You can conduct various experiments using bean seeds. They are useful to explore the effects of different conditions on germination times and plant growth. Beans sold for food may be subjected to treatments such as heating that kill the seeds. Unless you need a large volume of seeds, in which case dried beans are acceptable, it's a good idea to use bean seeds that are sold for gardens.
Also called butterbeans, lima beans are whitish or green in appearance. In optimum conditions they germinate in six days, but can take as long as 18. Lima beans prefer warmth. This, along with their shorter germination time, makes them a good choice for indoor experiments.
Dried kidney beans sold for food may still be viable, and their low cost makes them an economic choice. If possible, test a few beans for viability by placing them on wet paper towels inside a loosely covered container. If the beans sprout, the rest of the package should still be viable, too. If you are doing experiments with children, especially younger children, avoid using kidney beans. All dried beans pose something of a hazard, as they can be swallowed or pushed into ears and noses, but kidney beans are especially risky. Uncooked kidney beans are toxic. The sprouts of the growing beans are also harmful if eaten. Only use kidney beans in projects involving learners who are old enough to understand the risks.
Fava or broad bean seeds are large and colored pale green. Their larger size and light coloration makes them a good choice for experiments where the visibility of the seed is important. Dried fava beans are easy to find in stores, but as with other dried beans they may not be viable for germination. Outdoors, fava beans can take from one to two weeks to germinate.
Because of their speedy germination time and fast growth, mung beans can be an excellent selection for many experiments. Their small size means that they can be grown in more compact spaces. Unlike some other beans, mung beans respond poorly to being soaked in water, so minimal water should be used when germinating them. If you buy mung beans sold as food to germinate, only buy whole mung beans, as split mung beans are not viable. Mung bean sprouts are safe if eaten (sprouted mung beans are what we know as bean sprouts). If you're planning to eat the results of the experiment, however, make sure you buy mung beans that are intended to be sprouted for food and that they don't come into contact with anything unsafe.