Home » Plants & Animals » Home Landscaping » Selecting Plants: Will That Plant Grow Here? The Reality of Zone Maps. - Page 2

Selecting Plants: Will That Plant Grow Here? The Reality of Zone Maps. - Page 2

© Georgene Bramlage

Looking carefully at the map, I find that my yard is in zone 5 (-10° to -20°F). However, after thirty years of experience selecting plants, I know my best bet is to use plants ranked for zone 4b, zone 4, or zone 5a. If I carefully select one of the many microclimates within my yard, then I am usually successful with plants ranked zone 5, zone 5b or zone 6a.

Is it possible to learn this in less than 30 years? The USDA map Internet site lists the Cold Hardiness Ratings for Selected Woody Plants. The list of these indicator plants can also be found on the back of the large print USDA map. How does one use an indicator plant? The flowering dogwood (Cornus florida) is listed as an indicator plant for zone 5 (-10° to -20°F) along with:

• Slender deutzia (Deutzia gracilis)
• Early forsythia (Forsythia ovata)
• Common privet (Ligustrum vulgare)
• Boston ivy (Parthenocissus tricuspidata)and
• Multiflora rose (Rosa multiflora).

If all or the majority of these plants grow well in your yard or neighborhood, with successful flowering and fruiting and little or no winter dieback, then almost any plant rated for zone 5 should do well for you. However, if there is a spot where the deutzia or forsythia consistently winterkill or fail to blossom, then it's a safe bet that most zone 5 plants won't do well in that spot.

Your plants may survive the cold, but can they survive the heat? In 1997, to complement and make up for inadequacies in the USDA cold hardiness zones, the American Horticultural Society introduced its AHS Heat-Zone Map. This map is composed of 12 zones based on the average number of days each year when temperatures are over 86° F (30°C). These "heat days" indicate the point in time when separate groups of plants begin suffering physiological damage from heat. The physiological makeup of some plants can tolerate more heat than others, so the zones range from Zone 12, with more than 210 heat days, for plants which can tolerate much heat but little cold, to Zone 1, with less than one heat day, for plants which can tolerate little heat but extreme cold.

Extreme cold usually will kill plant tissue outright, but plant death from heat may be slow and drawn out. According to the AHS explanation, heat affects plants in ways that are subtle:

• Flower buds wither;
• Leaves droop or become increasingly attractive to insects;
• Chlorophyll tends to disappear causing leaves to appear white or brown and plants to weaken;

The copyright of the article Selecting Plants: Will That Plant Grow Here? The Reality of Zone Maps. - Page 2 in Home Landscaping is owned by Georgene Bramlage. Permission to republish Selecting Plants: Will That Plant Grow Here? The Reality of Zone Maps. - Page 2 in print or online must be granted by the author in writing.