Have you had issues with your food crops being eaten by insects and other pests? Do your crops fail due to a late frost? You need to do everything you can to protect your crops, especially just after planting transplants or direct seeding. Row covers are the answer to these problems and more.
You put a lot of effort into growing food crops. Whether you seed your own seedlings or buy them, you want to give them the best environment to survive in.
You can’t coddle them forever indoors, so when you plant them out, you need to protect them until they are established.
One way to protect them is by using row covers. These covers help to keep insects and other pests out, regulate temperature and moisture and are easy to install.
Let’s cover (pun intended) this useful garden aid in detail.
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What are row covers
Row covers are some form of temporary cover that are placed over your food crops to protect them. They are sometimes also called season extenders as they can help to extend the growing season by several weeks.
They come in different materials as we’ll see below. However first let’s look at why you would even want to use them.
If insect pests can’t reach your plants, they can’t damage them. This works especially well for crops such as brassicas (broccoli, cauliflower, cabbage, kohlrabi, etc.)
Nowadays it is better to avoid using any chemical pesticides. We are going back to natural ways of deterring pests as it is less harmful to the environment and provides your family with healthier food.
If you can keep the pests off your crops, they can’t eat them. I notice that whenever I don’t use row covers, I have more infestations of pests and as a result more damage to my plants.
It is critical to use row covers that don’t have holes and that are dense enough to avoid having very small insects crawl through the material.
Row covers can also protect your crops from larger pests such as raccoons, rabbits and birds. Raccoons however are persistent and either find out how to lift the row cover or more likely simple shred it to bits with their sharp claws to get at your crops. Row cover mainly serves to make your crops less visible and masks the scent of your vegetables to some degree so pests don’t find them as easily.
Row covers will help trap warmth in the soil and the surrounding air during the day so that at nighttime your plants benefit from the heated air that cools down more slowly under the cover.
The main advantage is that you can transplant your seedlings or direct seed several weeks earlier than uncovered crops. This will give you a head start and allow you to harvest earlier and longer.
One caution though: depending on what type of row cover you use, your crops are susceptible to overheating. That’s why I prefer fabric row cover (such as Reemay) as it breathes.
If you are using greenhouse plastic film or other plastic film, you will need to vent the row cover during the day when it is warm and sunny. This may not work well if you work outside the home during the day, as it may be too cold early in the morning to vent the row covers and be too cool in the evening when you come home.
There are some covers that have slits cut into them that will open and vent when it gets too hot. These work relatively well in milder climates.
Row covers do a great job in reducing evaporation so your crops will not need to be watered as often. In fact if you get enough rain and use permeable row covers such as Reemay, you may not need to water at all.
Moisture is especially important for young seedlings but also if you direct seed. Having to go out every day to water if it is not raining is time-consuming and you might forget. With row covers you may only need to water every few days.
For plastic film covers that do not allow rain to penetrate, you will need to either water your crops or remove the cover temporarily when it rains, at least for a few hours.
What materials are available
Reemay is a popular brand name for a breathable, lightweight and strong row cover. It is made from a spun polyester and comes in different weights, depending on the protection you need. It might also be called floating row cover as it is designed to be light enough to float on top of your plants without crushing them. This is my preferred row cover.
Greenhouse film is also a popular row cover that provides a bit more heat gain during the day for colder climates. However you need to be extra careful about overheating and remember to vent the row cover during sunnier days. It is quite heavy so I would recommend finding a local supplier for it.
Regular vapour barrier is a cheaper alternative to greenhouse film and can be found in any home centre or hardware store. It has the disadvantage of not allowing as much light transmission as greenhouse film so is not suitable for very young seedlings that needs lots of light to avoid getting spindly. The other reasons you may be better off paying more for greenhouse film is that vapour barrier usually is not considered food safe and may off gas chemicals, especially when exposed to the sun for a longer period of time. On that note it will also likely break down sooner due to UV exposure, costing you the same amount of money in the long run.
Shade cloth is a row cover mainly used to protect leafy crops from excessive heat and sunlight. It is designed to allow heat to escape so should be used later in the season, when you need to remove the other types of row covers to avoid overheating.
Cloches are covers for individual plants that have the same benefits as row covers. These can be made from glass, plastic and even cardboard boxes (removed during the day to allow sunlight to reach your plants).
Sizing the cover depends on how wide your beds are and how tall your supports will be. For a 4 foot (1.2m) wide bed, use a cover that is 7.2 feet (2.2m) wide. For length, add on at least 1 foot (30cm) for each end, so for an 8 foot (2.4m) bed use at least a 10 foot (3m) long cover. Most cloths and films are sold in 50 foot (15m) lengths which would be enough for two 8 foot (2.4m) beds if cut in half.
What else you will need
You will usually need something to keep the row cover from touching your plants. With the lighter weight Reemay you can actually allow the cover to simply float above the plants and in theory it will be pushed up by the plants as they grow.
I don’t do that as I think plants shouldn’t be subjected to any kind of downward force that could impact their growth. So I recommend using supports for any kind of cover.
You have several options for supports. What you choose will depend on what you have on hand, your budget and how permanent you want your covers to be.
Steel hoops are lightweight, easy to store and easy to insert into the ground. This is what I use. You can buy them either as uncoated steel or plastic coated. They are more susceptible to kinking and hard to straighten out.
PVC pipe is readily available at home centres and plumbing supply stores, quite strong and is easy to bend in the smaller diameter sizes (3/4″ is recommended). As it is thicker than the steel hoops, it may hold up better to high winds and animals jumping on your covers.
Wood frames can be easily built from 2×2 lumber in an A-frame shape to shed rain and snow. Because the shape is not rounded, plants at the edges of your bed won’t have much vertical room to grow. Alternatively you could also combine wood with PVC pipe or steel hoops for a hybrid frame style that can be made rounded. The frames are also harder to store when you don’t need them unless you find a way to hinge them.
Wood stakes can be knocked into the middle of the bed and used to support the middle of the row cover. They can get in the way when you weed or cultivate and take up some room that could be used for planting. As with wood frames, you will likely have a more A-frame shape unless you place shorter stakes on the edges. And they can damage the cover over time, especially if you get lots of high winds that will make the cover rub on the tops of the stakes.
The choice of your supports will determine what clips you can use.
For steel hoops I use clothespins. Or you can use binder clips although these will rust and also could damage the cover with their sharper edges.
For PVC pipe you can buy special clips. Or you can use short pieces of the same PVC pipe cut in half lengthwise and snapped over the row cover onto the PVC pipe ribs. Or use really big binder clips or clothespins designed for steel pipe.
For wood frames you can staple the row cover to the frame with a staple gun. For better durability however get yourself some lattice wood strips and attach them with screws or nails, sandwiching the row cover between the lattice and the wood frame.
Pins, rocks or lumber
These supplies complement the clips and are mainly to ensure there is no space at the bottom of the row cover where it meets the ground. Otherwise insects can find their way in and once they are in, they can decimate your crop.
Pins or sod staples work well but do damage the edges of your row cover and can actually be pulled out of the ground during high winds. They also can rust if not made from stainless or galvanized steel. Plastic ones are available but they won’t be as durable as metal ones.
Rocks if you have them cost nothing and are heavy enough to keep the cover in place during high winds. They do take up some space inside your bed, so you need to be extra careful of their placement so that they don’t crush any plants. Also rocks should be round and smooth so that they don’t damage the cover.
Lumber works best on the edges of the cover. It is easier to remove than the other two options when you need to check on your crops, water them or do some weeding.
Best time to install (and when to remove)
You want your row cover to be most effective in terms of warming up the soil and surrounding air so that you can plant earlier in the spring. Therefore it is a good idea to put up the row cover after you prepare your beds but at least a few days if not a full week before you transplant your seedlings or direct seed.
This way the sun will have a chance to warm up the soil and your transplants will have less of a shock when they leave the warmer, pleasanter confines of your seeding area. You can check the soil temperature with a soil thermometer or just put your finger in to see if the soil has warmed up enough.
Steps to install
Row cover doesn’t take much time to install, especially if you leave the supports in all year and just remove the cover for preparing the soil, transplanting/seeding and pollination.
Of course if this is the first time you are using row cover then you will need to install supports.
Installing the supports is usually the more time-consuming part. It depends however on what you are using. The critical point here is to use enough supports.
I usually try and put a support every foot or 30cm. It requires you to have enough supports on hand of course. And you might find too many supports will get in the way of doing weeding, watering or other maintenance around your crops.
You can simply push the supports into the ground like I do if you are using steel hoops. You can try and do the same if using PVC pipe but it can be a bit more difficult (see next paragraph for a better way.) Try to insert the supports at least 6 inches or 15cm, more being better to secure them well.
For a more permanent and sturdier support, you can also attached short lengths of appropriate sized PVC pipe to the inside of your raised garden beds (another advantage of raised beds vs. planting directly in the ground). Alternatively if using PVC supports, pound in a short piece of rebar that the PVC supports can fit over.
Wood frames are the easiest to install, but keep in mind that these can become airborne during heavy winds, especially if the wind finds it’s way underneath the cover. Elaborate hinged covers can be constructed that simply pivot up and out of the way for maintaining plants and to vent the bed if you are using raised beds.
Some gardeners also add a ridge pole that ties together all of the individual supports. The ridge pole can be of the same material. Use bailing wire or string to tie everything together. For PVC pipe you can instead use T and + shaped connectors to create a more sturdy support structure.
2. Placing the row cover
You may need a hand doing this, especially for larger covers. And avoid doing this if it is moderately windy as it will be almost impossible to do. These covers act as sail cloths, wanting to whip around and not cooperate in any windy weather.
Clip the cover in the middle at both ends of the bed as a start. Ensure the cover will reach down on both sides and is centered lengthwise to cover both ends evenly.
3. Securing the cover with clips
Using more of the same clips, proceed to clip the rest of the cover to the supports. I usually don’t bother using any clips on top of the intermediate supports. But do clip well at the ends of the cover and along the bottom of the sides.
Again you will be glad to not choose to do this during windy weather!
4. Securing the edges with pins, rocks or boards
The clips should help to keep the cover on at the bottom of the sides. But you will need to secure the excess cover at the ends and between the supports on the sides with something else.
You can push in pins especially made for row cover. These can tear the cover however, so I prefer to use smooth rocks or lumber.
Be careful not to crush any plants along the edges of the bed with the rocks or lumber. While I have a trim board running around my raised beds, I have found that I can’t use the ledge to try and hold the row cover with rocks or lumber. During high winds the rocks or lumber sometimes fall off or animals may knock them off trying to get at my crops. Placing these hold-downs inside the bed is more secure.
When to remove the cover
Remember to remove the cover when your crops start to flower (for pollinated fruiting crops such as tomatoes, cucumbers, peppers, etc.).
By then hopefully pests will have found your neighbour’s unprotected crops and won’t come back to yours!
Also monitor the temperature and if the daytime temperature under the row covers is getting too high even if you are venting, you may need to remove them at least during the day.
When you remove the cover for pollination or when it is no longer needed, you need to clean and store it. This way it is ready to go next time you need it. Here are a few maintenance tips.
- Always take care removing the cover, especially if it is Reemay as it is easy to tear.
- Clean it:
- Reemay can be washed by hand in a sink or large tub of hot soapy water and then rinsed a few times in clear water. Or you can wash it in a washing machine on the gentle or delicate cycle. It is best to dry it in the sun as it will also help disinfect it and brighten it.
- Greenhouse film can be hosed off or if really dirty, washed carefully with a sponge on a hard surface such as a patio, deck or driveway. Be careful not to move it around too much on a rough surface otherwise you will mar it and reduce light transmission.
- Fix any tears with greenhouse film tape. This special tape is UV resistant. This works for both Reemay and plastic film. If it is more than just a tear and an actual hole, you may have to apply a patch from a spare piece of cover or just use a large piece of tape on both sides of the hole.
- Fold and store. Careful where you store it as chewing animals such as rats and mice might take a liking to it (especially Reemay) and use it to build nests.
Row cover is an effective way to protect your crops from pests, frosts and unexpected spring cold snaps and retain moisture. Try it this year either in the early spring or early fall to improve the yield of your food crops.
Let me know in the comments if you try row covers for the first time.
Tranquil Garden, Victoria, BC