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
BerriesBuilding A Better Black Raspberry
March 27, 2015
Studies focusing on consumer preference, aphid resistance, heat tolerance, and genetics aim to capitalize on an expanding market. Read More
Fresh From Florida Strawberry Parfait recipe
BerriesNew Partnership Sends Florida Strawberries To Puerto Rico
March 26, 2015
Latest addition extends Sunshine State’s agricultural export reach in the Caribbean. Read More
BerriesGeorgia Blueberry Growers Suffer Chill Damage
March 23, 2015
On early varieties, some growers lost as much as half their crops. Read More
BerriesSecond Florida Strawberry Picking Challenge Packs Philanthropic Punch
February 25, 2015
Fundraising event at Wish Farms in Plant City raises $76,000 for Redlands Christian Migrant Association. Read More
BerriesGrowing Greenhouse Strawberries Can Pay
February 24, 2015
British trial shows much lower disease pressure, higher quality and bigger yields. Read More
BerriesFlorida Blueberry Crop Sitting Pretty — Weather Permitting
February 18, 2015
Barring a hard-freeze event, growers agree the season’s offering looks fruitful. Read More
BerriesUniversity Of California Davis, California Strawberry Commission Settle Lawsuit
February 10, 2015
The renewed partnership includes plans to develop varieties with the addition of a new breeder for the UC Davis Strawberry Breeding Program. Read More
The Latest
tomatoes and strawberries
BerriesScientists Seek To Save Flavor Of Tomatoes And Strawber…
April 17, 2015
A $500,000 grant will enable University of Florida researchers to focus on how light can affect the quality and taste of produce after harvest. Read More
Tom West Blueberries family
BerriesUrban Sprawl Doesn’t Stop 4th-Generation Florida …
April 16, 2015
Growing in town supports the evolution of Tom West Blueberries. Read More
BerriesSouthern Strawberry, Peach Growers Concerned About Cold…
March 31, 2015
Plastic coverings, sprinklers used to keep crops warm with consecutive nights of low temperatures. Read More
BerriesBuilding A Better Black Raspberry
March 27, 2015
Studies focusing on consumer preference, aphid resistance, heat tolerance, and genetics aim to capitalize on an expanding market. Read More
Fresh From Florida Strawberry Parfait recipe
BerriesNew Partnership Sends Florida Strawberries To Puerto Ri…
March 26, 2015
Latest addition extends Sunshine State’s agricultural export reach in the Caribbean. Read More
BerriesGeorgia Blueberry Growers Suffer Chill Damage
March 23, 2015
On early varieties, some growers lost as much as half their crops. Read More
BerriesSecond Florida Strawberry Picking Challenge Packs Phila…
February 25, 2015
Fundraising event at Wish Farms in Plant City raises $76,000 for Redlands Christian Migrant Association. Read More
BerriesGrowing Greenhouse Strawberries Can Pay
February 24, 2015
British trial shows much lower disease pressure, higher quality and bigger yields. Read More
BerriesFlorida Blueberry Crop Sitting Pretty — Weather P…
February 18, 2015
Barring a hard-freeze event, growers agree the season’s offering looks fruitful. Read More
BerriesUniversity Of California Davis, California Strawberry C…
February 10, 2015
The renewed partnership includes plans to develop varieties with the addition of a new breeder for the UC Davis Strawberry Breeding Program. Read More
BerriesHow To Prepare For Strawberry Pathogens
February 5, 2015
From Botrytis in the East to Fusarium and charcoal rot in the West, strawberry growers need a plan of action to contain disease. Read More
Apples & PearsBiopesticide Use Quadrupled From 2000 To 2012
February 4, 2015
Biopesticides are on the up and up in U.S. agriculture as confirmed by recent data from EPA. “The use of Read More
Berries‘Fresh From Florida’ Produce Star Of New TV Ad Campaign
February 3, 2015
Commercials shine the spotlight on Florida blueberries, tomatoes, and seafood. Read More
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
Apples & PearsA Better Understanding Of Biocontrol
January 27, 2015
The Biocontrols 2015 Conference & Tradeshow will help growers and PCAs incorporate new tools into their crop protection programs. 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