Row cover is a wonderful tool used for frost protection, moisture retention and heating garden vegetables.
The woven material allows your garden bed to breathe and water to penetrate. But it acts as a physical barrier to insects, such as flea beetles, cucumber beetles and potato bugs.
It also serves as a mini greenhouse over a garden bed by trapping the heat and moisture into the area around the crop and helping plants grow. This same effect can help protect your crops against wind, frost and heavy rains.
The benefits you seek will determine how you apply coverage and the type you use.
Row cover can prevent insects from accessing the tender leaves of your vegetables. This can be particularly important when a crop is small and vulnerable and hasn’t built up the natural lipid defense against the immense insect pressures we face in gardens.
Crops with common insect pests can benefit from this defense. Cucurbits, Solanaceae and brassicas are some of the families I most often use row cover with.
For brassicas, the enemy is three-fold:
- Flea beetles attack tender leaves of arugula and other young plants in early spring.
- Swede midges attack buds.
- Cabbage loopers settle on broccoli and cabbage heads as they develop.
For brassicas, roll out the material over the bed and weigh it down by spot applying with soil, row bags or chip mulch every 10 feet. Then seal by applying a thin layer of soil or chip mulch along the entire perimeter so nothing can get in.
Note that, if you don’t rotate your crops, this won’t help much as flea beetles remain in the soil under the cover.
I use a mid-weight row cover for cucurbits because I remove it in early summer. For brassicas, I use a lightweight cover; for some crops, like broccoli, I leave it on for most of the production cycle to prevent all its many pests and the lightweight cover means the crops won’t overheat in the summer.
Lightweight row cover also floats nicely and doesn’t need wire hoop support (more later on wire hoops). This is great for crops that won’t have the cover on for very long, such as arugula, which matures in 30 days.
Covering also deters larger threats, such as deer and rabbits, by blocking their physical access to and detection of crops underneath.
Row cover can help with seed germination, as the moisture retention it provides is very beneficial for germinating a crop evenly.
This is especially helpful to crops with slower germination, like carrots, which benefit from even distribution of soil moisture.
For seed germination, the cover doesn’t have to be sealed. Just spot with weight every 5-10 feet (depending on wind pressure). I recommend a mid-weight cover for this use, as generally speaking they last longer and can be reused to germinate many crops over the summer.
Row cover can improve yield of many crops by adding soil moisture and heat to the garden crops in the early season. This can often result in a one- to two-week boost in crop productivity.
For those spring days when it gets cool and field crops slow down, you can use row cover to hold field heat from previous days. In a similar fashion, you can create a pseudo-atmosphere around the crop by keeping rain moisture within the row-covered bed.
This can help soil tilth as well, preventing clay soils from cracking in the day’s heat.
This is particularly important for northern gardens with a short growing season, especially regarding long-season crops like winter squash, tomatoes, peppers and melons.
I keep the row cover on until crops push against it. Then I release them to sprawl or trellis the plants. I recommend a mid-weight row cover for this sort of production, as I am generally using it for crops that like heat and don’t like the cold.
This weight provides better heat retention in the evenings and cool nights.
Row cover can prevent and reduce frost damage. In a similar respect to the micro-greenhouse effect, it holds heat into the cold night to protect crops.
It also holds moisture. This is good because the freezing effect is focused on available moisture in the micro-atmosphere and soil, not on the moisture within crop leaves.
It also provides a physical barrier against the cold air, allowing it settle in other areas, away from the sensitive crops. For frost protection, depending on how cold it is, I may spot or seal the row cover along the whole length of the bed.
You can use row cover in both spring and fall to extend your growing season on both ends. Use a thicker-grade row cover in the fall to protect against frost and increase the length of time you can grow a certain crop in your area.
Using Row Cover
Row cover comes in many widths and lengths. For widths, find one that is at least 1.5 feet wider than your Permabed. I generally make Permabeds 4, 5 or 6 feet wide, depending on if it is a home garden, homestead or farm.
In some cases, a row cover the width of an entire three-bed triad (see my book “The Permaculture Market Garden” for more on triad management) will efficiently cover similar crops in a market garden. I avoid covering entire gardens, as they are difficult to handle and often hard to reuse efficiently from year to year.
Some row cover has thickened edges to help you handle without ripping, but be gentle with yours and it will last. If you do have small rips, you can still use it for frost protection or germination, though it won’t work for pest protection.
You can use wire hoops to help hold it off the crop, reducing accidental damage to plants.
Overall, row cover is a multi-functional tool for gardeners that offers solutions for pests, frost protection and improved yield in cold climates.