Cover Whole Plot? Multispan Tunnel / Greenhouse

[Kristen]

Hopefully I haven't asked this before! as the thought does occur to me periodically ...

I have a large greenhouse - 30' x 10' - for cropping. Tomatoes, Peppers, Melons, Aubergines, Cucumbers and some early crops - Sweetcorn and Dwarf French Beans

I struggle with some parts of the outdoor plot - wind rock on brassicas, enough heat for Squash ... probably a bunch of other things if I put my mind to it.

The solution I fancy is covering the whole plot. Either a multi span polytunnel, or a multipsan glass house.

(The glass house probably seems incredibly expensive on the face of it, but they come up on eBay for a £grand or less, the problem is taking it down and re-erecting it, and the price reflects the cost to the owner of clearing the site - anything that anyone will pay, if they will take it away, is bunce!)

I've had a chat with a couple of people who grow all / nearly all their veg under cover and it looks extremely promising. A few look like they need to be outside:

Runner Beans - pollination issues. They are happy to grow on same spot each year, no crop rotation, so that's not a problem.
Courgetttes - get stressed from heat (which surprised me)

Lettuce - struggle in the hot months, maybe there is a longer "hot period" under cover?

A synopsis of the discussion I have had with chums that already grow predominantly under cover is:

Upside is that there won't be any direct damp on foliage, so less / no? rust type fungal diseases. However there are issues from condensation dripping from roof in colder months (maybe that can be engineered out)

No carrot fly, could probably net Door and Vents to keep Cabbage White etc. out too, should be no issue with Pigeons.

A downside is that everything will need irrigation. I figure to lay leaky hose and run that off my irrigation system (we harvest rainwater from house & sheds, and the outfall from the cesspit-digester thingie, so don't actually need to "buy" water to put on the garden). Add rainwater collection from the tunnel roof to that store.

I currently plant everything (more or less) through woven weed-suppressing membrane (Mypex) so that reduces water evaporation, which should help under cover.

I'd love to hear of anyone's experiences, and any Gotchas folk can think of. Thanks

[Alison]

Personally not a route I'd want to go down as I like being out in the open air but I can see there would be certain advantages, especially if you have a good water supply. From experience in my much more modest tunnel (10' x 20') I find that brassicas will definitely sulk (and bolt quickly) if too warm in there except in winter so you'll struggle with summer brassicas or presumably the ones that are in the ground over summer for a winter crop (PSB, savoys etc) but the extra protection is great for the likes of spring cabbages and calabrese over winter too. With regards courgettes, I've put a spare plant in the tunnel before and it went mental, masses of crops although they turned into marrows in 5 minutes if you turned away! Not done it since as the plants got too big.

[Alison]

Oh and always grow some early carrots, peas, broad beans in there too, do very well with no pests but the legumes crop quickly then finish. No carrot fly damage (and it's really bad outside), pea moth (but rather early when I grow them) and never net my brassicas as they seem to prefer attacking the stuff outside.

[Kristen]

Very interesting, thanks Alison

Personally not a route I'd want to go down as I like being out in the open air

speaking for myself I have plenty of open air in the rest of my garden For my Veg I would like maximum productivity in the most effortless way possible, with minimal chance of failure and maximum flavour. Simples!

I find that brassicas will definitely sulk (and bolt quickly) if too warm in there except in winter so you'll struggle with summer brassicas or presumably the ones that are in the ground over summer for a winter crop (PSB, savoys etc)

I don't do Summer Brassicas (my pea-sized brain thinks of them as Winter veg), but the ones I do grow are long-season, so at risk from Summer heat stress. They seem to grow really well (in Tunnels) on Beechgrove, and I presume your weather in Cheshire is not exactly mild all the year round? but Down South is altogether different to Beechgrove of course.

My expectation is that a large structure could be opened up [but netted] at both ends so that it wasn't exceptionally hot in Summer - but it would keep the rain and breeze off and be mild at nights, so reduce stress / transpiration [due to wind]

[Scarlet]

I grow in 2GH8x20 and 8x12. I'd love to have more undercover space, love pottering when it's pouring down outside. In the summer I mostly use my undercover for toms, chillies, peppers. Courgettes are great and my butternut squashes really go mad. Spring cabbage and kale grow brilliantly over winter although I have been plagued with whitefly. Garlic and giant garlic were much bigger than my outside planted ones. I love have the warmer season extended either side of the summer. I do have trouble keeping it well watered though. I mulch with newspapers, I try to water every other day. I have 8 water butts and these are usually empty in no time at all.
I do have a major problem with mice...

Just read Alison's post... I've grown broad beans, had a reasonable crop but I found them to be very leggy with lots of soft growth. It was a pain trying to keep them supported.
Pretty warm down here in sunny Wilts!

[skeggijon]

It's looking like I will soon have my plot almost totally undercover. I started off with a 3m x 2m polytunnel, which was ok, but not quite enough. My OH then treated me to a 6m x 3m one which is fantastic. I then took advantage of the great B&Q greenhouse sell off and got 2 4ft x 6ft greenhouses, which I have bolted together to make a an 8ft x 6ft one. This week I was offered a free polytunnel by someone who's just bought a house with one taking up much of the back garden. This one is 10m x 5m.

At this rate I'm gonna have to demolish the sheds

[Two_Sheds]

I fancy ... covering the whole plot.

I did some training at Holt Hall a year ago, and was most impressed by their polytunnel crops, inc. courgettes, all cropping about a month earlier, & bigger, than my outdoor crops.

If I had the cash, I'd be shopping here: Polytunnels - Garden Tunnels from Haygrove - Poly Tunnels, PolyTunnel - Design & Buy PolyTunnel Online

[Bigmallly]

Good luck Kristen if you go down that route, it is something many folk can only dream about. A silly thought really but could netting be incorporated into the roofing to aid irrigation...........just one of my daft thoughts as I have recently done it with a greenhouse. I put polycarb in the top half of the heaves & netting in the bottom half so rain would go on the beds. The rest of it is polycarb.

[Kristen]

it is something many folk can only dream about

I know cost is relative, but I certainly aint planning on buying Brand New ... and I'm not sure I want a polytunnel. Glasshouses are relatively cheap, its just figuring out how to deconstruct and move, and then the cost of any concrete/footings needed for re-erecting. Other than that its just labour and I'd prefer to take a couple of weeks off to build a greenhouse than lie on a beach somewhere in the Med!

could netting be incorporated into the roofing to aid irrigation

I've got two thoughts:

1. Plants will need irrigating during dry periods, so need irrigation anyone (I favour leaky hose along the rows)

2. I'd prefer the foliage didn't get wet (Blight / Fungal infections), so would prefer not to water/irrigate from above at all.

Water collected off the roof can be stored and provided back again as irrigation. As a separate project I've managed to locate an 18' diameter grain silo that is going for a £hundred or so which will hold about 45,000L / 10,000 gallons - although I will have to fork out for the Butyl liner, and there are a LOT of bolts to be undone to shift it! So that will give me the water storage I need (for the whole garden, meaning that I can irrigate it all with rainwater rather than using potable water which, apart from the cost on the water meter, I feel is a dreadful waste to then chuck on the garden.

[Kristen]

If I had the cash, I'd be shopping here ...

Not come across Haygrove before, thanks. The covers look "loose"? and I'm never sure about that, compared to tight-as-a-drum. If I was to buy new I think I would be tempted by a Multipsan polytunnel from Northern Polytunnels:

CLASSIC Multi Span - Multi-Span Polytunnels - Horticultural Structures - Commercial Range - Northern Polytunnels

[Bacchus]

I have found that most of the big polytunnel producers have similar products - quality wise - and it really comes down to transportation / delivery costs as to which one works out to be the cheapest.

[skeggijon]

Not come across Haygrove before, thanks. The covers look "loose"? and I'm never sure about that, compared to tight-as-a-drum. If I was to buy new I think I would be tempted by a Multipsan polytunnel from Northern Polytunnels:

CLASSIC Multi Span - Multi-Span Polytunnels - Horticultural Structures - Commercial Range - Northern Polytunnels

If money was no object it would be very tempting, though I quite like the ethos of cheap or recycled polytunnels/ greenhouses on a lotty - cobbled together seems more in keeping somehow

[bravo2zero]

I have often thought about more undercover space but for me with a 20x10 tunnel and 2 8x6 greenhouses is enough. The first consideration is cost, i couldnt justify it. The time it takes to water and possible auto irrigation cannot be justified. Think about the extra water needed, I have 11 butts and twice this year ive had to refill them from a hose. Try using your existing indoor space to extend the season, this year ive sowed carrots in tunnel to overwinter them instead of risking an early sowing next year. Regards wind rock to brassicas try planting them in a trench 4/6 inch deep and earth up when big enough and stake the taller ones or erect a windbreak from scaffold netting. Squshes should do better. Do you grow in soil beds? Personally i woudnt do it but theres a book called Growing under plastic by Bernard Salt thatll help.

[Snadger]

I find that growing under glass or polythene is very labour intensive especially with watering and opening and closing vents. Another worry I would have is 'salts' build up in the soil. On a smaller scale it is feasible to change the bed soil periodically but if the whole plot is covered you can't do this.No ammount of irrigation can make up for a good winter of heavy rain!
Its really down to whatever floats your boat. I have three greenhouses which I try to utilise summer and winter. They are hard work compared to the area's open to the elemnts. Its nice to be potting plants on in a heated greenhouse in fFebruary but not so nice to be in the same greenhouse in the height of summer!