Mould in polytunnel

[bario1]

Hi all,

It's been my first year with a polytunnel - admittedly i didn't get it up (oo-er-missus, let's get that out the way) till late in the season, maybe July, so i wasn't expecting much from it - but it hasn't been great. The toms and aubergines i put in there all succumbed to mildew once they were fruiting, and this seems to an issue, there's too much moisture in there or something. I put pak-choi in pots in there recently, and some in my cold frame - while the cold frame ones are looking good, the ones in the tunnel haven't done much, and there's a layer of green slime on top of the soil in the pots. Even a jacket that i had hanging in the tunnel got covered in mould!

Is there a way to increase ventilation, or is the problem something else? It's a decent quality polytunnel with a clear polythene cover and wooden framed half-mesh doors at each end. It is small though, at 6x12'.

Is it normal to see this level of moisture?

Any thoughts appreciated.

[Alison]

What sort of tunnel do you have? Also did you leave the doors open in the summer to increase air flow? Maybe it would help if you put up some photos of the tunnel so we could understand more of the problem, however mould is usually caused by damp and no air flow. Does sound quite severe though, especially if your jacket got mouldy, how long did this take? Another question, how are you watering inside the tunnel, you could be adding too much water which would exacerbate the problem. I do get some condensation in my tunnel but if anything it's rather on the dry side in summer, mine's quite a bit bigger at 10' x 20' but you shouldn't really have the problems you describe and it obviously should help not hinder your growing.

[Bill HH]

I erected my tunnel a month ago and put in a lot of containers (Onions garlic etc) and my geranium cuttings etc, these were sodden wet from rain and that moisture seems to be hanging round alarmimgly. I do ventilate it but its so damp outside that it doesnt seem to be drying things out. In the end I have used an old dehumidifier that we bought from argos some years ago. It is helping, I take out at least two litres a day.Its only a small cheap one and uses 600watts, I only put it on for a couple of hours a day. Once dry I will be economic with the watering to avoid a reoccurance. My tunnel is on a paved area and when it rains the rain seeps under it so thats another area to attend to, if yours is on soil I think quite a lot of moisture will come up from that too.

[bario1]

Thanks for your replies - yes i did open both doors on hot days, one door when it was cooler, and have left both closed since the weather turned cold - i assumed the netted door vents would be enough, and wanted to conserve any heat. I don't think watering was the problem, i just watered the growbags and pots that were on the (soil) floor when they were dry. I stopped watering a couple of months ago because i noticed how damp it was in there. The jacket had been hanging there for a couple of months, i just noticed the mildew creeping up the arms yesterday. Possibly the problem is the site - the ground never drained well, that's why i put the tunnel there - i thought it might dry it out a bit. So, as i'm about to remove all my mouldy toms and aubergines, here's a few things i might try before next season to alleviate the problem:

Put in raised beds - i was going to do this anyway, but didn't have time when i erected it.

Dig a drainage channel under the central path with a pipe taking water away from the site.

Rig up drainpipes along the sides of the tunnel to divert rainfall into water butts at the side of it - this would be handy anyway, and might stop the ground under the tunnel from getting waterlogged.

Do these ideas sound any good? Does anyone else have suggestions? Bill, a dehumidifier is out of the question as i don't have access to electricity...

Cheers.

[Bill HH]

If the moisture is coming up from the damp ground, and I expect it is I am not so sure you will get rid of it by drains under the tunnel unless you can route them well away from it, more likely they will fill with water and make it worse. Maybe your best bet seeing as your putting in raised beds would be to cover the floor with a plastic sheet and then slabs or at least something to stop the moisture rising. The only other solution is to relocate the tunnel to a dryer spot.
You could try digging trenches round the tunnel and filling them with gravel to act as a drain providing its got somwhere to drain to. Its better on the outside than inside the tunnel as that will just hold the moisture and send it back upwards. That all sounds a bit jumbled but I'm sure you know what I mean,

[bearded bloke]

If the soil is perpetually wet by placing your poly tunnel on it you have basically created a humidor (great for epiphites ),you need to prevent the perpetual loop of evaporation to condensation,as ventilation at the ridge is not an option drainage channels to clear the excess water would be the way to go I think