Linaria, I had witch grass at one time. Probably still have a little of it in minute amounts somewhere in the garden. I had a large patch of it that became so bad I gave up vegetable gardening for 2 years. I had tried to get rid of it by pulling and then with a rottotiller which was a big mistake, just made it worse.

The only thing that worked for us was covering it with a very large sheet of clear plastic for a year. We had it left over from an ice rink that we didn't use it for any more, so it was 3ml thick and one piece to cover the entire area and weighed down with bricks. We started it in the spring and it was a hot dry summer that year, so I think that worked in our favor too. If it altered the biological activity in the area, I can't say. There are plants growing there now and I haven't seen any issues.

I don't remember if I tried the cardboard solution before the plastic. Sorry.

Hi prairiemonn,
that is so interesting, that you used clear plastic! I really have trouble locating black plastic sheets, unless I order a 12 feet role by mailâ¦
I thought black was essential, to block the light, but I reckon, blocking water and trapping heat is nasty enough to kill the weeds.

Thanks again, probably lean towards clear plastic.

bye, Lin

Oh,
just had an idea, how about a layer of cardboard to block some light and then clear plastic on top?

Clear or black plastic will work. I used black plastic on a Blvd garden and it killed all the grass and weeds, plus it made the soil temperature go so high, it also killed all the weed seeds in the ground. Once I removed it and planted my garden I had almost no weeds. I still don't.

Yes, it will also kill any organisms in the soil, but most people think as the soil temperature starts to rise, worms etc. simply migrate out of the area and return once the soil temp comes back to normal. In a situation like yours, I wouldn't even consider any other option. Those are some bad weeds you have there!

One other thought: Before you put down the plastic, make sure the soil is very moist. Wet soil holds heat better than dry soil.

Kevin

I wouldn't use the cardboard. Cardboard will block the sunlight and keep the soil from getting really hot. That's what you want - lots of solar heating.

Kevin

Thanks aachenelf,
it`s the little details that matter. And we just had some days of heavy rainfall, so the soil is almost saturated.

And the worms will migrate back, I guess. In my borders, the soil is very well populated and sometimes I spook some big worms when checking the mulch.

Yea, bad weed situation.

The only plus on this patch of land is a great apple tree, half standard, ca. 15 years plus, great cooking apple, with branches thick enough for kids to climb around.
We spare the drip line of the tree canopy and plant lawn seeds in September, edged with square concret stones

bye, Lin

I agree that the plastic is the best option - black if you can get it but clear if you can't. Wet soil, no cardboard makes sense too. What do you plant to plant there? I had couchgrass/quackgrass (what we call that grass....) sneaking into the north driveway border. When I went looking for information on it, I found this from the provincial Agriculture Ministry:

'Common to open areas, it is not found under conditions of continuous shade. Quackgrass can make up more than 90% of the biomass of an abandoned field; however, as shrubs and bushes begin to invade an area, it gradually become less prominent until it is eliminated.'

So the black plastic would have the advantage of shading the soil as well as heating it. I have been adding things to the driveway border to increase shade at ground level and that seems to help. At one place where the grass was sneaking in from the adjacent ditch by the roadside, I planted a division of my big 'Elegans' hosta. The hosta is doing well although it is in full sun (leaves more green than blue and are smaller - but the flowers are huge!) The couchgrass has disappeared from that area. So, you might want to plan to plant the area, after the soil treatment, with things that will shade the ground.

That's interesting Woody, because when I had the witch grass, which I believe is also called Quackgrass and laid the plastic over the area, when I removed it, the only area that still had some left in it, was under the drip line of a large Maple that was deeply shaded. The only explanation that I came up with, is that in the sun, it became hotter then in the shade.

edit: And I should have mentioned that the area I was covering was about 25ft x 25ft

This post was edited by prairiemoon2 on Fri, Jul 18, 14 at 11:55

Cardboard worked for me.

pm2 - I think the relevant words are 'continuous shade' - if there is sun under your maple at certain times of the day as the sun moves across the sky, that would probably be enough to keep some of the grass alive. That's why the hosta here seems to be working well - no sun gets under those leaves at any point in the day! If the grass ever got out of control completely, I'd probably do a big experiment in testing the sun tolerance of a lot of hostas :-) I've got the border planted quite densely, trying to shade the ground as much as possible. What grass still appears seems weaker now and easier to pull out. I currently have a few more open places due to ripping out asters last summer, so I'm watching closely to see if the grass tries to spread into those areas before the replacement plants get big enough to shade the soil. 'No bare ground' is my constant mantra for planting for a variety of reasons - the grass being a big one.

Whether or not clear or black plastic is better depends on how hot it gets in a particular climate. My completely non-scientific rule of thumb is that if you can stand to walk barefoot across a macadam driveway in the heat of summer, it doesn't get hot enough to do the job with clear.

Woody, yes, there is sun moving across that area in the morning and I'm sure the small amount of quack grass left there is being aided by that fact. It's been more than 5 yrs since I solarized that area and this spring I had to go in that area under the drip line and dig out small amounts of quack grass that were left. I also planted it densely with groundcover and other plants after I removed it, so I'm hopeful I won't have much left of it either.

I don't disagree with you, that the grass should travel and increase more in a sunny area. I think the fact the grass didn't die in the shade in my solarizing efforts had to do with how much hotter it became in the sun than in the shade. And since Linaria mentioned she has an apple tree in that plot, I thought it might help to expect she might not get it all under that tree.

I put down plain brown cardboard from broken down cardboard boxes such as are used for shipping or moving - double or more layer in the paths. Wet it down before placing it. Top with the cheap mulch of your choice. I water via drip irrigation. For things planted in rows, I place cardboard between the rows (like beans, carrots) and leave the row open for a couple of inches for the plants. You still have to weed, but only along the row.

Things like bindweed will still try to come up, but only along the edges - they can't poke through the cardboard, they have to run along under it until they find an open space. Again - much easier to deal with due to the limited opportunities for getting above the soil.

There is virtually no other way to deal with bindweed that I know of. It will spread and spread for frickin' ever if it gets a chance. If it is in your garden soil it will be there for YEARS, even if you doused the entire plot in roundup every other week. It's such a pretty little flower - too bad it is so crazy invasive. Every time I pull a bindweed plant out of my raised beds, I briefly consider tossing it all over the fence in revenge for the trumpet vine my neighbor on that side planted - I spend half my summer trying to eradicate all the runners that trumpet vine has sent into my yard. It's grown clear across the whole yard (UNDER it) and up into my rose bushes! However I stay good, and resist the temptation.

I just put black plastic down in a (former) garden that was infested with bindweed. We'll see how it does.

For other weeds , I have used cardboard and newspaper with great success.

I would just use two layers of cardboard and then layers of compost and straw on top. This would save the soil biota. You could plant in this right away if you want. You can't get rid of bindweed once you have it, especially in a situation like your allotment. The roots go down very deep, heat won't kill them. Also, they might just be lurking beneath your neighbor's patch just waiting until the plastic goes away and then they will be back. Here bindweed can grow horizontally two meters in a season. Boxes from the bike shop are the best. Good luck!

Thanks for all the input

We went for plastic sheet as they were easier to find in that quantity, clear, not UVresistant

We plan to take them indoors in Novermber and spread again in March, hoping that they last longer that way.

We managed to clear all and cover a third, and keep going after our holidays.

I felt the temperature yesterday, it was a very cloudy day and the soil umder the sheet felt very warm. And our concrete slabs get too hot to walk on on a sunny day, so I rhink that should work.

So thanks again,

Bye, Lin

Nice neat job! Looks promising. Fingers crossed for you! :-)

That IS very neat! The area I did this in with black plastic looks terrible. Means to an end, I tell myself.

Happy frying! =)

Lin

That looks absolutely fantastic! Even though there aren't any plants yet, it sure is neat and tidy. I think you're going to be very satisfied with the results next year and in the long run, it's going to save you a lot of time dealing with weeds.

Don't be surprised if you see weeds germinating under the plastic. They probably will, but will quickly die as the soil heats up.

Kevin

Classic Swiss, where even disorderly things look enviably neat. Nice work Lin!

Update

So we put down clear plastic sheets in July,

then followed an exceptionally cool and rainy August,

smothering didn't work, it looked rather like a green house with Portulac production.

In September we started weeding the worst annual weeds before they set seeds ( well, most of them),

So that's how the patch looked with all the new growth under the plastic

In fall a friend of mine found black plastic sheets, the real stuff at a farmer's store.

So after much howing, digging and leveling we put down black sheets, worked yesterda and today, right in time to catch the warm weather with temperatures around 68 around the end of the week.

I hope it will fry them properly this season, have a good start after Easter,

bye, Lin

Lin - It's a lot of work. I'm sorry the clear plastic didn't work for you. I hope you have better luck with the black plastic. I wonder how long you plan to leave it in place? A whole hot summer season I hope will do the trick for you! Good luck again! Thanks for updating your thread. :-)

Linaria - I think clear plastic only works in much hotter climates than ours. As you say, with cool temperatures and damp soils it just makes a greenhouse under which the weeds thrive. I used old carpet on my allotment back in the days before it was prohibited because of possible chemicals. Now I use black plastic. It works by light exclusion rather than heat imo. I also use cardboard under a thick leaf mulch but with our frequent rain it disintegrates quite quickly and perennials like convolvulus grow through it.

Oh, that's frustrating Lin! Our very cold winters here made my black plastic brittle and I had to pull it all up because it was ripping apart as the wind blew over it. I had hoped to keep it on for a full year since bindweed is so persistent.

I've decided to just put some grass seed down this week and keep the area mowed for a few years until I can dedicate more time to it. Hopefully by then the bindweed will be dead. Good luck with the black plastic!

Linaria, I wish that I had seen this earlier; I would have tried to turn you away from clear plastic. Solarization is a technique that needs to be done a certain way...or you end up growing plants, instead of killing them. Solarizing relies on high temperatures and lots of sunshine for a solid block of time, two or more months.

Your best bet will be to exclude the light completely by whatever means possible.

Yea well, you live and learn,

in an average summer the temperatures rise to 100 F and slightly more, just not last August....

And I think it slowed down some plants.

So now we have durable, sturdy black stuff in place, areas around the apple tree or which are too stony get covered with cardbord/ newspaper, which I started collecting last winter.

Now I am pondering to buy some thermometer gimick thingy to really clock maximum soil temperatures (there is a sciences nerd slumbering inside me...).

We planed to keep it covered till September, could check occasionally and play with lay out ideas in the meantime. One surprisingly annoying weed or wildflower is pilewort (Ranunculus ficaria) which IME can smother freshly planted perennials and is a nightmare in a veggie plot. Hope we get that stuff removed, well or resort to plan B and plant really tall perennials. :-)

Well than thanks for your comments, bye Lin

I went out this weekend and began clearing last year's plant debris from garden that had been under the black plastic. I was pleasantly surprised that there were almost no weeds, even though it has been uncovered since winter, due to the plastic becoming brittle. All my other beds have a fair number of weeds popping up so I really think the black plastic helped.

The few perennials that I did not remove from the bed due to the bindweed infestation were peeking out - Daylillies, yarrow and a peony. I think this method would have been great if I could have kept the plastic on longer. In any case, I dug out what was left and plan to plant the grass seed tonight.

Good luck with the new method Lin!

Another update,

The black plastic sheets worked and were durable, we removed them in October,

in November I sowed green manure/ winter rye which grew nicely.

now I start digging, turning the soil and planting a rose with perennial border, about 4feet deep, in the front of the alottment.

I went forscented roses, mainly teahybrids, a dwarf shrub and some scented polyanthas, all of them with healthy foliage, I don't intend to spray.

perennials: some Calamagrostis for structure, Geranium at the front, some Phlox and Salvias, odds and ends that I collected for a while, I only hope zhe Phlox wont clash with the roses ;--)

finally getting there, the border will probably need some editing, but the rough direction should be ok.

happy gardening to you all,

bye, Lin

sheets in mid October, sulphureus Cosmos in the background (the role of plastic ran empty before the whole garden was covered...)

And that's from Sunday, after digging, didn't manage to snap a pic of the newly planted bed from today ( not much to see anyway...)

Thanks for the update Lin! (It has been entirely too long since I checked in here - I even forgot my password)

So glad the black plastic worked out for you. What an enticing garden!

The area I was working on I planted with grass seed last spring. It has filled in nicely; and I hope in a few years that the bindweed roots will have been starved for long enough to completely die. I am focusing on trying to remove it from established foundation beds... and making extremely slow progress.

Your plant picks sound lovely!