Polytunnels/Hoophouses


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Polytunnels are just a row of big hoops, secured to the ground (in one of a number of ways) with a plastic film stretched over them, and doors at one or both of the ends.
They are used for the same purpose (moderation of climate) but have precisely opposite effects dependent upon the climate in which they're used.
There are two types, one for hot arid climates, one for colder areas.
The ones for hot climates have white, opaque, waterproof, coverings to reflect much of the sunlight, to protect from searing heat, and to retain as much moisture as possible, both in terms of in the soil, and as humidity.
Hot climate polytunnels also tend not to have doors (in areas where there is less wind, some don't even have walls which reach the ground) in order to maximise the cooling effects of what little wind there is.
It was discovered, many years ago, when some white polyethylene blew over a tomato plant, that it had, by retaining moisture and reflecting some sunlight, that the tomatoes were much bigger and the yield increased enormously.
Both types use irrigation for watering, and I'll explain my set-up later.
That's the purpose and theory behind their use, but unfortunately I have no definitive experience of how they are fitted, although I suspect it wouldn't be too far from the fitting techniques for cold/cool climate tunnels
The ones for colder climates have transparent, waterproof coverings, in order to maximise sunlight, raise the temperatures and also to give protection from biting winds.
They tend to only have doors and raisable side-screens, to allow ventilation when the weather is mild enough to permit, or when the temperature rises too much.
It performs very similar functions to a greenhouse, but not quite as well, but their beauty is that they allow, with reasonably moderate investment, the ordinary person like myself, to have a far greater growing area, and to have room to attempt tender annuals, or sub-tropical plants/fruits/vegetables even after growing a number of the usuals, like tomatoes and cucumbers.
As we usually have relatively mild winters here, I am attempting to grow veg 12 months of the year, and have, in the past five weeks, planted onions and lettuce, and sown carrots, which have come through, in one of the beds (16x3) and intend to plant some garlic, pak choi, mustard greens and radicchio in the two other (8x5) beds.
As you can see from the (video) links I've posted, there is a wide range of polytunnels to suit most purses, and mine, which is 3mx6m (approx 10ft x20ft) cost approx $350, and with the exception of the cover, which a friend spared me five minutes to fit, I erected it myself.
I dug a trench for mine, and sank the whole lot, including the cover, 30cm (1 foot) into the ground, used ground anchors to further secure the frame, and used some drilled angle iron to further brace the corners, as I live in quite a windy area.
It has the following layout:
I have an off-centre path which runs the whole length of the polytunnel from North to South (it's orientated that way because of the prevalent winds, which is also why I have the doorway at the Northern end)
On the Eastern side of this path, I have two 8ft x 5ft beds, with a pathway at either end, and another separating the two beds in the middle of the tunnel, whilst on the Western side I have one 16ft x 3ft bed, with a pathway to the South, and a small sitting/work area to the North.
This design allows me access to every plant without standing on the beds.

Irrigation:
I have designed a gravity fed drip irrigation system, and here's how it works:
I harvest rainwater from a shed close to the polytunnel into two 210 litre (approx 45UKgal/55USgal) water butts, whose taps are linked together with the appropriate fittings and 1/2inch (13mm) pipe.
The two fittings to the horizontal pipe are T fittings, and at one end the pipe is blanked off, which allows drain-down.
The other end continues past the water butts, and fits onto a timer, then past and using elbow and T fittings where appropriate, the pipe is fed under the ground and the frame of my tunnel near the Southern end, coming up under the Souther path adjacent to the 16x3 bed.
Again using the appropriate fittings, this pipe is fitted in a ring along the whole internal perimeter of the tunnel.
The ring system gives a constant pressure throughout the tunnel.
Leading from this ring are, at the correct spacings, little 4mm pipes, with an inline dripper or end dripper for each plant.
Having used it for this summer, which was good but quite dry, I know that full water butts will last 3 weeks at least, and more water is attainable from the taps (which I pour into bins to dechlorinate before adding to the water butts.

http://www.firsttunnels.co.uk/tunnel_vision.asp

Any questions?
 
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Polytunnels are just a row of big hoops, secured to the ground (in one of a number of ways) with a plastic film stretched over them, and doors at one or both of the ends.
They are used for the same purpose (moderation of climate) but have precisely opposite effects dependent upon the climate in which they're used.
There are two types, one for hot arid climates, one for colder areas.
The ones for hot climates have white, opaque, waterproof, coverings to reflect much of the sunlight, to protect from searing heat, and to retain as much moisture as possible, both in terms of in the soil, and as humidity.
Hot climate polytunnels also tend not to have doors (in areas where there is less wind, some don't even have walls which reach the ground) in order to maximise the cooling effects of what little wind there is.
It was discovered, many years ago, when some white polyethylene blew over a tomato plant, that it had, by retaining moisture and reflecting some sunlight, that the tomatoes were much bigger and the yield increased enormously.
Both types use irrigation for watering, and I'll explain my set-up later.
That's the purpose and theory behind their use, but unfortunately I have no definitive experience of how they are fitted, although I suspect it wouldn't be too far from the fitting techniques for cold/cool climate tunnels
The ones for colder climates have transparent, waterproof coverings, in order to maximise sunlight, raise the temperatures and also to give protection from biting winds.
They tend to only have doors and raisable side-screens, to allow ventilation when the weather is mild enough to permit, or when the temperature rises too much.
It performs very similar functions to a greenhouse, but not quite as well, but their beauty is that they allow, with reasonably moderate investment, the ordinary person like myself, to have a far greater growing area, and to have room to attempt tender annuals, or sub-tropical plants/fruits/vegetables even after growing a number of the usuals, like tomatoes and cucumbers.
As we usually have relatively mild winters here, I am attempting to grow veg 12 months of the year, and have, in the past five weeks, planted onions and lettuce, and sown carrots, which have come through, in one of the beds (16x3) and intend to plant some garlic, pak choi, mustard greens and radicchio in the two other (8x5) beds.
As you can see from the (video) links I've posted, there is a wide range of polytunnels to suit most purses, and mine, which is 3mx6m (approx 10ft x20ft) cost approx $350, and with the exception of the cover, which a friend spared me five minutes to fit, I erected it myself.
I dug a trench for mine, and sank the whole lot, including the cover, 30cm (1 foot) into the ground, used ground anchors to further secure the frame, and used some drilled angle iron to further brace the corners, as I live in quite a windy area.
It has the following layout:
I have an off-centre path which runs the whole length of the polytunnel from North to South (it's orientated that way because of the prevalent winds, which is also why I have the doorway at the Northern end)
On the Eastern side of this path, I have two 8ft x 5ft beds, with a pathway at either end, and another separating the two beds in the middle of the tunnel, whilst on the Western side I have one 16ft x 3ft bed, with a pathway to the South, and a small sitting/work area to the North.
This design allows me access to every plant without standing on the beds.

Irrigation:
I have designed a gravity fed drip irrigation system, and here's how it works:
I harvest rainwater from a shed close to the polytunnel into two 210 litre (approx 45UKgal/55USgal) water butts, whose taps are linked together with the appropriate fittings and 1/2inch (13mm) pipe.
The two fittings to the horizontal pipe are T fittings, and at one end the pipe is blanked off, which allows drain-down.
The other end continues past the water butts, and fits onto a timer, then past and using elbow and T fittings where appropriate, the pipe is fed under the ground and the frame of my tunnel near the Southern end, coming up under the Souther path adjacent to the 16x3 bed.
Again using the appropriate fittings, this pipe is fitted in a ring along the whole internal perimeter of the tunnel.
The ring system gives a constant pressure throughout the tunnel.
Leading from this ring are, at the correct spacings, little 4mm pipes, with an inline dripper or end dripper for each plant.
Having used it for this summer, which was good but quite dry, I know that full water butts will last 3 weeks at least, and more water is attainable from the taps (which I pour into bins to dechlorinate before adding to the water butts.

http://www.firsttunnels.co.uk/tunnel_vision.asp

Any questions?
I understand a lot more about it than I did at first but I do have a question or two. Are your planting beds raised or elevated and are they enclosed in some type of structure? As I understand it, in your climate it rains an awfully lot. How do you keep the rain outside from running into the inside and if it does come inside how does it manage to evaporate without complete cross ventilation. Is there some kind of barrier such as a French Drain? Also, I have a question of temperatures. How much warmer or cooler is it inside the tunnel than it is outside? I will probably going to have more questions but I can't think of any right now. I really need something like this. A greenhouse is just not in my budget and I need something to grow seedlings in during the winter months
 
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I'd like something, too.

I have an uncle (now retired) that was a gardener all his life. He had peach and cherry orchards, and a vegetable garden, and he also grew strawberries. In the region where I'm from, El Maresme, strawberries are perfect, and they are famous all over the country, so he made nice money selling the strawberries. I remember they were ready in June, but months before, when they were just starting, his fields were all full of polytunnels. Then they disappeared when the weather got nicer. I guess next time I talk to him I could ask him how he built them.
 
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Rain, it runs down the outside of my polytunnel and into the soil, and then drains evaporates.
Obviously, as there is more water where it drains than elsewhere, some of it helps keep my polytunnel soil moist.

Beds:
Because I didn't want to lose any more height in my tunnel after burying 1 foot of it in the ground, I actually dug very shallow trenches (about 6 inches) for the paths, which I topped up with ground up tree branches, and edged the beds with treated wood, which with the extra soil, and a layer of compost, are only four inches Higher than outside level, but still very usefull for drainage. No other drainage than natural is needed.

Temperatures, much can be achieved to lower temperatures in scorching areas: damping down, or using further shade, and my polytunnel is 3.5-5 F warmer than outside at night with no heating. I'd imagine that the colder temps you get, the higher the difference.
More could be achieved, with heat sinks etc.

During the day, if it's sunny, my polytunnel is warm inside, regardless of outside temperatures, and there are a number of reasonably priced heating options, which, with you being in texas, I'd imagine would be a lot cheaper to run.

If you were to get a secondary, hot tunnel cover to put over the first, I'd imagine you'd be able to grow tomatoes even in your summer.
 
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I'd like something, too.

I have an uncle (now retired) that was a gardener all his life. He had peach and cherry orchards, and a vegetable garden, and he also grew strawberries. In the region where I'm from, El Maresme, strawberries are perfect, and they are famous all over the country, so he made nice money selling the strawberries. I remember they were ready in June, but months before, when they were just starting, his fields were all full of polytunnels. Then they disappeared when the weather got nicer. I guess next time I talk to him I could ask him how he built them.
Water retention?
 
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Rain, it runs down the outside of my polytunnel and into the soil, and then drains evaporates.
Obviously, as there is more water where it drains than elsewhere, some of it helps keep my polytunnel soil moist.

Beds:
Because I didn't want to lose any more height in my tunnel after burying 1 foot of it in the ground, I actually dug very shallow trenches (about 6 inches) for the paths, which I topped up with ground up tree branches, and edged the beds with treated wood, which with the extra soil, and a layer of compost, are only four inches Higher than outside level, but still very usefull for drainage. No other drainage than natural is needed.

Temperatures, much can be achieved to lower temperatures in scorching areas: damping down, or using further shade, and my polytunnel is 3.5-5 F warmer than outside at night with no heating. I'd imagine that the colder temps you get, the higher the difference.
More could be achieved, with heat sinks etc.

During the day, if it's sunny, my polytunnel is warm inside, regardless of outside temperatures, and there are a number of reasonably priced heating options, which, with you being in texas, I'd imagine would be a lot cheaper to run.

If you were to get a secondary, hot tunnel cover to put over the first, I'd imagine you'd be able to grow tomatoes even in your summer.
I have a much better understanding now. Thanks. I have been thinking about erecting a shade cloth covering over a portion of my garden where I grow indeterminate tomatoes but it is still in the thinking process. What I really need though is something like a tunnel that I can grow tomato and other seedlings on a semi commercial scale. I need an income from my gardening and I am getting too old to grow as many vegetables as I would need to do so. My garden will keep a family of 4 in vegetables all year but that is about it. If I could grow 3 or 4 thousand seedlings per winter and it weren't too expensive to set up I could get by much easier, especially since I already have a lot of the required stuff..
 
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Chuck, tell me about your situation...

What I'd like to know is whether you're in an urban/sub-urban/rural environment.
Would you be able to sell your plants/produce direct or are there farmer's markets, other markets with stalls you could rent?
I have a much better understanding now. Thanks. I have been thinking about erecting a shade cloth covering over a portion of my garden where I grow indeterminate tomatoes but it is still in the thinking process. What I really need though is something like a tunnel that I can grow tomato and other seedlings on a semi commercial scale. I need an income from my gardening and I am getting too old to grow as many vegetables as I would need to do so. My garden will keep a family of 4 in vegetables all year but that is about it. If I could grow 3 or 4 thousand seedlings per winter and it weren't too expensive to set up I could get by much easier, especially since I already have a lot of the required stuff..
What type of seedlings do you want to grow?
Would you have a market for them?
If you have a polytunnel, it would be possible, with shading, to have a summer garden.
This stuff will both save heat in the winter and reflect it in the summer:
http://www.ebay.co.uk/itm/HEAVY-DUTY-GREEN-MESH-WINDBREAK-SHADING-NETTING-GREENHOUSE-GARDEN-1M-X-50M-/230926078007?pt=UK_H_G_Garden_Plants_Landscaping_Garden_Materials_ET&hash=item35c4445037
Would you have the facility to heat your polytunnel in an emergency?
What size are you thinking?

You DO realise that you'll have to smile for you clientelle?
 
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Chuck, tell me about your situation...

What I'd like to know is whether you're in an urban/sub-urban/rural environment.
Would you be able to sell your plants/produce direct or are there farmer's markets, other markets with stalls you could rent?

What type of seedlings do you want to grow?
Would you have a market for them?
If you have a polytunnel, it would be possible, with shading, to have a summer garden.
This stuff will both save heat in the winter and reflect it in the summer:
http://www.ebay.co.uk/itm/HEAVY-DUTY-GREEN-MESH-WINDBREAK-SHADING-NETTING-GREENHOUSE-GARDEN-1M-X-50M-/230926078007?pt=UK_H_G_Garden_Plants_Landscaping_Garden_Materials_ET&hash=item35c4445037
Would you have the facility to heat your polytunnel in an emergency?
What size are you thinking?
I live way way out in the country. The closest town 30 miles away.


I used to have a road side vegetable stand but regulations put a stop to that and besides that I just don't have the energy I once did to operate and maintain a farm large enough for it to be economically viable. The nearest farmers market is almost 100 miles away in San Antonio.
The type of seedlings I would grow would be mostly heirlooms although I would also grow hybrids that I know do well in this area. Mostly I would stick to tomatoes because I have documented years of growing hundreds of different varieties of them and know pretty much what will produce and what will not in this climate.. And yes, I would have a market. Just about everyone around here gardens and there are very limited places to purchase plants. In fact there is only one place in the entire county of Bandera to buy them and then half of the time they are really poor specimens. Many people want organically grown plants and they sure as hell won't find them anywhere.
I suppose that a shaded poly tunnel would work or at least help on a summer garden here, no matter what you do the temps are just too high for tomatoes to set fruit. So while you could probably keep the plants alive you still wouldn't set fruit on anything other than cherry and grape type tomatoes. Now having said that, a poly tunnel in the fall is a completely different story. I think you could be extremely successful having one. You could probably set fruit well into December and have tomatoes year round if the tunnel were set up correctly
 
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If you pay alittle extra, you can get, or build, a polytunnel with doors at either end, orientate it correctly, to suit prevailing winds, and you have a potentially cooling draught.
Use drip irrigation to "damp down" (are you familiar with the term?) and that'll not only cool the polytunnel by itself, but would multiply the effects of the breeze.
PLUS, as you could use sideshoots for your summer plants, it needn't cost much to try.
There is also the opposite effect of what I need: it may extend your spring season by a few weeks, and bring in the Autumn season a week or too earlier.
Are aubergines popular there?
Bell peppers grow in Caribbean.
Melons are native to Africa.
Corn and beans will grow in polytunnels.
Remember, you won't just be able to control temp, but water losses too.
 
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Chuck, I'm really thinking you can do this, if you can put enough time into it.
It shouldn't be too huge an effort.
With cheap or self-built staging, I'd say that 1500 seedlings were possible in a tunnel like I've got.
 
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If you pay alittle extra, you can get, or build, a polytunnel with doors at either end, orientate it correctly, to suit prevailing winds, and you have a potentially cooling draught.
Use drip irrigation to "damp down" (are you familiar with the term?) and that'll not only cool the polytunnel by itself, but would multiply the effects of the breeze.
PLUS, as you could use sideshoots for your summer plants, it needn't cost much to try.
There is also the opposite effect of what I need: it may extend your spring season by a few weeks, and bring in the Autumn season a week or too earlier.
Are aubergines popular there?
Bell peppers grow in Caribbean.
Melons are native to Africa.
Corn and beans will grow in polytunnels.
Remember, you won't just be able to control temp, but water losses too.
I used to snip side shoots off of indeterminate tomatoes (we call them suckers) and root them. I still do occasionally on a really impressive plant and carry it through until first frost. As for aubergines (egg plants here) many people love them. My wife likes them and I always grow 1 or 2 plants every year. I like them OK but they are not my favorite. Bell peppers here can be a great success or an abject failure It all depends on how hot it gets and how fast it does so. A long coolish spring means a good crop. A short cool spring turning hot early means stunted plants and small fruit. Other sweet peppers such as bananas and other longish tapered varieties do much better, almost as good as hot peppers do. Melons are iffy where I live. For some reason I cannot grow the musk melons or any green meated variety of melon at all. Most years I can grow cantaloupes very well and then the next year the same cantaloupe won't do a thing. Watermelons are even more iffy than cantaloupes. For some reason the watermelon will set fruit and grow for awhile and then will end up with something that looks just like blossom end rot on tomatoes. I think it has to do with my soil. The soil here where I live is naturally heavy in compost. 30 miles south of here is a town called Hondo. Their soil is very sandy and they grow all kinds of melons commercially. Thousands upon thousands of acres of them. Once in every great while I will a watermelon actually do what it is supposed to. But just to whip a dead horse I keep on trying. This year I am really beat myself up by planting an entire row of a small variety cantaloupe. Always before I have grown or tried to grow the great big varieties, sometimes with success sometimes not so much
 
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Chuck, I'm really thinking you can do this, if you can put enough time into it.
It shouldn't be too huge an effort.
With cheap or self-built staging, I'd say that 1500 seedlings were possible in a tunnel like I've got.
Time I've got, money is the problem. I'm going to study on this.

What is the mill thickness of the plastic and about how long will it last in brilliant sunshine do you think?
 
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Mine is reinforced 210 micron.

In British sunshine it'll last 350 years.

Seriously though, it's UV stabilised so will last about 5-10 years easy.
Wind more likely to be a problem.
You can buy a smaller polytunnel in this country for $80.
That'd probably do 500-600 seedlings.
 
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Mine is reinforced 210 micron.

In British sunshine it'll last 350 years.

Seriously though, it's UV stabilised so will last about 5-10 years easy.
Wind more likely to be a problem.
You can buy a smaller polytunnel in this country for $80.
That'd probably do 500-600 seedlings.
I'll have to do some online searches. Surely there will be something over here that won't cost a fortune
 
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My friends who grow a lot of their own produce do something like this to get things started in the spring. Kind of like setting up a little greenhouse over the rows so they grow faster and get established better. It's really a lot of work to make a big garden really successful.
 
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There are ways and ways of growing melons.
You may need to vary your watering regime, and you would definitely have to make sure they grew bushy, with pinching out techniques, rather than trailing, but you probably could grow melons.
 
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