|MadSci Network: Botany|
I like you am an avid gardener, although I prefer growing flowers. My main area of expertise is nutrition so I confess I'll spill the beans for you.
There are approximately 13,000 different varieties of beans belonging to the family - Leguminosae, including some odd species such as sweet clover, alfafa, and even mesquite! Of the main groups, the ones you're interested in belong to genus Phaseolus. These can be further differentiated by the way in which they're grown, either bush types which are self-supporting, or pole and runner varieties.
Green beans are genus Phaseolus vulgarus, a plant native to Central America and have been safely eaten raw for centuries. Green beans are picked at an immature stage while still tender and slightly sweet.
Other varieties of legumes such as peas, specifically snow peas or sugar snap peas can be safely eaten raw, as can another bean widely consumed in the raw state around the world, the peanut!
Green beans are not always green, but can also be yellow or purple,and different types come under various names such as; snap beans, Italian green beans, long Chinese beans, and purple or yellow wax beans and can all be safely eaten in their raw state.
Such safely eaten fresh beans should be contrasted with shelled, mature beans which should always be well-cooked to rid of their toxins. For example, certain types of lima bean contain cyanogens (cyanide); lentils contain purines, which can predispose susceptible individuals to gout, and most beans contain proteins known as lectins which can cause agglutination - (a clumping together of red blood cells). Lectins are found in raw lima beans, kidney beans and soybeans. The latter also contains protease inhibitors which can interfere with digestive enzymes, i.e. trypsin. Having said that, it is unlikely that lectins make it to the bloodstream as proteins are broken down in the digestive tract. Also, the amount of cyanide in lima beans is small, and besides, we eat varieties where such toxins have been bred out. In any case, it is recommended not to eat such shelled, mature beans. Even fresh soybeans, known as edamame, which are 80% mature are boiled prior to market.
Finally, there are hundreds of green and wax beans cultivars from which to choose from.
Hope that helps,
Reference and suggested reading: Rodale's All-New Organic Gardening - Published by Rodale Press, Penn.
Try the links in the MadSci Library for more information on Botany.