Not every edible flower is completely edible. In fact, for most flowers, you should eat only the petals. Talk to an expert, such as someone at your local cooperative extension service, and find out what parts are and aren’t edible for the flower you’re thinking about eating. For example, for roses, marigolds, chrysanthemums, and English daisies, the entire colorful petal is edible, but not the end, or “base,” of the petal—the whitish part that inserts into the flower. Find a cooperative extension office near you.
The same goes for railroad tracks and trails where dog walkers frequent. There may be petrochemicals and other toxic compounds from vehicles, as well as contamination with bacteria and other pathogens from animal manure. Don’t eat flowers purchased at roadside stands, farmers markets, garden centers, or florists, which may contain pesticides. Eat only flowers that are explicitly labeled as edible. Gourmet grocers often sell edible flowers, or you can grow your own at home, taking care to choose the right types and grow them right.
Just because the fruits of a tree or the roots of a plant are edible doesn’t mean the flowers from those plants are also edible. In fact, they could be poisonous. There are an estimated 500 species of poisonous plants growing in the U.S., including many flowers you may have in your own garden, such as rhododendrons, hyacinths, daffodils, and hydrangea. Reactions from eating a poisonous flower vary by plant and can range from burning of the mouth to gastrointestinal distress to death. Read a full list of poisonous flowers.
And find out if anyone has allergies, including hay fever or asthma. Flowers have pollen that can cause a severe allergic reaction in some people. Even if you don’t have allergies, it’s a good idea to test a flower you haven't eaten previously by trying a small amount first to see how you tolerate it. Also, you should generally remove the flower’s reproductive organs (stamen and pistil), which contain the highest concentration of pollen. (Some flowers, however, are too tiny to do this.)
Edible flowers can be a source of potentially beneficial compounds, including some antioxidants. A study in the Journal of Food Science analyzed 10 flowers commonly eaten in China and found them to be high in polyphenols, compounds with antioxidant and anti-inflammatory properties. One group of polyphenols are anthocyanins, which give a blue-purple color to some petals and are also found in blueberries, red cabbage, and cherries. The more deeply pigmented a flower, the greater the concentration of potentially beneficial compounds.
Once you get the flowers home, clean them by dipping them in room-temperature water, then let them dry on a paper towel. Don’t clean them aggressively, as you would with salad greens; that can damage the petals. To store flowers in the refrigerator, use a plastic container rather than a zip-lock bag where the flowers may get crushed. To reduce the risk of wilting, place the flowers atop a moist paper towel. They can keep for about two days.