What is Plant Hardiness and How Do I Find My Climate Zone?

What is Plant Hardiness

Do you love beautiful plants? I do, too!  Let’s fill our gardens with the plants we love – won’t that be perfect?  I’ll plant plumeria in Wisconsin, and you plant peonies in Florida!

Why doesn’t that work?

There are thousands upon thousands of plant varieties that thrive in the United States – but not every plant is happy in every single state.  Kind of like how we have both polar bears and alligators, but the polar bears are just in Alaska, while the alligators are just in the coastal south east.  Each lives in the climate and conditions to which they have adapted.  Polar bears (and peonies!) actually need the cold and ice to survive, and could never live in the Florida swamps no matter how much the alligator might love it there.  Plants are like that too.  And the best way to make a plant happy is to mimic the conditions of its native habitat all year round.

While most plants will be happy in nearly any part of the country during the spring, some like peonies, need a bitterly cold winter to trigger their new growth and blooming for the following spring, and simply will fail to do either without it. Others cannot survive a freeze and will die if they do - like plumeria. So a plant is considered "hardy" where it can be planted in the ground and left to grow there all year long. It gets all of is climate related needs met by nature out in the garden.

What are Climate Zones

That is what plant hardiness and climate zones or growing zones are all about.  The USDA divided the entire United States into climate zones to help gardeners to determine what plants would thrive in their gardens.  You typically see a map of the United States colored in according to their zones like the one above.

And we have this handy tool here, where you can just enter your zip code to learn your climate zone. What climate zone am I in?

 Climate zones are determined by the coldest average winter temperature the geographical area typically experiences.  You can see the coldest temps and their zones here, further divided into A (colder half of the zone) and B (warmer half of the zone).

So if you live in St. Louis Missouri, and your average coldest winter temperature is -5 degrees Fahrenheit, you can see from this chart that you live and garden in zone 6.  So plants and bulbs that need a seriously cold winter in order to survive and bloom and thrive, like most tulips, peonies, snowdrops or cherry trees, will do well in your garden. And those plants that will be harmed or killed by a freeze either should not be planted at all or should be brought indoors over the winter or treated like annuals.

Now that you know what climate zone you are in, you can use this information to make great choices for planting your garden.  Plants are listed as hardy to a range of zones, like Narcissus Grand Primo is hardy in zones 6-10, and Allium Atropurpureum is hardy in zones 4-8.  If you garden in zone 6, both of these varieties would thrive for you, because zone 6 is within the hardiness range of both plants!  But if you garden in zone 5 or zone 9, only one of these two would work for you.  Fortunately, there is a myriad of beauty that will thrive in every climate! And now you have the tools for determining which is right for you.

So - now that you know your climate zone and what it means and how to use it, does this mean you can never enjoy frost tender perennials like freesias or dahlias in your cold winter garden? Wouldn't that be too sad? You absolutely can plant and grow varieties that are not cold hardy in your climate - it just takes extra work to get the same great results, as you make up for the qualities the plant needs that your climate lacks!

In cold winter climates, plant tender bulbs and plants in the spring, so they grow, flower and go dormant before autumn turns cold. Then either bring them indoors or treat them as annuals. For mild winter climate gardeners who dearly love classic tulips and snowdrops, plant to pre-chill them for many weeks (10-12) before setting them outside in January or February. This way, you simulate the colder winter they need.

Explore the wild world of beautiful plants that do thrive in your climate. And for the one your heart craves that your climate doesn't suit - I'll bet it is worth the effort! :)

Happy Gardening!

← Previous Post Next Post →