The First Thing You Need to Know Before You Plant Anything (You’ll Regret It If You Don’t!)

Even if you aren’t familiar with hardiness zones, chances are you’ve seen the colorful map of the United States featured on seed packets and plant labels as you try to select flowers for your garden (and if you haven’t, you can find it on the USDA’s website). And whether you’re sowing seeds with children or picking out your annual hanging baskets, knowledge about these zones can help you choose plants that thrive in your area. 

However, with the release of an updated zone map at the end of last year, your region may have shifted slightly due to shifting temperatures. It’s something that’s important to consider as you head into fall planting, as it will affect the types of plants you can use in your garden as well as when you should plant them.

“Climate change has meant that global temperatures are rising,” says horticulturist and gardening expert Annette Hird. So what does this mean for you and your precious flowers? Here’s how rising temperatures and adjustments in hardiness zones may affect your garden.

Because the weather differs vastly all over the United States — consider mild winters in Florida as compared to frigid Minnesota! — a plant might not do well in each area. A tropical plant can’t survive subzero winters outdoors, and more cold-tolerant species would fade in the harsh heat of a Southern summer.

Zones can also vary within a state, depending on where you live. Knowing your hardiness zone can help you prepare your garden and plantings for a successful season. In fact, figuring out your hardiness zone is the first thing you should do before planting anything new in your garden.

The first step in understanding your area is to look at the USDA Plant Hardiness Zone Map and determine your zone, either by sight or by inputting your zip code. Your home will fall within one of the 13 different hardiness zones and will either have an “a” or “b” subzone designation. Armed with this information, you can head to the nursery with confidence.

Hird recommends using the hardiness map as a guide when shopping for plants so that you can select appropriate flowers and plant them at the optimum time. “As a general rule, warm-season plants are usually frost-sensitive, so these should only be planted after the last frost date has passed,” she says.

Hird also advises that you may have to wait until the heat of the summer has passed to plant cold-season crops so they don’t wither.

According to Hird, hardiness zones are indeed shifting.

“Hardiness zones are getting warmer, at least by a few degrees,” she says. The USDA also recognizes that zones are shifting, partly due to more data being collected and technological advances.

“These zone shifts can sometimes result in a cooler, rather than warmer, zone,” reveals the map creation section of the USDA site. So whether you live in a cold climate or a warmer one, checking the new map is important for selecting outdoor plantings.

With the slight temperature shift, Hird has noticed both positive and negative changes in her garden. “Plants are flowering for longer, and even vegetables, such as tomatoes and pumpkins, are continuing to grow and produce fruits well into the fall,” she says.

On the other hand, her cool-season, leafy green crops like spinach and lettuce are bolting (or going to seed) much faster — meaning that she hasn’t been able to harvest as successfully as in previous years.

The good news for Hird is that many plants are very adaptable and can adjust to a slight change in temperatures and hardiness zones. Additionally, plants tend to have a range of zones rather than just one. For example, French marigolds are suitable for zones 3a through 11b, but planting dates vary according to the specific zone.

If temperatures are rising in your area, keeping your plants hydrated is one of the best ways to help them adapt. “When it’s hot and dry for an extensive period of time, plants need to be watered more frequently,” advises Hird. She also suggests using mulch to help keep the soil cool and retain moisture. Bonus: It will also help shield plants during cold winters.