Gardening Basics - Know Your Garden Zone

USDA hardiness zones. Gardeners and landscapers are label readers when it comes to knowing a plant’s growing requirements and hardiness zone. I save every tag. Hardiness zones define the minimum extreme cold temperature a plant can survive. Here in Desert Aire, WA (and nearby), based on past readings, we live in Zone 6b (-5°F to 0°F), or even Zone 6a (-10°F to -5°F) according to some, which feels as rare as the temperature range in Zone 6b, but it’s a good reminder when investing in a tree or expensive shrubbery.

My pots are ready!

On the other hand, new zoning according to the USDA says we now live in Zone 7a:  0 to 5 (°F), which feels more accurate. So take your pick. If you agree with climate change scientists, which as a gardener I do, consider growing plants you might never have tried before. Be bold. Just bear in mind, we do get cold here in the winter with wind chill. And right now we are having record snow!

The United States was the first country to establish a list of hardiness zones. First created and published in 1927 by two Boston researchers at the Arnold Arboretum, hardiness zones have evolved overtime. A map was eventually designed to include half-zones as well as additional zones, which continues to be updated and used today.

Other countries have since followed suit but with modifications. Generally-speaking, there are thirteen zones. If you are unfortunate enough to live in Zone 1, a plant must survive temperatures ranging from -50°F to -45.6°F. Ouch. Examples are regions near the Arctic Circle, for instance, Fort Yukon, Alaska and northeastern Siberia. Believe it or not, the Lapland rhododendron is quite hardy there. If you happen to live in Zone 13 (60°F to 70°F) on the equator, say in Malaysia or Jamaica, you could grow bananas and pineapples.

Forsythia in front of house - Coming soon!

Given the fact there are other factors that can affect plant survival—heat, soil and moisture being three obvious ones—hardiness zones do have limitations. For instance, the zones do not account for the extra warmth a blanket of snow might bring to the soil. It explains why plants normally not hardy in an area sometimes survive over the winter. Right now, I'm counting on my potted fig tree's survival under the cover of a large aluminum hangar. Now that may not seem like cover enough, but it does protect it from wind chill, which is definitely a factor here. Stay tuned....

Happy gardening everyone! It’s been said that “Gardeners know the best dirt.”