Row covers for gardens

Row Covers For Garden Plants – How To Use Floating Row Covers In The Garden

Using row covers for garden plants is a great way to protect your prized plants from damaging cold or pests. Some of the best row covers include the floating garden row covers, which are lightweight and easy to use. You can also create homemade row covers for garden plants. Let’s learn more about how to use floating row covers to protect your plants.

What are Floating Row Covers for Gardens?

The use of garden row covers has increased in the last decade in the commercial and home garden. The best row covers for your garden depends on what you are using the row covers for. Some people use row covers exclusively for pest protection while others use them for frost protection or water irrigation.

Floating row covers are made of very lightweight woven

material that allows light and water to penetrate, but provides protection against sudden drops in temperature common in many growing regions.

How to Use Floating Row Covers

Giving cool season vegetables such as spinach, broccoli, cabbage, cauliflower, peas, lettuce and radishes, a head start on the season is easy when you use row covers for garden plants. Floating row covers grab the sun’s heat and cause the soil to warm up an extra 1 to 3 degrees.

Installing row covers is extremely easy. Because the material is so light, it does not damage plants but floats on top of them. Lay the fabric over the plants and secure it with anchor pins or pieces of two-by-four lumber. Keeping the edges securely anchored is important, as it will deter flying pests and worms, as well as birds and squirrels.

Homemade Row Covers

Gardeners wishing to save a little extra on their garden budget might consider making their own floating row covers and making homemade row covers is easy to do.

Measure the size of the bed you wish to cover. Fashion arched supports out of PVC piping that are wide enough and just tall enough to cover your garden plants. Use a small piece of rebar for support at each end of the PVC pipe hoops. Cover the hoops with the fabric of your choice. You can use sheer curtains, shade cloth or purchase row cover material. Be sure to secure the sides using anchor pins or pieces of lumber.

Ask Ruth: Quick, DIY Winter Row Covers

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Dear Ruth,

As we head into November, I am looking for an easy way to protect my fall garden from winter weather. Do you have any simple solutions?


Burnsville, NC

Dear Eddie,

In my own garden, I use a super-simple system. It’s fast, it’s easy, and practically anyone can construct it in just a few minutes. I will demonstrate the steps to “building” this DIY winter protection tunnel, and then talk about issues to contemplate when using this and similar systems, and finally offer a few other ideas. I have used similar shelters on a grander scale for lettuce for the wholesale market. Most of the lettuce was still in decent condition the following March – though some of the lettuce ribs were starting to get brown – but the lettuce was planted early enough that it was nearly full size by mid-October.


8’ Fiberglass Rods – these work for a bed width of 4 feet

Length of tunnel divided by 2 plus 1 = Number of rods you will need

For a 12’ tunnel, you will need 7 rods

Floating Row Cover –

Length: length of tunnel + distance to ground on both ends + 1’ minimum

Width: should be 7’ (minimum) to 8’ wide for 4’ wide beds

For a 12’ tunnel you will need a minimum length of 19-20’of row cover, at least 7’ wide

Rocks, Bricks, Soil

Enough rocks/bricks to weigh down floating row cover about every two feet

OR use soil to weigh down one long side of the tunnel. The soil technique will limit harvest accessibility on that side.


Lay out the garden area you are going to protect. You will be planting before you need to worry about frost protection, so site and dimension your fall garden accordingly. The rods can successfully span about 4 feet, so measure that width. Determine your length. It is sometimes easier to have two shorter tunnels than one long tunnel. If you like things to be really straight, lay out with string and a tape measure. In wintertime the sun will not be directly overhead. It will be at a lower angle in the sky. Make sure the area will still be in full sun during wintertime. If you have more than one tunnel, make sure one tunnel will not shade the other tunnel.

Take your fiberglass rods and jam them down in the ground every two feet on both sides of the tunnel. I try to set them about a foot deep in the soil. If you hit a rock, move the rod slightly and try again. If you want the tunnel shape to look consistent, make sure the angle of the rod going into the ground is the same everywhere. I don’t recommend setting the rods further apart than 2 feet. It will be too flimsy.

Now, pull your row cover across the rods. Center it widthwise and lengthwise. On all sides, you should have at least 6” of extra row cover lying on the ground. If you don’t have quite enough, try pushing the rods further into the ground. Rain/water does pass through floating row cover to nourish your plants. Floating row cover comes in a variety of weights. Lighter-weight row cover allows for more light transmission, offers a bit less frost protection than heavier covers, and can double as an insect barrier in warmer weather. Heavier-weight row cover gives you a little more frost protection, but less light transmission. I usually use lighter row cover.

Place your rocks/bricks over the extra flap of row cover on the ground. This will secure the cover and keep it from blowing away during a winter storm. Be generous with your rocks/bricks…it’s a bummer to have your cover blow away and see the devastating results in your garden.

The corners are important. You will need to scrunch the excess row cover at both ends of the tunnel. Gather the excess up in a few places along the tunnel end and make sure it is secure. I like to pull the sides tighter and flush with the ends. Extra rocks/bricks are helpful for securing the corners.

You’re done!

HINTS & More:

  • Plant early enough that your plants are nearly full size before frost. Your plants won’t grow much during cold weather, but if your plants are large already you will have plenty to harvest.

  • It is easier to plant the tunnel area first – before you build the tunnel.
  • Spinach and lettuce planted now won’t grow much, but they will quickly kick into gear at the first sign of milder weather in late winter/early spring.
  • Sometimes I put another layer of rods on TOP of the row cover. Then, when I am harvesting, I push the row cover up between the rods, and the rod-sandwich helps to hold the cover in place during harvest.
  • Anywhere the cover touches a plant, frost damage can occur. Plant taller plants toward the middle of the tunnel.
  • Mulch right up to the rods to keep weeds from sprouting in early spring. In fall, soil left bare inside the tunnel will stay warmer.
  • Soil can be used very effectively to batten down one long side of the floating row cover. However, you cannot harvest very conveniently from the side where soil is holding the cover in place.
  • Take good care of your row cover so it will last for more than one season. When you unearth the cover for use the following season, keep a lookout for spiders as you open it up, and then check for tears.
  • When it’s really windy, keep an eye on your floating row cover. It typically flies off at dusk in bitter weather with a nor’easter blowing.
  • Not a big problem, but sometimes animals will burst holes in your cover…maybe because they like the warmth inside.
  • Snow loads can flatten the fiberglass rods, but they will pop right back up – unfazed – once you dust the snow off the cover.
  • You could add plastic over the row cover to create a mini-greenhouse. The addition of plastic will require attention to watering and a ventilation plan.


# 9 Wire: Instead of the fiberglass rods you can use #9 wire. This is very thick sturdy wire. It comes on a roll and you will need to cut it to length. Because of its thickness, cutting it can be challenging. You can use bolt cutters or (with caution) a circular saw with a metal-cutting blade. I have used a chisel and a small sledgehammer (yes, it was labor intensive!). Usually the diameter of the roll is the right length for support hoops. Places like Southern States sell this wire. One downside: When I used this wire as bows for my tunnel, a snow load permanently distorted and somewhat flattened the arch of my wire bows (but they did not collapse completely).

PVC pipe: PVC pipe is more rigid than the fiberglass rods, but it is more complicated to work with, requires a supporting structure, and it doesn’t have the long term longevity. After it starts cracking, it ends up in the landfill. Alternatively, PVC gray “conduit” in the electrical section at building supply stores is treated to be sun-resistant, so it does not become brittle the way white PVC water pipe does. It will collapse under a heavy snow and pop back up as the snow melts like the fiberglass rods.

Wire ladder masonry reinforcement: Found at building supply stores, these wire ladders can be bent into an arch for use in low tunnels to support floating row cover.

High Tunnel Link: Here is a great link that Tom Elmore sent me for building a high tunnel/hoop house. This is a serious structure that would take some time and planning to construct. The fastening system can be used for constructing low tunnels also. Check it out:

SOURCES for materials:

The rods can be purchased locally at Reems Creek Nursery, Fifth Season Gardening, and possibly others. They can also be ordered from Seven Springs Farm

The floating row cover (also called Reemay) can be purchased at local garden supply stores, agricultural supply stores, and possibly at hardware stores.

Thanks for writing Eddie. I am just going to add that I LOVE the simplicity and ease of this fiberglass rod system. Besides being easy and quick, the rods take up very little room in storage. Ten rods take up about the same room as one PVC pipe.

All my best,


Gardeners: Got a question for Ruth? Email it to us at

Ruth Gonzalez is a former market farmer, gardener, local food advocate, and founder of the Tailgate Market Fan Club where she blogs at In her job at Reems Creek Nursery, Ruth offers advice on all sorts of gardening questions, and benefits daily from the wisdom of local gardeners.

Ask Ruth © 2012 Ruth Gonzalez & Organic Growers School

Author: Ruth Gonzalez

Ruth Gonzalez is a former market farmer, gardener, and local food advocate who wants to see organic farms proliferate and organic gardens in every yard. She serves on the Organic Growers School Board of Directors, and in her job at Reems Creek Nursery, Ruth offers advice on all sorts of gardening questions, and benefits daily from the wisdom of local gardeners.

Make an Easy, Inexpensive Mini-Greenhouse With Low Tunnels

Covers for Low Tunnels

Several studies have measured the temperature differences inside and outside low tunnels that are covered with various materials. During a winter in Durham, N.H., temperatures under tunnels covered with row cover and a second layer of plastic were more than 20 degrees Fahrenheit warmer than outside the tunnels. Additionally, the top 1 1/2 inches of soil inside the garden tunnels never froze, while the outside soil was completely frozen. Studies from The University of New Hampshire have shown that the combination of row cover topped with sheet plastic is the best way to overwinter onions, broccoli, kale and other hardy crops in the chilly Northeast. (Learn more in Use Low Tunnels to Grow Veggies in Winter: Quick Hoops.)

In climates with milder, sunnier winters, be careful when using sheet plastic to cover beds, with or without a layer of row cover underneath. On a sunny, 65-degree day, a plastic-covered mini-greenhouse can quickly heat up to 130 degrees or more, which can be lethal to most plants. From Zone 6 southward, plants are often safer beneath row cover than they would be tucked in with both row cover and plastic.

I like both perforated and slitted plastic row covers, which are made of thin plastic peppered with holes or long rows of vents. These covers capture daytime heat while allowing excess warmth to escape. They admit a little rain, but hail bounces off of them. At night, the covers deter rabbits and deer. Easy to handle and tolerant of substantial wind, most pieces of perforated or slitted plastic get at least three years of use. Best used during the last three weeks before and two weeks after your last spring frost, a season-specific mini-greenhouse is the best way to capture the warmth of sunny spring days for plants that need it, such as cucumbers, melons or early tomatoes. It’s also a great way to transition veggies that have become accustomed to the filtered light beneath row covers to the open garden. Expect to pay about $12 for a 6-by-20-foot perforated or slitted plastic row cover.

When it comes to using greenhouse tunnels to exclude summer insects such as flea beetles, squash vine borers and squash bugs, garden hoops are all you need to support lightweight row covers. It is usually best to hold even featherweight covers above the foliage to prevent friction with the tender new plants. To save money and material, consider reusing an old sheet or curtain. You may need stakes to keep covers from sagging. To keep the stakes from punching holes in your covers, slit tennis balls and pop them over the tops of the stakes.

Securing the Edges

Like many tunnelers, I used to struggle to keep my plastic in place during strong winds. I’ve learned that row covers and perforated plastic can be held steady with bricks, pieces of firewood, old bicycle inner tubes filled with sand or water, or sandbags. But even when I buried the edges, winds over 40 mph sometimes ruined tunnels, especially those made with unperforated plastic. Then a friend suggested using a second set of garden hoops over the first, on the outside of the row cover — a great technique that I still use to secure various covers over low tunnels.

But truth be told, lash lines work better than outer hoops when it comes to holding down plastic-covered tunnels. To create lash lines, diagonally cross soft nylon line (such as the kind sold for clothesline) over the hoops, threading the rope through hardware in your bed frame (or running board) on the long sides of the bed. In the permanent beds maintained at the Noble Foundation, a nonprofit agricultural institute in Oklahoma, ropes have been installed across low tunnels between pipe hoops, which are spaced about 3 feet apart. In addition to holding the plastic in place, the ropes make it easy to remove the weights from one edge, roll back the plastic for weeding, and then quickly pull it back into place.

My garden hoops and arches stay in the garden year-round, but I store covers that are not being used in a large storage bin. The less time the covers spend in the sun, the longer they will last, and it’s great to have them ready and waiting when I need a tunnel fast. Not counting my spades and hoes, my tunnel-building gear is among my most valuable garden equipment.

Want to see low tunnels in action: Watch our new video about season extension options, featuring Editor-in-Chief Cheryl Long in MOTHER EARTH NEWS Gardening Video: Season Extension.


Check out our best ideas for DIY cold frames, greenhouses and more with this great resource, Year-Round Gardening: Our Best Plans for Greenhouses, Hoop Houses, Cold Frames and More.

Plant Covers

Many ornamentals and garden plants need extra protection in certain times of the year. In the heat of summer, tomatoes and other vegetables can whither in the excess heat and sun. Mesh covers can help ward off insects while allowing light and air to get to plants. Thermal or thicker covers and wraps will help protect plants from winter weather so your plants will continue to thrive year after year.

Garden fabrics, also called floating row covers, come in different weights depending on the season. You can support the fabric over your plants with wooden stakes or frames, but make sure to secure the fabric to the ground or to the supports with staples or clips. Pre-made domes with mesh and other fabrics make it easy to set over the plants you want to protect.

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Plant Covers & Protection

If you have a larger garden, you may be looking for plant netting, row covers or tunnels, as well as materials such as burlap or anchor pins. Our selection includes poly, micromesh, and fleece tunnels that will not only keep your plants protected, but also maintain your garden’s aesthetics. If you’re simply looking for a cold frame or small greenhouse to protect your plants, we carry many styles to choose from. Quality materials and easy setup ensure you can protect your plants without being in the garden all day.

Row covers and plant netting have a range of uses throughout the year. If you’re heading into spring, you can use them to keep bugs off your plants or shield young plants from harsh winds. When fall arrives, there’s a chill in the air, and like you, your plants may need another layer. Garden covers can help keep your plants warm, while still allowing rain and sun to reach them. We carry many different types of covers and materials from trusted brands such as DeWitt, Winter Wrapz, and Juwel. Shop our assortment of plant covers, garden netting and other seed starting supplies today and make sure your plants are as healthy as can be!

Row cover hoops for frost and pest protection

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In my award-winning book, The Year-Round Vegetable Gardener I write extensively about the row cover hoops I use to stretch the harvest season in my vegetable garden. I use them to get a head start on spring planting, but also in autumn to protect from frost and cold weather. Simple row cover hoops can also be used during the growing season to shelter vegetable plants from pests like flea beetles, potatoes beetles, and squash bugs, or even larger pests like rabbits, deer, and birds.

Row cover hoops are one of my secrets of a healthy, long-producing vegetable garden. Plus, they’re quick and easy to set up which is very handy if an unexpected frost is in the forecast. Read on to learn more about the various ways you can use hoop tunnels in your garden, as well as the various materials I use to make my structures.

This super quick-to-build tunnel is made with wire hoops covered in a lightweight row cover. It’s protecting my collard green seedlings from cabbage moths and deer.

Two ways to use row cover hoops:

Traditionally, vegetable gardeners wait for the last spring frost to pass before planting most of their crops. By using protective covers, however, I plant weeks – sometimes months! – earlier. I’ve been using these handy covers for many years to grow more food in my garden and harvest year-round.

In spring, I’m sowing seed for cool season greens like arugula, leaf lettuce, spinach, tatsoi, scallions, and Asian greens beneath my tunnels. I’m also transplanting seedlings of crops like broccoli, cabbage, and artichokes. But, these simple covers are also a convenient way to keep frost-sensitive tomato and pepper seedlings insulated from the up-and-down weather of spring. The tunnels capture heat and create a microclimate around these tender plants which reduces the risk of cold damage.

My end-of-season basil is protected with a row cover tunnel to shelter it from cool evening temperatures and frost.

Pest protection

When using row cover hoops to prevent pests, remember that you also need to practice smart crop rotation. If you’re growing the same crop in the same bed year after year and having problems with the same pest, covering that bed with a row cover isn’t going to solve your problem. In fact, you’ll likely just trap that pest beneath the cover, giving them free rein to munch your crops. Instead, be sure to rotate crop families each year by planting them in a different bed or different section of your garden.

It’s also important to consider timing – when do you put the protective tunnel over your vegetables and how long do you have to leave them on? To be most effective, I place tunnels over my garden beds immediately after seeding or transplanting the pest-susceptible crop. Why? Because I’ve been in the garden transplanting broccoli seedlings into my garden with cabbage moths flying about my head trying to land on the broccoli plants. If you wait to cover them, you may be too late.

The length of time the crop needs to covered depends on several factors: 1) the type of pest, 2) when it’s most damaging, and 3) the type of crop. For example, flea beetles are most damaging to cabbage family crops like arugula in spring when the pests emerge from the soil. A lightweight row cover prevents them from accessing the arugula and can be left in place until you’ve harvested all of your crop. It’s a different matter for vegetables like cucumbers, squash, or melons which need to be pollinated to produce their crop. In this case, you can use row cover hoops to prevent squash bug or cucumber beetle damage to the young plants but then remove the covers when the plants begin to flower so pollination can occur.

These metal hoops will be covered with a row cover to protect the young seedlings from cold temperatures and frost.

The best materials for row cover hoops:

The materials I use for my row cover hoops are easy to source, inexpensive, and durable. To prolong their life, I store them in my garden shed or garage when they’re not in use. When making a mini tunnel, I space hoops three to four feet apart.

PVC hoops

For well over a decade I’ve been using half-inch diameter PVC conduit to make hoops for my garden beds. It’s an inexpensive product that’s easy to source at your local home improvement centre and comes in ten-foot lengths. PVC bends easily over a bed to make a quick hoop. You can insert the end of the PVC directly into the soil, but I find these hoops are more stable when a one-foot long rebar stake is inserted into the soil first and the end of the hoop is then slipped over the stake.

Wire hoops

Wire hoops are perfect for spring, summer, or autumn row cover hoops, but they’re not strong enough to stand up to any snow load so I don’t use them in the winter garden. I use nine gauge wire, which comes in a coil. I cut them into five to six-foot lengths to top three to four-foot wide beds. Once inserted into the soil, they’re about 18-inches tall. They’re fine for light frost protection, preventing fleas beetles from damaging compact crops like arugula, or for covering young squash plants to prevent squash bugs from accessing the crop.

It only takes me about one minute to bend a half-inch, ten foot length of metal conduit into a sturdy hoop for my garden beds.

Metal hoops

About five years ago I got a Quick Hoops Low Tunnel Hoop Bender from Johnny’s Selected Seeds and it transformed my winter low tunnels. I had been using PVC for these structures but I always had to add a center support down the middle to prevent them from collapsing under heavy snow. The metal hoops are much stronger and I can now build a quick mini hoop tunnel without needing to reinforce the hoops. Plus, bending a half-inch diameter length of metal conduit into a hoop takes less than one minute with the bender so it’s fast and easy to make super strong hoops. To read about my metal hoop upgrade, check out this article.

Kits for row cover hoops

Of course you can also buy pre-made mini hoop tunnels. I have several of these structures in my garden, some covered with row cover fabric and others with polyethylene. Last year, I got a Bio Green Superdome Growtunnel which has a polyethylene cover and appreciate its quick set up, height, and convenient venting sides. A row cover tunnel like a Tierra Garden Easy Fleece Tunnel is another instant structure that’s perfect for salad greens, squash or cucumber seedlings, or kale plants. If it’s insects you wish to omit, use a kit with a lightweight insect barrier cover like the Gardman Insect Mesh Grow Tunnel.

I use my Bio Green Superdome Growtunnel to shelter seedlings in the spring and fall from frost, as well as from pests like insects, slugs, and deer.

Types of covers for row cover hoops

Depending on the type of row cover, it can offer several degrees of frost protection, but remember that the thicker the cover, the less light will pass through. That’s not a big deal if you’re using it for winter protection when plants are mostly dormant. But, if you wish to encourage quick, healthy growth in spring, you’ll want a fabric that allows plenty of light transmission.

Row covers also come in a wide range of widths and lengths – read the package description carefully to make sure you’re buying the right size. Early on, I bought a seven-foot wide fabric thinking that it would be enough to cover my PVC hoop tunnels, but I was wrong! I was about six inches short on fabric and had to work hard to push the PVC hoops super far down in the soil so that I could completely cover the tunnel.

Insect barrier screening

More mesh than fabric, these durable mesh cloths prevent bugs, moths, slugs, birds, deer, rabbits, and other creatures from accessing your vegetables, herbs, or flowers, but still allow plenty of light and water to pass through.

Lightweight row covers

Lightweight row covers are the most widely used fabrics and are ideal for light frost protection, general bad weather protection (hail, downpours, etc.), and to omit insects and other garden pests. They allow about 90% of light to pass through to your vegetables and offer a few degrees of frost protection.

Row cover is one of the best ways to enjoy pest-free salad greens in spring, fall, and winter.

Medium-weight row covers

Slightly heavier than lightweight covers, these materials allow around 70% of light to pass through and provide up to a 6 degrees F (3 to 4 degrees C) of frost protection. I use these in spring or fall as a temporary cover if there is a hard frost in the forecast.

Heavy-weight row covers

Heavy-weight covers are used mainly as winter covers because they block 30 to 50% of the light. You can use them as temporary covers in the case of frost, but don’t leave them on for more than a day or two during the growing season as they block too much light.

I like to use snap clamps to hold row covers and polyethylene covers to my half-inch diameter PVC and metal hoops.

How to attach the covers on row cover hoops:

To be effective against pests, you’ll need to securely attach the covers to their hoops and weigh them down at the bottom. It’s amazing how easy it is for insects to sneak under an unsecured cover or for the cover to blow off in a storm.

There are a variety of ways to attach a row cover to a hoop. Here are the three materials I use to secure my row covers:

  1. Clips – There are many types of clips and clamps available at garden supply and hardware stores, and I’ve found snap clamps to be the most convenient. They pop on or off easily but hold the cover tight against the strongest wind gusts. Do be careful when you remove them from the hoops as if you’re not careful, you can easily tear lightweight fabrics. For insect prevention, I still secure the bottom of the row cover with weights or staples.
  2. Weights – If I’m using a cover for temporary frost protection I often just weigh down the fabric at the bottom with something heavy like rocks, logs, lumber, or small sandbags. Just be sure that whatever you use doesn’t have sharp edges which could tear the fabric.
  3. Garden staples – Garden staples or pegs do tear a hole in the fabric to hold them tightly to the soil. They work great and I don’t mind using these if I’ve got old covers, but if my covers are in good shape, I don’t like to put holes in them as it shortens their lifespan. Instead, I’ll weigh them down and use snap clamps.

For more information on protecting your crops from pests or extending the harvest, check out these posts:

  • Niki’s metal hoop tunnels
  • How to mulch root vegetables for a winter harvest
  • 8 vegetables to harvest in winter
  • Cabbage worm ID and control
  • Preventing pests in your garden: 5 strategies

Do you use row cover hoops in your garden to protect from frost or pests?

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PHOTO: Jessica Walliserby Jessica Walliser March 29, 2018

Row cover is a spun-bound, translucent fabric designed to “float” on top of plants. While at first it might seem odd to cover plants with a blanket of row cover, the truth is that there are many ways to use row cover that are extremely useful to farmers and gardeners. Today, we’d like to introduce you to 6 ways to use row cover that are designed to save time, money and energy in the garden.

6 Practical Ways to Use Row Cover

1. As a Pest Shield

Pest prevention is certainly among the most popular ways to use row cover. Row cover is made in various “weights” or thicknesses. The lighter weights are an especially useful pest prevention method because they’re more breathable than heavier grades and can be left in place all summer long. Covering a row of broccoli with a protective blanket of row cover means adult cabbageworm butterflies can’t access the plants to lay eggs. No eggs means no little green worms on your broccoli. Row cover also protects potato plants from leaf-munching Colorado potato beetles; it keeps leafminers out of your spinach crop; and it keeps destructive cucumber beetles off of cucumber vines. However, if you’re using row cover to keep pests out of the veggie patch and it’s covering a crop that needs to be pollinated in order for the fruit to set, you’ll need to make sure you remove the cover when the plants come into flower. But, since protecting young plants when they’re most vulnerable to pest damage is key, removing the cover when the plants reach maturity is typically not problematic.

2. As Frost Protection

Heavier weights of row cover are thicker and denser, providing a layer of frost protection when they’re placed on top of hoops covering crop rows. Useful both at the start of the season—when spring’s last frosts are still lingering—and at the end of the season—when fall’s first frosts begin to arrive—row cover is an excellent way to get a jump start on the gardening season or extend the harvest when the season comes to an end. Placing the row cover on hoops, rather than resting it on the plants themselves, also adds a layer of insulated air above the plants and keeps the frozen fabric off the foliage.

3. To Secure Mulch

If you overwinter carrots, beets, turnips, parsnips and other root crops in your garden, row cover comes in handy for this job, too. Insulating root crops with a thick layer of straw or shredded leaves protects them from deep freezes and destructive freeze-thaw cycles. But, often this loose organic mulch can blow away in winter storms. Covering the mulch with a layer of row cover and pinning down the edges with rocks, soil or landscape pins, holds the mulch in place all winter long. Plus, it’s easy to remove when you want to make a mid-winter harvest.

4. As Sun Screen

One of the most practical ways to use row cover is as a sun protectant. Cool-weather crops, such as lettuce, spinach and radish, begin to bolt or go to flower when summer arrives. Covering them with a layer of lightweight floating row cover keeps the blasting sun off them and can extend the harvest by a few weeks. When using row cover as a sun screen, don’t pin down the edges; instead, leave a bit of airspace between the fabric and your plants to improve air circulation and keep the plants cooler. Use hoops or plant stakes to elevate the row cover above plant tops. If you live in the south, where blasting summer sun can lead to sun scald on ripening tomatoes, eggplants and other fruits, a protective layer of row cover wrapped around the bottom half of tomato cages can protect low-hanging, ripening fruits from sun scald.

5. As a Support Sling for Vine Crops

If you grow melons, cantaloupes, pumpkins, winter squash and other large-fruited vine crops vertically on trellises, arbors or arches, you may find the fruits grow too heavy and the climbing vines are unable to support their weight. This can cause the vines to snap under the weight of the heavy fruits. To eliminate this problem, cut row cover into long pieces and create a sling for each growing fruit. It’s easy to tie the pieces of row cover to the support structure on both ends and lay the fruit in the middle of the sling.

6. To Eliminate Cross-Pollination

If you’re a seed saver, then you know how important it is to prevent cross-pollination from occurring in certain crops. If you’re aiming to save seeds from hand-pollinated squash, melons, cucumbers and other vine crops, you’ll need to keep the flowers you pollinated by hand from being naturally cross-pollinated by insects. Row cover can be very useful for this job. After hand-pollinating the female flowers in the morning, immediately cover the vines with a sheet of row cover and leave it in place until the flowers drop and fruit growth is underway.

As you can see, there are many ways to use row cover in the garden. It’s a useful tool to have around, and if you take good care of it, a single roll can last for many years.

Floating row covers protecting young crops.

Floating row cover is a spun-bonded or woven plastic, polyester or polypropylene material that is placed over plants to exclude pests, act as a windbreak or extend the growing season by retaining heat — all while still being permeable to light, water and air.

For Pest Control

Covering crops can eliminate many pests on a variety of plants, including:

  • caterpillars (imported cabbageworm, cabbage looper and diamondback moth) on cabbage, broccoli, and cauliflower
  • fleabeetles on cabbage, potato, eggplant or salad greens
  • onion maggot on onion
  • seedcorn maggot on beans, corn and other crops
  • early season cucumber beetles on cucurbits
  • thrips on a variety of plants
  • aster yellows (a disease transmitted by aster leafhopper) on carrot, celery, lettuce and many flowers.

Floating row cover is easy to use in the home garden.

The row cover prevents the insects from getting to the plants, so it must be put on at planting. Adult fleabeetles and onion and seedcorn maggots, however, emerge from the soil so you must be careful not to enclose plants over an infested area. It is therefore important to practice crop rotation and not plant related crops or those crops susceptible to a particular pest such as seed corn maggot, in the same location in successive years.

Also, you must remove row covers from insect-pollinated crops, such as cucumbers or squash, during bloom to allow for pollination — which obviously limits its use for pest exclusion on those crops.

As Season Extenders

Depending on the weight of the covering you choose, you can gain between 2 and 8 degrees of frost protection, or warm the local environment sufficiently to harvest certain crops a week or two early. You’ll get the maximum benefit if the crop is planted on a south-facing slope.

Types of Covers

Floating row cover protects lettuce plants.

There are several weights of these covers for different uses. Lightweight covers tend to be the least expensive and are suitable for most crops. They will protect plants from desiccating wind, but there is only a minimal increase in temperature beneath the cover. Because of the light weight they don’t require supports.

Different weights of floating row cover are made for different purposes.

Mediumweight covers help speed up crop maturation and increase yield. They are useful for extending the season in both spring and fall by retaining some heat. These types are suitable for use over cucurbits, lettuce, peas, carrots, radishes, potatoes, sweet corn and blueberries.

Heavyweight covers provide frost and freeze protection up to 4-8ºF, so are particularly good for early and late season extension for cool season crops. They can enhance crop growth, particularly for warm-season crops, since they raise ambient daytime temperatures 10ºF or more. But be aware that tomatoes and peppers may get blossom drop if the temperature beneath the cover exceeds 86ºF. Also, transmission of sunlight and water is reduced by these heavy covers. They are the most expensive, but can be reused.

Using Row Covers

Rebar holding down a stretch of row cover.

Floating row covers can be laid directly over low-growing, flexible crops. Just be sure to leave enough slack when covering rows so the cover can “expand” as the crop grows. You have to bury the edges completely if you’re using floating row cover for pest exclusion. If you are not using it to keep bugs out, you may use rough lumber or rebar to hold down the edges.

Broccoli plants covered with floating row cover stretched over bent PVC pipes.

It may be necessary to support the cover material on hoops for taller crops or sensitive plants, such as spinach, that can be abraded by the material if it sits directly on the leaves. PVC pipes are easy to bend and stick in the soil to create a framework over which to drape the row cover.

Remove covers gradually to harden off the crop. Choose a cloudy day to do the final removal. Store row covers out of direct sunlight, as UV rays will cause breakdown of the material.

Row covers provide a mini-greenhouse for the plants that grow beneath — this include weeds. Periodically you will have to remove the row covers to eliminate weed seedlings that have germinated.

Floating row covers generally aren’t used in flower gardens because of their utilitarian appearance, but you might want to consider using them over ornamental plants for limited uses, such as early in the season for starting seedlings outdoors, or for temporary protection of valuable plants.

Floating row cover can be purchased at larger garden centers or from specialty mail order catalogs.

– Susan Mahr, University of Wisconsin – Madison

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Row covers for frost protection and earliness in vegetable production

Editor’s note: This article is from the archives of the MSU Crop Advisory Team Alerts. Check the label of any pesticide referenced to ensure your use is included.

Row covers are used for many reasons including, season extension (frost protection), insect exclusion, heavy rain, and hail protection. When the main objective of row covers is to increase temperature, it is important to understand several factors including: row cover type, material used, level of temperature increase, and frost protection ability.

Types of row covers

Most row covers are either floating row covers or supported by hoops. Floating row covers are supported by the plant canopy. Therefore, for use on crops with a sensitive growing point (e.g. tomato) or a frail structure, they must be made of a light-weight material. Floating row covers can be installed over multiple crop rows. Hoop-supported row covers, also known as low tunnels, are installed on individual crop rows or beds. The height can vary from 12 to 36 inches from the bed surface. They are more expensive to install than floating row covers, but the installation can be mechanized.

Materials used for row covers

Most row covers are made with polyethylene plastic or spunbonded fabrics (polyester or polypropylene). Polyethylene covers are used for low tunnels. They are lightweight and come in either solid or perforated sheets. Holes on perforated covers are important for gas and water exchange with the outside environment. Spunbonded fabrics allow for ventilation and water to pass between the fibers. Polyethylene materials are available in various thicknesses while the spunbonded fabrics are available in various weights.

Temperature increase and frost protection

When using row covers always keep in mind that they are more efficient at increasing temperature especially during a sunny day than at protecting against frost. Even in the absence of a frost risk, some growers may consider using row covers because most warm season vegetables stop growing at temperatures below 40-50oF. A row cover may increase the temperature enough to promote the growth of these warm season vegetables. In general:

  • Polyethylene plastic materials build more heat than woven fabric (spunbonded).
  • Clear plastics increase temperatures more efficiently than white or colored plastics

Increase in temperature under the cover during daytime may vary greatly depending on the material used. However, when it comes to frost protection, the material used is critical. Most woven fabrics and polyethylene materials used in agriculture can only protect the crop down to 28*F, but some heavy materials have shown acceptable protection down to 20*F.
Some growers have combined row covers with bed covered with plastic mulch; others have added cover crop wind breaks. Finally, some growers have attempted to improve the level of frost protection by installing double or multiple layers of the row covers.
When the outside temperature is high enough, it is recommended to remove row covers. Temperature can get extremely high inside the covers and injure the crop, especially when non polyethylene row covers without holes are used. It is also important to remove the covers at flowering stage for pollination.
In a recent visit with a grower who was installing low tunnels on beds covered with plastic mulch, we measured a temperature increase from 86oF open air to 96oF (single layer) and 113oF (double layer) tunnels. More interestingly the change in temperature occurred within five to 10 minutes following tunnels installation.

Spunbonded row cover material used in cucumber production.

Perforated plastic row covers.

Dr. Ngouajio’s work is funded in part by MSU’s AgBioResearch.

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