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Heat-Zone Gardening

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Oh, my aching muscles...

A new approach to planning the garden

By Dr. H. Marc Cathey with Linda Bellamy
Using a plant-hardiness zone to determine which plants will thrive in any region has long been a tool of the plant-wise gardener. Today, however, as we become more conscious of evolutionary changes in the weather, tools such as water-thrifty gardening, the use of native habitat and gardening without chemicals or pesticides are fast becoming a way of life.

Still, more tools can help us wade through the piles of data and resources available, with the end goal of ensuring that our plants will be healthy and thrive in spite of changing weather. One such tool is the book, “Heat-Zone Gardening,” by Dr. H. Marc Cathey and Linda Bellamy. A colorful, 192-page text, “Heat-Zone Gardening: How to Choose Plants That Thrive in Your Region’s Warmest Weather” offers an overview of gardening in the 21st century, as well as tools for choosing climate-adapted plants, gardening in any one region in particular, and effective watering techniques.

Cathey, a renowned research horticulturist, is president emeritus of the American Horticultural Society. The book was co-written by journalist and garden writer Linda Bellamy, whose work has included contributions to The Washington Post, Garden Design and the Time-Life Complete Gardener book series. The purpose of this book is to help our plants succeed even through sudden unseasonable breaks in the weather—be they hot or cold.

“Cold hardiness… is only one factor in a plant’s chance of survival,” states the author, who adds that today’s gardener must recognize that summer heat can be just as devastating as winter cold snaps. “Global warming—the gradual heating up of the earth’s atmosphere due to an increase in atmospheric carbon dioxide—holds an obvious significance for gardeners everywhere,” according to Cathey.

He notes that while global warming seems slow to progress in our lifetime, the changes that have already occurred are dramatic. For example, “five of the 10 hottest years ever documented have occurred since 1990, with 1995 breaking all heat records for recorded weather history.” To the conscientious gardener, that means a gradual loss of winter. The frost-free season now begins approximately one week earlier than in the past, states the author. Longer heat waves or periods of drought, as well as concerns about diminishing water supplies, have left people across the country more concerned than ever about how to preserve existing resources. “Wherever you live ... waterside, heat-tolerant garden design makes good gardening sense,” Cathey says.

In response to environmental concerns, the American Horticultural Society has published a Plant Heat-Zone Map, and may continue to provide updates as evolutionary changes create new weather patterns nationwide. This up-to-date map indicates the longest periods of heat that gardeners can expect for their region.

In Western Washington, for example, depending on exact location, we can expect to see probably no more than 14 to 30 days with a temperature in excess of 86 degrees F. Southern Texas, Florida and Arizona might expect as many as 210 such days per year. The authors recommend combining this map with the standard hardiness-zone map provided by the U.S. Department of Agriculture. Such a combination will help home gardeners to select plants that may then live for years, adapting to excesses in either cold or heat.

Although it’s highly technical, the book is not difficult reading. And as easily as he talks about global warming in one instance, in the next he easily reverts to a poetic interpretation of gardening for all seasons. “Nature writes. Gardeners edit,” said Roger Swain, as quoted in “Heat-Zone Gardening.” Cathey goes on to say that “thoughtful planning (and) a bit of old-fashioned hard work,” as well as ingenuity, are key ingredients for any successful garden — be it in Texas, Savannah or Manhattan.

The use of doors, arbors, or other existing landscapes of all kinds can be immensely helpful, he writes, in creating the perfect microclimate for the plant in question. A marginally hardy fruit tree, for example, might do well in a sheltered spot near the home — whereas elsewhere, it might simply fail to prosper.

In another quote, he points out the value of designing gardens to match the climate. Michael Pollan said, “As soon as someone decides to rip out a lawn, he or she becomes perforce, a gardener, someone who must ask the gardener’s questions: What is right for this place? What do I want here? How can I go about creating a pleasing outdoor space on this site? How can I use nature here without abusing it?” Fundamentally, any gardener looking to “use nature without abusing it” will find many answers in this book.

More than half the text is devoted to plant profiles, offering specific cultural information. Cathey quotes Vita Sackville-West when he begins the section that features more than 450 plants. She once said: “Flowers really do intoxicate me.” If flowers intoxicate you and you care about your plants’ long-term success, you’ll want to consider “Heat-Zone Gardening” as a resource.

NWGN archive published July 1998

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