If you are just beginning to consider flowers in your food and extending your interest, you will feel most confident in using the well known traditional ones. However there is quite an explosion of interest in flowers in modern cuisine and you will be assured that the list of suitable flowers will grow as science confirms their safe use in your kitchen.
Flowers are often presented whole in garnishing for their color and aesthetic pleasure but if they are served to be eaten, great care must be made in their quality and preparation to minimize any of the bitter parts of the flower. Buying flowers are only safe for eating if they are guaranteed to be grown organically for obvious reasons. The safest way is to use them straight from your own garden where no sprays or chemical residues will threaten the quality and flavor of the blooms.
Although each flower is unique, the general rule is to reduce the base of the petal (near the flower centre) or the center in flowers that have bitter properties.
Perhaps you'll choose to try only the flower petals for starters. This is a list of popular choices -
Apple and plum blossoms - sprinkled last to a salad preparation or in garnishing savouries
Borage - remove the dark part to enjoy the appearance and taste of this blue flowered herb
Calendulas (English or pot marigolds) - sometimes called 'poor man's saffron' adding colour to rice dishes and soups or used fresh in salads
Culinary Herbs of all kinds produce tasty and safe to eat flowers or sprays of tiny blooms
English Daisy - an old cottage limited use of the petals in various dishes
Carnations - these vary according to species but often a spicy flavour
Chrysanthemum - popular in Chinese foods and drinks
Cornflowers - another delightful blue coloured flower- also offers a pink form
Gardenias - these are best used as garnishing on cold dishes only until subtle ways of using these highly perfumed flowers is learned
Geraniums (Pelargoniums) - these petals are tops for colouring as well as flavouring salads
Gladiolus - popular as a flower prepared by stuffing as a sweet dish (I have no personal experience of this one)
Lavender - there are many ways this lovely flower can be used including in ice-cream
Nasturtiums - a fine salad ingredient with typical cress type flavor and lots of vitamin C
Pansies - velvety affect in presentation of attractive dishes and snacks
Roses - bitter base of petals must be removed before use in dozens of ways - an adventure!
Safflower - yellow petals also can be used in place of saffron
Snapdragons - good to attract attention of children
Sunflower - yellow petals used mainly in curries
Violets - usually candied or chocolate coated as a snack