My veggie garden is already put to bed, we've had a couple nights with lows of 18 degrees.

You mention poor fall weather for fall crops - so how have your crops/fall harvests been fairing? Got any pics of your low tunnels? How do you like using them? Make them yourself or purchase?

I am still harvesting fall lettuce, spinach, radishes. Will be harvesting parsnips, turnips, carrots, and beets as needed as long as possible, hopefully into December (will top them with straw for frost protection when necessary). Will then dig up the remainder and put in cold storage. Will be harvesting and processing horseradish in early November. That will pretty much finish things out for the 2012 gardening season for me.

Veggie gardens 90 percent cleaned up at this point. Still need to work in leaves and compost, and prep an area for planting garlic in late October.

Very dry here. Rain missed us again - only one half inch of rain in the last six weeks, and that was three weeks ago. I am seeing a repeat of last fall occurring here.

Finished up processing hot peppers today. Made four different batches of pepper mash for fermenting for hot sauce (yellow mushroom/chocolate hab, Caribbean red, dorset, bhut). Rough day in the kitchen. Been sneezing all day. My hands are still burning from capsaicin residues. Happens no matter how careful one is, even wearing chemical gloves and all. Not complaining - wouldn't mess with them if I really didn't want to.

Take care,
-Tom

Oo hot sauce!

The fall crops are disappointing but I think I got them in about the right time but the fall isn't cooperating.
I have not harvested fall Napa, cabbage, broccoli, cauliflower, broccoli rabe or even turnips. I have been harvesting rutabagas, kohlrabi, peas up to last week, baby bok choy, swiss chard, beets, carrots, spinach, lettuce, kale and spring planted broccoli and all herbs but basil. Cilantro, dill and parsley love fall.
Nothing is even covered yet and everything was frozen up to about 11:00 on Friday when it was about 21. The only crop that looks damaged was Napa cabbage. I was sick for a week and should have row covered everything.Oh yeah and the wind lately! I am covering all on Tuesday after putting in the hoops Friday. Tuesday will be warm and covering them in the afternoon should hold some of that heat in.
I am making some low tunnels next year, proper ones. Up to now I have just done hoops from 9 gauge wire and row cover or clear film.
Yes watering sure gets hard with the cold nights and such dry falls! I have fall CSA shares to give any remaining stuff to. I am hoping to get some stuff to keep going until snow really comes. Like I said, everything bounced back from 20-21 except Napa, and I am not sure about the chard because the deer ate it. The inside leaves are fine.

Across the one area still going: Napa, head lettuce, turnips, broccoli rabe, bok choy, ruties, kohlrabi, carrots, radish, scallions and the peas remain on the end.
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Another area is big kale, leeks, baby kale, spinach, lettuce, arugula and some dead sunflowers.

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Third area still going is spring and summer planted brassicas. Some of the Romanesco are 4 feet tall and have tiny heads but I was really hoping they would be ready before the shares were over. The broccoli planted for fall has 2 inch heads and growing. The cabbage planted for fall is not going to make it.

Thanks for the pics. Quite the gardens! So with your fall crops, normally tunneled, you would be gardening well into, or possibly through November most years. My question is how do you get all that stuff cleaned up and gardens prepped for next season before the ground is hard frozen and the snow is flying? Must have to do some mad scrambling some years.

On your new low tunnels, do you intend on using remay type material, or white or clear UV protected plastic? What is your opinion regarding this system? I like the rebar-anchored black poly pipe idea with the clips (I am pretty certain I can design and make my own clips - already have some ideas for prototypes). I think I want some kind of easily attachable horizontal ridge pole running along the top from hoop to hoop to better support the cover between hoops, and would also tie everything together and add rigidity (probably use electrical conduit with through-bolts and wing nuts). I was thinking of going this route unless I come across a better system. I have been thinking of making ends out of plywood that would be anchored but easily removable, plus they would have adjustable openings for optional ventilation-in-place. I would have standard length low tunnels, maybe fifty feet or so, and plant accordingly. My biggest concern is always wind, wind, wind - we get some serious winds here and I just do not know how well any tunnel concept will hold up. One way to protect myself is to overbuild everything from a structural standpoint. This strategy generally works but I still have failures here and there. LMK your thoughts, they would be appreciated.

-Tom

That sounds very much like I have in my head. I am going to have a handy friend approve my plan but he tends to overengineer everything. You should have heard him talking about ideas for a better canopy for market. I had to remind him I need to carry it!
I have tremendous wind where I rent! I also thought of doing a lengthwise pipe of some kind, connected to each hoop maybe with something like these:
They sell clips around in all the gardening catalogs. Johnnys has them for 50c each. In my little hoops I use black paper binders but would get the real clips for the low tunnels.
I do not break my garden down like most people. I leave all the paths and beds as is, some with a dead crop when winter hits, some with a cover crop, some covered with manure and some covered with straw. It gives the good bugs a place to overwinter. I am having the two sides disced that had squash and melons and the area that was the disappointing potatoes, all have manure dumped on them.
My field space was 150 by about 120 this year and will be about 170 by 130 next year- half acre. 50 beds 3.5 by 50 feet each plus the two open sides have long growing spaces.

Here is a link that might be useful: connectors

Question about cauliflower.

I put three in around the Fourth of July when garden shops cleared out their stock.
Two came ripe last week but one is just now setting a head.
They were well watered so why did they ripen so slowly?

They weathered the twenty degree temperatures I had, very well, but the last one now has a hay bale on each side for protection anyway.
This is up in the St.Cloud area.

I do not know about little_minnie's crops, but my cauli was an utter failure this year. Everyone else I have talked to around me had a bad year with their cauli and cabbage as well. Broccoli was mediocre.

Have not heard any reasonable explanation yet as to why this occurred.

I apologize if this discussion is hijacking your thread...

Regarding our ideas for a low tunnel design, I made a quick mock up from stuff I had around the place. The black poly tubing is 3/4 inch and the conduit is 3/4". The connectors you referenced are perfectly acceptable, but by using U-bolts you avoid a special order plus shipping costs - everything is available at your local big box do-it-yourself store. The drawback of my idea is having to drill through-holes in the conduit, and having to be reasonably accurate when setting up the hoops out in the garden. The holes are easy enough to drill, though, and do not weaken the conduit.

The U-bolts would not be over-tightened so as to crimp the poly tubing, just snugged so that no slippage occurs. A standard conduit coupler would be used to join the standard 10 foot conduit lengths together. I figure to space hoops in such a way so that the conduit lengths would be coupled together away from the hoops for obvious reasons.

This hoop dimensions are as follows: Poly tubing is 5.5 feet long. Space between rebar anchors is 3.5 feet long (which in this case would be the low tunnel width). Height of poly tubing arch installed is 20 inches. Above-ground height of rebar is 7 inches. Total rebar length would be determined later, but would have to be long enough to anchor into undisturbed soil below till depth. I am thinking probably around 2 feet long max. I just used scraps, so I do not know how well all these dimensions would work in practice. This is where I would need some guidance from you or other people with experience with low tunnels. My idea is to keep design as low profile as possible to minimize wind issues. Arch height and hoop width would depend on the tallest plants I intend to ever grow under low tunnels, within reason. I think these dims would work fine for low growing stuff. My intention would be to only ever have to open the cover from one side so that the other side (the windward side) can be anchored heavily with soil. As such the low tunnel would have to be narrow enough for me to be able to reach to the furthest back row of vegetables (Is this how you do it?).

I still have to design the clips that would hold the sheeting to the hoops. I do not like what I have seen and think I can do better. The end walls would be pretty straightforward. I changed my mind regarding total low tunnel length and will probably go with 30 feet long low tunnels - using three 10 foot conduit lengths and five hoops spaced every 7.5 feet. LMK your thoughts.

That looks like it could withstand some serious wind. What will you use for covering. I never thought about doing a low tunnel, had thought briefly of a high tunnel but wind is certainly an issue here. If I did low tunnel I would have to make them small enough that I could roll them back by myself as my "help" is often not available when I need it.
This year was my first planting cabbage in many many years. It did very well, I grew it under row cover.

hostaholic2 - Glad to hear your cabbage did well this year.

I have not yet decided on the covering but leaning towards a UV protected heavy mil white poly. I have to do more research on this subject to learn pros and cons of each option.

I have to design stuff for one-person use as well and I have been considering this issue. One solution is to make 10 or 20 feet long tunnels and use cover clips to attach one side of the cover to one length or two connected lengths of loose conduit. A person could then simply roll the cover up and down on the conduit. I do not think this would work too well for any longer tunnel length, and I think even 20 feet might be a stretch for one person. This might be a good thing to do on both sides anyway to keep the cover nicely in place, even with using dirt to hold the cover down.

BTW forgot to mention that in the mock-up I used a piece of 3/4 inch thin-wall EMT electrical conduit for the ridge pole. I would use this material for the tunnels because thin-wall is strong enough and very cheap to acquire.

Also, I temporarily straightened out the black poly tubing in order to measure for the center of the length, and I used green electrical tape to mark the center for ease of locating the attachment point of the conduit once the hoop is installed.

Speaking of winds - as I sit here writing this, the winds outside are sustained in the 30s and gusting into the mid 40s. This would shred a poorly designed low tunnel and I would be out chasing plastic around the yard.

Ah that is pretty much what I had in mind. I think instead of holes in the pole I would use the connectors I linked above and I would buy the clips. The clips are crucial to the poly staying on! I have down enough little hoops to know this.

I would get real greenhouse sheeting for my low tunnel but possibly put row cover under it for warm times.

Ditto on brassicas, broccoli was ok, cabbage and cauliflower horrible and normally Grafitti cauliflower does great. I have Romanesco that are 4 feet tall with teeny little heads after all these months! The leafminers love cauliflower and cabbage and weakened many of mine.
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My low hoops now:
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These are just 9 gauge wire hoops not low tunnels. They do ok with enough blocks at this height but I had 3 thicknesses of row cover on my full grown peppers this fall and the wind kept whipping it off no matter how many rocks and blocks I used. That is why the good hoops with the good clips are important.

I had nice big healthy-looking cabbage, cauli, and broc plants too, they just didn't do anything. Ended up with small cabbage heads, spindly fibrous broc spears and no heads on the cauli. Then the worms showed up and I had enough of it and pulled everything out. I have had several poor years in a row, so I am due for a great crop and I am looking forward to next season. I miss my melted cheese and cauli/broc medley during winter time. I resort to buying the frozen stuff but it just is not the same as home-grown, of course. I can not get myself to buy the fresh stuff at the grocery store because the produce always smells like chemicals to me.

The price is cheap enough so I think I will order a bag of cover clips to test them out. If they work fine I will just purchase more rather than make my own. I doubt I can make anything any cheaper than what Johnny's is selling them for.

The wind problem you mentioned is very disconcerting. Exactly the reason I have not used tunnels yet. For my first one I will just use poly sheeting from the big box store. I will not invest in quality sheeting until this proves out. This is just a hobby for me - much more critical for you CSA folks. I was simply hoping to expand the growing season at both ends for a couple of weeks using a cheap, durable, easy to set up and take down system. We will see how well the first one works out before I make any more.

I used to have a cold frame and it worked pretty good - always had fresh lettuce, spinach, radishes, and green onions for Thanksgiving. The two negatives were lack of capacity, and difficult soil maintenance. After many years of productive use it finally rotted apart. Thought maybe there was a better idea out there to grow more stuff a little easier, hence my interest in trying the low tunnel concept.

Do you have an estimate on price for a low tunnel like we both are thinking about? How much is the tubing, rebar and conduit pipe? I want to do 50 feet and have it movable through the season: rebar every 4 feet with 9 gauge wire inside the tubing, tubing, conduit lengthwise pipe, connectors, and the greenhouse film or row cover or shade cover and clips. So I think 12 -13 tubes and I would like 9 feet wide and 3.5 feet high if possible. So that is what I will think about all winter!

I will get some general materials cost estimates, probably tomorrow (Friday). I can almost guarantee you that the cost of the UV protected greenhouse-grade plastic sheeting and the cover clips will probably cost as much as all the other parts combined.

Question #1: For what purpose do you want the 9 gauge wire inside the tubing?

Question #2: You state you want the tunnel to be movable - you mean movable in one piece with the plastic sheeting installed? This I think is doable but problematic. It is actually not a bad idea and I have not considered this option, but I think a few other things then have to be taken into serious consideration such as structural integrity. I will wait for your response to this question before I go into any further detail.

General Comments:
1.) 9 feet wide would equate to approximately 4.5 feet high. The poly tubing could probably be compressed down to 3.5 feet but some of the inherent material strength would be lost, causing a potential collapse, especially when considering the possibility of snow load on the plastic sheeting - which we both know can very possibly occur when the tunnels are being used either in spring or fall in Minnesota. The strength of poly tubing is completely destroyed once there is a kink in it, so if the hoops collapse they are then rendered useless.

2.) 9 feet wide is certainly doable, but I question whether 3/4 black poly tubing is strong enough material. That width may necessitate going to 1" poly tubing or even going to metal conduit or chain link fence top rail. Metal pipe is certainly strong and doable, but increases cost and adds complexity - necessitates using a pipe bender or bending jig. Also, metal conduit will rust where it comes into ground contact. Chain link fence top rail probably will rust as well because of today's poor quality galvanizing.

3.) Spacing the hoops every 5 feet would require qty. 11 hoops for fifty feet of tunnel. Spacing hoops every 4 feet would require qty. 13 hoops for 48 feet (spacing the end hoops at 5 feet would then make total length 50 feet). No offense but I think that hoops spaced that closely might not be necessary, but here is the thing: Hoops spaced closer would allow smaller diameter materials to be used because the load is spread over more hoops. A balance needs to be found between hoop quantity/spacing and hoop diameter/material, as compared to the cost of that material. The labor for set-up and the complexity of that setup should be taken into consideration as well.

I have to admit to you that I have not considered a structure of that size, and you are pushing the boundaries of my knowledge base. I strongly suspect that with those dimensions you are testing the limits of poly tubing and you may be going into the realm of having to use an all-metal system. Remember, for durability and long life your tunnels should be designed to survive a realistic worse-case scenario, which IMO would be to include snow-load. You may want to consult hoop house and tunnel design web sites - I will do so as well. We should exchange any links that we find that may help us figure out the best way to proceed.

I would love to hear what you two come up with it and how it works out. I'm just at the point of thinking about one. I know a CSA just a couple miles from me uses a high tunnel but they have more buildings and grove than I have here. Because of the nature of our building site, long and relatively narrow, I don't have room for a good expanse of trees. I have planted a double row and they are beginning to help but still a long way from creating a sheltered growing area.

I went to the local big box store and did some pricing. I came up with some cost estimates for a 2 feet high by 4 feet wide by 50 feet long low tunnel, using the concepts shown in my previous photos and discussed in that post. The one change I made is to space the hoops every five feet (after you brought it up and me doing further research, I have changed my mind and will now follow this spacing, but doing so does add a bit more cost to the project).

Note that following my design concept the plastic cover clips at Johnny's will not work (diameter too small), so I followed the pricing for the correct clips at Territorial which are higher cost. For the amount of clips I would want to use I consider their cost to be prohibitive ($1.15 ea. plus shipping), and I can make my own for much cheaper (approx. $0.30 ea).

UV protected greenhouse film is very expensive and not justifiable IMO for my hobby-use low tunnels so I am going to use 4 mil construction grade plastic to save money, at least on the prototype. Will see how it holds up. If the cheap-quality stuff lasts for two years then I believe it is actually cheaper in the long run than the more expensive material that lasts longer, just not as good regarding light penetration. Based on the prices I found, if the cheap stuff lasts for two years, the quality stuff would have to last for ten years to break even on cost. Now, if I needed these low tunnels for commercial purposes and income then I would seriously consider using the more expensive greenhouse film. That is a decision that people will have to make for themselves.

Materials cost estimate for low tunnel specified in first paragraph, using 6 mil UV protected greenhouse film and the cover clips from Territorial: Approximately $205.00 or approximately $1.05 per square foot. Shade screen not included. Shipping cost of greenhouse film and cover clips not included. Taxes not included.

Materials cost estimate for low tunnel specified in first paragraph, using 4 mil construction grade plastic and homemade cover clips: Approximately $100.00 or approximately $0.50 per square foot. Shade screen not included. Taxes not included.

There is an article in Mother Earth News regarding someone who made their own low tunnels and claimed to do it for around $0.10 per square foot. I consider their design to be weak and underbuilt and therefore unacceptable for my needs, but that is quite a low price (if that price in fact included everything). It is also a three year old article so I suspect the pricing is obsolete, but still would not approach the cost of my design concept. I feel my design concept is correct for my conditions so $0.50 per square foot is acceptable to me. $1.05 per square foot is not.

little_minnie - I do not know how well those cost estimates would extrapolate to the low tunnel size/design that you are considering, but I think they would give you an idea of minimum cost. Making your low tunnel structurally sound so as to be movable in one piece would also add significant cost, possibly another 25 percent. Everything is doable, it just depends on what you are willing to budget for.

-Tom

wow thanks for all that info. I am just in the idea stage right now but may have a friend help me make some decisions. Your info is very helpful. I will have to check my MEN mags for that article.
Ok so by movable I mean this- here are my dreams:
put in the rebar in very early spring or the winter before over some greens. Add the wire- for stabilization, the tubing, the plastic and the clips then the weights. Leave on until mid to late April and move it piece by piece to tomato plants going in. Repound in the rebar and stick everything back together. In a month it could be moved to some new greens and put shade fabric on. In September it could be all moved to some late planted determinate tomatoes, sweet peppers and basil (that is what I most want it for). When these die from a severe freeze, it could last be pounded in over some fall seeded greens and the cycle goes on...

So that is my musings right now for what I would like to use it for. My beds are 50 feet long. I really don't want to buy the pipe bender like in Johnny's because it only bends it to a 6 foot diameter which seems like a waste for 3 foot wide beds. I would want it to go over 2 greens beds or one bed of peps, toms, basil.
So the 9 gauge wire is not too expensive and would give that tubing some strength. One of the guys I rent this land from does irrigation (lawn) for a living and might be able to help me get cheap tubing. He has some lying around here and there that is right.

I highly recommend not using Menard's style clear plastic. I have used that many times in fall over tomato cages and peppers but it is not UV stable and breaks into pieces.
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Note the piece of plastic on this salamander that came when I brought my broken up plastic to the garbage can and little pieces went everywhere. LOL

Below is a link I got on the market gardener forum for a low cost high tunnel experiment. It might prove useful.

Here is a link that might be useful: low cost high tunnel

Mother Earth News, Low Tunnel Article

That is a very impressive high tunnel in that article you linked to - very well designed. They have some ideas that I might incorporate. One thing - I would never use PVC pipe, because as stated in that article, "Pipes should be painted with a latex paint. Experience has shown that non-painted pipe may cause plastic to degrade where it comes in contact with the pipe." I came across this issue on many greenhouse film supplier websites. Painting the PVC solves the problem but what a hassle, and if the paint ever chips off then the expensive greenhouse film can be ruined. Not worth the risk in my mind. I looked at the 1 inch black poly irrigation tubing at the store and I think that material would work just fine for what you want to do, rather than you having to use PVC or having to bend metal tubing. They also had a stronger, higher pressure (160psi versus 100psi) tubing available in 3/4 and 1 inch that looked really nice.

I am all too familiar with all those little "shards" of plastic. LOL Very frustrating indeed. I know that to do the project right and proper that I need the correct plastic. I will still use the cheap stuff for at least the first year though, because I want to prove out the concept prototype as cheaply as possible (plus I have the plastic left over from a construction project). Would be a shame to end up having to modify the low tunnel because of some unforeseen problem, and then the expensive plastic no longer fits or there is some other problem that would make the expensive plastic useless. That is my main concern.

The biggest problem I found regarding the expensive greenhouse film is that I could not find any supplier who sold by the square foot. They all sold standard sizes and the nearest size to what I wanted would have had a lot of waste. The best thing for me to do would be to order the size that would have enough material for two of my low tunnels. That is fine but I have no plans for two low tunnels in the near future. I never planned on doing a double thickness of plastic either, simply because I only want to extend the season a couple of weeks so I just want to protect from late spring and mild fall frosts.

I really like all your ideas regarding how you plan to use what you make. Potentially very productive, and you would definitely get your investment back. So you meant to dismantle to be able to move to another location - I understand - that is really the best way, and would not really take that much time to do. One thing I would do is have an extra set of the rebar stakes so you can lay out the new location and have the rebar stakes set. You can then dismantle and move the individual hoops to their new locations and install right away. Just be careful on moving day so no one trips and gets gored by a rebar stake. They do sell little orange safety and visibility cover caps for just this reason.

I have all the materials broken down by costs, sizes, lengths and quantities things are sold in, etc. So if you want a more detailed price list I can email you one. LMK All the stuff needed for my concept is carried in stock at Menards except the greenhouse film. As your plans and ideas gel, if you and your designer need any suggestions then let me know. I will also pass on my concept for my own cover clip design to you, once I prove it out completely. I made a rudimentary prototype that has proven that I am on the right track. I also have a very simple system for holding the plastic sides down, and I did not bring that up either.

My garlic planting season has now started so I may be too busy to further this discussion for a while. I enjoyed our conversations - I have been thinking about what you want regarding size, and have been considering the proper design and materials for it and will continue to do so (who knows, maybe I will want one that size some day). We can talk about it more during the off-season. I will still check here occasionally for new posts, probably not as often for a while, though.

Cute salamander...

Take care,
-Tom

Thanks so much. I think extra rebar would be a good idea.

I am also planting garlic. I have 1030 cloves ready to go tomorrow and a tiller that won't start and was dropped off at the repair tonight. Bummer. Garlic planting is always a hassle/ bad luck every fall! And my throat is so sore I am not swallowing or talking to my cats! Hub has brochitis and I really don't want that!

How do they bend PVC anyway?

BTW what county do you live in? Also would you consider selling clips you make for 3/4 inch tubing?

Sorry to hear you and husband are not feeling well. Definitely not nice weather right now for working outside, especially when not feeling well. I got most of my garlic planted and got leaves tilled into all the important veggie gardens. One garden left to till but I was not originally planning to work the soil in that one this year so it is not critical if it does not get done.

Miserable, wet, snowy day today. As far as I am concerned the early wet snowfall defended my belief in overbuilding my low tunnels! ;)

PVC is flexible by nature, but only to a degree, and it is not as flexible as the black poly tubing. Because it is not as flexible it is probably stronger for structural use, but that thing about having to paint it is a major negative IMO.

I reside in Renville county, southwest MN.

Regarding homemade clips: Once I am satisfied that my design is functional I will discuss with you privately. I guess it all depends on how much hassle they are to make. If I agree to make for you, I would not sell for profit but would request reimbursement for materials. Selling stuff is against GW policy anyways. :)

Get better,
-Tom

Just a thought or two. I have an 8x8ft walk in high tunnel made out of two cattle panels. cost of about 1.25 per growing square foot with a 24 square work area. panels are hooped the long way 16 ft length. they fall into a natural arch with out bending. I covered them with a construction grade 4 mill from the local farm supply. so far all I can get out of the plastic is one winter. The wind down here is just too strong and rips start to appear in the spring That being said the snow loading is great it took the 120 inches we had a few years back with no damage. I now plan on another one in the spring 12x8 ft. I love the long growing season it provides. Not so much for the length of season, but for the maturing of the crops inside compared to the out side crops. Tom I have read that tape can be used over the pvc pipe to protect the film.

Curt P.S. My cabbage did well both spring and fall crops

After a survey of the back yard this morning I have decided to lengthen my existing high tunnel by eight feet, as sunlight is at a premium due to surrounding trees. I do not want to block light to my existing beds just compliment length of harvest of kitchen vegetables.

Curt

I finally got my garlic planted today!
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This is bed #3. I dropped cloves and shallots to separate varieties in the trenches the tiller left. I then went along on my garden scoot with a hand trowel and poked them in. Each bed took 20 minutes to poke the cloves in. I smoothed the beds out, laid drip tape and covered with plenty of straw. 1050 total garlic cloves and 250 shallots. 15 varieties of garlic and 3 of shallots.

I made a prospective chart for crop succession in MN.
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These are some ideas but very dependent on weather. You can save and print the chart bigger or enlarge on the direct link possibly. I don't know any other way to put an excel file online. ?

Here is a link that might be useful: {{gwi:11491}}

Today I picked spinach, kale, lettuce, arugula, broccoli rabe, turnips, baby bok choy, beet grees and chard. I live in Big Lake. They have been covered with just 2 thin summer weight layers of floating row cover.
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Like this.
Yes December veggies are possible! And many are actually growing not just surviving.

Ok I am still thinking on the low tunnel thing and now I have to get to the point of placing orders for row cover and poly fabric. I will probably order that from Growers Supply/Farmtek. I am not sure what sort of poly film a low tunnel needs. I can call them.
I am also not sure how wide my tunnel will be so I can't order row cover for it.
Also I found this pic. below
It has the tubing go into plywood and seems moveable. With enough sandbags this might just stay. One per bed instead of going over 2 beds. But would this be that much warmer than what I already use? Probably not.
I want to cover 16 tomatoes and 120 peppers in early spring for early planting. They will be 2.5 feet apart- path in middle 2.5 feet wide. (one linear row of tomatoes, 2.5 feet, one bed of triple wide peppers). That is around 7.5 feet wide from edge to edge.
in fall I want to cover some other tomatoes and peppers in one bed. That will need to be taller but narrower. And I want to go in it for picking in October and November. For determinate tomatoes it will need to be 4 feet tall.

Over at my field, in the barn, there are rolls of tubing. Maybe I should go play around with them and a tape measure. That might help me decide how long the tubing will be and how wide the covers will need to be.

Here is a link that might be useful: pic of tunnel with plywood

Minnie:
Could you not take 4x4s or 6x6s and set, permanently or semi-permanently dowels made from the type of wooden rod you use, in diameter, to make clothe rack hangers in closets?

Drill the 4x4s and glue, or just slip fit, the cut dowels in at a length long enough so tubing will never slip off. Then in the fall when done pull the tubes off, and pick up the bases with the dowels and stack them in a shed till next year.