As always, when it comes to eating wild or garden plants, use common sense. Check a few different sources and compare photos to be sure you have the right plant. If in doubt, don't try it. I'm not an expert. I do research many different web sites and books and don't try something I'm not certain about. Make sure they haven't been sprayed with chemicals. Flowers along the roadside should be avoided as they would have pollutants on them from passing cars and other chemicals.
Flowers contain vitamins, minerals, antioxidants, protein (in the pollen). Some are used for medicinal purposes, and I'd eventually like to get into that part more and update these with more information later if I get time. The flowers have more moisture in them if picked in the morning.
Flowers make a nice addition to salads and as garnishes. Crystallized flowers (also called Sugared or Candied) are very pretty to put on cakes and other foods. Just be sure to mention to your friends that they can eat the flowers too. :) I did a separate blog post on how to do that with photos. (click here)
I'm sticking mainly to flowers common to gardens here in the north, but some of the links below include flowers not common to here. Also, these are all flowers that I will be trying myself (if I haven't already) as the season goes on; and I will do updates on how I think they taste. :)
(At the bottom of the page, I also mention some vegetable flowers and herb flowers that are edible as well as some annuals.)
vinegar in and let is sit for a few days.
Update: Here is the Chive vinegar I made.