Disclaimer ..... I don't know what this is and US natives are outside my experience. However, since nobody has come up with anything on this I'll say what it makes me think of. I get a sort of Scrophulariaceae feeling when I look at this. Something like a Mimulus or figwort. The wet site would support this hunch. The coloration may be a defining feature or it may be just a one off aberration in this particular specimen. Maybe someone else can take this idea further.

Wow!! it is *definitely* Salsola soda... Thank you, tyrlych... So maybe I should think about getting into the glass-making business?? (S. soda was historically used to create 'soda ash', which was used to create reliable, clear glass).

Ok, I'll bite. The first thought that comes to mind is Carphephorus paniculatus, but that isn't found naturally in Missouri. Which leads me to the closely allied genus of Liatris. So I'll guess Liatris aspera or Liatris pycnostachya. Both are native to Missouri, and both are found in moist areas. (Liatris spicata is also found in moist areas, but its stem lacks hair, which appears present in your photo.) Here is a link that might be useful: Liatris aspera

Wildflower seeds would probably fail. There are, however, a number of things you could plant that would not harm the wetland but spruce it up a bit. You could plant things like sedges, rushes, water iris, pickerel weed. These would add color to the area and still be very natural so that there would not be any problems with the agencies that established and/or oversee the area.