smothering old flower bed with black plastic (lawn, landscaping, growing)

[flatlander52]

Hello fellow gardeners! I live in WI.
I have an old crappy flower bed that I want to renovate. It's about 4 ft x 30 ft and all along the east side of my house.
So far, I have cleaned all the 'winter rubbish' out, and bought a roll of black plastic. There is some green growth showing already,
2" to 4" high.
There are a few plants I want to save, like daffodil bulbs and tall phlox from my Grandma, some autumn crocus, and a few bearded Iris.
So I plan on digging those out and moving them before I put down the black plastic, then anchoring with rocks and stakes.

I've never done this before, so I have a few questions...

1) Should I let the soil warm up more before I lay down the plastic? We have had some 60s, 70s, and close to 80F here during the day,
but it cools down at night of course. How do I know when all the frost is out of the ground? Or does it even matter?

2) How long does it take for the heat and lack of air to kill everything underneath? 2 months? 4 months?

3) There is lawn right next to this bed I'll have to mow, so it might be tricky to keep the edge anchored down but keep mowing the grass

4) Do all the roots die too? I hope so, there is some real nasty- I mean, really invasive- ground cover in that bed,
I think it's called Gout weed or Bishop's weed. There are also lots of wild orange daylilies.
I want all of these 2 plants DEAD!

5) Should I use Round-up on the plants before I lay down the plastic?


Any other advice? Thanks!

[flatlander52]

anybody? PLEASE help. or should I just use Round up?? I only have 2 or 3 months to do this.

[nuts2uiam]

I am not sure the plastic will work. When starting grass seed we would always cover with black garbage bags to cerate a "hothouse" effect to get the grass growing so I don't think that would work but I have no experience with what you are speaking about.

[jambo101]

wont be heat and the lack of air that kills everything under the plastic it will be the total lack of sunlight.
I'm not a big fan of spraying herbicide all around the house as it could have detrimental effects on pets and local wild life. I'd go with just the plastic for a couple of months then a thorough dig out of the remaining dead plant life..

[Wilson513]

Plastic looks opaque but it is not. Only the thickest plastic will kill everything. Not really a good choice. Round up then till it all in.

[jimboburnsy]

A cheap solution that, IMO, is better than landscaping fabric or plastic:

Old newspapers. Surely you, like everyone else, have a shopping bag full of old newspapers somewhere in the garage, right? Dig out anything you want to keep, cultivate, cover with a thick layer of newspaper, cover with potting soil or whatever you will use in your flower bed, re-plant your keepers.

[flatlander52]

Jambo, yes, lack of sunlight too. I can't dig it all up, I have a bad shoulder and a bad thumb/wrist.
That's why I'm trying to figure out an easier way.

These 2 plants have taken over this flower bed. I had a concrete driveway and sidewalk installed over part of this bed a few years ago, and the next spring they were coming up in a tiny crack between the sidewalk and the foundation of the house! The gout-weed spreads like mad and you can't keep up with it. I call it the plant from hell

[J&Em]

Goutweed does not respond well to most natural ways of eradicating it so glyphosate (Roundup is the commonly used one) is often recommended to get rid of it, and even then it requires monitoring and reapplication and plain old fashioned hand weeding. Solarizing has been somewhat effective as has cutting frequently when it is first growing in the spring.

I think what you are talking about doing is solarizing the soil in your garden. You need a clear plastic tarp for that. It kills plants, insects and bacteria in the soil by cooking it under plastic. It has to be done the right way or it isn't effective, and in cooler places it takes longer. Here are a few sites that describe the process:

http://www.ipm.ucdavis.edu/PMG/PESTNOTES/pn74145.html

Solarizing Soil | Horticulture - The Art & Science of Smart Gardening

[Butterfly4u]

Flatlander,
You don't need the plastic at all.
Buy 4 or 5 big bottles of Round Up.
Spray everything that is green.
Wait 2 weeks, then spray everything that is green.
Water it after 3-4 days after the first application.
Encourage anything that lived after the first application to grow back.
When it gets nice and big, about 2 weeks, spray it all again.
You should only have to do this 2 times.
In any case, in about 4 weeks, you should be able to plant
what you want.
Apply alot of mulch after planting the bed.
Don't let a piece of ground go uncovered.
Round up only works on the green growth, so that is why
you water it and encourage what ever is alive to grow again.
Use it on the bed freely throughout the summer, just protect
the plants around the weeds with something when you spray.
Try it, it works.

[cittic10]

Laying down plastic will sterilize the soil, except it has to be clear as someone mentioned and even then it takes a really long time. You don't want to do that.
I wouldn't recommend roundup around a food garden or any garden for that matter.
USe a hoe. It's gardening... It takes work.