Gwinnett Hardiness Zone & Frost Dates

Hardiness Zone
The purpose of the USDA Hardiness Zones map is for growers and gardeners to determine which plants will tolerate the area’s climatic conditions. The map’s basis is the minimum extreme temperature that can potentially occur, which is divided into 14 separate zones across the country. Gwinnett County is in Zone 7b, meaning that the winter temperatures could drop to five to 10 degrees, although the occurrence is quite rare. Zone 7b is too far north for some plants, such as citrus plants, which prefer the hardiness zones in Central and Southern Florida. Georgia’s coastal counties are in zone 8b, meaning the temperature could drop to as low as 15 to 20 degrees. Plants that thrive on the coast and the rest of South Georgia, such as oleanders and sago palms, could suffer in our zone during an extreme cold weather event. Most plants for sale at local garden centers have USDA Hardiness Zones on their labels. Make sure your purchase ones that are adapted to Zone 7b.

First and Last Frost Dates
In addition to knowing your hardiness zone, every gardener should know the average frost dates. These dates are the key to successful planting. Just look at the instructions on a seed packet or plant tag. “Plant in spring after danger of frost has passed.” Or, “Plant six weeks before the first frost in fall”. Frost dates are also important when it comes to pruning and executing pest control measures.
Average frost dates are based on historical weather data and may or may not hold true every year. In the spring, planting instructions often refer to the average date of the last frost, which is the date on which the last frost has already occurred. Remember – this is an average. This means that if you plant after this date, there is a good chance there will not be any more frosts and frost-sensitive plants should be safe outdoors. Still, you should watch the weather forecasts and be prepared to provide protection … just in case.
The first frost date of autumn helps you time fall plantings, when to bring your tender houseplants indoors and when to harvest tender vegetables. Again, the first frost date is an average and frost may occur before then. It is best to keep an eye on the weather and be prepared.

Timothy Daly, University of Georgia Extension Gwinnett County | Agriculture and Natural Resources County Extension Agent
Ann Langley, Master Gardener Extension Volunteer, Class of 2017

January 2020 Monthly Meeting

We were pleased to have Scott McMahan, who is the Manager of International Plant Exploration at Atlanta Botanical Gardens, speak at our first program of 2020 on January 20th.  Scott talked about “Plant Exploration with a Purpose” and shared his experiences on his work in India, Vietnam and China and shared information about his new evaluation nursery up in Gainesville.  

2012 Garden Tour Information


2012 Garden Tour & Plant Sale

Gwinnett County Master Gardeners

Saturday, May 19, 2012 – 10 a.m. until 5 p.m.

Proceeds from the garden tour and plant sale benefit the community projects of the Gwinnett Master Gardeners.  Master Gardeners will be available at each site to answer your questions and handle ticket.  Plants will be available for purchase at one of the gardens.  The location will be announced closer to tour day. Please check our website for the location.

General Information:

  • Tickets may be purchased on the day of the tour at any of the three private gardens.   Tickets purchased on tour day are $20. Tickets will not be available at Harvest Farm or Parsons Elementary School.
  • Please check our website before you begin the tour for any new garden tour information or possible changes.
  • No strollers in the gardens.  Parents must hold their children’s hands.
  • No pets are allowed in the gardens.
  • The garden tour will be held rain or shine.
  • Gardens are not wheelchair accessible.


Iris’ in the Bad Lands

By Kay M. Phiel, Gwinnett County Master Gardener
In early May, 2011,  a friend and I took a Road Scholar/Elderhostle program to the Black Hills, Bad Lands, and Mount Rushmore in South Dakota.  We were surprised to see a Prairie Homestead out in the very desolate-looking Bad Lands area of western South Dakota.  It was raining fairly heavily that day so we didn’t explore as much as we might have.  I picked up a brochure just before we reboarded the bus and was surprised to read a portion on Iris Gardens.   We did not actually see the iris’ when we were there, as they were in another area, but I thought you might find the brochure interesting.


Iris Gardens
(Retyped from a brochure about a Prairie Homestead in the Bad Lands, Philip, South Dakota)

“When the first Homesteaders came to this area many of them brought iris plants from home, knowing that the hardy plant could withstand the trip west for weeks or months on end, in the hot summer as well as the cold winter.  These little iris plants grew and multiplied rapidly, therefore they were shared with neighbors and used as decorative plants to place on graves.  There are still some of the original iris, often called flags, on the prairies where a homesteader once lived.  The buildings may be gone but the iris lives on at these abandoned home sites.  Throughout the Great Plains, from Mexico to Canada, iris can be found blooming in and around old cemeteries.
“After extensive research, we have found that there are also varieties of iris than can be found in the old cemeteries, many of them having been there for at least one hundred years.  Whenever we find iris that have spread away from the graves as well as outside the fences, perhaps in nearby ditches, we take samples and plant them near the north entrance to Prairie Homestead.  Many of these cemeteries contain graves dating back to the Civil War and the early 1900’s.
“It is also thought that early Episcopal pastors may have distributed a particular variety of iris to their parishioners here in western South Dakota, as the same color and variety can be found existing in many of their old cemeteries.
“The iris that we have collected indicate that they have lived and multiplied without any care, through intense heat, bitter cold and lack of rainfall, and are not one of the new varieties found today.  The samples are labeled on a small cross with the name of the cemetery and when possible the nearest town.
The iris around the entrance sign are a mixture of the old iris as well as some of the newest hybrids, many donated by interested family and friends.”