Mulching Strawberries For Winter Protection

Submitted by: Rich Marini, Department of Horticulture, Penn State University

Mulching strawberries is an old practice that helps protect the plants from low temperature injury during the winter and keeps the ripening fruit clean. This summer Kathy Demchak and I observed winter injury in the crowns of plants in strawberry fields that were not mulched until mid-winter. Although few plants were killed, the injury appeared severe enough in some plants that yield was probably reduced. For strawberries grown on raised beds, the potential for cold injury is high because soil heat may quickly dissipate from the increased surface area of the beds relative to the soil volume. Covering raised beds with plastic or row covers likely retards heat loss, but I am not aware of soil temperature data for raised beds with different types of covers. This article is intended as a review of the information on mulching strawberries and on low temperature injury, so growers understand how and when to effectively mulch their plantings.

In the late summer and early fall, strawberry plants enter a physiological stage referred as “dormancy.” There are different phases of dormancy, but that discussion is beyond the scope of this article. Although dormant plants do not appear to be growing, the buds continue to develop throughout the winter. The initial stages of dormancy are triggered by decreasing day length and declining temperatures, but strawberry plants do not become hardy until November. The term “hardiness” refers to the plant’s ability to resist low temperatures. As strawberry plants become dormant, new leaf development ceases, the leaf petioles become more horizontal, resulting in the “flattened” appearance of dormant plants, and older leaves turn red. Plants become hardy upon exposure to freezing temperatures, and strawberry plants continue to increase in hardiness until January. In late winter, after being exposed to sufficient chilling, the plants start to lose cold hardiness in response to warming temperatures. Upon exposure to sufficient heat, the plants begin to grow.

Mulch should be applied after the plants have attained substantial cold hardiness, but before low temperatures injure the plants. A rule of thumb, supported by research data from several locations, is to apply mulch after three consecutive days when the soil temperature is 40°F or lower at a 4-inch depth. This usually occurs after several hard frosts in the low 20s, and in Pennsylvania this usually occurs between mid-November and mid-December, depending on location.

Strawberry plants are covered with straw to insulate plants from low temperatures, to prevent temperature fluctuations that can lead to frost heaving, and to minimize plant desiccation. Mulch also delays soil warming in the spring and minimizes exposure to spring frost by delaying bloom. Following bloom, mulch helps with weed control, conserves soil moisture, and helps keep fruit clean. Several types of loose materials have been successfully used as mulch, but straw is most common in the northeastern U.S. Hay should be avoided because it contains weed seeds. For matted rows, about 2.5 to 3 tons of mulch per acre, providing a 2- or 3-inch-layer, is typically applied on top of the plants. Doubling this amount of mulch is typically suggested for raised beds. Snow is an excellent insulator, and snow combined with mulch is even better. My Master’s research at the University of Vermont involved laboratory experiments where plants were exposed to various temperatures to determine critical temperatures for plant growth, as well as survival of plants and flower buds. In a field experiment, non-mulched strawberry plants were compared with mulched plants. When the air temperature was -4°F, the temperature of non-mulched crowns was 1.5°F, but the temperature of crowns under straw mulch plus 8 inches of snow was 30°F.

Mulch is typically removed in early spring when plants begin to show signs of growth or new leaf emergence under the mulch. Earlier mulch removal will allow the soil to warm, resulting in earlier plant growth and bloom, which is susceptible to spring frost. The mulch should be removed with rakes or pitchforks in small plantings or with various types of mechanical rakes in larger plantings. A little mulch should remain on the plants, and this will work its way to the soil surface to help keep fruit dry and clean, but most of the mulch is pulled to the row middles for weed control.

 

Leave a Reply

4 comments on “Mulching Strawberries For Winter Protection

  1. I am a first time grower and I am trying two half whiskey barrels as containers I will probably wrap two or three layers of insulation around the barrel then hold the six to eight inches of straw down to the top with netting or other porous material

Berries Stories
hydroponic strawberries
Berries
December 31, 2015
Pick-Your-Own Berries With A Twist
A hydroponic strawberry operation in New York offers visitors a unique picking experience. Read More
Connect_meeting_2015_web
Apples & Pears
December 28, 2015
FruitGrowerConnect Solves Growers’ Problems One On One
More than 35 grower and supplier operations gathered at the beautiful Rancho Bernardo Inn in San Diego in November for Read More
UF/IFAS professor Jeff Williamson checks blueberries for cold damage
Berries
December 10, 2015
Precision Cold Protection Pointing To Profit For Blueberry Producers
UF/IFAS student, faculty search for and find cost-savings for growers. Read More
strawberries
Berries
November 30, 2015
Latina’s Election A Sign Of The Times [Opinion]
In electing a Hispanic woman to lead the California strawberry industry, growers strike a blow for common sense. Read More
lorena strawberry commission chair 2015-16
Berries
November 26, 2015
Trailblazing Latina To Lead California Strawberry Commission
Lorena Chavez and her family have long been involved with strawberry production, and she has plans for the commission moving forward. Read More
Washington-state
Berries
November 23, 2015
Washington’s Long, Hot Summer: Is Climate Change To Blame?
Looking back on 2015, which packed plenty of heat. Read More
Blackberry ‘Prime-Ark Traveler’ (AgriStarts)
Berries
November 16, 2015
North American Raspberry And Blackberry Conference Slated For Early March
Historic Williamsburg, VA, will be the setting March 1-4. Read More
The Latest
Berries
February 5, 2016
Moving Beyond Methyl Bromide With Biofun…
Editor’s note: University of California Farm Advisor Mark Bolda will present much more information on this topic at the Biocontrols Read More
Berries
January 27, 2016
Tips to Increase Yields and Improve Harv…
Removing old blueberry pruning stumps will help you extend the life of your berry plantings and hopefully make your job a little easier. Read More
Berries
January 3, 2016
Get A Grip On Weeds In Strawberries
Control techniques include properly timed herbicide applications and crop rotation. Read More
Berries
December 31, 2015
Pick-Your-Own Berries With A Twist
A hydroponic strawberry operation in New York offers visitors a unique picking experience. Read More
Apples & Pears
December 28, 2015
FruitGrowerConnect Solves Growers’ Probl…
More than 35 grower and supplier operations gathered at the beautiful Rancho Bernardo Inn in San Diego in November for Read More
Berries
December 10, 2015
Precision Cold Protection Pointing To Pr…
UF/IFAS student, faculty search for and find cost-savings for growers. Read More
Berries
November 30, 2015
Latina’s Election A Sign Of The Times [O…
In electing a Hispanic woman to lead the California strawberry industry, growers strike a blow for common sense. Read More
Berries
November 26, 2015
Trailblazing Latina To Lead California S…
Lorena Chavez and her family have long been involved with strawberry production, and she has plans for the commission moving forward. Read More
Berries
November 23, 2015
Washington’s Long, Hot Summer: Is …
Looking back on 2015, which packed plenty of heat. Read More
Berries
November 16, 2015
North American Raspberry And Blackberry …
Historic Williamsburg, VA, will be the setting March 1-4. Read More
Berries
November 10, 2015
Researcher Studying Benefits Of Growing …
The demand for blackberries, blueberries, and raspberries has exploded in recent years thanks to consumers who enjoy the berries for Read More
Berries
November 10, 2015
Study Suggests Florida Strawberry Grower…
Increasing competition and volatile market prices requiring shift in production protocol. Read More
Berries
November 5, 2015
$2 Million Grant To Sweeten Pot For Orga…
UF/IFAS researchers will concentrate on cover crops and how they could impact multiple production practices. Read More
Berries
October 31, 2015
Ensure Your Berry Production Success Wit…
Ensure Your Berry Production Success With Pollinators Planting bee-friendly food sources help native pollinators to continue their valuable work in Read More
Berries
October 30, 2015
Establishing Wildflower Habitat To Suppo…
Research from Michigan State University has shown that growers can increase pollination and yield of blueberry by planting wildflowers that support wild bees, like bumble bees, and as well as honeybees. Read More
Berries
October 30, 2015
Timely Tips For A Healthy And Productive…
When this issue of the magazine reaches you, you might be enjoying the nice fall weather on a tractor in Read More
Berries
October 19, 2015
USDA Awards $6.7 Million To Stifle Spott…
North Carolina State University’s Hannah Burrack will spearhead research. Read More
Berries
October 13, 2015
Whole Foods Gives Oregon Blueberry Growe…
Hood River Blueberry is the recipient of a $114,000 loan to help expand its packaging line and purchase a new Read More
[gravityform id="62" title="false" description="false"]