New garden patch, all weedy: smothering but how?

linaria_gwJuly 18, 2014

Hi there
I garden on an allotment, small thing, about 2'200 squfeet ( we rent it from the city council for as long as we want)
Our neighbour quit after years of neglecting her place and we just applied for it and got it now, after 3 other persons had turned down the offer.

It's covered in bindweed (Convolvulus) which has been spreading for years, some dots of a nasty weedy grass (Elymus repens) and just rounded off with mainly borage.

Glyphosate or any other herbicide are not allowed. I found an organic herbicid though, wich I will use on the bindweed and couchgrass once.

It is supoposed to kill off some roots, but strong established plants most likely could resprout.

So, I thought to cover the worst parts with something for a year or so, to kill off the permanent weeds for good.

My first thought was sturdy black plastic sheets (UV- resistant), from a farmer's shop.

But I got second thoughts whether the soil life and all the nice bugs and worms would die as well. The other option would be cardboard and/or newspaper.
Would probably last for a year if I put down thicker layers, holding it down with paving stones and things. Only problem is that the soil is not very level, so spreading newspaper could be a challenge, even if we flattend it somewhat first.

Or I do a mix. Plastic onto the area with the worst bindweed infection, the rest with papery stuff.

Any thoughts or comments?

We do have some time and planed to start planting some berries or fruit trees in autumn 2015, and perhaps growing green manure or annual flowers in larg areas in 2016 ( dear me, that sound like, quite a long way to go...)

So thanks for your thought, bye, Lin

And that is a pic of the patch

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prairiemoon2 z6 MA

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.

    Bookmark   July 18, 2014 at 3:27AM
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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

    Bookmark   July 18, 2014 at 4:17AM
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just had an idea, how about a layer of cardboard to block some light and then clear plastic on top?

    Bookmark   July 18, 2014 at 4:20AM
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aachenelf z5 Mpls

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.


    Bookmark   July 18, 2014 at 4:27AM
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aachenelf z5 Mpls

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.


    Bookmark   July 18, 2014 at 4:30AM
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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

    Bookmark   July 18, 2014 at 4:43AM
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woodyoak zone 5 Canada(5b)

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.

    Bookmark   July 18, 2014 at 10:36AM
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prairiemoon2 z6 MA

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

    Bookmark   July 18, 2014 at 11:38AM
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Cardboard worked for me.

    Bookmark   July 18, 2014 at 11:52AM
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woodyoak zone 5 Canada(5b)

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.

    Bookmark   July 18, 2014 at 11:53AM
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mad_gallica(zone 5 - eastern New York)

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.

    Bookmark   July 18, 2014 at 11:58AM
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prairiemoon2 z6 MA

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.

    Bookmark   July 18, 2014 at 12:07PM
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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.

    Bookmark   July 18, 2014 at 2:13PM
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greenhearted(5a IL)

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.

    Bookmark   July 18, 2014 at 2:31PM
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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!

    Bookmark   July 19, 2014 at 1:45PM
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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

    Bookmark   July 25, 2014 at 1:54AM
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prairiemoon2 z6 MA

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

    Bookmark   July 25, 2014 at 3:33AM
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greenhearted(5a IL)

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

Happy frying! =)

    Bookmark   July 25, 2014 at 12:15PM
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aachenelf z5 Mpls


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.


    Bookmark   July 25, 2014 at 4:03PM
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karin_mt(4 MT)

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

    Bookmark   July 25, 2014 at 6:42PM
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