In The Year-Round Vegetable Gardener
(Storey Publishing, 2011), author Niki Jabbour shows how you can enjoy
fresh-from-the-garden veggies even in the dead of winter using simple,
cost-effective techniques. In this excerpt from Chapter 3, Jabbour
expounds on the wonders of row covers: Made of semitransparent fabric
available in a variety of weights, row covers exclude insect pests,
protect seeds and seedlings, and insulate against frost and winter
weather.
You can purchase this book from the MOTHER EARTH NEWS store: The Year-Round Vegetable Gardener.
A
row cover is simply a piece of lightweight, semitransparent fabric that
is most often constructed from spun-bonded polypropylene or polyester.
In spring and fall, it’s used to protect crops that are tender from
frost. During the summer, it can be used to protect crops from a variety
of threats including insects, birds, and other animals that like to
munch on newly planted seeds or seedlings.
Even though row covers
are able to keep out so many things, they do allow water, air, and light
to pass through to your plants. Because of this, you can leave some of
the lightest-weight covers in the garden for an extended length of time,
as long as there is enough excess material to allow for plant growth.
Using Row Covers
Easy
to use, economical, and incredibly effective, row covers are an
essential tool for the nonstop garden. They are also multifunctional,
having a wide variety of uses throughout the year; you’ll find yourself
relying on them time and time again for the following tasks.
To Exclude Insect Pests
Certain
fabrics make excellent barriers for organic insect control. Some are
marketed specifically as insect barriers, whereas others are simply
lightweight row covers. They can be used for a variety of garden pests;
I’ve had particular success with them in the ongoing battle against
cabbage worms on my broccoli.
An insect cover works in several
ways. First, it creates a physical barrier that pests cannot penetrate.
Second, the cover hides the plants from sight, keeping many insects from
finding their target. Usually insect barriers are laid directly on top
of the target plants, but some gardeners prefer to use hoops to support
the fabric. Because these fabrics are virtually weightless, this
additional measure isn’t strictly necessarily, but many gardeners find
the sight of tidy tunnels over the crops to be pleasing.
However
you choose to install your insect barrier, the most important
consideration for this organic insect control is timing. The cover needs
to be in place long before insects become a problem. If installed too
late, you might simply be trapping the offending insects under the
fabric. They’ll be protected from the birds and predatory insects that
might normally eat them and instead spend their days leisurely enjoying
their favorite food — your veggies.
Typically,
an insect barrier is laid on the garden as soon as the bed is planted
or seeded. The edges of the cover must be buried well to prevent pests
from crawling under the fabric. Keep in mind that if you’re trying to
outwit an insect that overwinters and emerges directly from the soil,
you’ll need to combine a cover with a yearly crop-rotation plan. Even a
small garden will benefit from an annual shifting of crops.
Once
your row cover is in place, don’t forget to take an occasional peek
beneath the material to ensure that no pests have infiltrated your
defenses. Knowing the life cycles of some common garden pests is also a
good idea.
Also remember that many plants need to be pollinated in
order to produce a crop. Therefore, it’s vital that you remove the
insect barrier when these plants begin to bloom. Some plants that must
be pollinated are cucumbers, squash, peppers, tomatoes, and melons.
Certain crops, such as broccoli and cauliflower, don’t require
pollination and can be left under their cover until they’re ready to be
harvested.
To Protect Seeds and Seedlings
You
can also use row covers to speed up seed germination and protect newly
planted seeds and seedlings from a variety of pests. When you plant
seeds in a garden bed, you must ensure that the soil stays relatively
moist until the seeds germinate. In my area, the frequent spring rains
are a big help, but when a dry spell strikes, a light- or medium-weight
row cover can come to the rescue. When installed over a newly planted
and watered bed, the cover will trap some of that moisture, as well as
retain heat, helping seeds germinate quicker.
Row covers will also
help protect against heavy rains, which can cause soil crusting. Crusty
soil makes it difficult for small seeds to poke through, leading to
spotty germination among certain crops — notably carrots and parsnips.
Covers
also protect against birds. At times I’ve come inside after planting
seeds only to look out through the window and see a large flock of birds
feasting on the smorgasbord I've provided. I’ve also had birds nip off
the tops of my young bean plants, leaving just sad-looking stubs in the
soil. In times like these, I remember that securing a row cover would
have taken only a minute or two.
To Warm the Soil and Protect Against Frost
Extending
the garden by several weeks in both the spring and the fall is easy
with a light- or medium-weight row cover. In spring, cool-weather crops
such as radishes, spinach, arugula, lettuces, peas, carrots, and beets,
can be started directly in the garden a few weeks earlier than usual if
they’re covered with a light- or medium-weight cover. The cover will
trap daytime heat, warming the soil and protecting the vegetables from
frosty evenings. If you are using a medium-weight cover, remove it on
mild days to expose your plants to maximum sunlight.
Even
if no frost is imminent, you can still float a row cover over tender
vegetables as a temporary shield. Not only will this save you the
trouble of running outside in your robe and bunny slippers when you
discover a late frost is likely (it seems that I always hear about an
unexpected frost after I’ve hung up my gardening gloves for the night),
but it will also trap some of the daytime heat, creating a microclimate
and keeping your heat-loving vegetables a bit more toasty.
If you
are covering tomatoes, peppers, or eggplants, make sure that the fabric
doesn’t rest directly on top of the growing tips of the plants, as the
abrasive rubbing of the fabric against their foliage can injure the
delicate tissues. Instead, drape the fabric over tomato cages, hoops,
stakes, or other supports. Once the risk of frost has passed, remove the
coverings to allow air circulation and, eventually, pollination.
The
soil holds a larger heat reservoir in the fall than in the spring, and
you can use this to your advantage by covering up your tender vegetables
when the cool weather threatens at the end of summer. A row cover will
trap some of that heat, enabling you to protect your tomatoes and
peppers while speeding up the ripening of any remaining fruits left on
the plants.
Row covers can also be used in fall to provide
late-season protection to cool- and cold-weather crops. Salad greens —
arugula, spinach, winter lettuces, and mâche — along with late crops of
carrots, radishes, baby beets, and leeks will appreciate the extra
insulation of a medium-weight row cover on frosty nights.
For Ongoing Protection in Winter
For
a year-round gardener, ongoing protection is perhaps the best use of
row covers. Even if you’re not ready or able to invest in a winter cold
frame or mini hoop tunnel, you can still enjoy a handful of homegrown
winter vegetables all winter long with just a few minutes of work and a
length of heavyweight row cover.
With a layer of organic material.
In late fall, spread a 12-inch-thick layer of shredded leaves or
seedless straw over winter vegetables (this method works especially well
for carrots, parsnips, beets, celeriac, turnips, and leeks) and top it
with a medium- or heavyweight row cover. When the craving for sweet
garden carrots strikes in midwinter, all you have to do is pull back the
cover and reach inside.
Over hoops. A heavy-grade row
cover held on wire or PVC hoops can provide enough protection for
certain hardy crops to be held in the garden, awaiting a cold-weather
harvest. Some winter vegetables that can be grown this way are leeks,
scallions, mâche, arugula, kale, collards, and spinach.
An extra layer.
Use row covers to add an extra layer of protection to cold frames, mini
hoop tunnels, and unheated greenhouses. This pairing of season
extenders is key in creating a year-round vegetable garden that provides
a nonstop harvest and requires no supplemental heating.
Types of Row Covers
Several sizes and grades (or weights) of row covers are available, and each has its place in a year-round vegetable garden.
Insect barriers.
At the lightest end of the spectrum are the insect barriers. These
virtually weightless, almost transparent fabrics allow up to 95 percent
of light to pass through. They don’t offer much protection against a
frost, but they may be left in place over crops for weeks at a time to
prevent insect infestations. They work very well against a variety of
insect pests, from cabbage worm to carrot rust fly to the cucumber
beetle, as well as hungry birds and deer.
Lightweight covers.
The next step up from the insect barriers, lightweight covers are a bit
more substantial, weighing in at about half an ounce per square yard.
Lightweight covers are also ideal for protecting newly seeded beds from
birds and squirrels, or plants from insects, birds, rabbits, and deer.
They will even boost seed germination by locking in heat and moisture.
Most lightweight covers can provide up to 4°F (2°C) of frost protection
and permit 85 percent of light to pass through to your plants.
Medium-weight covers.
The medium-weight fabrics typically weigh from 0.9 to 1.25 ounces per
square yard and are most often used for light frost protection or as a
winter cover. Depending on the product, a medium-weight fabric will
offer up to 6°F (3-4°C) of protection. It will also hold a bit more heat
than the lighter-weight fabrics, but it may only allow 70 percent light
transmission. For this reason, the medium-weight cover shouldn’t be
used as an insect barrier during the growing season; there’s just not
enough light to provide optimum plant growth during the spring and
summer months.
Heavyweight row covers. The heaviest
covers are often marketed as frost blankets and are used to protect
crops from a heavy freeze. They typically weigh 1.5 to 2 ounces per
square yard and can protect crops down to 24°F (-4°C). Because these
covers offer only 30 to 50 percent light transmission, they are best
used to shelter winter vegetables or as temporary frost blankets. If
used in summer, they would block much of the light needed for healthy
plant growth, as well as raise the ambient temperature around the crops.
In winter, when there is less than 10 hours of daylight, the growth of
most crops slows dramatically. Therefore, even though a heavyweight row
cover prevents a good portion of the sunlight from reaching the crops,
the goal in winter is protection, not growth.
Floating Row Covers and Supported Row Covers
Often,
row covers are laid directly on the surface of the soil or on top of
growing crops. Because they are so light, they “float” on top of the
growing plants and are thus called floating row covers. But there are
times when the cover should be held above the crops and supported on
simple hoops: for example, when the cover needs to protect and insulate
against heavy frost or winter cold, particularly for any length of time.
If the cover is allowed to rest directly on top of the plants, the
foliage may suffer cold damage.
Types of Row Covers
Several sizes and grades (or weights) of row covers are available, and each has its place in a year-round vegetable garden.
Insect barriers.
At the lightest end of the spectrum are the insect barriers. These
virtually weightless, almost transparent fabrics allow up to 95 percent
of light to pass through. They don’t offer much protection against a
frost, but they may be left in place over crops for weeks at a time to
prevent insect infestations. They work very well against a variety of
insect pests, from cabbage worm to carrot rust fly to the cucumber
beetle, as well as hungry birds and deer.
Lightweight covers.
The next step up from the insect barriers, lightweight covers are a bit
more substantial, weighing in at about half an ounce per square yard.
Lightweight covers are also ideal for protecting newly seeded beds from
birds and squirrels, or plants from insects, birds, rabbits, and deer.
They will even boost seed germination by locking in heat and moisture.
Most lightweight covers can provide up to 4°F (2°C) of frost protection
and permit 85 percent of light to pass through to your plants.
Medium-weight covers.
The medium-weight fabrics typically weigh from 0.9 to 1.25 ounces per
square yard and are most often used for light frost protection or as a
winter cover. Depending on the product, a medium-weight fabric will
offer up to 6°F (3-4°C) of protection. It will also hold a bit more heat
than the lighter-weight fabrics, but it may only allow 70 percent light
transmission. For this reason, the medium-weight cover shouldn’t be
used as an insect barrier during the growing season; there’s just not
enough light to provide optimum plant growth during the spring and
summer months.
Heavyweight row covers. The heaviest
covers are often marketed as frost blankets and are used to protect
crops from a heavy freeze. They typically weigh 1.5 to 2 ounces per
square yard and can protect crops down to 24°F (-4°C). Because these
covers offer only 30 to 50 percent light transmission, they are best
used to shelter winter vegetables or as temporary frost blankets. If
used in summer, they would block much of the light needed for healthy
plant growth, as well as raise the ambient temperature around the crops.
In winter, when there is less than 10 hours of daylight, the growth of
most crops slows dramatically. Therefore, even though a heavyweight row
cover prevents a good portion of the sunlight from reaching the crops,
the goal in winter is protection, not growth.
Floating Row Covers and Supported Row Covers
Often,
row covers are laid directly on the surface of the soil or on top of
growing crops. Because they are so light, they “float” on top of the
growing plants and are thus called floating row covers. But there are
times when the cover should be held above the crops and supported on
simple hoops: for example, when the cover needs to protect and insulate
against heavy frost or winter cold, particularly for any length of time.
If the cover is allowed to rest directly on top of the plants, the
foliage may suffer cold damage.
