What is my Hardiness Zone and what does it mean?
The USDA Hardiness Zone maps were created to help gardeners and growers alike to pick plants for different areas of the country. This means that plants that will thrive in Zones 4 to 7 will likely perish in Zones 8 and above or freeze in Zones 3 and lower. When I am picking plants for my own garden, I try best to follow these guidelines.
The numbers for the Zone Map are determined by averaging the annual extreme minimum temperature over a 20 year period. By taking the average, we can eliminate years where mild winters occurred, which often make us wonder if we can plant plants that are not for our zone.
The lower your number, the colder the Zone that you live in. For example: I live in Zone 5b, which is just a short hop to Zone 6. I can grow plants that thrive Zones 3 to 5, and maybe a few plants from Zone 6, if they are planted in the right location.
What are micro-climates?
Micro-climates are locations within an overall landscape where the weather is different from the rest of the general area. Micro-climates can be created in a landscape by the use of evergreen hedges, windbreaks, screens, earth mounds, buildings, and the lay of the land.
For example: I live halfway down the hill of a south-facing slope. I have a large wooded area to my south and northwest. I also live close to a large body of water. Because of these factors, I have windy days as much as my neighbors who do not use the hill and trees for protection.
Also, the water near me helps regulate the temperatures during the day, keeping me warmer at night and cooler during the day. The hill blocks most of the northwest winds in winter, keeping my ground temperatures higher. Because of these factors, I can grow some Zone 6 plants in my garden, including Abelias.
What are Heat Zones?
Heat Zones are determined by the American Horticultural Society to help gardeners determine a plants thrive-ability based on the number of heat days during the growing season. A heat day is a a day with the temperature above 86 degrees Fahrenheit. Just like Hardiness Zones, the ratings for Heat Zones range from coldest to hottest in ascending order.
For example: If you live where the AHS Heat Zone is a 12, you would have more than 210 heat days per year, while a Heat Zone 1 has fewer than 1 heat days per year.
How do I use them together?
Unfortunately, not all nurseries recommend based on both Hardiness Zones and Heat Zones, though that may change as the climate changes.
By using both maps to pick plants for your landscape, you can insure the greatest possible survive-ability and thrive-ability of your landscape choices.