Plant Hardiness Zones

As a gardener, you see a plant you like and you want to grow it. Sometimes all this zone talk sounds so complicated and scientific that you just want to ignore it and do your own thing.

However, knowing the hardiness zones can help you select plants that will not only grow, but thrive, in your area.

How it Works

The plant hardiness zone map created by the USDA divides the continent of North America into eleven zones.

The coldest is zone 1 and the warmest is zone 11. With a few exceptions, when you look at the map, the zones run in a north-south pattern across the continent, with the higher latitudes up north having lower zone numbers and the lower latitudes down south having higher zone numbers.

The exceptions are created by mountains, desserts and forests where the climate may be very different from a neighboring area.

Each plant has a set range of temperatures in which it can survive. If you grow a plant that is hardy in your zone, it means the plant stands a better chance of surviving the winter in your area and your chances of success are greatly improved.

If a plant is classified as hardy to a specific zone, it means it can withstand the lowest temperature noted for that zone.

In other words, a plant hardy to zone six would not tolerate the extreme cold temperatures for zones one through five.

If a plant has a range of zones, it will only grow within those ranges, and cannot tolerate the extremes above or below those ranges.

Using the plant hardiness zone map is a good starting point for gardening, when used along with specific growing conditions of the plants you select.

Why it Doesn't Always Work

There are some misleading things about plant hardiness zones. Since they are based on the average coldest temperature in an area, they do not take into consideration the length of a growing season in a region, percentage of humidity, average inches of rainfall, or the effect of heat during periods of drought.

Moreover, as every gardener learns, sometimes the hard way, there are microclimates everywhere.

Every state, city and even in our own backyards create their own climates. Even in a small backyard garden, the flowerbed along the back of the house will experience very different climate than the bed at the far border by an open field.

The reflected heat and shade created by the house drastically alter the growing conditions for the plants.

This may allow you to grow plants that are not hardy to your area, or prevent you from growing some that should be.

These factors, along with soil conditions, rainfall, humidity and drought will affect how successful your gardening efforts will be.

Use the USDA plant hardiness zones as a gauge for selecting appropriate plants.

Learn the specific growth habits and growing conditions of those plants and select the ones that are best suited to your specific gardening site.

Using all this information, you'll have better results in the garden.

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