Just two, actually! These were found, again, in my garden gone wild in Northern California. The first picture stands alone, but the next two are of the same plant.
Wow. I just did some research, and it turns out that of the 14 flowers I've had you guys identify, only two are native, and a lot of the non-native ones are invasive. Is the situation this bad all over, or is it just particularly bad in disturbed areas (gardens, etc.)?
The answer is C: both A and B. The fact that it is disturbed soil, with a home that has been on it for a while means that there were many opportunities for invasives and nonnatives to colonize there. Some may have been directly encouraged, but most came in as seed from some source. Could have been tracked in on shoes or trouser cuffs, by animals, wind, flooding, or even in organic material brought to the gardens. But yeah, nonnatives are everywhere. Invasives may be more prolific in some areas, but are also found everywhere.