The Edible Flower Garden. Rosalind Creasy

      All herb flowers (above) are edible. Consequently, an herb garden is a great place to find more flowers for your salad. Here, my streetside herb border contains nepitella (Italian mint), lavender, and lemon thyme, all herbs that produce flowers. Not all herbs bloom, however. Included in the bed are variegated oregano and sage, which never produce flowers. For a larger selection of edible flowers, I added blue and yellow violas and pansies to the herb planting.

      The Encyclopedia of Edible Flowers (page 29) details which varieties produce the best edible flowers and provides information on growing all the plants mentioned—enough to get you started and give you an idea of how much care the plants need. Occasionally you may need to consult other books for different information—local cultivars or conditions, for example. Be aware that the authors of most of the flower-culture books in this country do not anticipate your eating the flowers and therefore occasionally recommend pesticides that are unsafe for human consumption. (Nontoxic, organic pest and disease controls are given in Appendix B, Pest and Disease Control, page 99.)

      Unlike vegetable varieties, the flowers bred at nurseries have been selected not for their flavor but for their appearance and growing ease. Therefore, taste as many varieties as possible before you plant. Visit the gardens of friends and neighbors and taste a few flowers at a time. But beware of poisons! Before you start tasting flowers, let alone planning your garden, you need a brief lesson on poisonous plants.

      Poisonous Plants

      What is poisonous, anyway? When I began my research I was naive enough to assume that I would be able to find a definitive list of poisonous flowering plants. No such luck. There are plenty of lists of poisonous plants, but none that completely resolves the issue of what is and is not poisonous. I had to do my own legwork, so I began at the beginning, with Webster's Third: poison: "A substance... that in suitable quantities has properties harmful or fatal to an organism when it is brought into contact with or absorbed by the organism."

So the two crucial factors are chemical contents and dosage. As to the former, plants containing alkaloids, glyco-sides, resins, alcohols, phenols, and oxalates are potentially poisonous, but their toxicity depends on the amount of these substances they contain. After all, many poisonous plants are also valuable medicines; it is the dosage that determines whether the end product is medicinal or toxic. In fact, some poisonous-plant lists actually include spinach and chard because they contain oxalic acid, which is poisonous in large quantities.

      Still, determining how much of a substance makes a plant or serving toxic is a matter for chemists. Obviously, the more you ingest—eating foxglove ice cream rather than just a single petal on a salad plate—the greater the hazard. My advice and the rule I follow is, Don't take chances. If a flowering plant is on any list of poisonous plants, I don't eat it—not even a single petal—until I have more information. And if I can't find the plant on any list of edible or poisonous plants, I assume it is not edible.

      Here are some guidelines I have gathered from food technologists and environmental botanists:

      1. Positively identify the plant—Latin name and all. As with mushrooms, identification is crucial.

      2. Birds and animals are unharmed by some plants that are poisonous to humans. The gray squirrel can safely eat the deadly amanita mushroom, and birds regularly gorge on the irritating red elderberry berries. So don't depend on guinea pigs of any species to guide you.

      3. Not all parts of toxic plants are necessarily poisonous. For instance, rhubarb stalks and potatoes are edible, but the leaves of both plants are poisonous.

      4. Some plants, such as pokeweed, are poisonous only at certain times of the year.

      5. Because individuals can be allergic to substances that are not generally poisonous—wheat and milk, for example—when you first taste a new food, eat only a small amount.

      6. Just because most members of a particular plant family are not poisonous does not mean that all are.

      7. Heating or cooking in water removes many toxins, but not all.

      8. Never use any flower as a garnish if it's not edible. In this day and age, when diners eat flowers, you're just asking for an accidental poisoning.

      9. Make sure it's clear to children that some flowers are edible and others can make them sick.

      10. And a most important point: You can cause damage and not even know it. Because a plant does not make you sick to your stomach or cause your heart to race or make you break out in a rash doesn't mean that it's safe. Some toxic reactions take time to manifest themselves; others will never be detected. For example, some plants contain chemicals that cause cancer, abortions, or birth defects; others are filled with chemicals that raise your blood pressure, rob the body of calcium, or tie up iron.