Just google "planting a prarie" and you will get several sites that discuss options for site preparation.

Creating a wildflower garden is not simple, as I found out. The inherant weeds will always win out. So, it is imperative that you guarentee to yourself that all weeds are dead before you spread expensive wildflower seed around. Also be careful in selction of seed. An awful lot of these so called wildflowers are control freaks that will over power everything else. In my case, the only thing that survived my first attempt was wild achillia. And it smothered everything. It took 2 years to eradicate that stuff. One little sprig in Spring became a 1 square foot area by fall.
I have a similar size area as yours that I am reclaiming this year that is overgrown with canary reed grass. My techique: I burned all the grass off in early spring. Then, the canary reed grass is so aggressive that it pushes up first. Then I sprayed it with heavy concentration of Roundup. I'm not afraid to use chemicals to get rid of non-natives. I will repeat the process again next Spring and then that should be it. Instead of just throwing seed on the ground, I'm moving sunflowers, Echinaceas, Rudbeckias, and other type prairie plants into the died out areas. They will reseed on their own very nicely once the bad grass is killed off.

For an area that size, I would smother it for the entire growing season. Cover the area with a tarp or black plastic and thick mulch now and leave it there until fall. When you are getting ready to plant, slide the plastic and mulch aside, and then seed the area. You can cover the seeds with the mulch and then fold up the tarp for use on your next planting area.

Make sure you get your wildflower seed mix from a reputable native plant source. Do not buy them from the local big box retail store.

To make sure all the grass roots are killed of you should cover with black plastic for AT LEAST a year. I normally use old, natural fiber, carpets as they do the same job, let in water and air to keep the soil good and finally rot down into the soil. If you use really heavy carpeting it can go on the compost heap after it's done it's job on the grass area.

Good Luck with your Wild Flowers.

JanAdy

Thank you

The short answer is smother it, or strip it, or poison it (or combinations of these).

dont forget when digging deep down there are many dormant"WEEDS" that are very nice wildflowers.the distinction between weeds and wildflowers is none.Nothin more beautiful than a buttercup meadow,nettles have a myriad of uses both medicinal and functional.All weeds are part of the same club and as ancient members all have their own niche and role.
john

I would thoroughly water before you put down the plastic. Wet grass seems to die more quickly than dry. If you have ever had a 'slip and slide' in the yard and left it out a little too long, you've discovered how effectively plastic can kill wet grass. In a week a slip and slide can permanently kill a lawn, and I have a rectangular dead spot in the yard to prove it! I still would leave the plastic on for all summer, just in case.

I just came in from using a propane torch on a similar size area of my front yard. I thought of smother, but that did not sound like fun. And I have young kids who suck their thumbs, so herbicides were not an option. Too big an area to cut sod, and cultivating would just break up the grass roots and expose weed seeds, so that would be two steps backward. I figure I'll have to burn it several times to exhaust the roots, which will take some time, but gosh it is fun. (FYI, I had water handy and good solid burn breaks and was careful to burn right after a rain so there was no danger of creating a suburban "wildfire."

I strongly agree with the recommendations to smother & WAIT. Think of this as a long-term project. Immediate results are not likely to be the best results in the long run.

In my experience, weeds are one thing -- grass weeds are another beast altogether.

I like the idea of using natural fiber carpet rather than plastic b/c the water can still get through. Otherwise, you can have runoff issues. If you start this in the summer, you'll have an even better chance of killing off everything. I know it's been several weeks since you started this thread, but in Dallas, we're in the middle of a run of triple digit weather, so its the perfect time for us to smother.

If you haven't started yet, "GOOGLE" lasagna gardening, in my opinion this is the easiest and most satisfactory method. Good luck and welcome to the interesting lawn group. Rai

Well a couple of months ago I got a bucket and a mop. I put roundup in the bucket and mopped a light application on the lawn. It's easy to see where one has mopped as long as there isn't dew on the ground. The area is still dead to this day, with only one or two weeds poking up. I'll spot apply again this fall. I'm going to seed with mostly annuals and review where I am with weeds and such this time next year.

I am sure I am very late to this thread, but I just came accross it. I recently wrote a piece on my new blog about removing a lawn- it might still be helpful or pertinent.
Good luck!

Here is a link that might be useful: Montana Wildlife Gardener