What Is a Hardiness Zone Map?

The following is a guest post from Julie Fischer, a gardening specialist who also works as a full-time gardener. She loves being outdoors, spending time with her cats, and is working on cultivating her own garden in California.

The growing zone you’re located in makes up the basis of knowledge for a healthy garden.
Understanding your growing zone for a better harvest is the best tool in your arsenal of
gardening knowledge. Many seed packets will have the best zones for the plant listed on the
back. 

A hardiness zone map has been a standard for determining what kind of plants can grow
according to annual temperatures. In the United States, it is produced and determined by the U.S.
Department of Agriculture (USDA) Agricultural Research Service (ARS). To get an exact
reading on your own plant hardiness zone, enter your ZIP code on the site. 

Knowing your USDA hardiness zone is crucial to knowing which plants can grow and thrive
outdoors in your area year-round. The different zones are based on the average annual minimum
winter temperature.  For example, tropical plants like the Monstera Deliciosa will do best in
zones of 10-12 where average annual winter temperatures don’t go below 30°F or -1.1°C. 

The Growing Zones 

There are 13 growing USDA zones with two different differentiations of (a) and (b) for each one.
For example, there is a 1a, 1b, 2a, 2b, 3a, 3b, and so on all the way through 13. Zone 1 has the
coldest average winter temperatures and 13 is the hottest. 

Each growing zone is separated by a change of 10°F. The USDA plant hardiness zones signify a
more specific indicator compared to just using the major climates zones of tropical, dry,
temperate, continental, or polar for planning your harvests. The USDA scale lets you know
which zone plants can survive the temperatures in your region. 

Even though plants may be able to survive the temperatures you live in, they still could perish
due to poor soil conditions. Check out this comprehensive guide to how to improve soil health
for your garden. This is important no matter what your growing zone is.  

Recognize Weather Factors

Once you know your exact growing zone, you can then organize the types of plants that are
appropriate to grow by searching on this handy tool. After finding the plants that are able to grow
happily in your planting zone, there are other important factors to take into consideration to
ensure your plants get the best care.  This includes the usual weather your area receives such as
the amount of rain, flooding, or wind. 

Even if your growing zone could be considered safe for a certain plant, you might live in a valley
that receives particularly strong gusts of wind.  If this is the case, you will want to take additional precautions to protect your plant. This could be planting it on a certain side of your home, or
installing protection for it from the elements. 

Another important facet of info to remember is your area’s frost dates. If you plant your crops but
have a few more days of frost on the way, they will be completely decimated. The Farmers
Almanac has a guide for types of freezes and an area to look up your area’s first and last frost
dates. 

Make a Plan

Although it may take some years of trial and error, a plan is your best bet for ensuring success. 
You’ll want to account for when you can plant certain plants and the best place to put them
within your garden. The best time to make your plan is in the early spring months, before your
last frost date. 

Then, when the growing season has begun, you can jump into action. In addition to the types of
plants and location, you can also plan for the type of supplements you may need and see if your
soil is healthy for growth. Many gardeners like to make a quick sketch of their garden layout or
even use garden organizing software. 

Colder zones have a shorter growing season,  so you’ll need to be tight with scheduling and have
everything ready to go before the season begins. 

Best Crops and Plants For Each Zone

Within each USDA plant hardiness zone, there are certain crops and plants that grow best. Some
growing zones do best more so with perennials and others do great with annuals. 

The difference between perennials and annuals is that perennials return year after year whereas
annuals live for one growing season and are gone. 

Zone 1-2

Zone 1-2 has the lowest temperatures of all the zones. The best crops for this zone are very
hardy.  Alaska, Siberia, and upper Canada are notable for being within these zones. 

The growing season is between April and September and allows for perennials to flourish and
then die back when the cold, extreme temperatures begin. Some perennials to grow in zone 1
include yarrow, lily of the valley, Siberian iris, creeping jenny, cranesbill, and false spirea. 

Lettuce, eggplant, broccoli, kale, arugula, cabbage, spinach, swiss chard, asparagus, and vine
tomatoes are the best crops for this zone. They can resist cold temperatures. 

Zone 3-4

Zone 3-4 are observed in the very upper portions of the US.  Minnesota, Wisconsin, North and
South Dakota, Montana, Wyoming, and some portions of Nebraska, Iowa, Colorado, and Idaho
are included.  The best crops are strawberries, potatoes, sweet peas, pole beans, winter squash,
lettuce, kale, broccoli, asparagus, spinach, eggplant, and vine tomatoes. 

The growing season is between April and October. A handy guide from the University of
Vermont on when you should plant each crop can be explored here. Zone 3-4 has slightly
warmer growing conditions compared to zone 1-2. 

Zone 5-6

Zone 5-6 is best for cucumber, tomatoes, corn, squash, melons, beans, strawberries, lettuce,
eggplant, radish, potatoes, and the other previously mentioned greens. The growing season is
between March and October. A planting schedule for zone 5-6 is a handy tool to ensure you’re
able to fit all your desired crops into the growing season. 

Zone 5 and 6 stretch horizontally directly through the center of the US. Some great perennial
flowers include tulips, daffodils, hyacinths, lilies, irises, delphinium, bee balm, butterfly weed,
and peonies. 

Zone 7-8

Zone 7-8 is best for corn, tomatoes, garlic, brussel sprouts, cauliflower, melons, squash, collard
greens, carrots, bush beans, asparagus, and leafy greens during the cooler months. The growing
season is between March and November. 

Zone 7 and 8 comprise the southern states of the US. Surprisingly, zone 8 stretches along the
coast all the way up to the state of Washington and up into Canada. Some Zone 7 perennial
flowers include black-eyed susan, hosta, shasta daisy, lavender, phlox, chrysanthemum,
coneflowers, forget-me-not, and penstemon. 

Zone 9-10

Zone 9-10 is best for tomatoes, melons, squash, corn, peppers, yams, citrus, peaches, figs,
bananas, salad greens, and sweet peas during cooler months. The growing season is from
February to November. 

Zone 9 and 10 can be found in these states:  Florida, Georgia, South Carolina, Texas, Alabama,
Louisiana, Mississippi, Utah, New Mexico, Arizona, Nevada, California, Oregon, Washington,
and Hawaii. 

Great perennial flowers for Zone 9-10 are purple coneflowers, spider lilies, scarlet sage, butterfly
peas, and the passion flower vine. 

Zone 11-13

The growing season for Zone 11-13 is year-round. The best plants to grow here are kale,
Okinawa spinach, pole beans, passionfruit, sweet potatoes, red potatoes, cassava, pineapples,
pumpkins, mango, papaya, Thai chili peppers, citrus, bananas, and taro.  

Zones 11, 12, and 13 can be found in Hawaii, Puerto Rico, and the bottom-most part of the US.
Although you may believe all plants and crops will do well in these zones, many plants do prefer
cooler temperatures.

If you try to grow those types of plants there, extra aid may be required
such as shade barriers. Watch your heat and moisture-loving plants grow nicely in these tropical zones. Zone 11-13 can support orchids, hibiscus, and passionflower.

Enhance Your Plants

If you live in a zone where you are unable to grow certain plants, a greenhouse is a wonderful
addition for a busy gardener.  Greenhouses allow you to control precise aspects like temperature,
humidity, light, and water.  You can also easily adjust additives such as high quality organic
fertilizer and keep a better watch on your pest situation. 

Now that you know your climate and growing options a little better, you’re one step closer to
even better plants and harvests.  Enjoy watching the plants meant for your growing zone thrive!