What an Expert Wants You Know About Rising Temperatures and Fall Planting

Depending on where you reside, you've probably noticed the weather hasn't cooled down much despite being fully into fall—it's a bit disorienting to sip a pumpkin spice latte while it's 80 degrees outside. And you're not imagining things, either: Summers across the United States are getting warmer, longer, and more dangerous due to the impacts of climate change, and they likely won’t slow down any time soon. 

While you may have already adjusted your air conditioning, kept your summer clothes out, and maybe even enjoyed a few more evening walks, you might be wondering what will happen to your garden. Should you start your fall or winter planting now or hold off until temperatures drop? Is there anything more you should be doing to tend to your garden? Should you choose different plants altogether?

According to Duane E. Friend, a climate specialist with the University of Illinois extension program, just about the entire country has experienced higher overall temperatures over the fall months. But when it comes to fall planting, the significant changes come later on in the autumn—so luckily, you have a bit of time left to plan.

“When we look at it on a monthly basis, we don’t see a big change in October,” Friend says. “But where we really see a bigger change in increases in temperature is in November and December, and this is true for the vast majority of the country—both increases in maximum and minimum temperatures.”

How to Adjust Your Gardening Accordingly

According to Friend, you don’t need to adjust the time of year you’re planting quite yet, but you should look out for certain indicators and potentially take some extra steps to ensure your garden thrives throughout the winter. From checking the average frost date and monitoring hardiness zone maps to simply supplying a little extra TLC, here’s what he suggests for keeping your garden in prime condition.

Watch the frost date

The frost date indicates the first and last days on which the temperature will fall below freezing—0 degrees Celsius or 32 degrees Fahrenheit—and therefore possibly damage or kill young, sensitive plants. According to Friend, you should pay more attention to the frost date than the temperature outside on a daily basis—and the these key dates actually haven’t shifted a lot.

“Even though we're still trending for a warmer fall, those fall frost dates really haven’t changed that much,” he says. 

The frost dates range quite drastically and depend on your region, so you’ll need to do some research to find your area’s specific information. The Old Farmer’s Almanac allows you to find your city or zip code’s frost date, and so does The National Gardening Association. 

Knowing the first frost date gives you plenty of time to start your garden, letting your plants grow and thrive before temperatures drop significantly. Plus, if you’re feeling adventurous, Friend says you might be able to push the boundaries of your normal gardening timetable.

“If you do want to kind of take a little bit of a risk, there are also maps that’ll show the 90th percentile of when the earliest frost will occur down to the 10th percentile, so you can kind of figure out, ‘Well if I want to take a little bit of a risk, what date should I be looking at for that?’” he says.

Because average first frost dates are still the same, you can stick to your normal routine. But looking ahead to spring, Friend says it's a smart idea to plan ahead.

“We’ve seen big changes in spring—frost dates in spring have moved backwards pretty substantially,” he says.

Reference hardiness zone maps

Another valuable resource to keep an eye on: the U.S. hardiness zone maps. Created by the USDA, these maps show you which planting zone you're in and how to use that information to plan your gardening choices and keep your plants as healthy as possible. Though they're only guides, these maps can allow you to avoid risks—but also to take them.

“Always look at the hardiness zone maps to understand that since we are getting milder winters, that may lend itself to being able to plant something that previously was kind of risky to plant,” Friend says.

“Since we're getting these warmer falls and winters that aren't nearly as harsh in terms of temperatures—and especially, our minimum temperatures have gone up quite a bit in wintertime—you may be able to push the envelope a little bit on on some of those things that really were kind of on the edge of the hardiness.” 

The freedom to take planting risks may be one of the very few advantages of climate change-induced temperature differences—but Friend cautions that you shouldn’t base all your plans off this chance.

“I wouldn't say to go out and just do it wholesale, but maybe do a little bit of experimentation,” he says.

Provide extra care

Friend says as of now, there aren’t too many risks associated with planting at the normal time in the fall—so garden away as you usually would. Just remember: Day-to-day temperatures don’t always dictate how quickly the seasons will change.

“The main concern would be if somebody was thinking that, for example, maybe we've had an above average September and they want to go out and still put in some things thinking that we're going to have an extended fall,” Friend says. “That may not always be the case.”

But with some plants, he adds that it's a good idea to pay closer attention as the fall and winter seasons in particular heat up.

“It’s going to depend on the type of plant that it is," Friend says. "If it's something that isn't dormant, you may have to look a little bit more closely at it in terms of care."

However, if you’ve planted something that’s already gone dormant and the fall months turn out to be warmer and drier than you expected, monitoring it closely for moisture will help it stay healthy. 

Sunscald—or tissue death that occurs on thin, young bark during thawing and refreezing periods—can also occur when temperatures are higher than usual. Using a light-colored tree wrap may help prevent this damage and provide the soil with moisture.

Check Your Resources

If you’re still unsure what or when you should plant, Friend recommends turning to as many valuable (and free) resources you can find. Look out for local citizen and community science monitoring projects, which provide location-specific advice and trend-based information to help you make decisions about your own planting. 

The National Phenology Network offers expert input about the national ecosystem, including frost times, hardiness zones, specific times you should plant specific species, and much more.

“There are many really good monitoring programs out there that people can volunteer for," Friend says. "That's a really a big benefit—providing that information for a particular region on what kind of trends they’re seeing in terms of changing weather patterns or climate patterns, changing plants, changing insects, all of those things."

Friend also suggests visiting your local university extension office or seeking out local gardening groups or master gardeners online—many of them provide top-quality advice for free. You can check out the USDA Climate Hubs for more detailed information.

“They have a multitude of different tools that are specifically for helping people determine when they should plant, what’s coming down the road, those types of things,” he says. “So they help some with some of the risk management related to that.”