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Are you zoning out? Don’t worry. Zones are simple to understand and a great tool to achieve gardening success.
Knowing what a zone is and how to use that information can be extremely helpful when planning your garden. Knowing what zone you live in can mean the difference between a successful harvest or frozen oranges.
Understanding zones also helps you choose the best landscape plants for your area to survive both hot and cold temperature fluctuations.
The U.S. Department of Agriculture (USDA) Agricultural Research Service (ARS) created the cold zone map. It is commonly called the USDA Plant Hardiness Zone Map, or Hardiness Zone Map.
Think of hardiness as the plant’s ability to deal with the cold. I need a jacket to deal with 30-degree temperatures; the plant doesn’t have that option, so you need to follow its hardiness guidelines by picking plants that don’t need a jacket when it gets cold in your area: plant jackets, good visual.
The Hardiness Zone Map (cold zone map) is created by taking the “average annual minimum winter temperature” and splitting it into 10-degree Fahrenheit zones. For example, Zone 3 is 10-degrees colder than Zone 4, and so on.
There are 13 zones on this map, but most people say 11 because the U.S. doesn’t have areas that often hit Zone 13. Zone 1 is the coldest, and Zones 11-13 being the warmest in the winter months. South Florida is Zone 11, while Maine’s zones range from Zone 3-6.
In 2012, they revised the map using new technology, extended measurement periods, and more sophisticated analysis. Some areas received a new zone during this time, so look at the 2012 version, not the 1990 version.
A great example of this zone change would be South Florida. Many areas in South Florida used to be 10 a or b but were adjusted due to new information (and climate change) to Zone 11. That means plants that do well in hotter areas like Puerto Rico or Southeast Asia may do well in South Florida because it is a warmer area in the winter months.
Knowing your zone impacts what you grow. Knowing that your area can deal with more heat-tolerant plants may lead you to experiment with plants that might thrive in a hotter climate, like South Florida. Knowing that your plants can deal with colder winters would lead you to pick plants that fit a more frigid zone like in Maine.
The average minimum temperature is calculated over thirty years and is a great guide to help us know how cold it gets in certain areas, on average. Keep in mind this has changed dramatically from year to year and will continue to do so as the climate shifts due to climate change. There is no way to know the exact temperature fluctuations, especially these days. Use the zone maps as a guide and use your innate connection to nature to make the best decisions for your garden.
Still, it is a good starting place and a helpful estimate to chart when the last frost might be in your area so you can get your summer crops started inside in preparation for warmer days. Armed with this information, you can be pretty sure that a plant labeled for your zone will do pretty well in the winter months.
But cold isn’t the only thing you need to think about for a successful garden. What happens when it warms up? Is the plant you picked suited for your zone when it’s hot outside? This is where a heat zone is valuable.
Lucky for us The American Horticultural Society (AHS) created a heat zone map that works in conjunction with the Hardiness Zone map to help us know the maximum, or estimated maximum, hot or higher temperatures in our area.
They consider 86 degrees or above as a heat day. Again, this guide lets us know how much heat a plant can take before it starts to decline and shut down. Tropical plants can take a lot more heat than plants that thrive in Maine.
That is why areas like Texas, Florida, and California can plant palms, but you don’t see many palms decorating New York City streets. New York City and Texas are in different zones, making a big difference to a plant’s health.
If you live in Zone 8b, you wouldn’t want to try a tropical plant from Zone 11 because that plant may not be able to deal with how cold it gets in Zone 8b in the winter, but you may try something from Zone 9 a or b and see how it does. You might also see if something from 7 a or b works.
At the same time, you wouldn’t want to pull something from Zone 3 and plant it in Zone 10 because it might not be able to deal with the heat. Some plants can deal with a vast range of zones. Check before you purchase.
I like to do my experiments with lower-cost plants or seeds that I’ve saved. This way, if it goes poorly, I’m not freaking out over that $300 fruit tree I bought that is dying because of a frost in my zone.
Instead, I grew it from a delicious organic avocado I ate and loved and saved its precious seed for the experiment. For me, that feels better. It is also how Mama Nature does it. She lets a bunch of seeds fall to the ground, and the one that makes it wins.
So back to zones. Let’s say Mama drops that avocado seed to the ground, or I planted my saved seed in Zone 9, and it is a bit cold that year. The seedling grows but never actually produces fruit. In the back of my head or my garden journal, I have a note that says I planted a plant that usually thrives in Zone 10-11 in Zone 9. Maybe it was just not the right setting for this plant.
But then the next year, it is hot, and I try again with another avocado seed. It is scorching that year and consecutive years after, and the seedling grows. It starts to fruit in five or so years, and I get a harvest of delicious avocados. I note that in my journal too. It was warm enough for that plant to thrive in all seasons. My zone may now be right for that plant.
Now, I can start to see patterns. The plants from the warmer climates are growing well; the plants from colder zones aren’t doing well. Using the zone information and experimenting with the zones above and below your zone will show you what will thrive in your garden.
Many plants have zone information on their tags. You can always look them up in a Google search as well. It is best to use the Latin name if you can find it. For example, the Latin name for a snake plant is Sansevieria trifasciata.
If you live in Zone 6, and the label says Zones 1-6, it is a pretty good guess that that plant will be ok over the winter in your area because it is ok in colder zones. If you picked a plant that said Zones 8-11 it wouldn’t do well in Zone 6 because it gets too cold.
The same goes for the heat zones. If you pick a plant for Zone 5 and plant it in Zone 10, it may die because it can not tolerate the heat during the summer.
I know I keep saying the same thing repeatedly because this is an essential concept to understand. Picking the right plant for the right place is what knowing your zone is all about. Understanding zones and the right plant, right place rule can make your gardening adventures a real joy.
It also helps give you a clear picture of how to plan your vegetable gardens the following year and how to create an easy to maintain landscape year-round.
Within your zones, you will also have microclimates. You could have multiple mini climates in one yard within your zone, and you need to look at that before planting.
Let’s say you are in Zone 7, but you have a massive tree in the yard that shades a lot of the space. Plants that enjoy the sun are not the best option for that area. Go with plants that thrive in Zone 7 and like the shade and coolness of that area under the tree. The tree has created a cooler area or a microclimate.
However, on the other side of the yard, you see the sun shines all day long; it is a bit dryer and warmer there, so maybe an apple tree would do well there if you are in Zones 3-8 (depending on the apple variety). Again, this is a microclimate in the same zone.
I’m giving mostly food examples, but this applies to ornamentals (plants that are there for their sexy good looks, not to produce food for you) as well. When you choose landscape plants (ornamental plants), you want to make sure they will do well in your zone during the winter and summer (cold and heat). You also want to look at the microclimate you are planting in. Full sun, shade, mixed.
So you can see how knowing your zones can make a difference in the success of your gardening. Most big box stores know this and carry plants for your particular area; see the plant tags for zone information. Some will have the hardiness zone, and some will have both the hardiness and heat zone information.
But beware that many of those big box store plants come from nurseries that clone their plants. We talked about this in the seed post that cloned plants aren’t the best option for a robust and healthy garden long term or the planet’s biodiversity. So keep that in mind.
Big box store plants are also usually covered in chemical fertilizers, pesticides, and fungicides to keep them looking show floor ready until you get them home—something to ponder.
So when you put together the cold zone and hot zone information, you get a good picture of your area and what to plant, and when.
Planting tomatoes in the middle of a Nor’easter won’t give you tomatoes, wrong zone. Growing those same tomatoes indoors a few weeks before the last frost in your zone is a great idea and gives you a jump on your summer planting season. You will know the approximate last frost date by looking at your zone.
Knowing how much heat those same tomatoes can take will provide you with the tools you need for the perfect planting time so you can enjoy a delicious tomato salad with friends and family.
So what zone are you in? How will knowing your zone change how you garden or experiment with gardening?
I’m looking forward to hearing your thoughts and questions.
Plant Power On!