Frost cloth is one of my go-to garden covers and I use it to protect my vegetables from frost, prevent cold damage, and keep pests away from my plants. These lightweight fabrics can be laid directly on top of crops or floated above on wire or PVC hoops. A frost cloth low tunnel is quick and easy to build and gives tender seedlings a strong start in spring or extends the harvest in autumn. Let’s learn more about how to use frost cloth in a vegetable garden.
What is frost cloth?
Frost cloth, also known as a row cover, frost blanket, reemay, or garden fleece, is a lightweight material made from spun bonded polypropylene fabric. I’ve been using it in my vegetable garden for decades and write about its versatility in my book Growing Under Cover: Techniques for a More Productive, Weather-Resistant, Pest-Free Vegetable Garden.
My goal is to garden smarter, not harder and frost cloth is an important part of my season extension and pest prevention strategies. Gardeners use the gauzy fabric as frost protection and freeze protection over vegetables during a cold snap in spring and autumn. It helps prevent damage to plant tissues. It’s also handy for sheltering crops from inclement weather like heavy rain, hail, and strong winds. It can even reduce or prevent damage from deer, rabbits, squirrels, and insect pests.
For frost protection, frost cloth works by trapping radiant heat that comes from the warmth of the soil. I actually started by using old bed sheets in the garden. They worked as insulating covers, but didn’t allow light penetration and therefore could only be left on plants for a short period of time. That’s where frost cloth comes in handy as it was designed for garden use. Below you’ll learn more about the various types and weights of frost cloth for short or long term garden protection.
Types of frost cloth
There are three main types of frost cloth available to gardeners; lightweight, medium weight, and heavy weight. You don’t need all of them, of course. If you wanted to invest in just one, I would suggest a lightweight frost cloth because it’s the most versatile. Here’s more information on the three types of frost blankets.
- Lightweight – Lightweight frost cloth is a great all-around garden cover. I use it in spring and fall for frost protection and in summer for pest prevention. The material is extremely lightweight with excellent light transmission. It allows about 85 to 90% of light to pass through. It can therefore be left in the garden for an extended period of time. I think of lightweight covers as garden insurance and use them over frost sensitive spring seedlings like tomatoes, peppers, and melons. They trap heat and create a microclimate around the plants encouraging a strong start to the growing season. This is also the cover to use for long-term pest prevention.
- Medium weight – Medium weight frost cloth offers several degrees of frost protection and can be used in spring or autumn when light to heavy frost is forecast. It allows about 70% of sunlight to pass through. This isn’t enough light for healthy plant growth and therefore should only be used as short-term frost or freeze protection. In mid to late autumn it can be used as winter protection for cold hardy vegetables like spinach, kale, scallions, and carrots. At that point, plant growth has slowed and the limited light transmission won’t affect crops.
- Heavy weight – This durable material provides heavy freeze protection to garden vegetables. It allows 50% light transmission and is best used as temporary frost or freeze protection in spring or as a late autumn and winter cover.
How to use frost cloth
There are two ways to apply frost cloth to garden beds. The first is to lay the fabric covers on top of plants. The second is to float them on hoops above garden beds. I prefer to float the lightweight material on hoops. Why? I’ve learned that laying it directly on top of the leaves, fruits, or flowers of plants can result in cold damage if there is a hard frost or freeze. During a cold snap, the material can freeze to the plants. It’s best to float a frost blanket on hoops if the forecast is predicting a hard frost.
Using frost cloth for frost protection
As the name implies, frost cloth is most often used for frost protection. It’s a game changer in the spring garden, particularly for gardeners like me who garden in cold climates. I keep an eye on the forecast and if there is a danger of frost, cover my beds with lengths of frost cloth. It’s an easy way to ensure worry-free frost and freeze protection. Medium weight or heavy weight materials don’t allow much light to pass through and are best used as temporary covers. You can leave a lightweight frost blanket in place for days or weeks. Once the risk of frost has passed and the weather has settled, I gather up the sheets of frost cloth and store them in my garden shed.
Using frost covers for pest prevention
Using lightweight frost blankets over pest-prone vegetables like cabbage, potatoes, cucumbers, and squash is a hands-off way to reduce pest problems. When paired with crop rotation, it’s ideal for preventing pests like imported cabbage worms, cucumber beetles, and Colorado potato beetles. Float lengths of frost cloth on hoops over garden beds immediately after planting. Be sure to weigh down or bury the edges of the material to prevent pests from sneaking under. The gauzy material allows air and water to pass through as well as 85 to 90% light transmission.
Don’t forget about pollination! The flowers of vegetables like cucumbers and squash, must be pollinated to produce their crop. That means you need to remove the fabric cover when the plants begin to flower. If you’re growing vegetables like potatoes and cabbage, which don’t require pollination, leave the barrier in place until harvest.
Using a frost blanket to delay bolting
Use frost cloth as light protection in late spring and summer. As the days get longer in late spring, crops like lettuce, arugula, and spinach start to bolt. Bolting is when a plant switches from vegetative growth to flowering. The quality and flavor of bolting crops declines and I try to delay bolting using frost cloth. I DIY a low tunnel with wire hoops and a length of floating row cover. This blocks a percentage of sunlight and can slow bolting by days or weeks.
I also use a frost blanket low tunnel in summer when I want to establish successive crops or autumn plantings. In early to mid summer the weather is typically hot and dry. This makes it challenging for seeds like lettuce, carrots, and cabbage to germinate. Blocking sunlight after planting helps the soil retain moisture and lowers the temperature beneath the cover. Once the seeds sprout, remove the low tunnel.
How to DIY low tunnels
It’s quick and easy to DIY low tunnels using frost cloth. There are two main components to a low tunnel: hoops and a cover. Below you’ll find more information on the three materials I use for hoops in my garden:
- PVC conduit – For over 20 years I’ve been using 10 ft lengths of 1/2 inch PVC conduit for garden hoops. You can source them from hardware or home improvement stores. They’re flexible and easy to bend into a U-shape.
- Wire hoops – In spring and autumn when snow isn’t a threat, I DIY lightweight low tunnels with lengths of 9 gauge wire. The length depends on the width of the bed and how high you need the hoop to be. For 3 to 4 ft wide beds, I cut 7 to 8 ft long wire pieces. These are fine for protecting low to medium tall vegetables like lettuce, beets, cabbage, and spring seedlings. Use wire cutters to clip the wire into the desired length and bend it into a U-shape with your hands. It’s very flexible and easy to shape.
- Metal hoops – A couple of years ago I decided to get a low tunnel hoop bender to bend 10 ft lengths of metal conduit into extra sturdy hoops. You can buy benders for 4 ft wide beds or 6 ft wide beds. Mine is for 4 ft wide beds as most of my raised vegetable beds are 4 by 8 ft or 4 by 10 ft. Metal hoops make strong and sturdy winter tunnels, but I also use them in my spring, summer, and autumn garden.
How to secure garden covers
In gusty winds, lightweight frost cloth can blow off garden beds or hoops. It’s therefore important to secure it well. There are three ways to keep frost cloth in place in the garden.
- Weights – The first is to weigh down the sides of the cover with rocks, bricks, sandbags, or other heavy objects.
- Staples – Another option is to use garden staples or stakes, but keep in mind that these secure the fabric sheets by poking holes through the material. Adding holes to frost cloth encourages rips and tears and can shorten the lifespan of the product.
- Clips or clamps – The final way to secure frost cloth is with clips or snap clamps. These fasten fabric sheeting to wire, PVC or metal hoops.
Where to buy frost cloth
Frost cloth is easy to source. Most garden centres and garden supply stores offer a good selection of grades and sizes. Remember that it may also be called floating row cover, frost blanket, or reemay. It comes packaged in a range of pre-cut sizes, but you can also buy it by the roll. I typically buy rolls of the lightweight material as it’s more cost effective. It’s easy to cut frost cloth to the desired size with a pair of sharp scissors. I re-use frost cloth for years, so a roll tends to last me a very long time.
How to care for frost blankets
With careful use, you can use frost cloth year after year. It doesn’t take long for a bright white cover to get dirty in the garden. I clean my covers by hanging them on a clothes line and hosing them off. You can also wash them in a bucket or container of water mixed with a mild detergent. Rinse with clean water and hang to dry. Once fully dry, fold frost blankets and store in a garden shed, garage, or other storage area until the next time you need garden protection.
For more information on extending the season and using garden covers, be sure to check out my best-selling book, Growing Under Cover, as well as these in-depth articles: