Figuring out your local growing zone is one of the most important steps when you start gardening. Your local climate growing zone gives you an easy-to-remember category for the plants that will thrive in your area. Once you’ve figured out how to find your growing zone, you’ll be able to select your crops with confidence!
Why Knowing Your Growing Zone Is Important
Have you ever gone out to your perennial gardens in the spring and discovered that some of your favourite plants haven’t made it through the winter? Or have you planted out some baby vegetable plants, just to discover one morning that they’ve been killed by frost?
Plants vary widely in their tolerance of growing conditions. This is especially true for their temperature requirements. Due to this range in tolerances, knowing your local climate growing zone is a key factor in growing a successful garden.
If you’re not aware of your local growing zone before you install your garden, any plants that aren’t matched to your unique climate may not survive. They simply aren’t adapted to the local environment. It can be so frustrating when you’ve spent time and money on a plant, only to have it die from external environmental factors.
How to Find Your Growing Zone: Plant Hardiness Zones
Fortunately, in most areas of the world, federal scientists have categorized geographical areas by climate. The climate categories they’ve created will help you learn what plants do well in your area. Finding your category, known as your Plant Hardiness Zone, is a crucial early step in garden planning (even before selecting your crops). Learning how to find your growing zone will help you get in the mindset for gardening in your local climate.
Although there are many different systems around the world, the most popular classification system is the USDA’s system of Plant Hardiness Zones. The categories in the system provide a numerical rating for the climate in a given area, based on the coldest winter temperatures in the area. The coldest zones on the scale are given the lowest numbers, with the zone numbers becoming higher as winter minimum temperatures increase. Zones can each also be divided into two sub zones, a & b.
When describing the lowest temperatures at which a plant will survive, gardeners will state the plant is hardy to a given zone. For example, if a given plant will survive in temperatures down to −28.9 °C (−20 °F), it would be “hardy to Zone 5a”.
How to Find Your Growing Zone Using Plant Hardiness Maps
The easiest way to estimate your growing zone is by referencing a Plant Hardiness Map. These maps will give you a general idea of your zone:
Check the map for your region and zoom into your local area. Make note of whether your garden lies within a defined zone, or if it’s close to a border between two different zones. Although the maps can give you a general idea of how to find your growing zone and which zone you’re in, they’re usually not detailed enough to account for microclimates and variations at zone boundaries.
The Limitations of Plant Hardiness Maps
Because most plant hardiness maps cover large areas of land, they cannot provide great detail for the boundary areas between zones. The maps may also fail to account for microclimates (small areas where external factors have affected the climate). For instance, you may live in a Zone 5b area, but be able to grow a few select plants rated for Zone 6a if they’re grown in a warm, sheltered area.
Plant hardiness maps also don’t take into account environmental factors that vary throughout time. For instance, a large amount of snow on the ground in the winter can actually insulate plants from harsh conditions, allowing the more tender plants to survive.
A particularly windy winter can also threaten plants that should traditionally thrive in a given zone. The wind-chill and desiccating/drying affect of the wind can lead to frozen, dried out plants that may not survive through the winter.
Outdoor temperatures can also vary widely from year to year in one area. A particularly cold winter may lead to injury or demise of plants which are on the edge of survivability in a given zone. For these all these reasons, plant hardiness maps should be seen as a general estimate rather than a certainty.
How to Use Climate Data to Determine Your Growing Zone
Hardiness Zones are generally based on the lowest temperature experienced in a given area. For instance, on the USDA Plant Hardiness scale, a plant that’s hardy to Zone 7a can survive in temperatures down to -17.8 °C (0 °F). Other scales do include additional variables beyond minimum temperature, but for practical reasons (plant import, global publications), the USDA classification system is often used.
When determining your growing zone, check the climate records for your local area. Climate data may be available from government websites, or even Wikipedia. Compare the minimum temperatures trends to the minimum temperatures in the zone table.
While you’re examining the climate data to determine your zone, also take note of the average frost dates. It is important to estimate the date of the last frost in the Spring, as well as the date of the first frost in the Fall. These two dates will help you schedule your seed starting and harvest activities.
Pinpoint Your Growing Zone by Asking Local Experts
If the growing zone map for your area is not clear, and you haven’t been able to locate reliable climate data, the easiest way to figure out your zone is to ask a local gardening expert. If you don’t yet have a trusted gardening expert in your area, try these suggestions to find a gardening mentor.
When asking local experts, consider asking a few opinions and take the most common response. Some gardeners live in their own unique microclimates, or may have different growing conditions than you (even locally). It may therefore be helpful to ask more than one person.
Planning Your Garden For Your Plant Hardiness Zone
Once you’ve determined your growing zone, write it down! You don’t want to forget or get confused after you’ve done all the research to decipher it.
Your free Garden Planner is the perfect place to record your zone, as well as the frost dates for your area. These are key pieces of data for your garden planning, so it’s nice to have everything in one place. If you haven’t yet downloaded your free printable garden planner, sign up here for your copy.
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