Hello, and welcome to the latest installment of the roadside flower series. This particular batch was all (with two exceptions) taken on Sunday, July 26, so they're not quite August flowers, but I figure they're all probably still blooming today, so it's close enough for PATSP. All of these pictures (again, with the two exceptions) were taken along the side of gravel roads between Iowa City and Lone Tree: not in somebody's garden, not in a park, just there next to the cornfields, getting covered repeatedly by gravel dust, soaking up car exhaust.
As always, the IDs are a little sketchy, and there are a few things I couldn't ID at all, so anybody who wants to suggest or confirm names is encouraged to do so. In fact, let's just begin with a kinda ugly NOID:
UPDATE: Lynn'sgarden, in comments, suggests wild mustard. There appear to be a few different things going by that name, in the Brassica, Hirschfeldia and Sinapis (on some pages, spelled Synapis) genera, some of which may be obsolete names. I totally agree that the flowers look like they belong in one of those, but I can't pin it down to any species in particular; the flowers all look more or less the same, but the growth habits never manage to match up right. Call it pending.
SECOND UPDATE: I lean toward Brassica rapa, I think, even though most of the B. rapa pictures I found don't look quite right, because this is for sure the same plant, and that's how it's identified there.
UPDATE: Thanks to Claude in comments, I have switched my guess to Physalis longifolia, or common groundcherry, which is the most common wild Physalis species in Missouri, according to this site. The leaves also match.
UPDATE: Rosemary, in comments, suggests that this is probably prairie coneflower, Ratibida pinnata, instead of Echinacea paradoxa. I am especially pleased to know this, because I was passing on someone else's misidentification before she told me this. I'm sure it happens more often than I'd like, but I do try not to perpetuate bad information.