Beginner Gardening: Growing wildflowers - where do all the weeds come from???, 1 by jzempel1

jzempel1 wrote:
This year I opened up a long strip of land (about 100 ft. long by 2 feet deep) in my back yard in front of the wetlands, with the intent to grow some annual wildflowers. Here is the history what I did and when:

- last summer I used my mower to mow close to the ground to cut the wetlands down to ground level ( to extend our yard back a bit)
- i tilled the new open area, and we brought in more dirt to level out the back yard in front of the wetlands
- we put landscape fabric and mulch over the new dirt (between the wetlands and our established yard)

- this spring I decided I wanted to TRY to grow wildflowers just in front of the wetlands, so I pulled up and cut out the landscape fabric (about 2 feet deep), and tried to rake out the weeds,
- I tilled the dirt along this long strip in front of the wetlands
- I added about 2 inches of a mixture of top soil and peat moss, and tried to rake or hand pull out all the weeds
- In early May, I planted various packets of wildflower seeds, sunflower seeds, zinnias, cosmos, allyssum...
- I watered some days, but not everyday as I should have (as it was a dry spring), so i think i lost a lot of my planted seeds

Result:
My sunflowers are doing great! I also got lots of cosmos, allyssum, some zinneas, lots of milkweed (i left many of these to attract monarchs), a few other wildflowers that i don't know the names, but mostly LOTS OF WEEDS!

OK, now I admit that this was an experiment and I didn't keep up with the watering as i should have (as my perennial beds and roses keep me busy, too), but my question is where do all those dog-gone weeds come from??? After some helpful weed identifications on this site from you all, I have pulled lots of pigweed, thistle, velvetleaf, ragweed, and other weeds. I'm just so surprised at all these weeds, as most of them don't even appear to be in the wetlands that are behind this new open dirt area.

Please let me know what I could do so that I can have better luck at this next year. I'm not sure that I want to do this again, since I unfortunately got more weeds than good wildflowers. I may have to just divide some of my "wilder" perennials (purple coneflowers, black-eyed susans, daisies, bee balm, ..) and move them back there and surround with mulch, as this may be an easier to maintain than attempting wildflower seeds on open dirt again. Do you have any ideas for me?