watering the polytunnel

[hedgewizard]

I just listened to an oceanographer speaking about why the water companies are doing hosepipe bans while the weather has been so wet. The gist of it was that the latter part of the summer is forecast to be hot and dry, so I'm going to get some leaky pipe and so forth to reduce my water usage in the garden.

The thing is, I'm new to the whole polytunnel business, and have a 24'x14' basic model (no raisable skirts or anything) with 6'x6' doors at each end. I have hanging shelving (although it's not up yet) and 18' deep soil beds. This year I'm growing saladings, cucumber, tomatoes, early carrots, caulis, and chillis. I've got overhead spray watering, but I'm thinking it probably will only get used on a timer when we're on holiday. Bernard Salt's book (Gardening under Plastic), the only book with much about tunnels that I can find, is as good as useless on the whole watering deal.

So, folks with experience, what's the deal on watering in a tunnel? Is it worth putting heaky pipe in those soil beds, or is that (along with the overheads) going to be too indiscriminate?

[ina]

When I worked in a market garden, I spent at least an hour every morning watering the tunnels, often more. We did have some sprinklers (although not fancy overhead ones), and I believe a leaky pipe in one place, too - but most of it was done by hand. That way you can water more individually, without having to move equipment round frequently. (We had five tunnels, one of them quite large - so it won't be too bad with your one!)

What's really import is ventilation. It does get hot some days - and then the tunnel can heat up enormously, which means opening up every hole that's openable! Might be a bit of a problem when you go on holiday - or go at a time when it's unlikely to get cold, and leave everything open.

[hedgewizard]

Might be a bit of a problem when you go on holiday - or go at a time when it's unlikely to get cold, and leave everything open.

That's kind of the plan, not that we can afford a holiday after the building work! What about when to water? Salt says "polytunnel plants should not be watered until they show early signs of dryness" but frankly that sounds like a crock to me. How do you know?

[ina]

Isn't that typical of these clever books... How can you say? I've no idea. It's all down to experience, I suppose. The only thing you could do - don't go away for long when you've just planted everything up. Wait until you've kind of worked out how much water it needs, and when, and how often. There's also "special needs" of certain plants that you'd have to consider when arranging them in the tunnel - some like higher humidity (cucumbers), others like it drier (tomatoes), so plant the first in a corner where there's less ventilation etc. But really, you can't solve all the problems in the first season, so don't expect it to be perfect.

[Wombat]

G'Day Hedgie,

Nice to see you back!

Consider mulching heavily, or maybe the chinese style where you use two large watering cans connected by a yoke over the shoulders.

Nev

[Martin]

picked up a really nifty gadget at a boot sale for a fiver - a "hozelock" auto watering timer - you shove your water supply in one end, a couple of batteries in the back, the outlet to the leaky hose, and then there's several choices of time/length of waterings! 8)
i Haven't tried it yet, but it should work well from a water butt

[hedgewizard]

Yeah, I've looked at watering timers but my main concern is that leaky pipe waters all along its length indiscriminately. (I could run it in both directions from the middle of a bed with taps each way but that's getting too fiddly for me.)

Cucumbers wanting higher humidity is a valuable bit of info Ina, no idea how I'm going to implement that... perhaps putting the cukes at the end I open least would be best next year. I'm going to invest in a moisture meter so I can get some idea of what's going on under the surface of my beds - they're actually 50/50 rough (woody) compost and topsoil and because it was such a big job I didn't bother mixing it; the bits where the compost is on top always look dry no matter what so the meter might help. I'm hoping.

I think I'm going to go for a short length of hose in the tunnel with a sprinkly end on it, with short stakes hammered in at the corners of the central bed so I can't accidentally pull the hose over it. I'm thinking that will be handy when I'm in a hurry, and I can fill a Hawes can from the butts when I'm not. The hose can also link onto the overheads when I'm on holiday, through a timer. But the leaky pipe... I'm not sure it's going to be useful in the tunnel since watering needs vary a bit. Sound about right?

[Boots]

I'm not sure if your polytunnels work the same as our greenhouses.... Probably not...

I don't like drip irrigation much (though I know orchardists always rave about it). That what you mean by leaky hose? Pretty useless if you have trays of seedlings, and lots of containers etc. but maybe you have full beds in there? Or just plant into the ground? Not sure what it is...

I use mist sprayers, which are pretty much great for everything we put in our greenhouses over here. I have one hose that loops up one side of the roof and back the other, with probably about 8 sprayers in there (those lil black screw in ones). I flick it on once or twice a week for about ten minutes (or longer if I forget). I don't buy that fancy black stuff, I just bung them into normal garden hose and clamp the end.

Bugger the watercan and individual watering... don't have time for that.

[hedgewizard]

The overhead system that came with the tunnel is a sprinkler type, probably not as fine as mist but I so far haven't been arsed to put it up. Leaky Pipe is a branded porous recycled rubber hose that sort of "sweats" water into the soil and lasts for a good long while. Yep, it's only any good for ground watering, and works best if it's just covered with mulch or soil or something. I'm using drippers for the orchard though.

Don't know about the differences with glasshouses and tunnels apart from tunnels diffuse the light, so there are fewer problems with shading... but they're crap insulators so they get cold at night. Figure that shouldn;t matter down here in Darrr-set though!

[ina]

tunnels diffuse the light, so there are fewer problems with shading...

Don't let that fool you into feeling safe from the sun - we had quite a few (smaller) plants affected by scorching, when we didn't get round to pulling the shades across on sunny days! early enough And that in rainy West Scotland... A bit of fleece helps. In one tunnel we had that fixed to the roof somehow with string (blue baling twine??? ), so that we could pull it over when necessary. I suppose once the plants are large and strong enough, you'll be ok.

Our cucumber tunnel had a small pond at one end - it helped with humidity, and was home to a frog - who helped with the slugs! And the tomato house had a lot more ventilation. I tried to do something like that here in the tunnel I can use (which is far from perfect), putting the tomatoes on the drafty side, and keeping the ground wet around the cucumbers. Unfortunately, all the cucumber plants I ever bought died on me . I think I picked one gherkin sized fruit one year, of two plants... Don't know whether I'll dare try again.

[hedgewizard]

Yet more useful info! Thanks Ina, with some sunny days forecast I reckon it's about time I threw the shade netting over and pegged it down pronto. So what was this multi-tunnel-with-pond setup you had, and what do you have now? I don't think I can stretch to a pond in mine!