What to know about starting your garden this spring as temps warm

The temperature is warming up in Iowa, but does that mean you should pick up your trowel and get in the garden?

Iowa experienced record-breaking warmth in February, reaching up to 78 degrees, according to the National Weather Service. The weather doesn’t look to be taking another downward spike away from spring-like temperatures, either.

Most Iowans start their gardens in late April, and some even wait until after Mother’s Day. But warmer temperatures in Iowa are making some gardeners ask: Is it time to start gardening yet?

While Iowa weather is unpredictable, experts say to keep an eye on dropping temperatures and to stick with hardy plants, at least for now.

What is your plant’s hardiness?

The likelihood of your plants’ survival lies within how hardy, or how cold-resistant they are. In Iowa, the further north you go, the higher chance you have of an unexpected frost.

Most Iowans wait until the last frost to dig their hands into the dirt and start their gardening but with unexpected warmth this year, it’s a little harder to tell when to start.

The U.S. Department of Agriculture has developed what it calls hardiness zones, areas of the country based on average minimum winter temperature, to help gardeners with their planting decisions. This is used as a general basis for choosing landscape trees and shrubs since winter cold is one of the main measures of where plants can survive.

In Iowa, zones from 4 to 6

In late 2023, the USDA updated the Plant Hardiness Zone Map, moving Iowa into a slightly warmer region of the map, ranging from zones 4 to 6.

Ames and much of Des Moines had been in Zone 5a, considered safe for plants that can tolerate temperatures down to minus 20 degrees. The new map puts them in Zone 5b, where the limit of tolerance is slightly more hospitable at minus 15 degrees.

The rest of Iowa now ranges from

Zone 4b, with a temperature threshold of minus 25 degrees, to Zone 6a in the extreme southeast and southwest, with a minus 10 degree threshold. The addition of 6a zones is a first for Iowa.

So, how’s the forecast looking?

According to the National Weather Service in Des Moines, the warmer temperatures across Iowa are likely to stick around even after a few cold snaps.

“We are expecting temperatures to warm up again,” meteorologist Jeff Zogg said. “The six to 10 day (forecast) is calling for above normal conditions. And normal high for this time of year is 43, so even though it’s relatively cool, it’ll still be above normal.”

The coming week calls for warmer temperatures, while the skies will be mostly cloudy and a chance of rain will likely continue throughout most of the week.

But, gardeners beware of the warmer temps, there’s still a chance of frost while temperatures dip to the low 30s overnight.

When will Iowa’s last frost be?

While the last frost is typically forecasted to be around April 18, the warmer temperatures may change that, according to the National Weather Service in Des Moines.

According to Iowa State Extension, the last spring frost in Des Moines is estimated to be April 9. The Old Farmer’s Almanac, which some gardeners swear by, says it will be around April 24.

No matter when the last frost of the spring will be, you’ll need to know what can and can’t survive the lower temperatures still forecasted.

What plants can survive frost, and which ones can’t?

Fortunately, you don’t have to wait until the threat of frost is completely gone to start planting your flowers.

According to Menards’ Early Spring Flower Planting guide, after the threat of the worst winter weather is behind us, hardy annuals such as pansies, marigolds and petunias are tolerant of later, unexpected frosts.

Cabbage, Brussels sprouts and radishes, as well as root vegetables, leafy greens, peas, and fava beans also are hardy enough to ward off some frosts.

Whether you plant them in pots or in the ground, however, you’ll want to be careful about freezing temperatures. Iowa State Extension Consumer Horticulture Specialist Aaron Steil advises covering them with a blanket or bringing them inside your garage to keep even your hardiest plants from succumbing to the cold.