Things it's worth knowing when buying your first greenhouse

I wasn't expecting to love my greenhouse as much as I do. I knew I wanted one, but I thought I wanted it for purely practical purposes. I wasn't expecting the joy it would bring.
The greenhouse came when we decided it was time to get a new shed, to replace the one that had practically fallen apart, so our greenhouse is part of a shed/greenhouse combination. This both saves space and is highly aesthetically pleasing - especially compared to the mishmash of non-matching shapes I was originally assuming I'd have to have if I bought shed and greenhouse separately.

Unlike many standalone greenhouses, instead of being built straight over the soil, this one is over a concrete base that came with the garden, so this one has a wood floor instead of opening straight onto the soil. This looks very pretty, but has an impractical side in that I tend to water the floor by accident when watering my plants. If it weren't for the existing concrete base, I'd have preferred one straight onto the soil. To deal with the wood floor, so far I've put trays and plastic sheeting under the shelves of plants (it's a shame I didn't measure before buying the first one, two of the longer ones would have been the perfect length).

I've also varnished the book cases I'm using as shelves for my plants with outdoor varnish, as these were starting to get water damaged. I intend to varnish the floor before I start putting plants in next year as well. If I'd known then what I know now, I'd probably have varnished the floor before I put any plants or shelves in at all (and then still bought the plastic trays). You can also buy purpose-made greenhouse shelving instead of using old book cases. Varnishing them took ages. On the other hand, because we already had them, they were free apart from the varnish. And they do look nice.

Another problem I discovered with the shed-greenhouse combo was that unlike a conventional greenhouse, there was little scope to cool the greenhouse down. It has no vents in the roof and only a small window that can be opened. I put a temperature data logger in to record the temperatures, and it already reached well over 40° by mid-May. What we did to solve this was to add a cabin hook, so the door can now be propped open without any risk of it blowing about in the wind and smashing the glass. I'm not sure if this is as effective as a ceiling vent, but it certainly helped.

The problem with leaving the and window open for ventilation though, is that it gives pests an opportunity to come in. This resulted in an infestation or two for us:

These are hell to deal with, especially if you're growing food, as there's so little you can spray at them. I initially kept the infestation down by crushing pests I saw between finger and thumb. I later discovered that taking all the plants out of the greenhouse and leaving them outdoors for a few days reduced the number of pests I had (this probably won't work for all pests in all climates).
I also need to completely empty and thoroughly clean the greenhouse before I put next year's plants in to remove any eggs that might have been left. I'm also thinking of buying a mesh screen door to keep insects out. I'm hoping that one you use for a house door will work, as that would be cheapest and most practical, plus I'll need an extra bit of mesh for the window. I don't know for certain if that will work, especially as my greenhouse is far from airtight around the corrugated roof, but I have hope and think it's worth a try. Edited: I tried, it was a bad idea. I kept the pollinating insects out with it, so had to hand pollinate, but the aphids still got in anyhow.

Another lesson I learnt is that tomatoes are incredibly thirsty plants, so although I grew each tomato plant in a pot that I'm pretty sure was bigger than a growbag, I still ended up watering them two or three times a day on hot days. In the end I decided to put them in large plastic crates. I haven't yet decided whether to drill holes in the bottom of the crates or rely on my ability not to over-water them. I think I'm going to try it without holes first, so I can return the crates to their original purpose later if I want.

Another lesson I learnt is that this sort of greenhouse is very pleasant for sitting in and reading, so it was well worth while leaving plenty of room for a chair and cushion. I got more joy from the chair than I think I could have done from extra plants - despite my love of plants.

And while we're talking about space, goodness do plants grow and need more room than you might think. I originally thought I was going to need another shelving unit for the end section where I grew the tomatoes. In reality, the tomatoes needed so much space an extra shelf would have been in the way.
Another lesson, that you can see partially implemented above is that plants look a lot nicer when they're all in uniform terracotta pots. I originally used what I had, which was fine in terms of housing the plants, but I was lucky enough to spot a really cheap offer for large terracotta pots at Wilko's. So next year I'll be using all the nice, matching terracotta pots I bought there for my plants' final pot. If they grow bigger than that, they'll just have to lump it, unless I find an offer for bigger pots.

Finally, I learnt that my most practical plants in terms of yield were the Cheyenne F1 chilli pepper and my Moneymaker tomatoes.

But the ones I loved the best were the purple ones.