Is this a good idea?

[LostInFrance]

Hiya. I'm new to this polytunnelling with my first 6x3m tunnel. I have an idea and want the experience bank's thoughts on this.
I've left one side of my tunnel bare earth for salads, onions etc but on the other side, I've laid a sheet of roof underlay felt (Protect stuff). It's black and waterproof - obviously lol
My thinking was I could cut squares out of the felt for toms, peppers, aubergines and water in the squares (or use a cut off coke bottle upside down to give a 2ltr watering pot direct in the ground near the plant). Is this a good way of keeping the weeds down & retaining moisture of does it need to be weed fabric?
Thanks in advance

[donnakebab]

I'm not an expert but I wouldn't use it for the same reason that some people won't plant in old tyres.

What's it made of?

[roitelet]

A friend of mine uses old slates for the same purpose and it works fine. Keeps the weeds down and moisture in, a mulch of sorts. Just check what the material is first.

[Potstubsdustbins]

Modern roof underlay should be OK . It is usually made from polyolefin (permeable) or polyproperlyn Impermeable). Its the old stuff with tar in it that could be naughty.

Colin

[LostInFrance]

Modern roof underlay should be OK . It is usually made from polyolefin (permeable) or polyproperlyn Impermeable). Its the old stuff with tar in it that could be naughty.

Colin

TY Colin. It's the modern impearmeable stuff. Thought I'd cut out foot square pieces for toms etc. Think it would be good to flood it in the summer to raise humidity in the tunnel?

[Snadger]

One problem I can think of is that it will be an ideal hiding place for nasties like slugs etc.............

Basically its an inorganic mulch that should help to conserve water though

One other thought is that because its black and in a greenhouse, it will absorb heat and might melt?(like road tar on a hot day, and bitumin is poisonous to plants)) or cause enough heat to scorch the roots?

Sorry to be a merchant of doom, but unless someone can come on here and say they've had success with it,I personally would give it a miss.

[Potstubsdustbins]

It may be my typo, it should read polypropylene. No worries about tar like substances there ain't any, thats the old stuff. No worries about melting general melting points 130`C to 171`C. Roofing stuff usually 155`C. You can recycle it code 5.

Slugs well thats another thing altogether.

Colin

[LostInFrance]

One problem I can think of is that it will be an ideal hiding place for nasties like slugs etc.............

Basically its an inorganic mulch that should help to conserve water though

One other thought is that because its black and in a greenhouse, it will absorb heat and might melt?(like road tar on a hot day, and bitumin is poisonous to plants)) or cause enough heat to scorch the roots?

Sorry to be a merchant of doom, but unless someone can come on here and say they've had success with it,I personally would give it a miss.

Hi,
Think that's a good description, inorganic mulch. It's one of the new woven roofing underlays. No bitumen. Have made a start today, too wet to do much else out there and will keep this updated. It just may work? Have cut 22 pockets out as flaps to fold under the sheet & plant through. Just need to think of 22 plants to fill them with lol

[Aberdeenplotter]

One other thought is that because its black and in a greenhouse, it will absorb heat
.

Spot on Snadge. There are three major problems to overcome when growing in a polytunnel. Moisture evaporation is a problem and the use of a membrane such as clear polythene helps in that respect. However, clear polythene encourages the growth of weeds so that is a no no. Black polythene would normally be the first choice to overcome this problem as it still prevents evaporation of moisture but it does cause absorption of heat. To overcome this problem a white polythene to reflect the heat would be a choice but it wouldn't block out enough light to prevent growth so the ideal choice is polythene black on one side and white on the other applied to the soil black side down with slots/holes cut out for planting stations.

I use this in my polytunnel where I grow my exhibition onions and the temperature sometimes exceeds 100f.

[LostInFrance]

Spot on Snadge. There are three major problems to overcome when growing in a polytunnel. Moisture evaporation is a problem and the use of a membrane such as clear polythene helps in that respect. However, clear polythene encourages the growth of weeds so that is a no no. Black polythene would normally be the first choice to overcome this problem as it still prevents evaporation of moisture but it does cause absorption of heat. To overcome this problem a white polythene to reflect the heat would be a choice but it wouldn't block out enough light to prevent growth so the ideal choice is polythene black on one side and white on the other applied to the soil black side down with slots/holes cut out for planting stations.

I use this in my polytunnel where I grow my exhibition onions and the temperature sometimes exceeds 100f.

That sounds encouraging AberdeenPlotter. This stuff is black on both sides. One side shiny coated and the other matt with like a felt cloth texture (I guess to help prevent condensation drips in a roof?) at the moment the black is a distinct advantage to help warm the soil but I guess as the sun peeks out a bit more, overheating could be a big problem. I thought about flooding the sheet to help with cooling and humidity levels?

[Aberdeenplotter]

I lay mine black side up to warm the soil before I plant and then turn it over to white side up before I plant. I don't think you appreciate how hot it can become in a polytunnel. Unless you are there constantly, your membrane will quickly dry out and the heat absorbed can be fierceome (spelling?). You could try laying white polythene over your black membrane.

[LostInFrance]

I lay mine black side up to warm the soil before I plant and then turn it over to white side up before I plant. I don't think you appreciate how hot it can become in a polytunnel. Unless you are there constantly, your membrane will quickly dry out and the heat absorbed can be fierceome (spelling?). You could try laying white polythene over your black membrane.

Certainly not a problem today. It's freezing! lol. I take your point though & will be on the look out for a white membrane to pop over the top when needed. This is fun. A touch of high school science mixed in with my peppers lol.

[Aberdeenplotter]

lol, install a few mirrors and add refraction to the mix as well

[Dead Dogs]

A touch of high school science mixed in with my peppers lol.

lol, install a few mirrors and add refraction to the mix as well

Mirrors mostly reflect, ie the light ray bounce of the reflective surface on the back of the glass. There is some refraction, as the light ray travels through the boundary between air and glass it is bent.

[LostInFrance]

That's it - Nearly May & the sun's shining this morning. First Toms going in! Fingers crossed, prays to the gardening heavens lol.