plants that have hardened, Blanchford says.

To reduce plant damage caused by extreme temperature swings, Blanchford says his company installs tried-and-true plants, amends soils and provides proper care to minimize plant stress. He and his employees also educate clients about how temperature swings affect plants. “We tend to tell our clients that this is Montana and the weather is variable and we do not control nature,” he says. “Most of our clients understand.”

Carter says unreliable temperatures have led him to steer clients toward plants and trees already thriving in his area as well as those that can endure an “unstable climate.”

Longer working seasons and greater risks
Until five years ago, Blanchford says his company’s working season reliably ended on October 31. Since then, however, his crews have been working until Thanksgiving or even Christmas, and the work season is starting in March rather than April. “We’ve added a month, probably, on either end of the season,” Blanchford says.

Jeff Korhan, president of Treemendous Landscape Company in Plainfield, Illinois, says his season also consistently ended by November prior to 2001. With the exception of last year, his company has worked until December since then.

Longer warm seasons can tempt landscapers into making bad business decisions, Martin says. The possibility of closing out a year with higher-than-expected profits because of two or three extra jobs squeezed into an extended season can be difficult to resist. As can the desire to please clients who come in late in the season and want their projects completed before the end of the year.

Late-season plantings can turn out fine, Martin notes. Then again, a cold snap could kill a large number of plants you’ll have to replace under warranty in the spring. “Those are the kinds of business choices facing the industry,” Martin says. “It can be very risky – more of a Russian roulette.”

Martin says his company was burned on late-season plantings 10 years ago, and now it won’t install evergreens after October 15. Every market is different, he says, but typically plants need at least a month to set their roots, absorb moisture, acclimate and harden off before they’re strong enough to withstand winter. Generally, clients are happier, even if they have to wait, than they are if they have losses, Martin says. Long-term profits are better off, too.

Unpredictable growing seasons also can affect maintenance-generated revenue. Martin says his company, like many, writes annual maintenance contracts on the assumption crews will take care of clients’ properties for a certain number of weeks. Revenue stays the same even if that number increases. Martin says the season began early in his area this year, and grass was growing in late August like it was still springtime. He plans to add a clause to renewal contracts allowing additional charges based on the number of mowings his company performs.

Long term, Furner says he thinks maintenance is the area where landscapers in his region will see the most losses due to weather changes. People are using more native plants because they handle temperature fluctuations better than marginal species, and the native plants require less maintenance over time.

But Korhan says hardscape maintenance can take the place of greenscape care. Homeowners have fewer lawn areas and more hardscapes than in the past, Korhan says, yet his maintenance crews spend the same amount of time at most properties. Instead of pulling weeds and cutting grass, they clean hardscape surfaces, scrub water features and blow debris off patios and decks.

Xeriscaping and dust bowl desperation
Where plants that traditionally grew well are struggling, a combination of drought and excessive heat typically plague them. For example, woodland trees such as dogwoods, redbuds and serviceberries are suffering in North Carolina because of rising heat and lack of water, says Stefan Bloodworth, a botanist at the Sarah P. Duke Gardens in Durham and owner of Pine Hollow Landscapes. Bloodworth says it’s not the heat itself that eventually kills the trees, but secondary infestations that occur because the plants are under stress. Pine trees, for instance, are attacked by pine beetles. Summers, especially this year’s, are warmer and drier in his area. “We’re having a horrible, horrible drought,” he said in August as the majority of the Southeast sweltered in record-high temperatures accompanied by record-low precipitation levels.

Of the 28.8 percent of survey respondents who said plants that grew well in the past are struggling because of changes in average temperatures, 64 percent said they are watering more or better managing irrigation in order to maintain them in existing landscapes. Seventy percent of respondents were experiencing less-than-average precipitation, and 68 percent of those say this is affecting their business. (See Page 45 for more about particular plants that are no longer thriving.)

Much of the already-dry West has experienced below-average precipitation in recent years.
Central California is in the midst of an “unprecedented drought,” according to one survey responder. Blanchford says Montana is emerging from a six- or seven-year drought, and Steinhaur says drought has scorched Colorado for the past three or four years. Scott McMahon, curator of the cactus collection at the Desert Botanical Garden in Phoenix, says a region-wide drought is in its sixth year, and plants are dying in the desert and at the gardens.

Water-supply systems in all these areas depend on the melting of mountain snowpacks in the spring to supplement rainfall. Less snow – either because it falls as rain or because winter precipitation overall is below average – is straining many water systems, leading to watering restrictions that tax plants already dealing with drought conditions. The situation has resulted in landscapes with low-water-requiring plants. Ellen Zagory, director of horticulture for the UC Davis Arboretum, says the plant palette in California has changed over the past 10 years as people have responded to the need to conserve water.

Some regions of the country that haven’t faced extended watering restrictions in the past are now. As a result, interest in drought-resistant plants and xeriscaping has extended beyond the West. In fact, 61 percent of readers surveyed for this story reported they are involved in xeriscaping. “I think the biggest impact on my business comes from the water restrictions imposed here in Atlanta,” says garden designer and horticultural author Tara Dillard, who anticipates extended mandatory restrictions. In Durham, North Carolina, where watering has also been restricted in recent years, Bloodworth says succulents such as agave, yucca and cacti are now able to survive winters. He recommends them because of their low water requirements.

In response to drought and a shrinking snowpack, Blanchford says his company has begun installing weather-based controllers for its irrigation systems and is creating a niche for itself as a water-conserving firm. The controllers monitor rainfall, evaporation, sun exposure and wind and take into account what types of plants are being watered in multiple zones.

Ellis with the American Horticultural Society says landscapers should be keeping a close eye on plants and replacing those not tolerant to heat with species that are. Several survey responders said they are taking that approach instead of trying to maintain heat- and drought-stressed plants. Ellis says it’s not something new. “In the past the climate has
gotten warmer and cooler and plants have migrated north and south in response,” he says.

At a time when so much information about climate trends and their effects on plants is in the news, Korhan says it’s easy for clients to misconstrue data or overreact. “It’s up to you to understand what’s going on so you can give the right answers to your clients,” he says. Korhan hopes to educate clients through a blog he updates at least once a week, often responding to information in the media.

“Are things changing? Yes,” he says. “But that’s not necessarily bad. You have to make the right adjustments. A plant or two might die despite your best efforts. Just as plants are responding to changes, people have to respond, too.”

To read about how warmer temperatures are affecting pests, invasive species and urban heat domes, go to

Plants thriving
Cactus in North Carolina

Succulents such as agave, yucca, cacti, simper vivum and sedum, along with plants native to the coastal plain, are now able to survive the winter in Durham, North Carolina, says Stefan Bloodworth, a botanist at Duke Gardens.

Zones 8-10 gardenia growing in Atlanta
Plants like todosporum, dwarf Indian hawthorn and gardenia jasminoides radicans were once considered tender shrubs in Atlanta and usually would not make it through a season, says Tara Dillard, a garden designer and horticultural author. Now they’re growing well year round, she says.

Drought-tolerant plants transform California landscapes
Drought-tolerant plants have become staples in California during the past 10 years, says Ellen Zagory, director of horticulture for the UC Davis Arboretum. For example, salvia greggii and the hybrid salvia x jamensis – hardy plants native to west Texas and north Mexico – are used as ornamentals in almost every landscape now.

Disappearing dogwoods
Largely because of its abundance in North Carolina, the dogwood is the state’s official flower. Today, the tree is in danger of vanishing from North Carolina’s borders because it can’t survive extended periods of heat and drought, says Stefan Bloodworth, curator of the Blomquist Garden of Native Plants at Duke Gardens in Durham.

Shrouded succulents
For the past three or four years, Scott McMahon, curator of the cactus collection at the Desert Botanical Garden in Phoenix, has been draping cacti with shade cloths and protecting them with temporary shelters from late May until October or November. The plants were turning yellow, then white and then dying because the sun was burning the chlorophyll in their cells, killing tissue.

Faltering evergreens
Heat stress is affecting evergreens in the Southeast and mid-Atlantic, says David Ellis, director of communications for the American Horticultural Society. Pines and conifers, such as Colorado blue spruce and White pines, in particular are struggling.

Tips for dealing with erratic weather

  • If extreme temperature fluctuations are damaging plants in your area, take note of the species least affected and use them more.
  • Set a cut-off date for fall plantings. Keep in mind plants need at least a month to set roots, acclimate and harden off before winter.
  • Rewrite annual maintenance contracts to allow for extra payments if the growing season is longer than usual.
  • Offer efficient irrigation systems if your area is experiencing drier-than-usual conditions or water shortages. Weather-station systems that monitor rainfall, evaporation, sun exposure and wind and take into account what types of plants are being watered have become more affordable.
  • Offer hardscape maintenance services. This can be a good way to prevent loss of maintenance revenue due to shrinking lawns and use of drought-tolerant plants.

Handling the next warming trend

  • When planting something marginal, research cultivars or work with a nursery that does. New varieties more resistant to heat, cold and pests, etc., are always being introduced.
  • If plants native to your area are suffering from heat stress, use cultivars from more southern climates.
  • Select plants and trees with wide temperature tolerances. If you’re in Zone 4, for example, choose a plant recommended for Zones 3-5.
  • If a client insists on a plant you don’t think will be successful, waive the warranty.
  • Monitor warmer-zone plants and consider using them if they prove themselves over time.
  • Replace heat- and drought-stressed plants with species thriving under current conditions.

Source: Several interviewed landscapers

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