Knowing your frost dates and planting zones can make a big difference in the success of your garden.
In this blog post, we'll go over what frost dates and planting zones are, why they matter and how to find them.
Being aware of your frost dates and planting zones is important for successful gardening because it helps you choose plants that are appropriate for your climate and plant them at the right time.
Planting too early or too late can affect the lifespan of your plants, so understanding your area's frost dates and planting zones can maximize your garden's yield and reduce the risk of losing plants to unfavourable weather conditions.
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❄️ What are Frost Dates?
Frost dates are the average dates of when you’re likely to have a light freeze in your area, based on historical data.
Your first frost date will be in the fall, and usually signals the end of the growing season. Your last frost date will be in the spring, and lets you know when warm weather is coming.
These dates are important because they can determine when it is safe to plant certain crops.
For example, warm-weather crops (like tomatoes) shouldn’t be planted outside until the risk of frost has passed. On the other hand, cold-weather crops (like lettuce) can be planted outdoors in early spring and will survive frost once you provide some frost protection.
Note: Frost dates are just an estimate and should be used as a guide to help you plan your garden. You will still need to check your local weather forecast to determine when you might have frost.
🗓️ How to Find Your Frost Dates
There are several ways to find your frost dates.
- If you live in Canada or the United States, you can use the frost date calculator from The Old Farmer's Almanac. Just enter your city, state or postal/zip code into the search bar and hit enter.
- Ask a garden centre associate in your area. Anyone who works at a nursery or garden centre should know this information.
- Google “average frost date” plus the name of your city.
🗺️ What is a Planting Zone?
Planting zones, also known as plant hardiness zones, are areas on a map that are categorized by the average minimum winter temperature.
Each zone is defined by a range of temperatures, and plants are rated based on their ability to survive in those temperatures.
Most plant catalogues and websites will mention the hardiness zones for perennial plants in their product listings.
You’ve probably also seen perennial plants at the garden centre that say something like “hardy to zone 5”. That means that, under the right conditions, the plant is likely to survive winter.
Knowing your planting zone can help you choose plants that are appropriate for your climate, and help you identify which perennials, trees or shrubs are likely be survive through the winter months.
When deciding on which plants to grow in your garden, choose plants that are rated for a zone that is hardier than yours.
For example, if a plant is hardy to zone 6, and you live in zone 7, that plant should survive. But if a plant is hardy to zone 8 (warmer than zone 7), it's not likely to do as well.
🇨🇦 How to Find Your Zone in Canada
The Canadian map (shown above) is divided into ten zones, where 0 represents the coldest zone, and 8 represents the warmest zone. Most of the zones also have sub zones where "a" is colder than "b" (i.e. zone 6a is colder than zone 6b).
If you're not sure what your planting zone is based on the map, there's another (easy!) way to find your zone.
The Natural Resources Canada website has a database of plant hardiness zones sorted by municipality.
Use the drop-down menu on that website to sort the information by province, and then search for your town. There you'll find 4 numbers listed for your municipality.
The first number is the 1961-1990 zone, this is the original zone for your area.
Over time, the data collection methods and climates in each area have changed, so the second number is the updated 1981-2010 zone.
I use both numbers as a reference to help me determine which plants I should grow as annuals versus perennials.
🇺🇸 How to Find Your Zone is the United States
The USDA also has a planting zone map (shown above) that can help you determine your zone.
For an easy way to find your zone, go to the USDA Agricultural Research Service website and enter your zip code or location. The map will show you which zone you are in.
Although both the Canadian and American maps use a similar naming convention, it's important to note that they are not measured using the same methods!
This means that Zone 6 is Canada isn’t the same as Zone 6 in the United States. But the general rule is you add 1 to the NRC zone. For example, a zone 6 in Canada would be a zone 7 in the United States. It's not 100% accurate, but at least it gives you an idea to start with.
😑 Why Planting Zones and Frost Dates Aren't 100% Accurate
It's worth noting that while frost dates and planting zones provide helpful guidelines for gardening, they may not always be completely accurate.
Factors such as proximity to bodies of water, mountains, and wind patterns can create microclimates that differ from the expected climate of your zone and frost dates.
Additionally, climate change has caused fluctuations in weather patterns, resulting in variations in frost dates from year to year.
It's important to consider other factors that can affect the success of perennial plants too, such as moisture and light conditions.
All that said, knowing your frost dates can still help you determine the optimal time to plant your seeds, and plan out the start and end your gardening season.
Similarly, understanding your planting zone can guide you in selecting perennials that are more likely to thrive in your winter conditions.
Keep in mind that while this information is helpful, it's not set in stone. If you have any questions, feel free to ask in the comments below.
👩🏽🌾 Get a Free Planting Guide
West Coast Seeds has created handy guides that tell you exactly when to start certain seeds based on average frost dates and hardiness zones for various areas. Guides are available for locations in Canada and the United States. Grab yours today!
🙋🏽Frequently Asked Questions
Yes, people often plant perennial plants that are outside of their planting zones and treat them as annuals. This just means that the plant will only last for the warm weather season and you'd have to purchase it again next year. If the perennial plant is hardy to a zone close to your own, you may be able to keep it alive by taking extra precautions to protect them from cold weather.
You can adjust your planting schedule based on your frost dates and planting zone by starting seeds indoors before the last frost date, planting cold-hardy crops earlier in the season, waiting until the risk of frost has passed to plant cold-sensitive crops and selecting varieties of plants that are adapted to your specific zone.
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