You will find that you will need to vent the tunnel when covered with plastic, else everything inside will cook on warm days. One layer of 6 mil plastic is not a good heat keeper at night, so your temperature retention will be minimal and you'll want to supplement with cloth of your preference when falling near or below freezing if you are growing tender cool seasons. You will want something other than the painter's plastic at the BigBox as well, as it breaks down in UV light.

Use The Google to find shade cloth in your area, else the best mail-order price for you; very common at decent nurseries. You will also want heat-adapted, slow-bolting lettuce as there is only so much temperature reduction you can get under shade cloth. Even with all that, you'll find there will be a couple months where you aren't growing edible lettuce in warmish years.

SCH40 PVC is probably easiest-cheapest. You can also try 3/4 black poly irrigation pipe. I find all mine dumpster diving at construction sites. I scored 20ft of 1" black poly several weeks ago, enough for three hoops in my raised beds and will hold up to heavy wet snow in spring.

Plenty of other opinions besides mine can be found using the 'search' function on this site.

HTH.

Dan

Dan, thanks for your quick response.

My thought on heat retention was gallon milk containers with black spray paint.

I was planning on pinning a sheet of screen door screening to each end and pulling the ends of the plastic up for ventilation (but hopefully still bug prevention) on warm days.

I think I've found a 'cheap enough' source of 4 mil plastic from Johnny's seeds ($75 +$6 +standard shipping).

For the black plastic I may use standard Big Box stuff since it is a flat layer and will have holes in it - good for 1 season/planting only.

I used the rolls of planting paper in some of the beds last year - we could watch the weeds growing up underneath it.

Andy, I use black containers, and they won't last all night in the cold, even 2.5 gals under one layer of plastic near freezing. Two layers with an air gap maybe. One layer with a ~1.5 oz cloth yes (surely with water). I'm in Denver area and grow veggies all winter under hoops and in a cold frame in a raised bed:

{{gwi:311316}}

Coldframe foreground, hoops behind spigot and near gate. Not sure of you can tell, but there is sagging on farthest hoop from snow weight. Something rigid at apex alleviates this fact. No fotos yet this year with addition of one more set of hoops.

I'm a Johnny's Seed fan and that's just an OK price, but just fine if combined with some seeds.

Dan

So using fabric instead of plastic will keep things noticeably warmer at night?

I intend to do the same thing as the OP next season. I'd like to find a way to grow heat-loving crops in places other than the greenhouse. I need MORE tomatoes! (Well, maybe I don't, but I might like to try.)

I also like the shade cloth idea for summertime lettuce; that is in my plan too. Finding shade cloth is easy. You can order it in almost any size and weight. As Dan said - just search for it online.

karin - I can calculate the size I need for shade cloth, but I have no idea what weight would be appropriate. Any idea how one should judge this?

Dan - you're suggesting a 1.5 oz cloth (I assume that is searchable) on top of the plastic in the evening when the temps are very low is the proper addition to my clear plastic? This could be rolled/unrolled from one end as needed.

Is the 1.5 oz cloth considered 'shade cloth' and is it the right weight? That would be too easy.

Andrew

I love Johnny's for seeds, but their supplies are too pricey for me. Check out Morgan County Seeds. They are in Missouri. Very low priced. Good prices and service, just slow on delivery during the busy spring.

They have your plastic and row cover. The plastic may be larger than you need, but I would just cut it. Buying the standard sizes is always cheaper than custom sizes.

I use Agribon 15. When it gets really cold, I usually double it up. This works good inside my high tunnels. Outside, it is ok, but you will need to weight down the side really good.

Inside the high tunnels I just use 9 gauge wire bent into hoops. I like this, cheap and easy but I am going to buy a 3 foot hoop bender this winter with some speaking money. I already have a 6 foot one. I am happy with them. They are from Lost Creek Greenhouse.

As for summer lettuce, Try some of the summer crisp/Bavarian lettuce from johnny's I was happy with it two years ago. I transplanted it all. This was grown outside, and got afternoon shade from a high tunnel.

Jay

Here is a link that might be useful: Morgan County Seeds

o So using fabric instead of plastic will keep things noticeably warmer at night?

Yes, but plastic on outside cuts the wind, which takes away heat. The whole is greater than the sum of the parts.

o I can calculate the size I need for shade cloth, but I have no idea what weight would be appropriate

Shade cloth usu is sold by % light transmitted. Any decent nursery will have this labeled. Row cover-frost blanket has a different purpose, and Johnny's Seed has decent explanation on the weight.

o Dan - you're suggesting a 1.5 oz cloth (I assume that is searchable) on top of the plastic in the evening when the temps are very low is the proper addition to my clear plastic?

Mr Slick the market grower can override me with his layering regime, but you want plastic to stop the wind. The fabric goes under the plastic. Currently, my hoops (not the coldframe or mini-greenhouse) have two layers of 4 mil plastic and two layers of 1.5oz fabric - from outside to inside I have plastic, two layers of fabric, plastic with an air gap. I see that the hoop with the thermometer is 40F right now, temp hasn't moved in almost two hours, and ambient temp is ~33F with winds ~12-14 decreasing to current ~7kts; I expect to wake up to ambient around 24F and inside hoop around 34F with some wind tonight (I'm an old weatherman, so kinda geeky like that).

I'm with Mr Slick on Johnny's prices if you are doing single purchase. Buying seeds helps defray shipping. They have a film for warming soil that is very nice, much better than black plastic. But they definitely are more expensive than Morgan's, esp at the quantity Mr Slick buys. And I admire and respect Mr Slick, but we disagree on the hoop bender (maybe the only thing) and IMHO one should build their own hoop bender in addition to learning how to bend conduit with a tool. YMMV.

Dan

Dan,

I would agree with everything. Plastic and fabric is the way to go, if you want to really battle the elements. With my high tunnels, it isn't worth the added plastic. I am going to start replacing my plastic at the end of next year and I am going to cut up the old stuff for low tunnels. Then we will see what happens. You are correct, it will warm up real quick with plastic on low tunnels. You will have to vent. Even in the dead of winter.

I would love to build my own hoop bender, I really like your ideas and pictures. I just don't have the time now. Too many papers to grade at school and things going on at home.

I can bend conduit with a bender, built my two movable building that way. Nothing like bending 24 foot 1 3/8 pipe into a 16 foot wide structure. Talk about patience and stress. I only bought two extra pipes and ruined one figuring out my bends!

Such a learning experience.

Jay

If I were a market grower and using high tunnels, I'd purchase pre-bent, personally. For a typical gardener using hoops, this is just fine:

{{gwi:117813}}

I'm pretty sure I'm near the sweet spot for typical backyard/offseason allotment/urban garden small-scale production design, & I'll share details on this board.

Back outside as totality nears.

Dan

Andrew, you can try 40% or 50% shade cloth for growing summer greens. Is your area very hot or sunny? If so, go with a higher percentage of shade. I would think that something higher than 50% will limit plant growth though. I like Jay's recommendation of a summertime lettuce variety. I tried Iceberg last summer and although it looked a lot more like romaine than Iceberg, it did produce lettuce in July and August.

I suppose you could also use a very lightweight row cloth as a shade cloth. But the shade cloth will last a lot longer. The lightweight row covers are rather wispy.

Dan and Jay - thanks for sharing the details. My husband is a bicycle framebuilder so he is in charge of bending the metal pipes. I know that PVC would be cheaper and easier, but I much prefer metal.

Glad you stayed up for the eclipse. We did too as it was one of those brilliantly clear winter nights. Wonderful!

wow, a topic so close to my heart it inspired me to sign up so i could post ! a book i highly recommend on the topic of row covers is Eliot Coleman's The Winter Harvest Handbook. That book along with Shane's book are a great resource.

Karin, tell your husband I have a frame built by Steve Rex. If he's a west-coaster he should know his work. Steel is real!

The two main BigBoxes around here have EMT conduit for cheapcheapcheap. I have several trellises and hoops bent from it in various shapes, including the daughter's garden:

{{gwi:311317}}

the trellis is now a very attractive purple and pink.

I also bent some cattle panel to see how it worked:

{{gwi:311318}}

but I wouldn't recommend it as a project. The finished product does what it needs to & not expensive, but too hard to fabricate and fold-hold film:

{{gwi:311320}}

I suggest for up there using 3/4 EMT and fabricating your own clips out of 3/4 black poly cut to 2" lengths and about 10-15% of the circumference cut out lengthwise like in the foreground (covering potatoes against CPB):

{{gwi:113727}}

Just some ideas about the many ways to go about holding up material. I keep black poly hoops over my peppers all season, and have rolled-up fabric connected at the bottom to protect against hail and downdrafts.

Dan

Dan,

I like the cattle panel one. How did you bend yours? I have bent them before by laying a 2 by 4 at the location of the bend and then pulling it over the 2 by 4 until it is in the correct angle.

Those panels are so light weight now days. When I was younger, growing up on a hog farm, they use to be almost impossible to bend. If you find these older they are worth the $$.

Jay

Thank you Jay. I purposely use the lighter-weight panel to use as trellis, pea/pepper support, etc. as it is easier for my family to work with & heavier is overkill in our small yard. I bent that shape with an old 2x4. That's a Sun Master film from Growers Supply in two layers with an air gap (the reason for the purlins inside).

BTW, for anyone curious about temperatures in winter, the temp under my hoops with the cabbage and spinach has gone up 6 degrees F so far this morning (still in shadow), and the ambient is ~26F and has only increased ~3 degrees F in that same time. Plus the wind is gusting in mid-teens already.

Last crazy gardener bit then back to work: there is a story in the paper today about a woman in the mountains - a former big-name skiier - who grows all winter as well. More and more people are taking advantage of the new materials and old wisdom to greatly extend the season on both sides. Its addicting.

Dan

This is excellent info, thanks!
The conduit is just the material I need - that is an excellent suggestion. I have tried just one section with cattle panels but I find it awkward to use and to reach through for weeding or harvesting.

I like your little potato house - the homemade clips are a nice idea too. Every year I try a new way to seal up the broccoli plants from the caterpillars, and every year I don't quite get it right. Your setup looks like it would work.

For bigger, heat-loving crops I think the conduit will work great because I can make fairly tall tunnels.

We know of Steve Rex's work - very nice!

The article about Alison Gannet is interesting. It is becoming more and more popular to go back to eating with a lighter footprint. This is a good trend. I see greenhouses and tunnels cropping up all over the countryside nowadays. Canning is enjoying a big renaissance too. The photo with all the jars of canned goods is enviable - I wish my stash were that extensive!

If you are going to do the clips, Karin, I suggest using a file and filing off the sharp edges and esp the corners to prolong the life of the fabric, esp in our wind. Just takes a couple seconds on each one. Also for summer insect barrier, leave 6-12" on all sides and roll ends around conduit-PVC then anchor with a brick or three. Much, much easier.

Dan

Got it, thanks! Now let's hope I can remember this come springtime.

Oh, you'll remember it after your first bout of late spring wind, trust me!

Dan

Sorry to hijack my own thread back.

Still have a few questions.

I'd like to grow brocolli this Spring and start early. I'd like to leave the cover on the entire time - we get bugs in the heads which creep all of us out, but especially the kids and I'd like to have them eat the veggies.

My raised beds are 4' wide.

Could someone suggest, from Morgan's website, specifically what I should buy to meet my needs?

I understand which weed barrier to purchase - no problem.
Can't quite figure out which of the other products for warmth, yet sunlight OR for more shade in Summer.

I'm planning to use PVC with elbows to make hoops in the beds and have the two at the ends covered with insect screen (screen door screen) so that I can uncover the ends for ventilation/etc. without letting the bugs in.

Lastly, are the row covers water permeable so that the sprinklers will penetrate?

Help?

Thanks.

Andrew

Thanks guys.

I would use the Agribon-19. It will give some protection from frost and it will be strong enough. The 15 is really light, it would work too, but it will probably only last one season.

Water will go through the row cover, but would check and make sure they are getting enough moisture.

As far as the bugs, are you talking about the green caterpillars? If so, just spray with Bt, it is an organic spray and it does wonders. You will have no bug problems. Just spray on a regular schedule when you plant them out.

Jay