Lows Wednesday night could be killer for plants

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Wednesday, September 14, 2011
— The 2011 growing season in southern Wisconsin is not likely to break any records.

Unless, of course, you count the possibility of a record-breaking early frost.

The National Weather Service predicts patchy frost tonight or Thursday night in the Janesville area. Lows are predicted of 35 and 36 degrees those two nights, meaning frost would be possible in low-lying areas.

Janesville since 1948 has never had a killing frost—when the air temperature hits 32 degrees or less—before Sept. 20, according to Gazette records. The Sept. 20 record is held by the years 1956 and 1991, when the temperature dipped to 29 and 32 degrees, respectively.

The average first frost happens Oct. 9, according to Gazette records. The Gazette uses data collected at the Janesville Wastewater Treatment Facility on the city’s south side.

Conditions also are unusually dry, according to Gazette records. As of Tuesday, Janesville has gotten 8 inches of rain this summer. Average summer rainfall is 11.6 inches. Spring rains also were below average. The city got 9.5 inches of rain as opposed to the average of 10.6 inches.

The Rock River was at 3.2 feet on Tuesday afternoon at the United States Geological Survey station in Afton. The USGS website does not include average gauge depths.

It does collect date about discharge, or the volume of water flowing past the survey station. The average daily discharge for Sept. 13 since 1914 is 1,200 cubic feet per second.

On Tuesday, the gauge showed 868 cubic feet per second.

Some rain would be welcome for cash crops such as alfalfa and winter wheat that must survive the winter, said Jim Stute, UW Extension crops and soils agent. A little rain wouldn’t have much affect on the corn or soybeans, he said.

Nor would a little frost, Stute said.

Remember the “heat dome” that in July trapped humid, hot air across much of the United States? Who can forget the four days we spent living in the basement or sticking our heads into the freezer?

The heat wave was tough on crops, but it did correct what had been a below average number of growing-degree days, Stute said.

That means corn and soybeans are maturing at the normal pace, Stute said. Many Rock County cornfields are mature or very close to maturity; soybeans are more varied but for the most part are close to maturity, he said.

“The impact on yield loss would be pretty minor,” Stute said of the predicted frost.

Allergy sufferers and some exhausted gardeners might welcome an early frost. UW Extension horticulture agent Mike Maddox said he’s “had it” with vegetable gardening this year. However, he’s not ready to say “goodbye” to his ornamental plants, Maddox said.

If you want to keep harvesting warm weather crops such as tomatoes, eggplant, peppers or beans, cover them with a sheet or floating row cover, Maddox said. That should trap enough heat to protect the sensitive plants.

“For some people, they’re ready for the frost,” Maddox said. “Others are going to fight to the end.”

A light frost wouldn’t affect cool weather crops such as carrots, beets, greens or peas. In fact, it could be an improvement, Maddox said. Frost triggers the plant to store extra sugar, which makes your Brussels sprouts and other late vegetables even tastier, he said.

A little frost would be good for the apples, too, said Connie Brockhus, owner of the Apple Hut at 1718 W. Walters Road in Beloit Township. Cool weather pushes apples to ripen, she said.

Like corn and soybeans, this year’s apple crop will be average, Brockhus said. Early ripening apples already are picked. Three or four varieties will ripen every week for the next month or so, she said.

The Apple Hut is picking Cortlands this week and will have honey crisp apples this weekend, she said.

The apples can tolerate the cold as long as the temperature doesn’t drop below 26 degrees for more than six hours at a stretch, Brockhus said.

“They’re pretty sturdy,” she said.

Last updated: 6:21 pm Thursday, December 13, 2012

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