A website from UGA Cooperative Extension

by Carole MacMullan, Fulton County Master Gardener Extension Volunteer

This article is part of Garden Buzz, a series from Appen Media and the North Fulton Master Gardeners, where rotating columnists explore horticulture topics like herbs, insects, and wildlife conservation. Find all Garden Buzz articles here.

It seems like we hear comments about global warming every day. As the weather reporter or meteorologist can tell you, the average summer temperatures are increasing, but on the other hand, are the winter temperatures increasing or decreasing? In December of 2022, we had one day in North Fulton and surrounding areas when the temperature reached a low of 6 degrees for the first time in 30 years. As a result, many shrubs lost a significant number of leaves, died or had their overall growth significantly impacted.

Some of the shrubs most significantly impacted by last year’s hard freeze were the camellias, azaleas, lorepetulum and gardenias. These four shrubs are evergreens, do not lose their leaves in the fall and are green throughout the winter. As a result of the deep freeze, some of my azaleas partially died and did not bloom last spring, and one of my large Camellia japonica sadly lost all of its leaves, and its flower buds were frost damaged and did not bloom as they normally do in late February.

When I saw what I thought was a dead plant, my impulse was to cut it down and remove it from my landscape. But fortunately, I got busy, and several months later to my amazement it started to show signs of life and began to produce a new crop of green leaves! I am happy to report it is alive and well, and this year it has 100 plus flower buds.

If you lived anywhere in the Atlanta metropolitan area on January 28, 2014, I am sure you remember the history-breaking, catastrophic snow and ice storm that covered all of the roads and brought traffic to a halt. This storm even has a name, Snowmeggedon! It not only paralyzed everyone’s ability to get home from school, work or shopping, but it also had a devastating effect on plants in our yards, on the Georgia’s farm economy and people with nursery businesses. In my yard, every Indian hawthorn planted by the builder in 2004 died.

Because the Indian hawthorns outnumbered all the other landscape plantings, I lost 35 bushes as a result of the storm. When I researched to determine why these shrubs failed to survive while most of the other plantings survived, the answer was that the shrubs were the wrong plants for my planting zone. Indian hawthorns are winter hardy in zones 8 through 10.

Although the Indian hawthorns survived for nine years during mild winters, 2014 was too much for these zone 8 plants! As a result, I caution all gardeners in north metro Atlanta to carefully read the plant tags and note the Plant Hardiness Zones. Think carefully before purchasing any plant recommended for zone 8 and higher and determine if there is a safer option.

During the current winter season, the temperatures dipped into the mid and low 20s for several days. Taking these high and low temperatures into account, what effect do these temperatures have on the plants we try to grow in our landscapes and flower and vegetable gardens? What are the current planting zone designations, and have the plant zones changed because of global and regional warming?

If you do an internet search to determine your planting zone, you will find two sources of information. Based on the USDA 2012 Plant Hardness Zone map, North Fulton, Cherokee, and Forsyth Counties and most of north Georgia were identified as zone 7b. In November 2023, the USDA modified the Plant Hardiness Zones for Georgia, and now Fulton, Cobb, Forsyth and Cherokee have been reassigned to Planting Zones 8. These changes are based on weather data collected over a 30-year period from 1991 to 2020. The 2023 map reflects a half zone shift for our area of Georgia.

CAUTION – Even as the climate warms, there will always be extreme weather events, and new plantings should be selected with these extremes in mind.

How can you avoid an expensive landscaping mistake? My suggestions are: do not fall in love with a zone 8+ plant, and look at the plant tag before you purchase any plant. The gardenias and camellias are especially vulnerable to single-digit temperatures because some of the cultivars are zone 8 plants. If you want to purchase a gardenia, I would suggest the two most frost-tolerant cultivars, Frostproof or Foolproof. Both of these cultivars are designated as zone 7 plants. The same is true of camellias. Some camellias are more frost-tolerant and are designated as zone 7. Here is a quote from Tom Money, a landscape designer from Scottsdale Farms in Milton, when asked about planting zone 8 plants: “l would not plant zone 8 plants because in a year or two I would need to return to replant.”

Please compare the 2012 and 2023 planting zone maps that accompany this column and note the current changes. If you are a vegetable gardener, I suggest you read the Georgia Vegetable Planting Calendar.

Happy Gardening!

Learn More

> 2023 USDA Plant Hardiness Zones Map
> New USDA Plant Hardiness Zone map shows most of Southeast has gotten one half zone warmer (Pam Knox, UGA)
> UGA Vegetable Planting Calendar

portrait of the author

This week’s “Garden Buzz” guest columnist is Carole MacMullan, a master gardener and a Milton resident. She taught biology for 35 years in the Pittsburgh area. In 2012 after moving to Milton, Carole completed the Master Gardener training program and joined the North Fulton Master Gardeners (NFMG) and the Milton Garden Club. Her favorite hobbies are gardening, hiking, biking, and reading.