Your Cart is Empty

  • Seed Trays
  • How Do Frost Blankets Help To Prevent Crop Loss?

    October 11, 2023 12 min read 0 Comments

    Frost Blanket over low tunnel hoops

    Do you know what causes frost on plants? Curious about how to protect your plants when the weather turns cold? In this article, we will review the different factors that cause frost on plants, how it can damage your plants, and how to prevent the damage. 

    What exactly is Frost?

    Frost is a thin layer of ice that forms on solid surfaces when the temperature drops below freezing (32°F or 0°C). The ice crystals form when water vapor in the air comes into direct contact with a cold surface and changes from a gas to a solid, bypassing the liquid state. This process is known as deposition.

    The Perfect Frosty Conditions

    Now, let's look at how different environmental factors affect frost formation.

    • Clear Skies:  Clear skies at night allow more heat to escape from the Earth's surface. This process, called radiational cooling, can drop the surface temperature below the dew point—the temperature at which air becomes saturated—and cause frost to form.
    • Calm to Light Winds:  Calm air or light winds allow cold air to settle. If the wind is strong, it can dry out the air near the surface, which might prevent frost even if the temperature is below freezing. Therefore, calm to light winds often favor frost formation.
    • Cool Temperatures:  The surface temperature must drop below freezing for frost to form. The colder the surface temperature, the greater the potential for frost formation.
    • Topography:  Frost is more likely to form in low-lying areas because cold air is denser than warm air and tends to sink. This phenomenon, known as 'cold air pooling,' can create 'frost pockets' where frost is more likely to form. On the other hand, slopes and hillsides may be less prone to frost because the cold air can flow down them, similar to water, and pool in lower areas.

    Understanding these factors and how they create microclimates conducive to frost allows you to take preventive measures to protect sensitive plants from frost damage. These include covering plants, using heaters or fans to circulate air and raise temperatures, watering soil with overhead sprinklers to increase its heat capacity, or choosing planting locations less prone to frost formation.

    More information on identifying and using microclimates on the farm is available here.  

    What Happens to Plants During a Cold Snap?

    Frost Damage on Crops

    Frost can significantly impact leafy plant tissue during a cold snap. When frost forms on the leaves of plants, it causes the water inside the plant cells to freeze. As water freezes, it expands, causing the cell walls to rupture. Once the ice thaws, the cells cannot regain their original shape, leading to wilting and browning of the affected tissue.

    Frost damage can be seen in various ways:

    • Wilting:  The first sign of frost damage is often wilting. As the water within the plant cells freezes and expands, the cells rupture, losing their turgidity and causing the plant to wilt. (In a biological context, turgidity helps explain how plant cells can stand upright despite lacking a skeletal structural framework.)
    • Discoloration:  Frost-damaged leaves initially turn dark green, then brown or black.
    • Softening and Collapse:  Frost-damaged tissue becomes soft and water-soaked as the frozen cells thaw. Eventually, these areas dry out and collapse.

    Long-Term Implications of Frost on Plant Health

    The long-term implications of frost damage depend on the severity of the frost and the susceptibility of the plant species. Some plants may recover from light frost damage, while others may be severely affected or even killed by heavy frost. Even if the plant survives, its growth and productivity may be reduced. For example, frost damage in strawberries can reduce yield as the damaged tissues may not produce flowers or fruit. You risk losing sellable products or stunting the plant growth in leafy greens like lettuce, kale, or brassicas.

    5 Ways to Prevent Frost Damage on Your Crops

    1. Choose Frost-Tolerant Plants:  Some plants are more tolerant of frost than others. Choosing species suited to your local climate can help prevent frost damage. Knowing local growing conditions is why forming a relationship with a seed company and the reps servicing your area is valuable. Those reps might know about slight crop selection variety adjustments that can stretch your growing season. 
    2. Use Frost Blankets or Covers:  Covering plants with frost blankets can help to trap heat and protect against frost.
    3. Water Before a Frost:  Wet soil can hold more heat than dry soil. Watering your plants before a frost can help to keep the ground warmer and protect the roots. It also increases humidity.
    4. Mulching:  Mulching around the base of plants can help to insulate the soil and protect the roots from frost.
    5. Placement of Plants:  Planting in areas less likely to experience frost, such as near buildings or on slopes, can help protect plants.

    Remember, the best protection against frost damage is prevention. By understanding the conditions under which frost forms and protecting vulnerable plants, you can help ensure their long-term health and productivity.

    Frost Blanket over Raised Bed

    Using Frost Blankets in the Garden or Farm

    Frost blankets, also known as floating row covers or horticultural fleece, are essential for farmers and gardeners looking to extend their growing season. They protect crops from frost and ward off pests. 

    Choosing the Right Weight Frost Blankets

    Choosing the right weight depends on the specific needs of the grower. Bootstrap Farmer carries a 1.5, 2.5, and 4 oz weight option for frost blankets. Factors such as the type of crops being grown, the local climate and weather conditions, and the particular stage of plant growth all play a role in determining which frost blanket is most appropriate. Talking to neighboring farmer networks and seed reps may help you decide the level of crop protection and varieties you may choose to grow. 

    Layers of Frost Blanket
    The weight of the frost blanket, measured in ounces per square yard, determines its protection level.
    • 1.5 - Ounce Frost Blanket: This lightweight cover is typically used during the late spring or early fall when the risk of frost is minimal. It allows maximum sunlight and water permeability while protecting a few degrees of frost. It's also useful for pest control during the growing season.
    • 2.5 - Ounce Frost Blanket: This medium-weight cover offers more frost protection, typically up to 4-6 degrees Fahrenheit, making it suitable for early spring and late fall use. It still allows for good light and water penetration but offers better insulation than the lighter-weight blanket.
    • 4 - Ounce Frost Blanket: This heavy-duty cover provides the most frost protection, often up to 8-10 degrees Fahrenheit. It's typically used in the dead of winter or regions with particularly harsh winters. While it allows less light and water to reach the plants, its superior insulation properties can protect crops from severe cold damage.

    Layering Frost Blankets

    Options for Layering Frost Blanket:

    Layered 1.5 Ounce Frost Blankets:  Lightweight 1.5-ounce frost blankets can offer flexible temperature control. On warmer days, one layer can be removed to prevent overheating, while during cooler nights, an additional layer can be added for extra warmth. This approach also aids in pest management, allowing the farmer to add or remove layers depending on the level of pest activity.

    Layered 2.5 Ounce Frost Blankets:  Layering 2.5-ounce frost blankets offers more substantial frost protection than 1.5-ounce blankets while maintaining good light and water transmission. This strategy is beneficial during the shoulder seasons (early spring and late fall) when temperatures fluctuate dramatically.

    Layered 4  Ounce Frost Blankets:  Using multiple layers of heavy-duty 4-ounce frost blankets provides the most robust protection against extreme cold and harsh weather conditions. This approach best suits the coldest parts of the year or regions with severe winters. The multiple layers create an insulating air pocket that can protect crops even when temperatures drop significantly below freezing. 

    Layering 1.5 oz with 2.5 oz or 4 oz Frost Blankets:  Some farms may use layers of different weights if their temperatures fluctuate. A farmer may add a first layer of 1.5 oz, which lets in the most light and water for non-severe frost protection during daylight morning hours. And then, at night, the farmer may add a 4 oz or 2.5 oz, depending on predicted weather, for overnight frost protection. 

    Layering frost blankets of different weights is a strategy used by farmers to provide adjustable and enhanced protection against varying degrees of frost, wind, and pests. Using different weights, farmers can ensure that their plants are protected throughout the year, regardless of weather conditions.


    Why Layer Frost Blankets?

    This layering or complete uncovering is useful during freak cold snaps, unusual shoulder season weather or storms, cold fronts, or unusually warm winter days where no layer may allow the plants to soak up all usable daylight. By layering frost blankets of different weights, a grower has the flexibility to adapt to changing weather conditions and plant needs.

    This strategy provides a range of options for optimizing plant growth and health. It maximizes light and water access during the day and offers substantial insulation in colder climates overnight.

    What are frost blankets made of?

    Frost blankets, also known as floating row covers or garden fabric, are typically made from lightweight, breathable materials that allow sunlight, air, and moisture to reach the plants while protecting them from frost and pests. 

    Spunbonded Polyester or Polypropylene:  This is the most common material for frost blankets. The fabric is lightweight and durable, allowing light and water to reach the plants. It's designed to trap heat from the sun during the day and release it at night, creating a microclimate that can protect plants from frost.

    Insulated Thermal Blankets:  These are heavier, quilted, layered, synthetic blankets. They provide greater frost protection but allow less light and water to reach the plants. These are typically used for more severe weather conditions.

    Polyethylene Plastic:  Some frost blankets are made from clear plastic. While these can provide good frost protection, they don't breathe as well as other materials, so they must be removed or vented on sunny days to prevent overheating.

    It's important to note that while all these materials can protect plants from frost, they each have strengths and weaknesses. The best choice depends on the specific needs of the plants and the local climate conditions.

    Can Growers Use Sheets as Frost Blankets?

    Gardeners can occasionally get away with using a sheet to protect landscaping plants here and there. A farmer or large scale grower would choose to invest in a frost blanket over a sheet or tarp for several reasons:

    1. Material: Frost blankets are typically made from lightweight, breathable polypropylene fabric that allows sunlight, air, and moisture to reach the plants, while sheets or tarps may block these essential elements for plant growth 
    2. Protection against varying weather conditions: Frost blankets can protect plants efficiently against cold winds and extreme temperature fluctuations that a regular sheet or tarp might be unable to handle.
    3. Won’t retain moisture: Because polypropylene is hydrophobic, water can permeate down without being absorbed. The non-adding weight will not harm the structures that hold up the frost blanket. 
    4. Heat Retention: Unlike sheets or tarps, frost blankets insulate and slow the heat loss rate from the soil, thereby providing a warmer microclimate for the plants (source: Iowa State University Extension).
    5. Pest Control: Frost blankets also double as a physical barrier against pests, which can significantly benefit crop yield
    6. Durability and Reusability: Frost blankets are more durable and reusable than sheets or tarps, making them a more cost-effective solution in the long run.
    7. Ease of Use: Frost blankets are designed for agricultural use, making them easier to install and manage over large areas than sheets or tarps.
    8. Size Matters: Square-like sheets are made for sleeping beds, not garden beds. Bed sheets will likely be too wide or not wide enough. For row crops, sheets will always need to be longer. These non-growing shapes will make unnecessary open or weak seams in what should be continuous protection. Added infrastructure cost and labor to secure will quickly make sheets a lousy investment for frost protection.
    9. Light penetration: Sheets do not allow light to penetrate as plastic or spunbonded material does. The limited light causes leggy plants and slow growth. 

    By investing in a frost blanket, farmers are ensuring the protection and productivity of their crops, leading to better yields and profitability.

    How Frost Blankets Work

    Frost blankets, or floating row covers, can help insulate plant roots in a few ways:

    Heat Retention - Frost blankets trap heat from the soil and create a warmer microclimate around the plants. This warmth extends to the root zone, helping to keep roots insulated against freezing temperatures.

    Physical Barrier - The frost blanket provides a physical barrier against cold air, frost, and snow. This prevents these elements from directly contacting the soil surface and thus reduces the cooling effect on the roots below.

    Moisture Conservation - By reducing evaporation, frost blankets help maintain soil moisture. Moist soil tends to stay warmer than dry soil, benefiting root insulation.

    Snow Protection - In areas that receive snowfall, frost blankets can allow snow to accumulate on top of them. Snow acts as a natural insulator and can help protect the roots from freezing temperatures.

    Tip:  Remember to secure the edges of the frost blanket to the ground to prevent wind from getting under the cover and to ensure maximum protection against the wind chill. This can be done with sandbags or rocks or by burying the edges with soil. 

    Methods for Installing Frost Blankets

    It's important to note that while frost blankets are effective in many situations, they may not provide sufficient protection in frigid temperatures or for sensitive plants. Always consider the specific needs of your plants and the severity of the winter weather in your area. 

    Ways to install frost blankets over your garden:

    1. Directly on Plants: One method is to lay the frost blanket directly on the plants you wish to protect. The weight of the blanket itself should be light enough that it doesn't damage the plants.
    2. Floating on Hoops: Another standard method is to float the frost blanket over hoops above garden beds. Suspended frost blankets keep the fabric off the plants and allow for better air circulation. EMT hoops can be bent using a hoop bender and used season after season. Snap Clamps help secure the frost blanket to the EMT hoops. 

    Learn more about bending EMT into hoops here.

    Frost Blanket over crops

    Four Season Growing with Frost Blankets

    Growing four seasons to feed your community and family is a rewarding endeavor that can be profitable. However, it means developing a winter sales outlet, choosing crop varieties wisely, and long-term weather forecasting, planting schedules, and harvests. It also means having the right tools for the job before you need them. 

    Please do not procrastinate ordering supplies. As weather patterns change, frost dates can come at any time. Shipping delays may mean a day late and many dollars of damaged crops. So measure twice and order once early to be prepared. Early prep not only applies to frost blankets, low tunnel hoops, and the task of constructing that infrastructure. You may also be filling sandbags, setting rebar pins for hoops, and mulching in preparation for winter weather. 


    In conclusion, frost can be detrimental to your plants and crops if it is not taken care of properly. Frost blankets are an important resource for protecting your plants from the cold weather as they trap heat and deflect moisture. With the proper preparation and utilization of frost blankets, you can prevent crop loss due to frost. To further ensure protection against frost damage, it is also important to stay up-to-date with changes in weather conditions daily.

    Ultimately, by understanding how frost affects your plants and how a frost blanket can help protect them from damage, you can feel confident that your crops will remain safe throughout the winter months. So what are you waiting for? Take control of your crop loss prevention today! Was this helpful? Tell us in the comments below!


    How do I keep my row cover from blowing away?

    Anchor the frost blanket properly to prevent it from blowing away in the wind. Anchoring can be done using garden pins or weights like pipe, scrap lumber, or the preferred sandbag. You can keep the ends tighter by folding inward like you would wrap a present. We also recommend using snap clamps when floating the frost blanket over hoops for secure attachment.

    Will frost blanket suffocate my plants?

    Properly used, frost blankets will not suffocate plants. They're designed to allow air and moisture to reach the plants while protecting them from cold temperatures. However, they should not be wrapped too tightly around the plant, which could cause damage.

    How do you keep frost blanket from sagging on low-tunnel hoops?

    A tight application will keep frost blanket off plants, prevent air gaps during snowfalls and heavy precipitation, and reduce flapping and loosening in the wind, leading to sag. Batten strapping or string crisscrossing between hoops can help take the sag out of the frost blanket. If you live in windy areas or are prone to heavy snow, consider using 3⁄4 EMT and spacing the hoops closer together. Four-foot hoop increments are a standard starting point. 

    Do frost blankets only protect against the cold?

    While their primary function is to protect against frost, these blankets can shield plants from pests, strong winds, and even harsh sunlight. However, it's important to remember that some plants need insect exposure for pollination, so the blanket should be removed at the appropriate time (University of Florida IFAS Extension).

    Can you leave frost blanket on all winter?

    It's not advisable to leave frost blankets on plants all winter. They should be removed during warmer days to prevent overheating and to allow for watering and sunlight penetration.

    At what temperature should I uncover my plants?

    We recommend uncovering frost blanket when temperatures are above 32℉ or above freezing.  It is crucial to verify the daily weather conditions and to add or subtract frost blanket layers as needed. Crops could be at risk of overheating if not uncovered when temps rise. Just be sure to recover before sunset to ensure that you secure some of the day’s solar gains inside your low tunnel to help maintain temperatures into the overnight.

    Can you wash frost blankets?

    Yes, you can clean a frost blanket. Remember, a significant benefit to using frost blankets is the ability to keep out the frost while allowing light for photosynthesis and soil heat build-up. Because frost blankets are close to and touching the ground and often moved in wet or dewy conditions, frost blankets can get dirty. This dirt impacts the allowable light to the plant. Rinsing off the blankets on warm days will help keep your blankets working as designed. 

    Tip:  Using landscape fabric between rows can drastically reduce mud and dirt buildup around your frost blanket servicing areas.