April’s cold start in Missouri reminds gardeners that planting date is a matter of risk versus reward, said University of Missouri Extension horticulturist David Trinklein.
“Growers who plant early risk crop damage or loss to freezing temperatures,” he said. “However, if the latter does not occur, they are rewarded by earlier produce, which commands more competitive prices at the market.”
Many parts of the state averaged more than 15 degrees below normal for the first 10 days of April, said MU Extension climatologist Pat Guinan. “It’s hard to believe, but we’re on pace for experiencing the coldest April on record for Missouri,” said Guinan.
The current record for April was set in 1907, when the statewide average temperature for the month was 47.2 degrees—8 degrees below normal. April 1983 ranks as the second-coldest April on record. Records date back to 1895.
Let soil temperatures, not the calendar, determine when to plant, Trinklein said. “Soil temperature would indicate whether spring is ‘early’ or ‘late’ in a particular year.”
Both vegetables and flowers fall into two temperature preferences: cool season and warm season. Plant cool-season flowers and vegetables after the soil is 45 degrees or more. Cool-season plants, also known as cole plants, can withstand moderate frost.
Warm-season plants, such as tomato, pepper and sweet corn, like their day in the sun. They prefer to grow when soil temperatures rise to at least 60 degrees. This is especially true for direct-seeded crops.
Prevention remains the best cure for temperature-related injury, Trinklein said. Plant at the proper time for your area and be prepared to protect plants as needed.
Trinklein suggests planting dates in a downloadable vegetable planting calendar at extension.missouri.edu/g6201(opens in new window).
Missouri Mesonet provides a map of real-time soil temperatures at 2 and 4 inches for locations around the state at mesonet.missouri.edu(opens in new window).