[shokkyy]

Later on this year I intend to go shopping for a decent greenhouse. Right now I'm stuck with a tiny hexagonal job which is much too small to be very useful, not remotely weatherproof and right under the shade of a lilac tree. I've got room to put something about 12 X 8. It'll have to be solid flooring inside as the spot I want to put it already has ancient concrete down and it would be a heck of a job to get it all up. One long side of it would be fairly close to a 5' stone wall (a couple of feet away) but that shouldn't really affect the light too much since the other three sides would be wide open to the light.

So any tips on what sort of greenhouse to go for? Is the stuff sold by the warehouses like B&Q and Homebase ok? Does it matter what shape the roof is? Any opinions on whether it's best to go for safety glass, horticultural glass or polycarbonate? How about vents, double or single doors? I know nothing about greenhouses and there's such a big choice in the shops that I'm just looking for some pointers on what to look out for and what to avoid.

Thanks

[BostonInbred]

I like glass panels. That Polycarbonate stuff is too light for my liking,  doubt it'll stand a 90 MPH gale.

[Kristen]

One long side of it would be fairly close to a 5' stone wall (a couple of feet away) but that shouldn't really affect the light too much since the other three sides would be wide open to the light.

If the wall is on the South side I think it would make a lot of difference ... but if on the North it will make no difference.

Later on this year I intend to go shopping for a decent greenhouse

If its "not immediately" I would recommend setting up a search on eBay (i.e. so that you get an EMail when a suitable match comes up). I've had two, large, greenhouses off eBay that saved me a lot of money.

Any opinions on whether it's best to go for safety glass, horticultural glass or polycarbonate?

My view is that you only need safety glass if there are kids about who could career into it (bottom of a hill that they use for their go-karts, for example [])

Personally I favour glass over polycarbonate as I think the weight helps keep the thing on the ground.

How about vents, double or single doors?

My opinion:

You want convection cooling, not a draught. A draught causes the plants to transpire more, so they have to drink more water and that stresses them more.

To achieve this I think you need the largest greenhouse you can afford / have space for (much harder to keep a small greenhouse cool).  Plenty of vents at the top and a few louvre vents at the bottom enable convective cooling (whereas throwing the doors open means that more of a draught-effect is created)

Double-doors help if you want to get a wheel barrow into the greenhouse,  if you are going to grow in the soil (rather than in pots / grow bags) then you will have to change the soil, and getting a barrow in will be important.  If not growing in the soil then you could get away without a barrow / wide door.

Personally I think growing Tomatoes and other crops in the greenhouse is easier done in the soil. I've done pots / growbags etc. in the past, more time & effort spent watering, and the pots themselves reduce the height-to-roof so you get probably one less truss of fruit. (I have lowered the beds/floor in my greenhouse to maximise roof-height)

Consider if you want automatic openers for the roof vents. I haven't bothered, because I like to open them on the side away from the wind (in mid summer I have to open everything of course), but if you will be away from home etc. then the vents have to be opened by a neighbour / automatic device []

Also consider a water butt. Most easily arranged at the back (opposite door) so that the gutters from both sides can be joined to a single water butt (or have two at the front ..). Slope the base very slightly so that the gutters run towards the water butt end 

Electricity to the greenhouse? (Heating / light / propagators)

Heating?  Gas / Parrafin heater to keep the frost off in the spring? or do you want to heat it in the winter too?

Staging (tables)? Plant raising in the spring, and a collection of Orchids or somesuch [] - or are you going to grow Tomatoes / Cucumbers / Melons?

Cropping wires? You can get small bolts with funny shaped heads that "slot" into the aluminium frames and have a wire ring on the end - through which you can put a decent strength wire end-to-end in the house, and use that to train Tomatoes up to etc.

Some pictures of my greenhouses on my blog

[shokkyy]

If the wall is on the South side I think it would make a lot of difference ... but if on the North it will make no difference.

The wall will be on the west side, with the two ends of the greenhouse facing north and south. It's not ideal to have the exposed long side facing east, i know, but it's quite a sheltered spot yet not really shaded other than that wall. It's a big garden (half an acre) but actually quite difficult to find a place with no tree shade as there's an awful lot of big trees in it. I was going to put the door in the north end so I could have some plants growing across the south and east sides, using the west side for staging/workbench.

Personally I think growing Tomatoes and other crops in the greenhouse is easier done in the soil. I've done pots / growbags etc. in the past, more time & effort spent watering, and the pots themselves reduce the height-to-roof so you get probably one less truss of fruit. (I have lowered the beds/floor in my greenhouse to maximise roof-height)

Yes, I know what you're saying, but it looks like it would be an awful lot of work to do anything about the concrete that's already down there. In addition to that, the same slab of concrete also supports the filtration boxes for the septic tank and the base of the wall, so I'm a little nervous about doing anything to destabilise that. But when I get people to quote me for putting it up, I will mention it to them and see what they think.

I was thinking of automatic openers because I can't always be there to do it. Do they work off a temperature guage so they open when it reaches a certain temperature?

I wasn't going to do a water butt because the garage will be fairly close to the greenhouse and I already have a butt filling from the garage guttering. I should also be able to use the mains socket in the garage for anything electrical, as it's plenty close enough to run an extension cable.

I was considering some heating, mainly spring heat for starting off seeds, spuds, etc. early. It would be nice to be able to grow some salad stuff in the winter but I'm not sure it would be worth the cost of heating the greenhouse just for that. The cropping wires sound like a good idea because I will be growing tomatoes, peppers, chillis, aubergines, cucumber in there and built in supports would be very useful.

I hadn't thought of looking on ebay, but it's a good idea and I'll do that

I'll take a look at the pictures on your blog, and thanks for all the tips, I appreciate it.

[Kristen]

looks like it would be an awful lot of work to do anything about the concrete that's already down there.

Sorry, I missed the bit about concrete in your original post. On the plus side chucking water on it ("Damping down") in the summer will increase the humidity and lower the temperature

I was thinking of automatic openers because I can't always be there to do it. Do they work off a temperature guage so they open when it reaches a certain temperature?

I think they have some sort of wax that expands so the vents open progressively as the temperature rises.

"

I was considering some heating, mainly spring heat for starting off seeds, spuds, etc. early.

Electric thermostatically controller fan heater (outdoor / greenhouse one obviously!) is easiest to control (dunno about Electricity cost v. Paraffin/Calor gas). Paraffin (and to a lesser extent Gas) generates quit a lot of moisture, and just guessing the wick setting is a bit hit and miss!

"

It would be nice to be able to grow some salad stuff in the winter but I'm not sure it would be worth the cost of heating the greenhouse just for that.

I grow winter lettuce, leaf beet and Kohl Rabi without any heating - plus a late Autumn crop of French Beans (they don't need insects/bees for pollination) until the cold kills them!