The most common (and safest edible flowers) are nasturtium, pansy, violet, Johnny-jump-up, calendula, chive, and sage. These flowers are easily grown without the use of chemicals or pesticides. Many roses are delicious, but you need to be sure they are grown organically. A good rule of thumb is: If you cannot positively identify a flower as edible, don't eat it. Also, if you have asthma, hayfever, or other allergies, do not eat flowers.
Never eat flowers from a nursery, garden center, or florist; they are likely to have chemical residues that concentrate in the flowers.
So best advice? If you aren't sure about the organic nature of your flowers, grow and harvest your own! or plant seedlings from organic seedling sources.
Here's a look at some of the most common forms of edible flowers to add 'Pretty' to your dishes