What are Growing Zones and Do They Even Matter?

This lantana is an example of a perrenial that grows well in zone 9B

If you've spent any time online looking into gardening, you have probably heard people talking about growing zones (or hardiness zones). For example, I'm in Las Vegas, Nevada and my zone is 9B. So what does that mean? Well, basically the United States Department of Agriculture split the US into 13 different zones (which are then split into A and B sections) that are supposed to describe the hardiness of the area based on the highest and lowest average temperatures. How does this effect your gardening? Short answer, it doesn't really.

Knowing your zone can give you a general idea of the area that you are in. The lower zones are in colder areas, while higher zones are warmer. So if I'm looking for advice on when to plant pepper seeds where I am in 9B, I'm probably not going to pay very close attention to someone who lives in 4A. While there is probably still a lot that I can learn from that gardener, their planting times will vary wildly from mine.

First and Last Frost Dates

What you need to know the most when figuring out your gardening schedule is your first and last frost dates for the year. This will help you determine when you should be planting seeds for each season. For example, if the last average frost date in your area is March 25th, and you know that you want your pepper plants to be around 8 weeks old when you transplant them (which is usually the recommended age) then you just count back 8 weeks from March 25th. So now you know that you need to start your pepper seeds around January 25th. Possibly sooner since some pepper seeds can take up to 2 weeks (or more) to germinate.

Knowing the first frost date of the year will be helpful if you're trying to push your garden as late in the year as possible. So if it's September 1st and you want to see if you still have time to plant one more zucchini, you want to first look at the seed packet to see how long it takes for the plant to reach maturity, and then check your first frost date to see if you have time. If it takes 120 days for the zucchini to reach maturity, but your first frost date is November 15th, you probably won't have time to grow that plant before the cold kills it. In this case I would recommend looking for a variety with the word "early" in the name, as those tend to mature faster. You can find your first and last frost dates by simply googling your zip code along with "first and last frost dates". Just keep in mind that these are average dates, so it's also good practice to keep an eye on your forecast to make sure there are no surprise frosts earlier or later in the year than expected.

When Do Growing Zones Matter?

Growing zones are good to know when you are looking into planting perennials, or plants that you expect to stay in place year after year. Most vegetables are annuals, which means that you plant them freshly each year, they grow to maturity, and then they die. Perennials will keep coming back even if they slow down their growth or die back during winter. The hardiness zones tell you what the lowest and highest average temperatures are in your area, which is really helpful when choosing which perennials to plant. It's important to choose ones that will do well in your climate so you can ensure their success. These include anything from large trees, to the hedges that line your walkway. All of these need to be strategically chosen to fit your area. If I want a nice flowery bush with lots of color where I live, something like a hydrangea will not work for me. They will likely die in the summer and not come back again, unless I baby them constantly. I would instead choose something like a lantana. They come in lots of different colors, they grow very fast, and are extremely drought and heat tolerant. They die back in the winter, but come back in full swing as soon as the temperatures reach the 80s again. Usually your local plant nursery will carry what works best in your area, but you can also determine if something will work by googling the plant you're interested in, along with your zone.

While growing zones do play a role when planning the landscaping around your house, they don't have very much impact on your vegetable garden, beyond giving you a general idea of the temperature in your area. The best thing that you can do is become familiar with the climate that you live in. Start seeds at different times and see what works for you, pay attention to what gardeners in similar climates (hi!) are doing, and keep a close eye on the forecast during those transitional spring and fall months in case you get an unexpected heat wave or frost.