Ragwort (Senecio, ?)

This would appear to be a member of the Senecio Genus (Ragworts) which in turn are part of the larger Daisy (Asteraceae) family. This may be a Senecio plattensis, but it appears to have a different base leaf than the sample shown in Missouri Plants.

I have yet to take the picture that shows their peculiar growth pattern, often standing alone, like sentinels in short new-grass pastures.

For a larger introduction to all things senecio: http://en.wikipedia.org/wiki/Senecio