Row cover is graded by weight and the trade is direct: 0.5 oz fabric transmits about 85 percent of light and gives 2 to 4 degrees F of protection, while 1.2 oz transmits around 70 percent and gives 6 to 8 degrees F. The AlpineReach 10 by 30 ft cover at roughly $30 is the useful default. Use lighter fabric in spring when light limits growth and heavier in fall when the crop is holding.
0.5 oz fabric
2 to 4 F, 85% light
1.2 oz fabric
6 to 8 F, 70% light
Winter grades
Under 50% light
Covers compared
6
Researched from published specifications and verified owner reviews · Updated 2026-08-16
Row cover is the cheapest frost protection there is, and choosing it comes down to a single number that most listings bury: fabric weight in ounces per square yard. That number predicts both how many degrees of protection you get and how much light you give up, and the two move against each other.
The useful default is a heavy 1.2 oz fabric such as the AlpineReach 10 by 30 ft cover at around $29.99, which buys 6 to 8 degrees F, enough to be the difference between losing a crop of lettuce and not.
Heavy 1.2 oz spun-bonded fabric, which is the weight that does the job most home gardeners actually need: roughly 6 to 8 degrees F of protection, enough to carry hardy crops through the frosts that end an unprotected season. The 10 by 30 foot size covers several beds or one long tunnel run without joining pieces, and joins are where covers tear. Spun-bonded fabric is permeable, so rain and air pass through and it can rest directly on foliage without scorching, which plastic film cannot.
Agfabric Frost Blanket, 0.55 oz, 10 x 100 ft ($32.61). A much longer roll for covering a whole plot or making repeated cuts to size, which works out considerably cheaper per square foot if you are covering more than a couple of beds.
Fabric weight, which is the whole decision
Spun-bonded polypropylene row cover is graded by weight per square yard, and that single figure determines its behaviour. Heavier fabric traps more heat and blocks more light. There is no fabric that does both jobs well, which is why many growers own two weights.
Figure 1. Row cover fabric weight against protection and light·7 rows
Figure 1. Row cover fabric weight against protection and light
Fabric weight
Light transmission
Frost protection
Primary use
0.3 oz, insect weight
About 90%
1 to 2 F
Pest exclusion, minimal warming
0.5 oz, light
About 85%
2 to 4 F
Spring growth with light frost risk
0.9 oz, medium
About 75%
4 to 6 F
General season extension
1.2 oz, heavy
About 70%
6 to 8 F
Hard frost protection, fall and winter
1.5 oz, winter
About 50%
8 to 10 F
Overwintering, protection not growth
2.0 oz, extra heavy
Under 50%
10 F plus
Emergency and dormant protection only
Insect mesh, fine
About 85%
Negligible
Pest exclusion only, no warming
Researched typical values. Protection figures are for a still, clear night with the cover suspended on hoops rather than laid directly on foliage, which performs better. Doubling a light fabric gives roughly the protection of a single heavier one while transmitting less light than either, so a single correct weight beats layering in most situations.
The trade inverts across the season, which is the part most growers miss. In spring, light is frequently the factor limiting growth and frosts are light, so the lighter fabric often produces better crops despite protecting less. In late fall the crop is holding rather than growing, light matters much less, and the heavier fabric wins. The same reasoning applies in a cold frame or tunnel, as covered in extending the season with row cover.
The three tiers
Crop covers in three tiers
3 tiers · priced at the time of writing
Beginner
A few individual plants, or occasional frost nights rather than a season-long strategy.
A pop-up cover needs no hoops, no clips and no cutting to size. It goes over a plant in seconds when a frost is forecast and folds away afterwards. For someone protecting three tender plants on the two or three nights a year it matters, this is the correct scale of solution and everything more elaborate is over-engineering.
The trade-off:
It covers one plant or a small group, so it does not scale to a bed. The enclosed volume is also small, which means it heats quickly on a sunny morning and needs removing early rather than left on.
Heavy 1.2 oz fabric at a size that covers multiple beds or a full tunnel run without joining. This is the weight that carries hardy crops through the frosts that would otherwise end the season, and the permeable spun-bonded construction means rain and air pass through so it can be left in place for extended periods rather than being managed daily.
The trade-off:
At 70 percent light transmission it costs growth if left on through bright spring weather, which is why a second lighter fabric is worth owning. It also needs securing properly, because a loose cover in wind abrades and tears within a season.
Fine insect mesh excludes pests physically, which is the only control method with no resistance, no residue and no harvest interval. For brassicas against cabbage white butterfly, carrots against carrot fly and cucurbits against squash vine borer, exclusion is dramatically more effective than any spray, and it works from the day it goes on.
The trade-off:
It provides essentially no frost protection, so it is a different tool rather than an upgrade. It also excludes pollinators, which means it must come off any crop that needs insect pollination during flowering, and timing that correctly is the main skill in using it.
Spun-bonded fabric can be laid directly on foliage, which is called floating, or suspended on hoops. Both work and they suit different situations.
Floating requires no hardware and is fast to deploy over a whole bed. The fabric rises as the crop grows. Its weaknesses are that the fabric rests on leaves, which in wind causes abrasion damage on tender growth, and that any point where the fabric touches foliage is a point where frost can transmit through. Floating suits robust crops such as brassicas and salad, and is poor for anything with delicate growing tips.
On hoops using garden hoops or a hoop and cover kit creates an air gap, which improves frost protection measurably because the trapped air is the insulation and because no leaf is in contact with the cold outer surface. It also removes abrasion entirely and makes the cover easy to lift for access. It is the better method wherever the extra effort is affordable.
Individual cloches are the same principle applied to single plants, and they suit early transplants going out ahead of the safe date, where a handful of plants need protection rather than a whole bed.
Watch out
Secure the edges, or the cover becomes a sail
Row cover fails by leaving the ground, and it takes the crop with it when it goes. The fabric is what lifts, not the hoops, so the edges are what need pinning. Landscape staples through the skirt every 18 inches, with soil, timber or sandbags laid along the edge, is the standard method. Leaving a generous overhang to bury or weight is far more effective than pulling the cover tight and pinning the corners. A cover that flaps abrades against every hoop contact point and will tear within a season regardless of its quality.
Insect exclusion, which is a different job
Fine mesh is worth understanding as a separate category, because it is the most effective pest control available to a home grower and the least used.
Exclusion works by physically preventing the adult insect from reaching the crop to lay eggs. Against cabbage white butterfly on brassicas, carrot fly on carrots and parsnips, leek moth on alliums and squash vine borer on cucurbits, this is close to complete control, with no resistance developing, no residue on the crop and no pre-harvest interval to observe.
The two requirements are that the mesh goes on before the pest arrives, since it excludes rather than removes, and that it is sealed at the edges. A mesh with a gap at one end is a shelter rather than a barrier, and pests that get inside are then protected from their own predators. Rotation matters too: mesh over a bed where the pest overwintered in the soil traps it inside with the crop.
The critical limitation is pollination. Mesh excludes bees and hoverflies as effectively as pests, so any crop that requires insect pollination has to be uncovered during flowering, or hand pollinated. Brassicas grown for leaves, carrots, and salad crops are unaffected. Squash, cucumbers and beans are. The same problem applies inside a greenhouse and is addressed in pollination in a greenhouse.
Ground cover and weed barrier
A related fabric category worth covering here because it is frequently bought at the same time and serves a different purpose.
Woven weed barrier laid on a greenhouse floor or on paths does three useful things: it suppresses weeds, it keeps a soil floor from turning to mud, and it lets water through rather than pooling. In a greenhouse specifically it also reduces the splash that spreads soil-borne disease onto lower leaves during watering.
The distinction that matters is woven versus spun. Woven barrier such as the Pro 5 is permeable, durable and intended to be walked on for years. Lighter spun barriers suit temporary use under a bed or a path but degrade in UV if left exposed, so they need covering with gravel or bark.
Neither should be laid under a growing bed where you want soil biology to function, since barrier under a bed prevents worm movement and root penetration into the subsoil. Use it on paths and floors, not under beds.
How we chose
We did not measure light transmission or conduct frost trials, and any site claiming controlled frost testing across six fabrics is telling you a story. Protection and transmission figures here are researched from published horticultural extension guidance and manufacturer specifications, and where sources vary we have given the conservative figure.
Product selection weighted stated fabric weight above everything else, because it is the only specification that predicts performance and because many listings omit it. A cover described only as a frost blanket, with no ounce figure, could be anything from 0.3 to 1.5 oz, which is the difference between one degree of protection and eight.
On durability, the failure mode across the whole category is tearing at stress points rather than fabric degradation, so edge reinforcement and the availability of generous sizes that avoid joins scored highly. Owner reports consistently show that covers fail where they were pinned, clipped or rubbed against a hoop, not in the middle of a span.
What covers work with
The rest of the protection system
Fabric is half of it. These four are the hardware that keeps it on the crop, plus the lighter weight worth owning alongside a heavy one.
The fabric is what lifts in wind, not the frame. Staples through the skirt every 18 inches with a weighted overhang is the standard and effective method.
+- How many degrees of frost protection does row cover give?
It depends directly on fabric weight. Light 0.5 oz fabric gives roughly 2 to 4 degrees F while transmitting about 85 percent of light. Heavy 1.2 oz gives 6 to 8 degrees F at around 70 percent light. Winter grades at 1.5 oz and above give 8 to 10 degrees but transmit under 50 percent, which makes them protection rather than growing fabrics. Suspending the cover on hoops performs better than laying it on the crop.
+- What weight row cover should I buy?
1.2 oz as a single default, because it gives 6 to 8 degrees F, which is the range that carries hardy crops through the frosts that end an unprotected season. If you buy two, add a 0.5 oz light fabric for spring, when light rather than cold is usually limiting growth and the heavier cover costs you more in growth than it gains in protection.
+- Can row cover sit directly on plants?
Spun-bonded fabric can, which is called floating, and it is fast to deploy over a whole bed. The drawbacks are abrasion damage on tender growing tips when the fabric moves in wind, and reduced protection at every point where a leaf touches the cold outer surface. Suspending it on hoops creates an air gap that improves protection measurably and removes abrasion entirely.
+- Does insect mesh protect against frost?
Essentially not at all, and it is a different tool rather than a lighter version of frost fabric. Fine mesh at around 0.3 oz gives at most one to two degrees. Its purpose is physical pest exclusion, which is the most effective pest control available to a home grower, with no resistance, no residue and no harvest interval. It must go on before the pest arrives and be sealed at the edges.
+- Will row cover stop plants being pollinated?
Yes, and this is the main practical limitation of any cover or mesh. It excludes bees and hoverflies as effectively as pests. Crops grown for leaves or roots, such as brassicas, carrots and salads, are unaffected. Anything requiring insect pollination, including squash, cucumbers and beans, must be uncovered during flowering or hand pollinated. Plan the timing before the crop reaches flowering.
+- How do you stop row cover blowing away?
Pin the fabric edges rather than only the hoops, because the fabric is what lifts. Landscape staples through the skirt every 18 inches, with soil, timber or sandbags along the edge, is the standard method, and a generous overhang to weight down is far more effective than pulling the cover tight and pinning the corners. A flapping cover abrades at every hoop contact and tears within a season.
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