new garden spot - cover w/ plastic to kill weeds over winter?

We excavated for a new patio in the spring and have a large berm of relocated topsoil that's just right for a pumpkin patch next year.
The berm is totally covered in a very common weed here in NC - looks like bamboo/grass, easy to pull, grows 2ft tall or so. Just mowed it down, but was wondering if I could kill the weed seeds by covering it now w/ black plastic until next May.
Have ordered Dills Atlantic Giant pumpkin seeds - anyone have any experience in nc growing these? Should I ammend soil now in preparation for next year? thx!
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I have heard that covering soil with plastic isn't a good idea. It has something to do with the air not being able to get into the soil, as well as problems with the water getting in. Apparently it can make the soil sterile or at least not the best for growing things well. I think mulches of almost ant sort are a much better solution.
Jen
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Yes, when done properly it's 'solarizing' the soil. Black plastic laid down, with a few large rocks or other objects which give a bit of air underneath here and there is all you need. Over the winter, the heat generated beneath the black plastic will of course cook all the weed grass, and as an added bonus also cook the thousands of dormant weed seeds the excavation brought up. If it was me, I might also lay down as much organic material as possible (yard clippings, leaf mulch, etc.) before the black plastic. All that material will compost and make a great topsoil layer.
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David J. Bockman, Fairfax, VA (USDA Hardiness Zone 7)
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Where I live in Ohio I've done this with plastic several times, but in the summer. I doubt if it's hot enough here for it to work well in winter. I've never grown pumpkins, but I grow watermelons every year. With those there's only a small area that the vine roots in, the rest is the sprawl of the main plant. I've used plastic for this area, but now I use newspaper covered with grass clippings and leaves. It's important to set up drip irrigation on the root area before planting, as you can't get to it once things are really growing. So maybe you could do something like that, dig up the grass in your rooting area, and put down a mulch that will stay through next season where the vines will sprawl.
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I had better luck with corrugated cardboard boxes. I happened to have a lot of them after moving into a new house. Laid them over the soil, covered with leaves, hosed it down heavily, and it pretty much stayed put all winter. It was easy to chop up with spade & fork in the spring, except for a few boxes whose packing tape I overlooked.
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I've heard that thick bunches of newspaper are good too, especially if covered with heaps of mulch. And it can all be dug in later to improve the soil as well.
Jen
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Quite doubtful. If you're willing to forego a year's pumpkin growing, you can solarize with clear plastic, but unless you think you can get the soil temp up to about 140oF this winter, you're not going to do yourself much good. (BTW, don't cultivate the soil after solarization, you'll bring up viable weed seeds from 6" or so down.)
FWIW, clear plastic works much better for heating the soil; black plastic really just keeps light out, and it's expensive and messy compared to a lot of other mulches.
Is the weed you're trying to control annual or perennial? If it's an annual, I'd just dig the bed over now and in the spring, then use a light- occlusive mulch when you plant your pumpkin seeds. Cardboard is great for this; it's a nice clean mulch, so helps control some soil borne diseases, helps keep the soil moisture even, and you can dig it in next fall with no muss, fuss or bother. <g>
If it's a perennial you're trying to control, it's best to identify the problem. Sometimes breaking up a perennial weed with cultivation is the wrong thing to do... things that have "runners" like quackgrass or nutsedge just start new plants from broken bits left behind in the soil. Or they'll "hide" under your mulch and send out new plants just beyond the mulch. Other perennials are relatively easy to control with a good digging-over of a plot.
Kay
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Note that something like bamboo can easily penetrate a clear plastic.
Kay Lancaster wrote:

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Also black plastic, wood, asphalt, concrete... depends on the species of bamboo being grown.

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Kay Lancaster wrote:

The weed in question is almost certainly Japanese stiltgrass (Microstegium vimineum). It's an annual. Using a layer of mulch around the pumpkin plants will minimize the germination of the stiltgrass seeds, and any seedlings that do appear are very easy to weed out, due to the weak roots.
Cutting the existing stiltgrass now will prevent it setting seed. Repeat the mulching, weeding, and late season cutting for several years to get rid of dormant seeds in the soil.
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