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
Apples & PearsSurvey: Positive Indicators For Biocontrols In U.S. Horticulture, Agriculture
January 22, 2015
Preliminary results of a survey conducted in December 2014 of more than 850 readers across six Meister Media Worldwide titles Read More
Apples & PearsReal-World Solutions Highlight First Biocontrols 2015 Conference & Tradeshow
January 22, 2015
Topping the inaugural event's marquee are presentations on “Driving Crop Quality and Productivity Using Biocontrols” by representatives from two of the largest produce growing organizations in the country. Read More
Apples & PearsRosBREED 2 Program Focuses On Disease Resistance And Quality
January 19, 2015
The next generation of the federally funded RosBREED research program uses DNA techniques to deliver varieties that benefit both growers and consumers. Read More
BerriesCalifornia Strawberry Commission Awarded More than $1 Million To Reduce Fumigation
January 14, 2015
Strawberry farmers are dedicated to finding sustainable alternatives to fumigants such as methyl bromide. Read More
BerriesStrawberry Growers Get New Disease-Fighting Smartphone App
January 12, 2015
Southeast Regional Fruit and Vegetable Conference attendees get first look at ‘MyIPM.’ Read More
BerriesWhat You Need To Know About Aronia, Goji, And Saskatoon Berries
January 2, 2015
Leading researchers and universities offer some advice and basic information about relatively unknown berry plants. Read More
BerriesGrowers Try Their Hand At Next Wave Of Berry Crops
January 2, 2015
Saskatoon, goji, and aronia berries can provide new options for growers looking to expand their berry offerings. Read More
The Latest
BerriesDormant Pruning Tips For Your Berries
January 28, 2015
Proper dormant pruning increases berry size and improves overall health of blackberry and raspberry plants. Read More
BerriesWhy You Should Be Growing Black Raspberries
January 27, 2015
Amazing health benefits for consumers and production and marketing benefits for the grower make this berry a must-consider option for your operation. Read More
BerriesIf You Could Plant Any Type Of Fruit, Consider A Canebe…
January 23, 2015
Raspberries or a blackberries present some berry good options. Read More
Apples & PearsSurvey: Positive Indicators For Biocontrols In U.S. Hor…
January 22, 2015
Preliminary results of a survey conducted in December 2014 of more than 850 readers across six Meister Media Worldwide titles Read More
Apples & PearsReal-World Solutions Highlight First Biocontrols 2015 C…
January 22, 2015
Topping the inaugural event's marquee are presentations on “Driving Crop Quality and Productivity Using Biocontrols” by representatives from two of the largest produce growing organizations in the country. Read More
Apples & PearsRosBREED 2 Program Focuses On Disease Resistance And Qu…
January 19, 2015
The next generation of the federally funded RosBREED research program uses DNA techniques to deliver varieties that benefit both growers and consumers. Read More
BerriesCalifornia Strawberry Commission Awarded More than $1 M…
January 14, 2015
Strawberry farmers are dedicated to finding sustainable alternatives to fumigants such as methyl bromide. Read More
BerriesStrawberry Growers Get New Disease-Fighting Smartphone …
January 12, 2015
Southeast Regional Fruit and Vegetable Conference attendees get first look at ‘MyIPM.’ Read More
BerriesWhat You Need To Know About Aronia, Goji, And Saskatoon…
January 2, 2015
Leading researchers and universities offer some advice and basic information about relatively unknown berry plants. Read More
BerriesGrowers Try Their Hand At Next Wave Of Berry Crops
January 2, 2015
Saskatoon, goji, and aronia berries can provide new options for growers looking to expand their berry offerings. Read More
Apples & PearsFour Highlights You May Have Missed At Great Lakes Expo
December 16, 2014
Record-setting crowd sat in on presentations featuring precision orchard management, mechanical berry harvesters, biocontrols, and more. Read More
BerriesSpotted Wing Drosophila Regional Workshops Held In New …
December 1, 2014
Management tips, early warning signs, and pest biology are among topics discussed at one-day events. Read More
BerriesSuspected Borer Could Be Big Bother To Florida Blueberr…
November 24, 2014
Producers warned to be on the lookout as scientists probe samples. Read More
BerriesPackaging Company’s Campaign To Benefit Future Organic …
November 19, 2014
Sambrailo Packaging of Watsonville, CA, has partnered with California Certified Organic Farmers and will donate a portion of the sales of clamshells made from plastic bottles. Read More
BerriesGeorgia Is The Top Blueberry State In The Nation
November 17, 2014
The Peach State experiences extreme growth in production of blueberries in the last 20 years. Read More
BerriesTop 10 Things Berry Growers Need To Do Before 2015
November 11, 2014
Preparation, management, and control can help you get your canes off to a great start in the next growing season. Read More
BerriesNew Berry Growers Are Innovative
November 11, 2014
In this electronic information age, these new, first-time berry growers are quick to locate berry growing information resources, including local and university Extension/research-developed production and marketing information for their area. Read More
BerriesOrganic Strawberry Research Gets $200,000 Boost From Wa…
November 7, 2014
Scientists from University of Florida and North Carolina A&T forge ahead with studies, seek more grower feedback. Read More