Attention gardeners: Heat wave was a blast from the future

Contributing columnistJuly 21, 2012 

When daytime highs topped 100 degrees earlier this summer, including 105 one day, and rain was in short supply, gardens and gardeners suffered. A look around now at the lawns, trees and flowers that dried and died as a result is a wake-up call. Hotter weather is likely to continue in coming summers.

Statistics compiled by the National Climatic Data Center at the National Oceanic and Atmospheric Administration indicate that our climate is heating up. In a statement on its Web site, the agency says that compiled data "represents the latest information from several independent measures of observed climate change that illustrates an overwhelmingly compelling story of a planet that is undergoing global warming."

Taking steps to deal with climate change can start with awareness of what's going on in your own garden, and learning how to maintain a home landscape and lifestyle that is environmentally friendly and sustainable.

Here are a few ideas to get you and your greenery on track for beating the heat.Cold and heat zone maps

The standard USDA hardiness zone map, which indicates the cold extremes that various plants can tolerate, is well established. Zone listings appear on many of the plant tags found in garden stores. It's important because cold has nearly instant killing power for plants.

In Kentucky, we are mostly in USDA hardiness zones 6a and 6b, with parts of Western Kentucky in zone 7a. From the time the map was instituted in 1960, zones have shifted slightly.

Lesser known is the American Horticultural Society's heat zone map, which delineates zones based on the annual number of "heat days," those above 86 degrees.

Most of the eastern half of Kentucky, including Lexington, is in zone 6 (more than 45 to 60 days above 86 degrees), and the warmer western half is in zone 7 (60 to 90 days). But there are small pockets that are in zones 4, 5 and 8.

Note: The temperature information on the heat zone map is based on readings taken between 1974 and 1995, so the current zones might vary in zone borders.

Some plant tags carry heat zone markings, added as a zone range after the cold-hardiness listing.

Part of the discussion of these zone markings is about excessive heat causing developmental delays or damage to plants. An example of this is the recent failure of tomatoes and beans to set flowers when temperatures soared; only now that the heat has abated have the survivors begun to bloom again.


Did your lawn survive the heat? Depending on your yard's soil, turf variety and condition, shade, and watering schedule, you might be seeing some greening-up again now that we've had some rain. This is the perfect time to do some investigative work to understand how your yard fared.

You might plan to reseed and renovate in the fall, plant some small shade trees, install ground-watering soaker hoses, or even replace some lawn with more environmentally friendly landscaping.

When watering, remember to give your plants a thorough soaking, so water reaches deep into the soil, where roots absorb moisture. Generally, an inch of water each week is what plants require, but other factors, including heat, might indicate that more is needed.

When temperatures are hot, it's better to water your lawn in the morning. Watering in evening can cause leaves to be warm and damp all night, and that condition can promote disease.

A series of useful publications on turf are available from the University of Kentucky Cooperative Extension Service; go to

Native plants

Landscapes around Lexington with well-established shade have generally withstood the drought and scorching sun better than those in completely open and newly planted areas. Look around your neighborhood for ideas.

Native plants, which are naturally adapted for their climate, make good choices for providing shade and can be habitat for local wildlife.

Online resources can offer insight into native plants. State and local organizations include the Kentucky Native Plant Society (, the Lexington chapter of the Wild Ones native plant club (, and Shooting Star Nursery in Scott County, which specializes in plants native to Kentucky (

One of my favorite blogs on native plants is written and packed with gorgeous photographs by Tom Barnes, an extension professor and wildlife specialist at UK. Find it at


More and more, succulents — those water-retaining plants native to arid conditions — are appearing in retail garden stores, especially in large container collections. With low water requirements and a tolerance for heat, these plants exemplify xeriscapes, or low-water landscapes.

At High Country Gardens (, an online retailer specializing in water-wise plants, cold-hardy specimens including hens and chicks, yucca, and certain agaves are listed. Yucca, an evergreen that I have seen in Central Kentucky yards, survived the heat well. A bonus: Its spiky flowers attract hummingbirds.

A mail-order source for unusual succulents is Tony Avent's Plant Delights Nursery, near Raleigh, N.C. Avent travels the globe searching for plants. Colorful accent specimens, such as the giant, spike-toothed "Jaws" agave, must be taken indoors here for the winter so it won't freeze, but such specimens are gaining in appeal as easy-care patio container plants under the hot sun.

Local resource

One final recommendation: Visit Springhouse Gardens, Richard Weber's plant shop and display gardens at 185 West Catnip Hill Road in Nicholasville. The shop's Web site,, is packed with photos and ideas for making sustainable choices and creating garden shade. There is no better place to find butterflies enjoying a sip of nectar from their favorite plants. That's very cool.

Susan Smith-Durisek is a master gardener and writer from Lexington. Email: Blog:

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