growing under cover: tips from paul gallione

I PLAN TO GROW Crucifers and Cucurbits under cover this year, and the rampaging local woodchuck is the least of the reason why. But I wanted to get the details right from the sometimes-overwhelming catalog choices—the appropriate weight of fabric, and the gear to support the row cover and hold it in place, among other tips—so I called Paul Gallione of Johnny’s Selected Seeds in Maine for some advice.

Gallione, in his position as Technical Services Technician in the research department at Johnny’s Selected Seeds in Maine, is used to answering gardeners’ questions. I started at the beginning with mine: Why grow crops under cover, anyhow?

There are two basic uses for fabric row covers, Paul explained:

  • To modify temperature (for heat retention or frost protection, most early and late in the season with heavyweight fabrics);
  • As a barrier to keep out insects, crows, and chipmunks, to name a few common troublemakers.
  • (Note: You can also create some shade, perhaps for summer salads—though usually with a different type of fabric—but Paul’s and my conversation was about the first two situations.)

tackling flea beetles on crucifers

TO HELP THWART flea beetles on cruciferous plants like broccoli, cabbage, cauliflower and such, Paul uses fabrics to keep them out. A note: If you had a flea beetle infestation last year, a new generation can hatch from the soil, so don’t plant the same thing in the same spot and expect the cover to solve things. Rotate your planting space!

On direct-seeded crops like arugula (top photo), he says, “I lay the fabric right over the top immediately after sowing—allowing a little play, but not so loose as it will hit the emerging plants.” Other cruciferous relatives of arugula, like radishes and mustard, would benefit similarly from this type of protection strategy.

With Crucifers, the fabric stays in place from four to six weeks. To have complete control, the material can have no holes, and its edges must be buried in the soil (trench alongside the row on both sides with a hoe, then bury the fabric in the trench, using the soil to weight it down–the video below shows how). Or it can be pinned down with ground pins or sandbags for 100 percent coverage. (Rain or sprinkler water permeates.)

Another trick: Paul also uses fabric to protect his corn from hungry, seed-stealing crows (as I do with my peas right after planting, to fight off the chipmunks), leaving the fabric in place for about two weeks.

A lightweight fabric, such as Agribon 15 (called “insect barrier”) or Agribon 19, would be ideal for these uses. The video below explains the use of other weights of fabric, up to heavy “earth blanket”-like frost protectors. An 83-inch width is ample for covering four-foot-wide beds on top of hoop supports; wider fabrics can be cut for custom uses. This pdf compares fabric types and their uses.

keeping cucumber beetles out

CUCUMBER RELATIVES—or Cucurbits, including melons, cukes, pumpkins and squash—are especially vulnerable to the striped cucumber beetle, which spreads deadly bacterial wilt as it chews foliage.  But these plants are less tolerant about having fabric touching their growing points, so some form of support is required to elevate the material, Paul says. Wire hoops (perhaps made from #9 coiled wire) or other supports, such as bent pvc piping or electrical conduit, are among the popular choices.

You can shop for pre-formed hoops or make your own; Johnny’s even sells a tool for bending conduit (seen in the video below, and thoroughly explained in this 12-page illustrated pdf about creating them and growing under cover).

a cozy start (and finish) for peppers

SOME CROPS need more help with staying warm than with insect pests. Peppers, for instance, might benefit from some extra warmth at both ends of the growing season.

Gallione preps his raised beds with black plastic mulch to warm the soil for these heat-loving plants, then covers the seedlings with light-to medium-weight fabric “to get them off to a good start.” Peppers aren’t sturdy enough to have fabric laid right on top of them, he explains; use the wire hoops or other supports, such as bent pvc piping or electrical conduit, as with the Cucurbits, with this exception:

“If I direct seed the Cucurbits,” Paul says, “I lay the fabric right over the bed—but I wouldn’t do that with tender transplants.”  He removes the fabric once they grow up enough and need the room, and the plants are far enough along to be past major beetle vulnerability.

Besides, the flowering pumpkins, squash and cucumbers need insects to get to them for pollination—as do the peppers.

“Once I see blossoms, the covers come off,” says Paul—though with the peppers he may cover them again late in the year. He therefore leaves the supports in place. What you’re creating with hoop-style supports is essentially the architecture of a “low tunnel,” and the framework can support a number of materials, Paul says—“from plastic to lightweight or heavier row cover to shade cloth [below] to bird netting.” Not only is the framework versatile, but it can also be moved to other beds of the same width in subsequent seasons.

other row-cover tips

ROW COVERS AREN’T a “set it and forget it” tool that let the gardener off the hook. “There’s no substitute for human observation,” says Paul. “You have to be aware—especially as the season heats up.” Always ask yourself:

  • Is it hot out, or has it been dry for a period? Rain (or sprinkler spray) permeates the fabric, but remember, so does up to 90 percent of sunlight: It’s a little warmer in there; plants may get thirstier.
  • What crop is it, and what stage of development is it at?
  • Does it need your attention–to have the fabric vented (below, mine with clothespins added as an extra “clip” to hold the fabric open) to have supplemental water, etc.?

If you’re careful in handling them, you can get a few years out of most fabrics (the lightest-weight ones being the most vulnerable to ripping). Some precautions:

  • When pinning them down, use the same holes each time. (The large red Re-Pin brand ground pins that Johnny’s sells may make this task easier.)
  • Two people are better than one for rolling out (and rolling back up) fabrics.
  • Save the roll itself that the material comes on–to use to store fabric again.

What about all that used fabric that’s no longer in good enough shape to use as a cover again? I hate to throw it away–which has always been one of my issues with row covers: all that waste.  Paul had a suggestion:

“I use it to line recycled bulb crates to force Belgian endive,” he said….which got me thinking: It would likewise help turn tag-sale baskets and other not-quite-soil-ready containers into planters. Waste not, want not.

more information, and supplies

  1. door251 says:


    Love the blog, you def have a new follower.

    I was wondering if you knew what kind of plants are good for heavily shaded gardens? we have a tiny tiny city garden, but it is surrounded by big oak trees which i suspect are sucking the life out of everything, couple that with it not getting an ounce of sun and me being a complete novice, i’ve no idea what to plant in there, everything from last year died.

    thanks for your help!!

    1. margaret says:

      Hi, Door251. You may want to start in my archive of shade-garden stories (but beware: heavy shade and lots of tree roots is the hardest place of all). Sounds like you need to do some thinning of those oaks or else!

      Hi, Be Self Sufficient. Yes, they have many uses, and I a trying to get more “with it” this year — and take advantage of the benefits.

      Nice to see you, LynnAnn, and no — water will permeate the floating row covers (unless you use plastic as with a greenhouse!).

      Hope to see you all again soon, and thanks for your feedback.

  2. Great post! Thanks.

    I think this is such an important attitude: I am always peeking undermine and observing what my garden is saying.

    It seems there is biodegradable horticultural fleece which can be composted. I use just a light-weight one, and will layer them if more protection from frost is needed. I am able to tuck easily the fleece under the overlapping terracotta roof tiles framing my level block beds.

    I use the older and more ratty-looking fleece to line my harvest baskets (recycled, plastic, wide-weave holders for nursery pots). An essential use of fleece in my garden is to prevent birds from eating peas, beans, and pulling out young onions and as a preventive for carrot fly.

  3. Good tips. I’m gardening in a cool summer climate in the Pacific Northwest. I prefer the Agribon 19 as a good all purpose row cover. Good insect protection and some extra heat. The second and third seasons when my lengths start to get holes can be used where I’m trying to enhance for heat and wind protection rather than insects.
    I make my furrows for burying the edges of mulch or row covers with an old Planet Jr. wheel hoe. I have a nifty furrow attachment that looks like a mini moldboard plow. The newer wheel hoes have a two sided furrow/hiller attachment which might work as well. It’s quicker and easier for long rows. I use a plastic pipe (1/2 or 3/4″) to roll up my row covers. It makes it easy to roll up and roll back out over the beds by myself. I use pieces of wire for hoops similar to what Paul G.shows above. You can buy a roll of heavy gauge wire at a hardware store.
    As for plastic mulch I like the green IRT mulch. It seems to warm the soil up much quicker earlier in the season than the black plastic does. Makes a big difference for crops like peppers in our cool climate. I would be curious if anyone has tried the new bio-degradable mulches that are approved for organic growing?
    By the way, I haven’t found it necessary to worry about taking the row cover off of peppers for an extended period when they are flowering like you do for cucurbits.
    Enjoying your blog.

  4. Corrine says:

    I’m also in the cool summer climate of PNW.

    Biodegradable mulch?
    I’ve used overlapping sheets of newspaper, straw, burlap bags (between large plants), & used coffee grounds topped with dried grass clippings (no spray) around vegetables & fruits with good results.

    I bought a roll of the inexpensive brown wrapping paper at the thrift store for $1 to use around larger plants like zucchini. I plan to lay it down & cut holes in it. I don’t know if it will work or not, but I’ve read to coat both sides with vegetable oil, so will use a foam brush or small sponge to spread it on the paper after I unroll the section I need. I think this is going to be a 2 person job!

    1. margaret says:

      Hi, Corrine. A friend uses rolls of “red rosin paper” from the building supply store (it is the stuff the contractor covers your floors with before making a mess, for instance). Cheap, easy to work with, and sort of pre-oiled, almost. (Though not greasy!)

  5. George Morrison says:

    Great article, Margaret. You mention protection against insects but you might take advantage of that attribute by recommending tje use of

    1. margaret says:

      Thanks, George, for the kind words — and the reminder about parthenocarpic fruit….something else I need to study up on again and write about. Much appreciated for the nudge! See you soon, I hope.

  6. CYNTHIA ROCKA says:

    Living in far west central Texas we have a LOT of wind this time of the year. To protect young tender tomatoes, cukes ect. I use a product called GRO-WEB. it looks like the white fabric product in this article. I cut it in strips 32″ to 36″ wide and put it around my Texas Tomato Cages and clip fabric closed on one of the legs with clothes pins. The plants have their own little mini green house and love it. When the wind stops sometime in May I take it off and put away for next year.

    1. margaret says:

      Great idea, Cynthia — I have used clear plastic sheeting for this, too (but you really have to fasten it on well!). Thanks for the reminder; much appreciated. Hope to see you again soon, and hope your weather is kind to you this year (a.k.a., you get enough rain!). Here, none to speak of so far, but last year we nearly washed away. Sigh.

  7. The Zone 3 Gardener says:

    I want to echo the points in your post. Here, north of Duluth, Minnesota, there’s no way to do any serious gardening by stretching our short growing system without row cover (at least). It serves so many useful purposes, even if cold temperatures aren’t your primary concern.

  8. Dd says:

    I have been using them for several years now to cover my greens and they have made quite a difference. I am still struggling w squashes and pumpkins. As soon as they come off the beetles come and they are devastating

    1. B. J. Cicco says:

      Have you thought of pollinating squash and pumpkins with a soft camel hair brush, and replacing the covers over the plants?

  9. Beth Urie says:

    I just realized that this revives your post from last Spring. We have used both Agribon 15 & 19, over beds prepped, drip line laid, with the Solar Mulch (black/IRT) over that, then 4′ x 4′ Low-Hoops to support the fabric. Last season, we set a grid horizontally about 1′ above the Solar Mulch – used old lengths of bamboo to make, wiring up the grid supported by grade stakes cut short so as not to poke holes in the fabric above – and trained Defiant PhR tomatoes to lay atop the grid instead of up a stake, under Agribon 19. This provided the best we could think of, short of a green house, for water & protection all season. Also under there, we had peppers and eggplants, stakes also shortened adequately to prevent impaling the fabric as it moves/luffs in wind.

    The results were amazing – huge success. As plants grew, the confines under the
    hooped fabric were challenged by the lush growth, and I did prune the tomatoes as normal for determinant tomatoes. As temps grew hot, we vented the fabric by pinning up its ‘skirts’ to reduce heat. The ‘roof’ over the top of the plants then acted as protection against brutal storms containing hale – predictable around here at least once a summer! Agribon 19 was rugged enough to withstand the onslaught.
    When we knew that type of storm was expected, we lowered the sides back to grade and weighed them down extra well, since high winds will take the fabric like a kite – good to use those clamps recommended on the hoop piping as well.

    Regarding re-using the fabric, we find it gets holes and rips, especially from clamps and weather violence, but I have used recycled pieces for small areas directly over certain crops, and to cover fall-planted things (spinach, lettuce) as fall mulch and early spring climate enhancement. Larger pieces can be used to make protection for individual plants – late season wraps around tomato cages for example.

    I have wondered about using fabric to ‘cool’ the soil, like a white mulch laid right on the soil, for crops seeded in the heat of summer for harvest in fall – brassicas for example – poking holes for seedlings as they sprout. I will test that this summer with Agr-19 (recycled). We find AGR-15 fine insect protection, but not tough enough for our weather events.

    As weather continues to become more volatile, our challenge is to anticipate what might happen next in order to protect what we can, if we can. All the best to you, and thanks for all you teach!

  10. Norma says:

    Does anyone know where I can get some defiant tomato plants in nw Ct? A friend grew me some from seed because I get the blight in my garden but I would like to find more. Thanks .

    1. margaret says:

      Hi, Norma. I’m afraid I don’t know the local availability where you are — why not ask your garden center if they can get it for you, as they can perhaps check with their vegetable-seedling supplier?

  11. shannon stoney says:

    I use these a lot in winter over my kale, to make it stay a little nicer-looking over the winter.

    ONe drawback: the voles love it. They move in and live there over the winter. This is not a problem for kale, but it is for carrots.

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