Greenhouse growing v polytunnel growing

[Odsox]

This is a follow on from my previous posting comparing polytunnel growing against growing outside.

I have always been a greenhouse man, in fact I can't really remember a time when I didn't have one. Not always totally recognisable as a greenhouse and almost always home made. I love greenhouses and certainly would never willingly be without one, I would give up all my garden and polytunnels if that was the only way to keep a greenhouse.
With that in mind, it has taken me until 4 years ago to get a polytunnel as I had thought that a tunnel was just a "poor man's" greenhouse and a bit pointless if you have got the real thing.
Of course I was totally mistaken in that and I am now converted to having both, because they are distinctly different and really do complement each other.
There are also many people, some on this forum in fact, who think that a polytunnel is just the same as a greenhouse, and in my opinion they are just as mistaken as well.

My latest greenhouse can be seen here .. http://www.selfsufficientish.com/forum/ ... 38&t=18367
The back wall has about a dozen climbing French beans and I shall pick the first ones for next Sunday dinner. The rest of the back wall has about 30 climbing Borlotto beans growing up it with a cucumber at each end.
In growbags on the floor are 15 tomato plants now in full flower and 3 pepper plants which still look a bit sad.
On the windowsill are strawberries and a few pot grown Gartenpearl tomatoes.
In the back bed are various plants, some experimental and some (like carrots and lettuce) are just taking advantage of the ideal growing conditions, also a grape vine at one end and an apricot tree at the other.

I have tried French beans, both bush and climbing, tomatoes, cucumbers and peppers in my tunnel and found they didn't like it at all, mainly because of the high humidity and cooler temperatures. The beans tended to go mouldy, as did the strawberry fruits, tomatoes got blight and the cucumbers just didn't grow.

To finish, I planted out some Romaine lettuce plants on the 19th April, some in my tunnel and some in the greenhouse.
This is what they look like in the tunnel .......

Lett2.jpg (138.75 KiB) Viewed 4280 times

and this is one in the greenhouse .....

lett1.jpg (106.4 KiB) Viewed 4335 times

[grahamhobbs]

Odsox, I wonder if the brick wall in the greenhouse doesn't also have a lot to do with the difference between your greenhouse and polytunnel, although I accept that a greenhouse will always be warmer than a polytunnel.
With both the problem is usually controlling ventilation, especially if it's on an allotment and not outside your back door, although with greenhouses it is easier to install automatic ventilation controls.
Our experience is with what we inherited on our allotment, a couple of small cheap green houses and two largish polytunnels. The greenhouses became too expensive, replacing sheets of glass each year. At least once a year a gale would take out a few panes. We now leave panes out at an upper level so that the wind can whistle through, without causing damage, but plants lower down get some shelter, this we find ideal for lettuces and outdoor tomatoes (the roof keeps the blight away).
The polytunnels are where we grow most of our veg under cover. Because we are not there every day we have to err on over ventilation as more damage is done by overheating. But we grow melons and cucumbers as well as sweet corn, tomatoes, peppers, etc quite successfully in them. In winter we grow a wide selection of lettuces and brassicas, and peas.
With our polytunnels we do not bury the plastic around the edges but have a 'skirt' that can be lifted, with the gap covered in fine mesh, to ensure the tunnel is well ventilated, without draughts at low level, and thus avoiding excess humidity.

[Pennylane]

Last year was a year of rain here, the polytunnel did not do so well as the plants were not getting enough light now that my cover is getting old..as has been said, two very different enviornments...

[Odsox]

Graham, yes the back wall acts like a huge heatsink as does the soil surrounding the submerged base. I was in there last night at midnight hunting an elusive slug, and the temperature was a balmy 22c in there compared to about 10c outside.
I didn't go in my tunnels but I bet the temperature in there was probably only slightly above ambient.

My opinion of the two is polytunnels are more or less just protected gardens, protected from wind and excessive rain (and a few pests) where a (admittedly large) greenhouse is a totally controlled ideal growing environment.

My greenhouse glass in 4mm and has survived 110 mph winds unscathed, but I do have 5" x 2" rafters to carry the weight.

[pelmetman]

I will follow this thread with interest.

[grahamhobbs]

Regarding the smashing of glass by the wind, I think it really important to ensure that the glass is well secured in some way. Our allotments are in fairly central London, so not the windiest of places, but the greenhouses we inherited were cheap aluminium types and the sheets were only clipped in. At least once a year some would be smashed.
But worst was someone who bought a big greenhouse and erected it on their allotment. Again what looked like a standard cheap one, a week later there was a gale, every single sheet of glass was smashed!
So if buying or constructing a greenhouse it is essential that the glass is securely fixed into the frame, not just a few clips.

[Odsox]

So if buying or constructing a greenhouse it is essential that the glass is securely fixed into the frame, not just a few clips

Too true, and it also shows the benefit of building you own from materials of YOUR choice.
My glass is set into rebates in timber, bedded on clear silicone sealant and fixed with nails.
Using silicone instead of putty means that if a pane gets broken it still won't fall out.

[JulieSherris]

I've been told at the weekend that one of the first things we will be doing when the MIL 'goes'.... will be the double glazing around the house.
This comment came about because himself is painting the house at the minute & the putty around every one of our single glazed windows was just put on using fingertips (CSI would have a field day with their fingerprint equipment here!!) so painting the putty & trying his hardest NOT to paint the windows is proving extremely frustrating for him - bless!

So...... I was counting the windows & mentally measuring... I have enough for a cracking proper glass greenhouse - woohoo!!

Oh... I've not told him yet... plenty of time for that

[Millymollymandy]

The only greenhouse I've ever owned had polycarbonate instead of glass (a lot more expensive). It was fine in all winds except the storm that took out an enormous conifer in a neighbour's garden and we lost one pane which blew off somewhere never to be seen again, which we replaced with perspex. Maybe this is something you should think about if you are constantly losing glass to wind?