Article originally appeared in the Spring 2004 newsletter
Copyright 2005 by Adam Levine
Wet weather, in its liquid or frozen forms, is easy to define, simple to measure: inches of rain in the gauge, feet of snow on the sidewalk. Wet is tangible, in the squish of soggy shoes, the shower of drops from a rain-soaked dog, the drip-drip of a leaky roof, an overflowing sump in the basement. Wet can also be dramatic, powerful, even violent. Some of our most vivid garden memories feature the havoc wrought by wet weather. Plants are flattened, beds washed out, limbs snapped, trees toppled. Landscapes are redesigned in a flash, sans client consultation.
The flip side of wet, for gardeners and farmers and anyone trying to draw life from the earth, is drought. A drought can kill plants and crops and people as well or even better than wet, but it acts more slowly, insidiously. Those who live in desert areas understand that human, animal and vegetable life survive there only with the aid of artificial irrigation, whether from a goatskin or an oasis or the lake behind a 500-foot-high dam. Anyone in Arizona (perhaps short for "arid zone"?) who has the audacity to nurture a lush lawn and garden also knows that the moisture needed for such miscreations comes not from the sky but out of a faucet, courtesy of the Army Corps of Engineers.
Dry weather is part of the definition of a desert, but in temperate areas like the Northeastern
The History of Philadelphia's Watersheds and Sewers
Compiled by Adam Levine
Philadelphia Water Department
United States, where we expect regular precipitation, drought always takes us by surprise. Long stretches of any single type of weather, wet or dry, is an anomaly here, so it always seems possible, no matter how many months into a drought we may be, that the next day will bring a change. If that eternal optimist, Little Orphan Annie, had been a gardener during a drought, she might have sung something like, "The raindrops will fall to-MOR-row!"
It is no mistake that the ever-popular Annie voiced a longing for sunshine. As gardeners, our longing for rain during dry spells casts us as cultural outsiders. For most people, increasingly divorced from the natural world and its needs, dry days are desirable, even a hundred of them in a row--as long as no restrictions are put on watering the lawn or washing the car. Even gardeners will admit that there are definite advantages to reasonable stretches of dry weather. All forms of travel are safer under clear skies with unlimited visibility. Outdoor plans don't need to be altered at the last minute. The barbecue doesn't have to be dragged into the garage, vacations aren't spoiled. Human life, at least, can proceed more smoothly when we know that the sun will come out tomorrow. But for those of us who love plants, drought is clearly a case where too much of a good thing is bad.
The Web site of the Pennsylvania Department of Environmental Protection (PA-DEP), which declares drought emergencies for the state, bases its decisions on stream flows, precipitation, reservoir storage levels, groundwater elevations, and the Palmer Drought Severity Index (a soil moisture calculation made by the National Weather Service). Needless to say, when we are in a drought, those measures are all heading downward. This points out one of the difficulties measuring a phenomenon that could be considered less than nothing. Drought, after all, is no more than a cumulative lack of wet.
According to Elizabeth Culotta, co-author of Nature on the Rampage, drought "has more than 150 different meanings, assigned by meteorologists, farmers, economists, hydrologists, and others. It's not simply scarce rainfall, since the amount of moisture that yields a bumper crop in North Dakota might bring a drought in Great Britain. Many geographers use a simpler rule of thumb: A drought occurs when there's much less moisture than people expect and need."
For an alcoholic gardener, one day without a drink could be considered a drought, Most of us are more tolerant of dry weather, but asking a dozen gardeners for their definition of drought is likely to elicit as many responses. Needs and expectations vary, and depend on whether a particular gardener is willing to accept the effects of drought as part of the natural cycle of life, or needs to fight it with water, water and more water. Another variable is the variability of weather itself. While a region, state or county might be under drought restrictions, based on assessments like those described above for Pennsylvania, actual rainfall always varies from place to place. What might be three months without a trace of rain for one gardener could be a dry but tolerable stretch for another only a few miles away. It all depends where those "scattered thunderstorms," which litter the summertime forecasts like so many losing lottery tickets, happen to drop their rain.
It may not come as a surprise to learn that droughts are nearly impossible to predict in the United States and other non-tropical regions. According to the Web site of the National Drought Mitigation Center (NDMC) at the University of Nebraska/Lincoln (www.drought.unl.edu), drought is caused by a confluence of variables--including precipitation, air, soil and ocean water temperature, and fluctuations in ocean currents--for which scientists as yet been unable to create accurate long range models. Meteorologists can provide fairly accurate weather forecasts for specific metropolitan areas within a 48-72 hour window, says Mark Svoboda, a climatologist with NDMC. "But the problem with drought," he adds, "is that it does not develop in such a short time. In the long term, looking ahead 30, 60 90 days, or three, six, nine months, can I tell you where drought is going to be? The answer is no."
Svoboda doesn't rule out such predictions in the future; in fact, the NDMC is best known for its monthly maps of current drought conditions, which include predictions of neighboring areas to which these conditions might possibly spread. But until better computer models are developed, it's still safe to assume that we won't know we're in a drought until we're in it. Wrote I. R. Tannehill in the 1947 book, Drought: Its Causes and Effects: "The first rainless day in a spell of fine weather contributes as much to the drought as the last, but no one knows how serious it will be until the last dry day is gone and the rains have come again." At the NDMC, Svoboda says, "We like to joke that the next drought starts on your next sunny day."
The climate extremes of the past several years--periods of drought followed by periods of excessive precipitation--"are all signals of climate change," Svoboda says. While human activity might be exacerbating the current patterns, he noted that they were certainly not out of line with the historical weather record. "In the past it's been both wetter, drier, hotter and colder than it is now," Svoboda says. Wherever the long-range weather patterns land us, it still might be prudent of gardeners, as a group in tune with the earth and its needs, to begin planning our gardens, and gardening practices, so we use less water. Commonplace recommendations, if widely accepted, could help mitigate water shortages that some experts say are inevitable based on current upward population trends.
Several inches of organic mulch will both reduce evaporation from the soil and, if turned into the soil over time, improve the soil's water-retention capacity. Water deeply, to encourage plants to develop deep root systems that will have more access to water in dry weather. Avoid overhead sprinklers and relying on soaker hoses puts any water we use right where we want it, at the plants' root zones. Drought tolerant plants including epimediums, rudbeckias, butterfly-weed and others can certainly be as beautiful as their thirstier counterparts, such as daylilies, hostas and astilbes. Planting natives which have adapted over time to the cycle of wet and dry in our area is another good practice, and has many additional benefits as well. We can also set priorities in watering, perhaps focusing on the most vulnerable plants, or the most expensive, such as newly-planted trees and shrubs. Finally, letting go of any notions of horticultural perfection will also help us accept the affects of drought which, like any natural phenomenon (insects, critters, wet weather, windstorms, etc.) works against our best-laid plans, our fantasies of how the garden could or should look.
Carl Groff, owner of Groff's Plant Farm in Kirkwood, PA, writes on his Web site about watering: "I fear that many of us water because the sun just came up, or the sun is about to set or maybe because we saw the neighbor do it or even to prove that we are affluent enough to own a water hose. If you aren't watering based on observed plant needs, you are watering too much."
Groff invites people to take his challenge: "Cut your watering by half, and if you don't see any difference, to cut it in half again. During the severe drought we had in 2002, I didn't water anything in my garden, and some things weren't happy, but I didn't lose any established plants." The key is to water a plant only until it develops a strong, deep root system by which it can support itself. For trees, this may take a couple of years, but for perennials, Groff says, it can take as little as a couple of weeks.
"The problem I see is that people will water and water, and when they
start to get a little root rot the plant is not quite happy, what they do
is water more, which nails the lid shut on the coffin," Groff says. "With
my perennials, I lose more in a wet year than in an obnoxiously dry year."
Around and around we go, our moods (at least during gardening season) always subject to the whims of something over which we have no control. "You can make your best models and predictions," says Kurt Knaus, press secretary at the Pennsylvania DEP, "but the weather is scattered and neurotic. It does whatever it wants, and we're left to suffer the consequences."