Knowing Your Plant Hardiness Zone: The Map vs. Reality
One of the most important parts of gardening is knowing what you can grow in your garden and when to grow it. The unfortunate part about gardening is that we can’t plant everything we wish we could. Each part of the world has different temperature ranges, different length of seasons, and different amounts of moisture. Let’s break down plant hardiness zones and when/what we can start growing based on that zone. We’ll also look at the discrepancies between what plant hardiness zone maps say and what reality actually tells us.
Plant Hardiness Zone Maps
A great tool that researchers have put together are plant hardiness zone maps. Plant hardiness zone maps show different growing seasons based on a temperature range across the entire world. Most people view these based on their country but you can find zone maps that show the entire world at once–which I personally find really fascinating. The world is split up into 13 different zones. Each zone has two subsections listed as a or b such as zone 6a or 7b.
It’s important to remember that wherever you live your country, county, city, etc. is unlikely to have just one zone. The world is a diverse place and things like water access, elevation changes, etc. All affect the accuracy of these zones.
These zone maps are great especially if you’re just beginning in gardening and you don’t have outside knowledge about the temperature range from year to year within your area. Each zone and subsection has its own color to help viewers differentiate the changes in these zones across an area within the map.
Typically here on The Busiest Bee Garden I reference things based on the United States, specifically the western half, as that is where I have the most experience gardening. So remember to check out these zone maps to find out what applies to your areas. The United States Department of Agriculture has a great interactive map of the U.S. for these zones.
Starting Seeds or Plants
Now beyond the zone map telling you what your average temperature range is across an entire year for your area, the zone map also helps guide you in understanding when you can start growing seeds and/or when you can begin sowing directly outdoors.
When plants are younger they are not stable enough for more extreme conditions. Typically the hotter your zone is the longer your growing season is. So you can begin growing plants a lot sooner than a colder zone. I live in a zone that fluctuates between zones 6 and 7, so typically I know that I can start seeds indoors or in the greenhouse in March. I can then begin transplanting and sowing directly into the ground in mid May through June. But in colder zones sometimes outdoor planting can’t occur until mid to late June.
These seed starting times also give you a better look at what plants you can grow in your area. Some plants, like tomatoes or melons, don’t do well in the cold at all. That means they need to be planted well away from the last frost of the season. Other plants are more cold hardy, like broccoli or cabbages, so if a frost hits later than normal they usually survive. Sometimes they even like the cooler temps.
Knowing your growing zone will help you determine if you need to be starting seeds indoors to give them a longer growing season. Growing zones will help you determine if you need to make them more hardy to the conditions outside before planting. Growing zones can help you know if you even need to forgo growing the plant in your area at all.
Harvesting Plants
Another thing that growing zones can help us with is understanding our harvest. In much the same way that growing zone guide our planting times they also guide our harvests. If you wait too long, you might loose out on valuable produce to an early frost.
Some plants need a longer amount of time to grow before harvesting and have to be planted indoors in advance. Or they need to grow in an area that has a longer growing season. Pumpkins are a good example of this, as some varieties need over 100 growing days before harvesting. Radishes, however, grow more quickly and are ready to harvest in only 25-45 days.
Zoning Discrepancies
It’s really important to understand that while these zoning maps are a great place to start trying to figure out your area it’s not going to be 100% accurate. These are average typical temperatures. It’s impossible to be able to completely predict what each year is going to be like.
In my experience just recently, normally I start some seeds in advance but wait mostly until mid May to begin planting outside. I was taught this by my grandmother, who always said never to plant before Mother’s day. Even though I’m always ready to get started as soon as possible on my garden each year, I try to stick by this rule.
This last year in 2021, I planted as usual the weekend of Mother’s Day and the weather was beautiful and warming up so nicely for the whole week. The garden was coming along nicely, and I was so excited for the prospect of a bountiful garden. However, in an unusual fashion, the first weekend of June it got extremely cold and even snowed several inches. It remained cold for the next two weeks. Nearly all of the plants died and I had to start over in mid June.
While I did have success in some plants, I couldn’t get everything back to the way I hoped. Once the cold front moved on, the temperature rose back to normal June weather almost immediately and some of the new starts just couldn’t take the sun intensity at that small size.
This is just one example of how there are always going to be some discrepancies within the zone guides, especially with climate change affecting our “typical” weather.
Another discrepancy you need to take into consideration is elevation change. Elevation can change whether you are colder or hotter at different times of the year and there can be quite vast changes even within a small area of land.
I live in a county where some areas are at around 4500 feet above sea level, but I live in the benches of our local mountains. This means that where I live my elevation goes up to 5800 feet above sea level. So when there are cold and rainy days in the county’s lower elevations, it might be snowing at my house. This change isn’t a drastic or consistent enough difference to warrant a different zone. But it’s enough to keep in mind when I’m starting the planting and harvesting times of year.
Final Thoughts
Of course there are lots of parts that go into starting seeds and understanding how to grow plants well, but we’ll cover more of this in future posts!
Sometimes if you are new to an area you may not know what happens from month to month. Or if you feel that things have been changing in your area it’s important to record and track weather patterns. This can help us determine what is needed for your gardens. Check out my Free Guides page to grab a copy of my Garden Weather Tracker. This will help you begin to get a good sense of what weather is like in reality for your area, instead of solely relying on the zone maps.
Thanks again for growing with me here at The Busiest Bee Garden!
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