Just to be on the safe side, eat only the flowers that you have grown, since those are the only plants you have a complete known history. Your own plants will only have been exposed to what you have introduced to them, so if you plan to eat your harvest keep it organic and free of poisons. One more suggestion, be cautious when you are trying to eat or cook flowers for the first time. There are some possible allergies, particularly for individuals that suffer from other plant allergies or hay fever, so try a small amount and be sure you do not have an allergy to eating the flowers of your choice before diving in. Now that all the dire warnings are out of the way, we can move on to the fun stuff, which plants are generally accepted as edible.
Lavender is one of the most common flowers used in cooking today. The plant is simple to grow in a sunny and dry location. It is an attractive addition to a vegetable or flower garden, with the beautiful purple flowers. Those flowers can be used to make a soothing tea, in chocolate treats, to flavor lavender vinegar, to flavor jams or mixed with savory herbs in soups and stews. Lavender flowers are particularly good in wine reduced sauces and as a garnish for beverages or sorbets. You can also use the flowers as a bath water additive for a relaxing soak. Lavender has a fresh, clean scent that is soothing and can be used in gentle insect repellents.
Scented geraniums are a nice low-maintenance perennial. The flowers tend to be tiny and pink. They are profuse in the spring. The scents of the geranium leaves vary, the most common are rose scented however, there are also lemon, peppermint and ginger scented plants as well. The flowers are often used as garnishes, most notably on wedding cakes. You can also use the flowers as floating garnishes in beverages. Just be sure to note which scent you have, since some flavors match up with your beverage of choice better than others. I strongly suggest steering clear of the Citronelle variety, since there are high doubts about this strain being edible, much less tasty.
Borage grows best in areas with full sun, but can still grow well in light shade. This plant grows easily from seed and will spread out like a ground cover and self-seed for future years. The flowers are delicate and star shaped in a brilliant shade of blue, similar to a forget-me-not (Myosotis). The blossoms are small and sweet with a cucumber type flavor. The borage blossoms look fantastic as a garnish for beverages like lemonade and sorbets. The leaves can be chopped finely, mainly to lessen their furry texture, and used in salads.
Chamomile is best known for its use in teas and lotions. Chamomile grows best in full sun to part shade. Once the plant is established, it will self-seed for future years. This annual can grow between two and three feet high with finely cut leaves and tiny flowers that resemble daisies. The flowers and leave have a slight apple fragrance. While it is easy to grow and harvest for a soothing cup of tea, I suggest avoiding chamomile if you are allergic to ragweed. It is likely you will be sensitive to this plant as well. To make a fresh tea with chamomile, you should harvest the flowers when the petals have begun to droop. Put around three teaspoons of fresh flowers in boiling water and allow the flowers to steep for around three minutes. They you can simply strain and drink. If you prefer a lighter chamomile flavor, you can blend the flowers with the tea of your choice.
Johnny-Jump-Ups, or violas, are a favorite in my garden simply because I love the combination of purple, yellow and white colors and the ease of growth. This annual takes very little care. It will bloom profusely in sun or shade. The plant does best in cool weather and has a light wintergreen flavor. Once planted or started from seed this flower will self-sow. The flowers can be used as a garnish floating in a punch bowl or decoration for a dessert or salad. The flowers can be crystallized or candied for a wider variety of decoration and culinary use. Pansies and violets are related flowers and can be used in the same way.
Nasturtiums are often seen as an invasive weed. This annual grows best in full sun and poor soil. Part of the beauty of intentionally growing this flower is that it is not bothered by neglect, so it is great for beginners and forgetful gardeners. The plant has round shaped leaves and beautiful sunset shaded flowers grow on a vine. The leaves and blossoms are both edible and are great in salads, omelets, sandwiches and soups. The flavor is close to that of watercress. Varieties of Nasturtiums all grow easily from seed; including a tall, dwarf, and climbing vine which grow between one and three feet.
Pot marigolds or Calendula are often already in your vegetable garden, I usually use them as a companion plant around the edges of mine. These are low maintenance annuals which can easily be grown from seed and which will self-sow for future years. The plants can grow up to eighteen inches tall and do best in full sun. Calendula is at its peak during the early summer, and will start to fade a bit in the hottest days of summer. For optimum growth cut the plant back after the first bloom to help encourage more growth. The orange or yellow flower petals can easily be harvested from the flower head and be used fresh in a salad. Petals that have been harvested and dried can be added to chowders, paella, or muffin mixes. The dried petals can also be used as a substitute for pricey saffron.
Flowering onions (Allium) includes around four hundred species including shallots, onions, leeks, garlic and chives. All members of this genus do well in well-drained, rich soil in a sunny area. Seeds, nursery plants or bulbs for these plants can be planted in mild wintered areas during the fall. All parts of these plants are edible, and all members of the genius are edible with the flowers having a slightly stronger flavor that the leaves. The flowers within this genus tend to be lavender colored, some more pink than light purple. The flowers and leaves are a nice addition to salads. Leaves can also be added to stews and soups. The florets can be broken apart and added to egg dishes, potatoes, cream cheese, and cooked vegetables for added flavor.
Rose petals are another popular addition in the kitchen. The flavor and ease of growth depends on the rose you grow. All rose varieties have edible flowers, with the flavor of the darker flowers being stronger than the lighted shaded petals. When choosing a rose to harvest petals from choose the roses with the strongest scent, as those will have the most flavor. The petals can be added to butters, fruit salads, meat dishes, jellies, beverages, syrups, and a variety of desserts. Roses are also a great addition to brewing teas and soothing baths. One helpful note, the white section of a petal is bitter, so it is best to remove that potion of the petals before using.
There are quite a few poisonous flowers that you absolutely need to steer clear of ingesting, but still look terribly pretty. These include the daffodil, foxglove, calla lily, azalea, crocus, hydrangea, hyacinth and wisteria among many others. You also need to avoid the leaves of a few friendly vegetable plants like those of tomatoes, potatoes eggplant and peppers. I know I have seen some of these non-edible plants as garish or decoration on desserts. So again, I recommend that you do your research and make sure that the plant, and the part of the plant that you intend on eating, is edible before you harvest it. Not everything that is used as decoration is strictly edible, so do not eat it if you do not know it is safe!
Harvest your flowers in the morning if you can. Like any other plant product you want to eat, flowers will need to be washed. Simply rinse the flowers in cool water, gently shake them to remove excess moisture and then let them dry on a paper towel. I recommend doing a second check of your flowers before eating or cooking, just to be sure that there are no tiny pests hiding out in the flower petals or on the undersides of leaves. It does not hurt to give the flowers a second, or even third wash if you feel the need. After the flowers are clean and dry it is time to use them or store them. If you do not plan on eating or cooking with the flowers right away then keep the plants between layers of damp paper towel in your refrigerator. Another rinse and check of stored flowers before use is suggested, not necessary if you did a thorough job the first go round.
There are many more edible flowers out there, and many more ways to use them. These are the easiest to grow and ones that I suggest for getting started in the tradition of cooking and eating flowers. For a more comprehensive list, and more ideas, I suggest talking to fellow gardeners, chefs and staff members of a trusted garden center. You can also visit How to Choose Edible Flowers – Edible Flower Chart for a more comprehensive guide to flowers and how you can use them.