What Gardening Zone Am I in?
"Yeah, but what gardening zone are you in?"
"Easy for her to say. She's in zone 7."
"My garden zone changed! I still can't believe it!"
These are the type of comments I get on pretty much every video I post on social media. I feel like I need to wear a name tag that says, "Hi, I'm zone 7b," because that's all some people seem to care about.
This hyper focus stems from a profound misunderstanding of gardening zones and how useful they are to you if you have a vegetable garden or kitchen garden. Your zone does not tell you what plants you can and cannot grow. It doesn't even tell you when you can grow something.
So the short answer to what your garden zone means, as I'll explain further, is... not a whole lot.
What Are the USDA Hardiness Zones?
You know that map of the US with the colorful bands sweeping across the country? That was created by the US Department of Agriculture for farmers. The USDA assigned a number from 1 to 10 to each location based on average minimum temperature. There's a 10°F-range within each zone, so they further divided each zone into two subgroups: a and b.
The lower the zone number, the more arctic the climate, and the higher the number, the more tropical.
(You can check your garden zone here or google "[city name] hardiness zone".)
What Your Gardening Zone Can Tell You
Zones are based on your yearly cold temperature average over the last 30 years. This information is useful to know when you're considering which perennials you can grow in your garden or landscaping. Perennials are often only hardy down to certain zones, so knowing your number will help you pick plants that will survive the winter in your area.
Let's say you're considering buying some perennial herbs for your garden. You pick up a rosemary plant, and the plant tag says something like "USDA hardiness zones 8 and 9". That means this particular herb is unlikely to survive your typical winter conditions outdoors if you live in zone 7.
You'll need to pick a hardier variety (like Arp rosemary) or an herb that can withstand lower temps (like oregano), unless you plan to pot up your herb and overwinter it indoors. Otherwise, you'll have to consider rosemary an annual herb in your climate.
That's really all your gardening zone can tell you. Now, let's look at what your gardening zone can't tell you and what to pay attention to instead.
What Your Gardening Zone Cannot Tell You
Unfortunately, there's way more your gardening zone can't tell than what it can. Your zone can't tell you...
...Whether Your Plants Can Survive Your Hottest Temperatures
The USDA hardiness map focuses on cold temperatures, but plants can also suffer in climates that are way too hot for them.
Seattle, Washington, for example is zone 9a. That used to be my zone when I lived in Houston, Texas. I'm sure we all know that Seattle and Houston have very different climates. The average high temp in Seattle for the month of August is 73°F, and the low is 55°F. Houston's average high, in comparison, is 95°F, and the low is 75°F.
Did you catch that? Houston's average low temp is higher than Seattle's average high temp! Gardeners in these two zone 9 cities are experiencing completely different weather during the summer. So many plants that would thrive over the summer in Seattle would, at best, struggle and, at worst, sizzle up in Houston's heat.
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The American Horticultural Society came up with a heat zone map to address this pretty glaring oversight back in 1997. They collected data by region based on the average number of times the temps exceed 86°F per year. Unfortunately, this map never caught on with gardeners. (I guess they don't have as good of a PR person as the USDA or something.)
Here's What You Should Know Instead of Your Zone
Look up your average high temps for your summer months. If you see an average high temp that's 85°F or higher, then you have what we call a hot season in your neck of the woods. You'll want to stick to growing these heat-tolerant herbs, veggies, and flowers in your vegetable garden.
...How Long You Might Experience Extremely Low Temps
Your hardiness zone doesn't really tell you anything about how often or how long you can expect freezing temps.
There are many frost-tolerant plants that will survive brief freezes, especially if you use garden covers like frost cloth or even just some old blankets to protect them during cold spells. These frost-tolerant plants, and even some frost-resistant plants, will die if extremely cold weather persists.
Here's What You Should Know Instead of Your Zone
Look up your average high temps for your winter months. If you see an average high temp that's 34°F or below, then you have what we call a cold season during that time period when your temps are typically below freezing. This will be the only time of year you have to "shut down" your vegetable garden. (Unless, that is, you're growing under cold frames or in a greenhouse.)
...What Vegetables You Can Grow When
Your gardening zone can't tell you what herbs, leafy greens, root crops, or fruiting plants you can grow throughout the year.
Let's go back to the Seattle vs Houston example (because it never ceases to amaze me). Gardeners in Seattle can potentially keep cool season plants like lettuce alive well into June, when their average high is only 72°F. Houston's already getting an average high temp of 75°F by March, which is why their best time to grow lettuce is actually during their winter months.
Houston goes on to enjoy a long hot season, and they have the perfect climate to grow okra. Gardeners in Seattle can also grow okra because they're in the same zone as Houston, right? Wrong! These plants are unlikely to thrive there. Seattle rarely gets long stretches of the hot temps okra needs to thrive.
Here's What You Should Know Instead of Your Zone
Use your average high temps to determine your growing seasons throughout the year. Your growing seasons give you a much better picture of what's possible in your garden each month. I came up with our growing seasons system after living and gardening in five completely different climates, and I can tell you, it works for every region.
I've already discussed the cold and hot seasons. There's also the cool season, which is when your average high is between 35 and 64°F and there's still a chance of frost at night. This is when you'll grow plants that love cooler temps.
Finally, there's the warm season, which is when your average high is between 65 and 84°F. The warm season includes classic "summer" vegetables like tomatoes, cucumbers, and squash.
Your Gardening Zone Is Not a Magic Number
Don't let your hardiness zone dictate what you can and can't grow in your garden. Your zone barely gives you a glimpse into your growing possibilities throughout the year.
It's a great idea to seek local gardening advice to learn more about what you can grow each month in your area. Connect with your local extension for free advice or find the nearest Gardenary-certified coach. I recommend following any gardening experts in your area on social media so you can see what they're planting in their own gardens. You can also reach out to them for coaching sessions or gardening classes.
For a really easy way to learn when to plant something in your garden, download our free Garden Calendar. All you have to do is tell us your first and last frost dates, and we'll tell you when you can plant based on your growing seasons.
Now you can use your zone when it's helpful and seek out the right kind of information when it's not!
Never Miss a Planting Date Again!
