Mary's Veggie Garden

May 16, 2017

Protecting the Harvest with a Row Cover: Part 2 – Size and Installation

Filed under: Floating Row Cover,Insects,Vegetables — marysveggiegarden @ 7:26 am

Why use a floating row cover? See Part 1.

A floating row cover protects crops by providing a barrier to insects. An effective barrier covers the plants completely from the ground, up the side of the plants, over the top and back down to the ground. It also covers the plant completely through time – from the day the seeds sprout or the baby plant is transplanted into the garden through harvest.

How big should a row cover be?

I size my row covers to fit the plants at maturity. Vegetables grow quickly in June and many are full sized within a month.

The width of a floating row cover should be the sum of the width of the planting area plus 2 times the height of the plants plus the width under the anchors. A 10′ wide row cover will cover 2 rows of 2.5′ tall plants in a 4′ wide bed.

Potatoes under a row cover.

My row cover is 118″ wide – just shy of 10′ wide. The potatoes above are planted in a bed 3.5′ wide and the plants get 2.5-3′ tall. There is about 6″ of row cover under the boards on both sides which anchor the fabric to the ground. The extra width is drooping between the rows, but a few weeks later that row cover was stretched tight.  A similar arrangement works for growing bush beans in a 4′ bed.

I’ve used a 6′ wide row cover to cover a single row of broccoli plants. That worked until I harvested the main head but afterwards the plants outgrew the row cover and lifted it right off the ground. I keep my spring broccoli in my garden until fall and continue to harvest side shoots. The 10′ wide row cover is wide enough to cover the broccoli until fall.

In the picture below, a mix of rocks and boards holds the row cover against the ground. The extra width of fabric is held under the boards on the right and released slowly as the plants grow.

A row of broccoli protected from cabbage worms.

When should a row cover be installed?

A row cover should be installed when the plants are planted. If you plant seeds, cover the planting before the sprouts are visible.

Unprotected plants are very inviting to insects. Bean beetles and cabbage moths quickly find the crop and lay their eggs on the underside of leaves where they are difficult to see. Covering a crop that is already infested creates a bad situation because you can’t see the pests and the row cover blocks their predators.

How is a row cover anchored to the ground?

I use old wooden fence posts as shown in the pictures. I carefully remove all staples and nails which might snag and rip the row cover. I also use rocks. I stretch the cover tight between the rocks, pleat any excess fabric and place it under the rocks.

I always anchor excess fabric to the ground under a board or rock. That stops the fabric from blowing in the wind and rubbing excessively on the plants.

A newly installed floating row cover.

I planted a mix of seeds and transplants under the row cover above. The printing goes down the center of the fabric and I gathered about half the fabric (everything to the left of the printing) under the boards on the left side.

Does a floating row cover ever need support?

Occasionally I support a row cover, mainly when my transplants are very small or if the plants have been protected in a greenhouse without exposure to wind. The support should be something smooth that will not snag the fabric. I’ve used gallon milk bottles half filled with water. As the plant grows under the row cover the new leaves become accustomed to the movement of the fabric. Remove the support when the plant is taller than the support.

What about weeds?

In the community gardens, red root pigweed grows to 5′.  It can grow right through a row cover. I control weeds by mulching early and thickly with shredded leaves. I mulch transplants immediately, leaving a clear space 1″ around the stem. I mulch big seeded crops like beans before planting. I cover the entire planting area with shredded leaves then clear a strip 3″ wide and the length of the row to plant the seed. There is very little weeding needed after the plants emerge.


Water flows right through the row cover. It is best to water the roots, not the leaves, so I water my entire garden with soaker hoses.

How long is a row cover useful? Is there any use for an old row cover? Agribon AG-15 lasts one gardening season. By autumn it’s developing thin spots and tears.

Save an old row cover to protect germinating corn or other seeds from animals.

May 14, 2017

Protecting the Harvest with a Row Cover: part 1, Why a row cover?

A row cover is a non-woven fabric covering used in vegetable gardens to protect plants. Row covers come in different weights for different purposes. The lightest covers pass the most sunlight and are used as an insect barrier. Heavier row covers protect plants against frost but pass less light.

In this post I will discuss the lightest weight floating row cover which is used to exclude insects from the vegetable plants and the specific pests I protect against in my garden. My next post will cover how and when to install a floating row cover in the garden and how big a row cover is needed.

A floating row cover protects potatoes against successive pests in my garden: in May flea beetles, in June Colorado Potato beetles, in July potato leaf hoppers.

Some Motivation

Have flea beetles ever killed eggplant transplants in your garden? Flea beetles are tiny, black insects. They jump when disturbed so you may never  see one, but you might recognize the damage they leave behind. Flea beetles prefer to feed on hairy leaves in which they chew tiny holes. In my garden I use a floating row cover to protect Chinese (Napa) cabbage from flea beetles.

Flea beetles and their feeding damage on Chinese cabbage. (Greatly enlarged to show insects.)

Growing kale and other cabbage family crops has gotten more and more challenging. First there were imported cabbage worms.  I remember the first time I cooked my own broccoli and discovered that imported cabbage worms turn grey when cooked. Yuck! About 4 years ago I saw the first cross-striped cabbage worms which are even more devastating. The adult moth lays her eggs in clusters of 20 or so and when the caterpillars hatch and start feeding they quickly turn a kale plant into lace and frass.

Cross striped cabbage worms devastating my kale.

Imported cabbage worm on cabbage.

Do squash borers kill your zucchini every year just as the harvest starts? The adult borer is a moth who lays her eggs on the stem of zucchini & summer squashes starting about the time the chicory blooms and finishing up by the end of June in Dutchess County, NY. It is safe to remove row covers from squash plants on July 4. Squashes are pollinated by bees and must be uncovered for pollination.

Mexican bean beetles are a plague in the community gardens. Many gardeners mistakenly protect these voracious pests because of their close resemblance to their ladybug cousins. Although shape and size are identical, bean beetles are  orangey-brown or copper while ladybugs are red. Bean beetle larvae are bright yellow and feed on the underside of leaves. A row cover provides effective protection for bush beans. Most beans are self-pollinating so the row cover can be left on the plants through harvest. I’ve covered edamame soy beans and bush beans grown for drying.

Mexican bean beetle adults and larvae.

A Floating Row Cover

In my garden I’ve been using Agribon AG-15 Insect Barrier. It is 118″ wide. Here is the description from

Lightweight grade for insect control.

Also for heat-sensitive crops – only a minimal heat increase during the day. … Effective control of insect pests on potatoes, greens, cabbages, and radishes. 90% light transmission. 0.45 oz/sq.yd.

What does this mean? Light weight – the row cover doesn’t need support. It is light enough to be supported by most plants as they grow. It is also light enough that heat does not build up under the row cover. I’ve kept my broccoli covered all summer, uncovering only briefly to harvest.

90% of the sunlight reaches the plants under the row cover. In full sun plants don’t notice any difference in sunlight. I’ve covered zucchini squash in my part-sun home garden. The plants might have preferred a bit more light in their youth, however they lived through a full season because of the early summer protection from squash borers.

Water easily passes through the AG-15 row cover. Rain reaches the planting through the row cover.


Alternatives to a floating row cover include hand-picking the insects off the plants and spraying various insecticides. It is easy to hand-pick cabbage worms from kohlrabi because the leaves are flat and the crown of the plant is open and easy to inspect. In contrast, it is almost impossible to find cabbage worms feeding in a head of broccoli so I always row cover my broccoli.  The insecticide Bacillus thuringiensis is rated for organic gardens and is very effective against cabbage worms but it must be sprayed every 7 to 10 days to protect new growth.  Can you maintain a regular spray schedule? It is a challenge.

Flea beetles are  very jumpy, impossible to see and hand-pick. Squash borer eggs are laid on the stiff main vine of the plant which is quite stiff and difficult to inspect for eggs. Once the borers hatch, they chew their way into the stem which keeps them well hidden.

Because I’m a lazy gardener, I choose to protect some crops plants with a floating row cover rather than spray or hand-pick.

In my next post I will explain when and how to install a floating row cover in your vegetable garden.

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