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 japonicas 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, Forsyth 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 cited in the “Learn More” resources.
Happy Gardening!
All of us here at Appen Media want to know, and try to help answer, the questions you have about our community.
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North Fulton Master Gardeners, Inc. is a Georgia nonprofit 501(c)(3) organization whose purpose is to educate its members and the public in the areas of horticulture and ecology in order to promote and foster community enrichment. Learn more at nfmg.net.
FAQs
Growing zones are based on average annual minimum winter temperatures and separated out by a margin of 10 degrees Fahrenheit. USDA growing zones range from 1 to 13, but the continental US only ranges from 3 to 10. The official USDA zone map is now further divided into subcategories of a and b with a 5 degree margin.
How many planting zones are there in the world? ›
The original and most widely used system, developed by the United States Department of Agriculture (USDA) as a rough guide for landscaping and gardening, defines 13 zones by long-term average annual extreme minimum temperatures. It has been adapted by and to other countries (such as Canada) in various forms.
How many zones are there for planting? ›
The USDA map is separated into 13 growing zones. Each USDA zone represents a 10-degree range of temperatures based on the zone's average annual minimum winter temperature.
Where is zone 7 in the US? ›
From east to west, it begins in small areas of southern Connecticut. It then stretches south through Virginia, east through Tennessee and northern Arkansas, and southwest through the Texas panhandle and New Mexico, then narrows and winds north through Nevada, California, Oregon, and Washington.
What are the zones in the United States? ›
United States and regional time zones
| Time zone | Standard | DST |
|---|
| Eastern | UTC−05:00 | UTC−04:00 |
| Central | UTC−06:00 | UTC−05:00 |
| Mountain | UTC−07:00 | UTC−06:00 |
| Pacific | UTC−08:00 | UTC−07:00 |
7 more rowsZone 3 plants can withstand cold temperatures of -40°F to -30°F. The upper Midwest states and some northeast states hold most of Zone 3, such as northern parts of Montana, North Dakota, Minnesota, Wisconsin, Wyoming, New York, and Maine. Common Plants: Foxglove (Digitalis selections)
Have US plant zones changed? ›
Half of the US has shifted to warmer plant zones
The new map for 2023 has pushed half the country into a warmer half zone, while the rest of the country has remained in the same zone, the USDA said in a press release. With the latest map update, some areas of Omaha, Nebraska have moved from 5b to 6a.
Where is zone 8 in the United States? ›
In North America, Zone 8 is one of the warmest zones, containing much of the southern quarter of the United States, including much of North Carolina, South Carolina, Georgia, Alabama, Mississippi, Florida, Louisiana, Arkansas, Texas, Arizona, California, and coastal Oregon and Washington.
What colors of white light do plants absorb? ›
In plants, chlorophyll a and chlorophyll b are the main photosynthetic pigments. Chlorophyll molecules absorb blue and red wavelengths, as shown by the peaks in the absorption spectra above.
What zone is best for growing vegetables? ›
Many of our perennial flowers and herbs are hardy as far north as zones 3 or 4. Cool-season vegetables, most of which tolerate or even like a little frost, will grow well in zones 7 and southward in the fall. This is roughly where we distribute transplants to your local garden center at the proper time for planting.
USDA Plant Hardiness Map:
The map is based on the average annual minimum winter temperature, divided into 10-degree F zones. The map is available as an interactive GIS-based map, users may also simply type in a ZIP Code and find the hardiness zone for that area.
What is the difference between a perennial and an annual plant? ›
The difference between annuals and perennials is simple: Annuals die off when temperatures get too cold, which requires you to plant new ones the following spring. Perennials will come back and regrow year after year.
What are US planting zones? ›
Description. The USDA Plant Hardiness Zone Map is the standard by which gardeners and growers can determine which perennial plants are most likely to thrive at a location. The map is based on the average annual extreme minimum winter temperature, displayed as 10-degree F zones and 5-degree F half zones.
What vegetables grow best in zone 7? ›
Zone 7. In zone 7, cool-weather vegetables can usually be planted outdoors in early February. These crops include beets, broccoli, cabbage, carrots, lettuce, onions, peas, potatoes, radishes, spinach, turnips, kale and collards. Plant corn in March.
Where are zones 9 and 10 in the United States? ›
Zone 9 includes central Florida, southern Louisiana and Texas and stretches up the west coast in a narrow band on the western coast of California. Zone 10 encompasses south Florida, southeast California, the southernmost tip of Texas, and much of Hawaii.
What is the difference between zone 7a and 7B? ›
Hardiness Zone 7's coldest temperatures fall between zero and ten degrees Fahrenheit. It's subdivided into Zone 7a—encompassing territories with zero- to five-degree temperatures—and Zone 7b—encompassing territories with five- to ten-degree temperatures.
Is Portland zone 9? ›
Portland falls into USDA hardiness zone 8b (with average low temperatures from 15 to 20 degrees Fahrenheit) or 9a (with average lows from 20 to 25 degrees Fahrenheit) for parts of inner Portland.
What is Zone 6 in the US? ›
Zone 6b has a minimum average temperature of -5F to -0F. Zone 6 stretches in a long arc from Long Island and New Jersey, through Pennsylvania, Ohio, Indiana, Illinois, Missouri and Kansas, and then right up through The Rockies into Washington State – with colder zones at higher altitudes and warmer zones at lower.
