In this section, we’ve summarized some of the problems — and blessings—that El Niño bestowed upon gardeners this year. We’ve included a sneak peek at what to expect from La Niña, as well as tips on how to cope with or minimize the effects of severe weather. We’ve also put together a short history of some time-honored practices and tools gardeners have used to predict the weather.

INDEX
El Niño and La Niña
What’s El Niño?
Folk Predictions
Beating the Heat

El Niño and La Niña
by Mark C. Mollan

El Niño left its mark on North America this year with some of the worst weather ever recorded. Eastern Canada and New England were pounded by severe ice storms. Many parts of California, wracked by seemingly never-ending rains, received more than two-and-a-half times the normal precipitation. Florida set records for rainfall this winter and early spring, followed by the driest summer in the state’s history. Devastating tornadoes cut a 100-mile-long swath across central Florida, followed quickly by wildfires that spread from Lake Okeechobee north to Daytona. Texas and Oklahoma experienced a severe drought, including 30-plus days of temperatures in excess of 100 degrees.

Gardeners suffered along with everyone else. “All the intense rain we received this spring depleted the oxygen in the soil, so many plants were lost or damaged due to fungal diseases,” says Los Angeles resident Karen Dardick, a regular contributor to The American Gardener. “Also because of the unusually cool weather in California due to the rains this spring, our growing season was six weeks late. My tomatoes didn’t come in until mid-August.”

Scott Aker, horticulturist at the U.S. National Arboretum in Washington, D.C., says “the constant rains in D.C. triggered an increase in foliar diseases. This spring and summer’s drought has favored stress-related disorders, especially Botryosphaeria canker.” On the other hand, he points out that the unusually warm weather caused everything to bloom two to three weeks earlier than normal in most of the Northeast.

Like Florida, eastern Missouri also experienced a wetter and warmer-than-usual spring, followed by a somewhat drier, hotter summer. “With this weather, the vines are growing incredibly well this year, but sweet gum trees all over the St. Louis area are cracking and breaking,” says Christine Fuerhoff, an AHS member who lives in Saint Charles, Missouri. Chip Tynan of the Missouri Botanical Garden explains that this damage was caused by “a bumper crop of fruits that weighed down the trees every time it rained.” The warmer winter in the Northeast proved a boon for farmers and orchard managers. Chris Blanchard of Beech Hill Farm in Mount Desert, Maine, a supplier of organic produce, said the farm prospered as a result of the abnormally warm weather. “We were very lucky only losing one main branch of a tree in our 150-year-old orchard in the ice storms. Aside from that, spring was beautiful. We were able to head into the season early with a wide variety of produce.”

After suffering through the 1990s with everything from cicadas to record snowfalls, a deep freeze, tornado hits, and devastating floods, Brent Wearren, a 19-year tree nursery veteran and partner of Waterford Valley Nursery and Wearren and Son Nursery of Taylorsville, Kentucky, finally enjoyed a disaster-free year. “All we have been getting is a constant, steady rain, so for us it has been a great growing year.”

Even California residents such as Dardick could see a bright side to El Niño. “All the rain leached out the heavily salt-laden soil that stems from over-fertilization and other gardening-related activities, which can eventually be harmful to plants.” Increased fungal activity even had a beneficial side, as it took a toll on mites that have been wreaking havoc on honey bee populations in the West for the past few years. As a result of El Niño, bee populations were expected to increase 40 percent from 1997.

Preparing for La Niña
El Niño may be behind us now, but what can gardeners expect from the weather patterns associated with the La Niña season? “Most of our weather models are showing that La Niña is expected to remain a factor in North American weather until March,” says Stephanie Kenitzer, public relations officer with the National Weather Service. “The dryness the American Southwest experienced throughout the late spring and summer is forecast to continue into the fall and spread east to the Atlantic later in the winter, perhaps as far north as Virginia. The northern tier of the country from the Pacific Northwest to the Great Lakes region should experience wetter-than-normal conditions. And Atlantic states will see much-enhanced chances of hurricane activity this late fall and winter.”

Coping with Extreme Weather
It is often impossible to prevent problems caused by severe weather—flooding, high winds, drought, ice storms—but good gardening practices and plant selection can help minimize the damage. “If you use plants that are found growing naturally in your area,” says Aker, “they are adapted to the region’s extremes of climate and will survive better than exotics, even in abnormal weather conditions.” (For more detailed information on selecting plants appropriate to your area, see the article on provenance on pages 45 to 52.) Understanding microclimates within your garden also helps in choosing appropriate sites for plants. Plants that are not heat tolerant should be placed where they get morning sun, but are shaded in the afternoon when the sun is most intense. Plants that are barely hardy in your area should be planted near a south-facing wall and protected from winter winds. Avoid planting tender plants in low areas of the garden, where cold air tends to pool. A good discussion of microclimates in the garden can be found in Jane Taylor’s Weather in the Garden (see Resources, page 13).

The best way to combat problems created by short-term flooding is by steadily amending soil with organic matter and avoiding activities that lead to soil compaction. “Plants need pockets of air in the soil as a source of oxygen for their roots, so amending is very important,” says Dardick. “It cuts down on the fungal activity that can occur when soil is waterlogged for a period.”

To lessen potential damage from ice storms, thunderstorms, and hurricanes, trim weaker limbs from your trees and make sure there are air channels through the canopy to reduce the likelihood of blowdowns.

If you have plants in your garden that just drag along from year to year or require constant infusions of water, fertilizers, or pesticides to stay alive, you should consider replacing them with something better adapted to the site. “If you do lose plants to extreme weather conditions,” counsels Aker, “don’t think of it as a loss, but as an opportunity to make your garden stronger.”

Mark C. Mollan is communications assistant at AHS.

What’s El Niño?
by Mark C. Mollan

Each year in late December, an ocean current off the coast of Peru draws warm, nutrient-deficient water southward, forcing fish to seek cooler waters. Local fishermen either draw in their nets and head home for a brief holiday respite or sail further afield in search of the teeming schools. Because of the Yuletide timing of this warm water spell, the fishermen call the annual phenomenon El Niño, which means “the little boy,” a reference to the Christ child.

Every two to seven years, this rush of warm currents is unusually extended, reversing the flow of undercurrents and thus preventing the normal upwelling of cold water further off the coast. As early as the 1500s, local farmers understood the connection between the arrival of these warmer waters and the subsequent increased precipitation that brought bountiful harvests and gave birth to gardens in normally barren lands. In appreciation, Spanish colonial farmers called the phenomenon “anos de abundancia,” or years of abundance. Sometimes, following the warm spell, a cool pocket of water takes its place in the equatorial waters of the eastern Pacific. Today, meteorologists refer to the cycle of warm water as El Niño—Southern Oscillation (ENSO), or El Niño for short. La Niña—also known as El Viejo, or “the cold tongue”—is the catch phrase for the cold cycle.

The origin of the name is much easier to pinpoint than the cause of El Niño. According to Stephanie Kenitzer of the National Weather Service, “El Niño and La Niña are complex interactions between the ocean and the atmosphere. Changes in the ocean affect the atmosphere and climate patterns around the globe. In turn, changes in the atmosphere affect the ocean temperatures and currents.”

Mark C. Mollan is communications assistant at AHS.

Folk Predictions
by Christina M. Scott

Weather folklore has been associated with farming and gardening since well before humans began recording their history. Weather played an integral role in the daily lives of our ancestors as they made the transition from hunting and gathering to farming. Back then, people didn’t have access to television weather forecasters equipped with space-age meteorological monitoring equipment. They relied on seasonal patterns and the accumulated folk wisdom passed down from generation to generation. Because a knowledge of weather was so important—especially to farmers, whose lives depended on their ability to predict the weather and plant crops accordingly—a large body of folklore developed over the centuries. Farmers and gardeners spend much of their time outdoors, so much of the folklore revolved around cultivated and wild plants and the organisms that feed on them. Some folklore is strongly rooted in keen observation. The Ozark folk saying that a tree showing the bottom of its leaves is a sign of rain shows a recognition of the windiness that often precedes a storm front. Other lore is harder to link to scientific processes, including the old belief that if the first snow sticks to the trees there will be a bountiful harvest.

As meteorological technology has improved, much of this folklore has moved into the realm of fun rather than as serious indicators of Mother Nature’s intentions. According to the Oxford Dictionary of Plant Lore, compiled by Roy Vickery, one Englishman relates that during his boyhood in the 1930s, pennywort (Umbilicus rupestris) was a relied-upon gauge of dry weather. Taking two large leaves, he and his friends would spit on them, press them together, and throw them into the air. If the leaves were still pressed together when they hit the ground, rain was on its way; if they separated before reaching the ground, dry weather could be expected. Asked if the practice really worked, he replied, “Being Devon, it usually rained, but, on reflection, I incline to the view that the liberality of spittle was the main determinant of the outcome. But this, of course, was the main fun involved!”

Phenology
A more scientific offshoot of folklore is phenology, the study of the response of living organisms to seasonal and climatic changes. Cyclic events are monitored for specific plants and animals from year to year so that trends can be analyzed and used as the basis for farming or gardening practices. For example, the dates of first leaf, first flowers, and full flowering might be recorded for a specific plant. Phenology—derived from Greek roots that translate literally to “science of appearances”—has been used by a wide variety of cultures over the centuries. Planting times for crops were often based upon characteristics of wild plants. According to the Horticulture Gardener’s Desk Reference, by Anne Halpin, Native Americans in New England planted corn when oak leaves were the size of the ears of mice.

Horticulturists who study the phenology of plants in their local climate can often find patterns in the relationships between plants, insects, and the weather. In this way, phenology serves the same purpose as integrated pest management: By anticipating the arrival of pests, gardeners can control infestations before they get out of hand, thus reducing or eliminating the need to use pesticides. Scientists have been particularly interested in phenology in recent years because of the threat of global warming. Understanding how and when plants and animals respond to seasonal changes may provide clues to their response to major climatic changes such as global warming. In addition to folklore, other means of predicting weather have had popular appeal over the centuries. Planting according to lunar cycles has been practiced by the Chinese since at least 200 b.c. and still has adherents worldwide. The theory behind planting by lunar cycles is that the moon affects the circulation of plant fluids as much as it influences the level of tides.

Almanacs
In the late 18th and early 19th centuries, almanacs of weather predictions and advice for farmers became popular. Among the most enduring of these was The Farmer’s Almanac—“Old” wasn’t officially added until 1848—first published by Robert B. Thomas in 1792. Today, the almanac contains information on such things as food and fashion trends, hot collectibles, and just good old-fashioned trivia, but its biggest selling point is still its legendary annual weather forecast. The almanac’s current authors still base their predictions on a secret weather forecasting formula that Thomas developed by analyzing natural cycles, enhanced now by modern calculations of solar activity. This original formula—which the almanac’s publishers claim has maintained an accuracy rate of about 80 percent for more than 200 years—is safely tucked away in a black tin box at the almanac offices in Dublin, New Hampshire.

The almanac divides the country into 16 regions in order to provide a detailed forecast for each area, but it also gives a general nationwide weather forecast. So what should we expect for 1999? The almanac forecasts colder-than-normal winter temperatures for much of the nation as well as above-normal snowfall in the Northeast and Northwest. Spring is also expected to be cooler than usual, except in the Pacific Northwest. The summer months, according to the almanac, should be closer to normal for most of the country, although it warns of above-normal hurricane activity, particularly in the first half of September. Finally, fall is expected to bring warmer conditions to the central United States but near normal temperatures elsewhere.

Although we now have advanced technical methods of finding out the weather, almanacs, folklore, lunar cycles, and phenology are such an integral part of our horticultural history that they will surely never lose their place in the gardener’s bag of weather-forecasting tricks.

Christina M. Scott is assistant editor of The American Gardener.

Beating the Heat
by David J. Ellis

If the global warming doomsayers are to be believed—and evidence is mounting to support their case—gardeners in North America and elsewhere are going to have to learn to cope with hotter summers, bitter winters, and drought. Even that bastion of gardening traditions, England, was hit with unseasonably warm weather and drought this year, and plants usually considered reliable there perished from the heat. In our own gardens, we’ve seen normally tough annuals wither away and drooping leaves on both native and exotic woody plants.

According to the National Oceanic and Atmospheric Adminstration, this past August was the eighth consecutive month to set a record for average high worldwide temperature. Six of the 10 hottest years on record have come in this decade and it appears likely 1998 will surpass 1995 as the warmest year since weather records have been kept. With most forecasters predicting a continuation of this trend, gardeners need to be prepared to take steps to minimize damage and loss of plants.

Taking the Heat
As he traveled the country this year lecturing about the AHS Plant Heat-Zone map, AHS’s President Emeritus H. Marc Cathey had a perfect opportunity to see which plants were thriving in this summer’s heat and which ones weren’t. “The annuals were having a terrible time,” he says. “Many of them were infested with spider mites, which thrive under hot, dry conditions.”

Annuals and newly planted perennials often suffer from heat, because they don’t have well-established root systems, but Cathey says what was particularly remarkable about this summer was “plants that have been in the ground for more than 20 years were dying.” Among native plants that were particularly hard hit were dogwoods and redbuds, which in gardens are often planted in full sun rather than in the full or part shade that characterizes their native habitat. On the other hand, Cathey observed that many tropical, subtropical, and Mediterranean plants seemed to thrive this past summer. “In Shreveport, Louisiana, bougainvillea, crape myrtles, and crotons were doing very well,” he notes.

Research
Plant breeders have historically spent more time trying to develop plants with increased cold hardiness than they have working on heat tolerance, although continued evidence for global warming is likely to affect that dynamic. But Cathey points out that gardeners need to be alert to the availability of some heat-tolerant plants. These range from lilacs—known as the Descanso hybrids—with reduced chilling requirements and heat tolerance, to lettuces bred to not set seed as quickly in hot weather, and heat-tolerant tomatoes such as ‘Sunmaster’ that will set fruit even at temperatures over 90 degrees. Several plant breeders, including Alabamans Tom Dodd Jr. and Eugene Aromi, have successfully taken on the challenge of producing heat-tolerant azaleas for the Deep South.

Even if you can’t find heat-tolerant selections of the particular plant you want to grow, choosing plants appropriate to your climate will be easier this coming spring, as more nurseries will be including heat-zone codes on their plant labels.

Choosing Plants Wisely
Re-evaluate the plant choices in your garden. Think back to last summer. Which plants suffered through the hot weather or required inordinate amounts of watering to survive? Look for more heat-tolerant plants to replace them with this spring. Plants native to your region or exotic plants from areas with similar climates to yours are the best bets. Also look for new cultivars or selections bred specifically for heat tolerance.

Developing Sound Cultural Practices
“Our watering and fertilizing practices need to be improved. We have been coddling our plants too much,” says Cathey.

Once established, plants shouldn’t have to be coddled. Encourage the development of deep and extensive root systems by watering new plants deeply two or three times a week at first, then slowly reducing frequency as they start putting out new growth. After one full growing season, most woody plants and herbaceous perennials shouldn’t require supplemental watering except during an extended drought. Mulch with shredded leaves or bark to keep down weeds and reduce moisture loss.

Don’t addict your plants to excessive rates of chemical fertilizers. Encourage plants to spread their feeder roots deep and wide into the soil in search of nutrients and beneficial associations with mycorrhizal fungi. Feed them a couple of times during the growing season with a balanced combination of nutrients in organic fertilizers such as blood meal, seaweed, and compost.

Avoid plant-stressing activities during the hottest months of the year. Do your pruning, transplanting, dividing, and other such tasks in spring or fall to prevent additional stresses on your plants. This winter and spring, keep your eyes out for plants labeled with the new AHS Plant Heat-Zone codes and select plants appropriate for both your hardiness and heat zones.

David J. Ellis is editor of The American Gardener.