Scientist studies strawberries in winter

A December strawberry growing in Independence County was found just before Christmas. (Special to The Commercial/Matt Davis/University of Arkansas System Division of Agriculture)
A December strawberry growing in Independence County was found just before Christmas. (Special to The Commercial/Matt Davis/University of Arkansas System Division of Agriculture)

Strawberries, which are typically ready to pick closer to Mother's Day, have been found growing and ripening before Christmas in Jackson County.

In Arkansas, strawberries are typically planted in September to early October. Depending on planting date, row covers are applied to help with growth prior to dormancy. Row covers help to trap heat from the soil and are made of white, lightweight, non-woven fabrics.

"Christmas strawberries?" asked Matthew Davis, Jackson County extension staff chair for the University of Arkansas System Division of Agriculture, in a Facebook post on Dec. 21. "Warm weather has prompted a few strawberries to form under the row covers."

The National Weather Service at Little Rock said temperatures were 2 degrees above average in November, and December saw an estimated 4 degrees above average.

"Every year, you're going to have some strawberries show when you see warm weather like we've had this fall and early winter. The row covers have something of a greenhouse effect," he said. "They're usually eaten by insects or damaged by cold though."

The precocious berries are part of research Davis is doing on new strawberry varieties and gauging how they react to winter weather.

Once acclimated to cold temperatures, strawberry plants are cold hardy to around 10 degrees Fahrenheit and leaves are hardy to around 22 degrees. Shorter days and colder temperatures signal the plant to prepare for dormancy.

"It's inevitable. You always have row covers blow off," Davis said. "We typically use row covers to help with fall growth due to delayed planting. Due to labor restrictions, row covers are often applied and may not be removed until early March. The issue is that row covers are keeping the plants potentially from reaching dormancy."

In his trial, Davis is leaving half of the plants in his strawberry rows uncovered. He will be making weekly visits, noting damage and growth in the "crown or branch crowns," which are the growing parts above the soil line in the center of the plant.

"We are really wanting to see if the use of row covers may be delaying plant dormancy," he said. "Strawberries need a transitional time that allows the plant to go dormant. During that dormant time, we get concerned when we see temperatures at or below 15 degrees Fahrenheit. When temperatures reach that low during dormancy we would look to cover or recover any plants that might be exposed.

"The cold may affect each variety differently," Davis said. "Plants will form two to five branch crowns leading up to spring. We would like to see one to two branch crowns forming in the fall along with the main crown. Cold weather can damage the crowns and cause delays in maturity or plant death. These plots will give us the opportunity to see any variety differences in crown formation, damage and dormancy."

Among the varieties in Davis' trials are Camino Real, Fronteras, Ruby June, Chandler, and a few numbered varieties.

In northeast Arkansas, the covers generally come off the strawberries at varying times and when labor is available, Davis said, adding that he hopes to see if the covers are having a positive or negative impact on yields for his growers.

For areas not closely observed, it's difficult in March to tell whether damage to strawberries was due to cold or other factors, such as the plant not rooting properly.

Of use to growers is the fact sheet Small Fruit Cultivar Recommendations for Arkansas, FSA6130.

The Cooperative Extension Service has a chart showing the type of damage that may occur to various fruit crops at specific temperature thresholds.

To learn about extension programs in Arkansas, contact a local Cooperative Extension Service agent or visit www.uaex.uada.edu.

Mary Hightower is with the University of Arkansas System Division of Agriculture.

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