Row cover and frost blanket are not two products. They are the same spun bonded fabric sold at different weights, and the weight is the only thing that changes. Light fabric buys roughly 2 to 4 degrees Fahrenheit and passes enough light to stay on for weeks. Medium buys roughly 4 to 6. Heavy buys roughly 6 to 8 and shades the crop enough that it should only go on for the cold nights themselves. Cloches are a different idea entirely: they protect one plant, and the water filled kind stores real heat rather than merely slowing its escape.
If you buy one thing, buy a medium weight roll and a set of hoops. The hoops matter more than most people expect. Nearly all of the protection comes from trapping heat radiating out of the soil, and foliage pressed against fabric that has frozen on the outside freezes with it, so a cover draped straight onto the plants gives away much of what you paid for.
| Pick | Best for | Price | Link |
|---|---|---|---|
| Agfabric Floating Row Cover, Lightweight Best lightweight | Insect exclusion and light frost, left on for weeks | $ | Check price |
| Agribon AG-19 Floating Row Cover Best all purpose | One roll that covers most of what a home garden needs | $$ | Check price |
| Agribon AG-50 Heavyweight Frost Blanket Best for hard freezes | The nights that would otherwise end the season | $$ | Check price |
| Bootstrap Farmer Low Tunnel Hoops The part people skip | Turning fabric you already own into real protection | $$ | Check price |
| Wall O Water Plant Protector Best cloche | Setting tomatoes and peppers out weeks early | $$ | Check price |
Price tiers are relative to each other rather than actual prices, and fabric is usually sold by the roll, so compare per square foot rather than per package.
What each weight actually does
| Fabric weight | Rough protection | Light through | Use it for |
|---|---|---|---|
| Light | 2 to 4 degrees F | Most | Insect exclusion, first light frosts |
| Medium | 4 to 6 degrees F | Much | General season extension, the default buy |
| Heavy | 6 to 8 degrees F | Noticeably reduced | Hard freeze nights, deployed and removed |
| Clear plastic | Varies widely | Nearly all | Day warming only, vents or cooks the crop |
Light fabric is roughly half an ounce per square yard, medium around an ounce, and heavy in the range of one and a half to two ounces. Those numbers are on the packaging and they are the only specification worth comparing, because everything else in the listing follows from them.
Two clarifications that save money. Clear plastic sheeting is not frost protection on its own. It traps heat beautifully during the day and then radiates it away at night, and anything touching it freezes hard, so plastic belongs on a tunnel with fabric underneath or on a frame that gets vented every morning. And the degree figures above assume the cover reaches the ground and is sealed there. A cover flapping loose on one side is a chimney.
Start from your frost date, not from the forecast
The cover you need depends on how many marginal nights your autumn actually has, and that follows from your first frost date.
Enter your US ZIP code for your USDA zone, frost dates & planting calendar.
You can also browse frost dates by city for the nearest major station. What that date does and does not promise is covered in first frost date and frost protection, and the short version is that it is a 50 percent probability from a thirty year average, so half of all years frost earlier than yours.
Hoops, clips, and sealing the edges
Hoops are the cheapest upgrade in this category and the one that changes results most.
Fabric held four to twelve inches clear of the canopy creates an air space, and that air is the insulation. It also stops the wind whipping fabric against stems, which shreds both. Purpose made low tunnel hoops push straight into the soil and hold shape. Half inch PVC bent over rebar stakes does the same job for less if you do not mind building it.
Clips are what stop the whole thing leaving in a gust. Snap clamps, the plastic C shaped clips sized to the hoop, are the standard answer and they take a second each. At the ends of the run, gather the fabric, twist it, and weigh it down with a brick, a bag of soil or a landscape staple.
Seal the long edges to the ground with soil, boards, sandbags or staples. This is not tidiness. The protection comes from ground heat, and an unsealed edge lets it escape all night.
When to cover and when to uncover
Cover in the late afternoon, while the ground still holds the day’s warmth. Waiting until nine or ten at night means you are sealing in air that has already cooled, and you lose much of the benefit.
Uncover in the morning once the air is back above freezing. Two exceptions. Lightweight fabric can stay on through a cold week without harm, and most gardeners leave it over brassicas continuously from spring for insect reasons. Flowering squash, cucumbers and melons must be uncovered during the day, because they need insects to set fruit and a covered plant sets nothing.
Take heavy fabric off after the cold spell. It shades enough that leaving it over a bed for two sunny weeks costs you more growth than the frost would have.
And watch for the sunny day problem under plastic. A closed plastic tunnel on a clear 50 degree day can get hot enough to damage a cool season crop, so it needs venting even when the night before was freezing.
Old bedsheets versus bought fabric
A bedsheet works. For a single unexpected frost in early October, throw sheets over the tomatoes, weigh the edges down, and you will save the crop. There is nothing wrong with it, and anyone who tells you otherwise has not lost a bed to a frost they were not ready for.
Over a season, the differences add up. A sheet blocks essentially all light, so it has to come off every morning without exception. It absorbs rain and dew and then sags heavily onto the plants, which is exactly the contact you were trying to avoid. It does not let water through, so every watering means uncovering. And the cotton rots when you store it damp.
Bought fabric passes light and water. That single difference is what turns frost protection into season extension, because a cover that can stay on is a cover that is actually over the bed on the night it matters. The next step up, for greens you want to keep harvesting into December, is a rigid lid: the cold frame guide has sow-by dates by zone and the venting rules that go with it.
The picks
Agfabric Floating Row Cover, Lightweight
Best for: Insect exclusion and light frost, left on for weeks
The fabric you use most often. It passes enough light to stay over a bed continuously, keeps cabbage moths and flea beetles off brassicas all season, and covers the first few light frosts of autumn.
Pros
- Light enough to leave on for weeks without shading the crop
- Doubles as insect netting, which is most of its value
- Cheap enough to buy a long roll and cut to fit
Cons
- Only a few degrees of frost protection
- Tears at clip points if you reuse it hard
- Not enough on its own for a hard freeze
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Agribon AG-19 Floating Row Cover
Best for: One roll that covers most of what a home garden needs
The grade market gardeners default to, because it sits at the useful middle: enough light transmission to leave on, enough weight to matter on a frosty night, and durable enough to fold up and reuse for several seasons.
Pros
- Good balance of light through and heat held
- Tougher than the cheapest fabrics, so it survives being reused
- Sold in wide rolls that cover a 4 foot bed on hoops with edge to spare
Cons
- Costs more per square foot than budget fabric
- Still not a hard freeze solution
- Wide rolls are awkward to handle alone in wind
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Agribon AG-50 Heavyweight Frost Blanket
Best for: The nights that would otherwise end the season
Heavy fabric for the handful of nights each autumn and spring when a few degrees decides whether the bed keeps producing. It shades too much to live on the crop, so you deploy it and take it off.
Pros
- The most protection available from fabric alone
- Holds shape over hoops without sagging into the plants
- Lasts several seasons if stored dry
Cons
- Shades enough that it should not stay on for long stretches
- Heavy and bulky to handle over a long bed
- Overkill for insect exclusion or a light frost
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Bootstrap Farmer Low Tunnel Hoops
Best for: Turning fabric you already own into real protection
Hoops are what separate a cover that works from one that freezes onto your plants. They cost a fraction of the fabric and they roughly double what it buys you, because trapped air, not the fabric itself, does the insulating.
Pros
- Holds fabric clear of foliage, which is where the protection comes from
- Reusable indefinitely
- Makes covering and uncovering a one minute job
Cons
- One more thing to store
- Needs clips or clamps, usually sold separately
- Light hoops can lift in strong wind unless staked well
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Wall O Water Plant Protector
Best for: Setting tomatoes and peppers out weeks early
Water filled tubes around a single plant store heat all day and give it back overnight, which is genuine protection rather than a windbreak. This is the tool that lets a cold zone gardener plant a tomato before the last frost date and get away with it.
Pros
- Protects well below what fabric manages, because water stores real heat
- Also shelters young plants from wind
- Reusable for years if stored out of sunlight
Cons
- One plant per unit, so it does not scale to a bed
- Filling and moving them full is awkward
- Has to come off once the plant outgrows it
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What your crops actually need
Frost tolerance decides how much fabric to buy, and it varies more than people think.
Kale needs almost nothing. It takes a light frost without damage and gets sweeter for it, and a light cover is enough to keep it in usable condition weeks past the first freeze. The same goes for spinach, which in most zones is sown in autumn to overwinter rather than to harvest before the cold.
Lettuce is the crop where cover pays best, because it is hardy enough to keep going but not hardy enough to ignore a hard night. A fall sowing in zone 6b has to go in by around August 29 to finish before frost, and it will keep producing for roughly two weeks past the October 18 first frost on its own. Medium fabric on hoops turns those two weeks into a month or more. The specifics are on the lettuce planting page for zone 6b.
Tomatoes, peppers, basil, beans and squash get nothing out of fabric in autumn. They are finished at the first light frost regardless, and a cover that buys 4 degrees on one night does not change that they have stopped growing in 45 degree soil. Harvest them instead. Fabric earns its money on those crops in spring, at the other end, where a cloche or a tunnel gets them into the ground weeks early.
When not to bother
Skip it if the forecast low is well below what your fabric covers. A 6 degree blanket does not save a tender crop at 22 degrees, and pretending otherwise just means you are outside at midnight for nothing.
Skip it on a windy night. Wind mixes warmer air down and usually prevents radiational frost entirely, which is why a breezy 33 degree night often does no damage and a still, clear 36 degree night can.
Skip it for anything already killed. Frost damage shows up hours later, so a bed that looks fine at dawn after a hard freeze may not be fine by noon, and covering it afterward does nothing.