Daisy fleabane and related species of Erigeron
These plants are common in waste places and they often come up in gardens too--many are pulled as weeds. But many of these beautiful daisies are native plants. They are in a family of plants know as composites, and they are characterized by "flowers" that are actually inflorescences. This whole family has specialized in grouping many tiny individual flowers together into an inflorescence that acts to attract pollinators. So when a bee visits a daisy, it actually can pollinate many flowers with one visit! This is apparently a very successful evolutionary strategy because the composite family is wildly successful.
If you want to be sure which species of fleabane you, you will need to examine the hairiness of the leaves and how many white ray flowers are in each daisy. Erigeron philadelphicus may have more than 300! Erigeron annosus, pictured at the left, has more in the range of 50-100 or so.
We love to see these along the trail because they have features that make them valuable for pollinators and other animals--a long bloom time and lots of nectar and pollen. They colonize disturbed areas that might otherwise be filled with non-native species that have less value to wildlife. The fleabanes are aggressive enough to compete with some of the invasive non-native species that occur in lots of places.
It isn't really clear why these plants have been called fleabanes, which would imply that they can repel fleas. There doesn't seem to be much evidence that they produce chemicals to repel fleas. Those who are devotees of these web pages may have read about bedstraw and new ideas that the sticky hairs on this plant actually might impale bedbugs or other pests. Some of the fleabanes are quite hairy! It might be an interesting study to see if the flea-repelling reputation of these plants comes from using them as a physical repellent instead of a chemical one.
The image at the left shows the characteristic hairs on Philadelphia fleabane. http://www.bio.utexas.edu/courses/bio406d/images/pics/ast/erigeron_philadelphicus.htm