[miggs]

As most of you on here are far more experienced than me regarding these items I need advice.
Which one do I get?
I have had quite a large greenhouse before, about 6yrs ago where I used to live and loved it. We are moving house in about a month and want to get another or do I go the polly route? Had a look at a polly at our local garden centre earlier today and they do look good. Had a look at some on a certain well known auction site and there are loads of them. Thing is, I dont know whether its going in the back garden or down at the plot. When we move house the plot is about a 5min walk away. What point do I look for? Any advice would be really appreciated.
Thanks Ste.

[Sparkyrog]

Personally I think they are both very different ,I am lucky enough to have both and both have totally different purposes ! It depends on what you want to achieve as to which is the best choice for you 

[grinling]

personally what with damage caused at allotments, I would keep at home. Also very handy for keeping an eye on seedlings etc.
If kids then no glass. I have a polytunnel, but have to open door when hot, next door has autowindow in greenhouse, also whitewashed. I have 2 kids, next door grandkids with loads of taped up glass.

[miggs]

Personally I think they are both very different ,I am lucky enough to have both and both have totally different purposes ! It depends on what you want to achieve as to which is the best choice for you 

Give me an idea what you use both of yours for and it could well help me with my decision.
Thanks.

[miggs]

what I want to do is have a place that I can start my seedlings off in. At the moment I have nowhere to start them off properly and as we are moving house soon I will have the space for something.
The thing I get will also be used for Tomatoes, Chilies, Peppers etc.

[Kristen]

My opinion, but interested to see what others think:

Tunnel temperature will fall at night faster than glass - so if heating it then glass may be better.  If heating it "often" (many nights) then insulation will be important anyway - typically bubblewrap.  Dunno if that is easy to do in tunnels, plenty of framework in greenhouses to attach it to.

If risk of damage to/by kids then greenhouse can be clad with safety glass, or polycarbonate (although the later has a habit of blowing out in high winds, typical solution is to silicon the panels in, but that makes them hard to remove if that was ever necessary)

Ventilation easier and more controllable in a greenhouse - however I think that most of the models I see have too few vents as standard. I think a  10' long greenhouse needs 4 vents, and preferably a louvre (in the side, or end) as well so that convection cooling can be used most of the time (in heat wave it will still be necessary to throw the door open for forced draught cooling, which increases transpiration stress for the plants.  Easy to attach automatic openers to greenhouse vents, if you are away for the weekend, or working shifts, not sure if that can be done with tunnels?

Greenhouse vents can be set "ajar" to allow gentle ventilation - useful to keep a small airflow to prevent moulds etc. in cold weather. Similar can be achieved with tunnel where sides can be raised (usually insect netting is installed on the sides as well) but I think that introduces cold air close to the plants. Might be more of an issue in a tunnel if Paraffin / Bottle Gas heater is going to be used as they generate a lot of condensation.

Cropping near the sides of tunnels can be difficult - worth choosing a model with "near vertical" sides

Tunnel has ongoing, but infrequent, labour effort and cost of replacing the plastic.

Alternatively early seed raising might be achieved using artificial lighting in the house or garage. No issues with temperature (or a dreadful late spring with dramatically reduced light, like Spring 2013), but as soon as the plants get to a certain size they need to move to something more spacious.  Supplemental light, indoors, won't help with protected crops in the Summer either, but might be worth considering instead of heating the greenhouse / as much.

[allotmentann]

I think the temperatures in a poly are more extreme than in a greenhouse, so if it is mainly starting off seedlings I think that you would be better with the greenhouse. I also think that a greenhouse in a garden would probably last longer than a poly if well maintained. I would never use glass on my plot. Not just the risk of vandalism, but broken glass is so difficult to remove from a plot. Even the best poly tunnels only guarantee their covers for about 5 years, so that is another cost to bear in mind.
If you were thinking of a poly carbonate house on the plot, I wouldn't, unless it is a really, really sheltered site. The frames twist very easily. A plot holder near me had one, it didn't last six months and he had to do major repairs in that time too.
On the other hand, the cheap tunnels I have used have been worth the money. I have started seeds off in them, but generally in a mini greenhouse inside the tunnel, to try to stop the cold at night stunting them too much. In a garden it might be easier to control temperature in there than at a plot. I wouldn't mind opening a tunnel at 6 in the morning at home, I will never be at the plot at that time, and we are not allowed on site after dark so that also has an effect on temperature control. 

[Sparkyrog]

what I want to do is have a place that I can start my seedlings off in. At the moment I have nowhere to start them off properly and as we are moving house soon I will have the space for something.
The thing I get will also be used for Tomatoes, Chilies, Peppers etc.

for that purpose I think you would find a GH best ,as spring light levels are better in a GH in my opinion 

[miggs]

Thanks for all the info. Looks like a GH at home for me. Now what size greenhouse?

[JayG]

Thanks for all the info. Looks like a GH at home for me. Now what size greenhouse?

That's an easy one - at least one size up from what you're currently thinking about! 

[Kristen]

That's an easy one - at least one size up from what you're currently thinking about! 

Only one eh? 

The crunch point, in Spring, is when seedlings need pricking out, as it is the space for things once pricked out that is at a maximum.

Worth thinking about a cold frame for hardening off, then with a succession of seeds coming on some stuff will already be ready for moving out to the cold frame.

But "size" is basically a cost-benefit-equation, unless you happen to blag a big greenhouse on Freecycle, or get a big one cheap-enough on eBay, but the larger they are the easier it is to control the temperature.  I reckon anything smaller than 10' x 8' is difficult to control the temperature in mid Summer, and bigger than that is OK. 

Dunno how others plant theirs, but mine is 10' wide and allowing for a narrow path up the middle I get three rows of "crop" on each side. I grow a row of Toms nest to the path (for max height to ridge), then Peppers / Aubergines and then Melons against the glass, plus 3 Cucumbers on the end wall

Personally I prefer growing in soil. Much easier to get the watering right, and plants will survive for the weekend watered well before we go away, whereas when I used to grow Toms in [big!] pots they would often need watering twice a day.  I change the soil annually, and replace it with 50;50 compost heap and rotted manure - which is relatively light to handle, compared to the clay in my beds.  After a year in the greenhouse it makes lovely loam for a mulch or potting things up - I use it to pot up & start off Dahlias & Cannas in Spring, for example.

But 10' wide means significant wide staging - probably 4' - and its hard to reach anything at the back.  I live with that to have the maximum area for plant raising, and once growing crops its not an issue as I squeeze between them trying to do as little damage as possible, but 8' wide would be easier in that regard.