1) No. You want greenhouse film.

2) With greenhouse film, the 4 mil usu has a 1-year 'warranty', you can find 6 mil with a 4-year 'warranty'.

3) Slugs will find a way. Unless you can secure the plastic without billowing, that likley won't work as the film will tear at the interface.

Dan

dan - What's the problem with the builder's plastic? Is it just the uv thing? Is it weaker? Not enough light transmission? Something else? I may not be able to get greenhouse film in time. And since it's more expensive, I was hoping to experiment with the cheaper stuff first, so I don't mess up an expensive piece of plastic. I was hoping I could just get by with the builder's plastic while I'm working the bugs out of my design.

I was worried the holes might weaken the plastic. So I'll have to rethink that part. Assuming I found a way to secure the plastic, do you think that's enough ventilation? I'm hoping I can at least minimize the slug problem using screens. But like you said, sooner or later they'll find a way.

I am doing the same thing with tomatoes. I use 3/8 rebar 18" long 12 in ground 6 out 10'pvc 1/2" sched 40 make 5' wide and about 3' tall I cover with 6 mil builders plastic secured with sand bags and 3/4 " black plastic clips I make a door at each end with another pipe bent around with a 1x4 bolted at bottom covered with plastic. take doors off for ventilation. Yeah, i should use green house plastic but this is dirt cheap and works great. I am going to be taking down the one I have with carrotts and lettuce growing that survived a cold, windy and heavy snow winter just fine John

john - It sounds like I should be able to get by for at least a while then, thanks. I don't want to buy plastic twice. But this is my first time doing this, so chances are I'll mess something up. And I'm thinking I should try a smaller tunnel first, so I don't waste as much. When do you put your tomatoes in the tunnel? Do you grow them under lights first? I was thinking about germinating mine inside, then moving them outside as soon as they sprout. But so far I haven't found anyone who's tried it. So I don't know if it'll work.

I just reread my last post, and it didn't sound too clear...

I'm thinking of germinating _indoors_, not inside the tunnel. Then moving them into the tunnel after they sprout. I'm hoping someone's tried it, so I'll have an idea if it'll work.

Builder's plastic breaks down quickly in sunlight. Those of us who have tried it abandon it post haste. Good greenhouse film is cheaper when you amortize over the life of the product, esp when you consider the labor involved in cutting and re-cutting plastic and time spent at the BigBox.

The other issue I see you have is ventilating while you are at work. This is a serious issue, esp here at 5700+ feet and abundant sunshine. There is no cheap way to do it. I'm lagging on this task now that spring is here, but I'm replacing my old hoops to supplement my cold frame, using cattle panel. That is all cut and bent and ends made secure, and I have to build a window to be opened by automatic vent opener. This is easy to secure to the cattle panel frame, much more difficult to hoops, which is why I'm using cattle panel. You'll want a brace or frame to span two hoops and easily securable, likely with drilled holes in the bracing and affix with galv wire, preferably on the north side so you can insulate well without affecting light transmission.

Dan

dan - Thanks. It turns out they had a remnant about the right size. So it cost about the same per square foot, including shipping, as the builder's plastic. And they said it should get to me by next wednesday. So if everything works out, I should have it just before my seeds start sprouting.

I'm working on an idea for cheap semi-automatic ventilation. I'm thinking about strapping coffee cans with the ends cut out, at either end of the bar that goes across the top of the tunnel. I think I can find a way to securely wrap the plastic around that. Then I'll add some screening to keep bugs out. And I thought I'd rig up some kind of automatic vent opening thing, using an ice cube as a heat sensor switch. Either that, or I'll just make ice cubes the right size to fit in the cans. I'm thinking I only have to worry about venting on nights we have frost warnings. And if the ice is inside the tunnel, at the top, it should melt pretty quickly when things start heating up in the morning. I just have to do a little more research on how much venting I'll need. I'm not sure if 2 coffee cans will be enough. Or if I'll need to strap a few of 'em together.

That cattle panel looks like a good idea. But I think your daughter's going to turn it into a playhouse if you're not careful:)

Perfect! Let us know if your opening method works, as there are plenty of folks looking to lower the price of venting. One of the reasons I haven't finished the low tunnel is that our daughter keeps hauling it out and playing in it...

Dan

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I have some plants started that I am going to put out in my low tunnel this weekend. they were germ. inside in Feb. we'll see if it works. I put a min/max thermometer in the tunnel last fall. the coldest it got in the tunnel was 5 degrees when outside temp was 20 below. I consider my low tunnels to be short term solution. I can take it down or put it up in any location in minutes. I plan on putting up a high tunnel this fall. IMHO, that is the place to put the money to make sure it last. A 5' x 18' low tunnel with a door at each end is about $25 expense. about $10-12 of that is the plastic. I buy the plasstic in 100' roll about $70 at lowes, will be enough for 7 or 8 low tunnels. So far I have 6 months on plastic will use it about 2 more this spring and if it is still good will use it in the fall. I can produce far more than the cost of the hoophouse each cycle. John

dan - Are you from Michigan? I can't figure out what zone you're in from your header, but it looks like you're a Redwings fan. My stepdad says he used to play for them. But he's about 93, and I don't even know if they existed that long ago:) I'll let you know how the vent thing works out. And I think you're gonna need another cattle panel. Or at least work out some kind of timesharing arrangement with your daughter.

john - Do you completely seal the ends at night when it's really cold out, and open them up in the morning? Or is there still some air circulating into your tunnels from outside? I'm working on some ventilation ideas, and was wondering how quickly a tunnel will heat up in the morning, after a night where it gets down to about 30. It sounds like I won't have a problem with cold. But I'm still wondering about it getting too hot or humid in the daytime. Also, I was reading that large rocks can raise the temp in a cold frame a few degrees, so I might try that. You might want to check out that link that Dan posted. I found a 48 foot x 13 foot, 6 mil greenhouse film remnant there for just under 9 cents per square foot, including shipping. So it was a little more expensive than the builder's plastic I priced at home depot. But not much more. I wonder if prices went up on the builder's plastic recently. I always thought it was a lot cheaper. But I don't think I ever needed 6 mil before.

gc, I grew up in Warren, moved away at 19 many years ago and never looked back. Except for funerals and to say goodbye to the beloved old yard at Michigan & Trumbull, last game.

I use water to moderate temp - dark colored water in clear containers. Or paint black. Lots of cold nights at 5700ft and I grow thru winter. is in January, old hoop . Water hold heat far better than anything else affordable, there is a formula for water and sf/glazing amount, my coldframe has 30l & only once below freezing, corner of cover blew off in wind during night of single digits.

Dan

dan - I grew up in Trenton. I moved away when I was 19 too, after my first year in college. But then I moved back. Still not sure why. I was kinda sad they abandoned Tiger Stadium. Now they have Comerica Park. It just seems too corporate.

Did you have any trouble bending your hoops? I noticed your picture with the hoop bending thing. I was going to try something like that. Or maybe I'll look for a dead tree, and see if that'll work. I was thinking about using some large, dark colored garbage bags layed flat, and filled with water. But I'm not sure how much heat they'd collect if the seedling trays were on top, blocking the sun. I was also wondering if warm soil, just outside the tunnel would work, if it was covered at night. Would the warmed up soil transfer much heat to the soil under the tunnel, if it couldn't easily escape through it's own cover?

Hoops bent no problem. I used a 2 1/4 keyhole drill bit & saved the inside disk & all scrap wood.

All you need is the warm water inside of your structure and sun shining on water. Heat doesn't conduct well horizontally in soil like you want. It serves more as a prevention from heat inside moving out - heat moves from hot to cold.

Dan

I have 2 40 foot low tunnels covered with tufflite GH plastic I brought from Johnnys seeds.
10 ft lengths of 1/2 conduit every 4 feet.
LOVE it. would not trade it for the world. The GH plastic is far better at keeping the heat in at night then the small area I was doing before this with builders plastic. Soil has been 80 degrees for about 2 weeks. Seeds germinate in a few days
Slugs... well so far no problem.
I use hardware clamps to secure the plastic to the hoops and some old copper pipes I had to weigh down the edges. I roll up one or both sides depending on the days temps.

If you can get it go for it. Its worth the cost and I'll just reuse the same piece next year. ( or cut it up and use on smaller areas I am going to be working . if you want it fast I DO NOT recommend johnnys .. it was very slow. Still waiting for Agribond I ordered on 3/4.

dan - I'll have to do some experimenting with the water once I get the basic tunnels set up. My plastic's on its way, and I got some conduit. So I'll probably try bending it on wednesday. I should have some seeds sprouting in a few days, so I should be testing everything sometime this week.

ontheteam - How is the 4 foot hoop spacing working? And about how far do you push them into the ground? I was thinking either 4 or 5 foot spacing, with a piece of conduit running across the top. And I thought I should push them in about a foot. I'm also wondering if it would be easier to ventilate 2 or 3 shorter tunnels, instead of 1 longer tunnel. I'm thinking I might not have to worry about rolling up the sides if they're short enough. Maybe slugs won't be a problem, since it won't rain inside the tunnels. I have a lot of slugs, so I'm considering lining the bottoms with row cover material. That might at least slow them down, if they become a problem.

I just wanted to add my own comments and questions:

I did a low tunnel with a very small area (like 6x5 I think) last year and it made a huge difference with my tomato plants, they really grew faster and earlier. However, it was very very humid inside that tent. I think the humidity interfered with pollination, because the plants that required pollination (some tomatoes don't) seemed to not develop blossoms while in the tent, or the blossoms dropped. Also I think the humidity helped some of the plants to develop bacterial leaf spot or mildew or something, because while the plants did well in early summer, many of them also seemed to get sick and decline early than I expected.

So I am wondering: for a small tunnel like the one I am talking abut (6x5, maybe 3-4 ft tall, lots of water bottles for heat sinks) would cutting out some small windows and patching in fabric such as remay or similar row cover material keep them dry without sacrificing heat to the extent that just leaving the tent open does?

One problem I have is that my tomatoes are in my community garden plot, not my back yard, so I can't go out there twice a day to open and close the tunnel.

If you can engineer a door or window on the ends, there are automatic vent mechabisms that will open/close your vents. There is a weight/size/cost ratio to consider.

This late in the season would you consider wrapping a cattle panel tom cage instead of a tunnel? You get inclement weather protection w/o venting/excess humidity hassles.

i've used low tunnels for tomatoes for many years but i use row cover material not greenhouse plastic and i don't need to vent it at all. i plant in the low tunnels in mid april and remove the covers june 1st or so. usually there will be tomatoes on the vine by then. all plants benefit from the wind and insect protection and for those that don't need pollination the covers don't have to be removed. its very good for broccoli and cabbage.

randy - I was considering row cover material, instead of greenhouse plastic. But I was worried the rain would go right through, and pulverize the soil blocks I planted my tomatoes in. I'm not sure that would be the case though. If I thought it wasn't a problem, I'd probably be using row cover material too. I have some row cover, so I probably should try an experiment to see what would really happen.

plantslayer - I'm kinda concerned about humidity, so I'm holding off using the tunnels until I absolutely have to. And then I'm planning on lots of ventilation. Right now my plants are really small, so they all fit on a manageable number of trays. So I can move them in the house in bad weather. But once I start potting them up to larger blocks, it's going to be difficult moving them around. I'm putting screened sides on my tunnels, and plan to keep them open most of the time. And I'm hoping I'll only have a couple cold nights where I'll have to close them up, once I finally move my plants in. I thought about cutting in some windows, like you said. But I don't know how well that would hold up if it got really windy. I was thinking that cutting a bunch of small holes, and taping over them with some screening might be ok though, if there spaced so that they don't weaken the plastic too much. But this is my first year trying tunnels, so I don't have any experience to go on.

gardningscomplicated-my tomatoes are started in soil blocks. i then plant them out in plastic mulch with a low tunnel covering them.

randy - You're doing the opposite of what I'm doing. Mine will get planted in an open field. I think the blocks would hold up to a little rain though. They're outside now, and they're doing ok with a light rain. But my cardboard trays will probably turn to mush if it rains a lot.

Ya'll talking about low tunnels. High tunnels can be considered too. Read Dan Mielke's report on them:
http://www.growerssupply.com/farm/supplies/ExternalPageView?pageKey=EXTERNAL_PAGE_157

His website has good info on growing veggies:
http://www.mielkesfarm.net/hightunnels.htm

Miwa

Here is a link that might be useful: High Tunnel Agriculture

ontheteam - How is the 4 foot hoop spacing working? And about how far do you push them into the ground? I was thinking either 4 or 5 foot spacing, with a piece of conduit running across the top. And I thought I should push them in about a foot. I'm also wondering if it would be easier to ventilate 2 or 3 shorter tunnels, instead of 1 longer tunnel. I'm thinking I might not have to worry about rolling up the sides if they're short enough. Maybe slugs won't be a problem, since it won't rain inside the tunnels. I have a lot of slugs, so I'm considering lining the bottoms with row cover material. That might at least slow them down, if they become a problem.

So I now have 3 long tunnels... we used an iron bar driven in to the ground to make the holes to put the rebar in. At this point I do not "vent" per say but have the tunnies coverd on the north side w/ the original tuff lite bad the south face is the agribond. I use big spring loaded clips at the top of the arch where the materials meet and then use them every few feet on the bottom to keep critters ot. I usually have slugs galore.. but so far so good.. I did use LANDscape fabric on the ground. one lg roll from Costco was just wide enough to cover the whole floor in width and in the 3 40 foot long tunnels. I started tom seedlings right in the tunnels in late March They are now a respectable 4-6 inches tall
.

Here is a link that might be useful: links to p ics...