Typically grown as ornamental plants on trellises and arbors, runner beans are a type of green bean. These climbing beans--particularly the scarlet runner bean--reach heights of 10 to 15 feet and attract hummingbirds and butterflies to their bright red blooms. Vines produce slender green pods that may reach lengths of 10 inches. When harvested young, these green beans are tender and flavorful. Saving seeds for the next year's vines provides a free source of seeds to grow new beans in the spring.
Examine the bean plants for any signs of disease or insect damage. Note the characteristics of the plant that you would like to encourage, such as early blooms, tall vines or abundance of flowers and fruit on the plant. These characteristics are often passed on genetically via the seed.
Mark the plants by tying a piece of bright string or yarn to the vine. Inform family members and guests that vines marked with string are for seed saving and should not be picked.
Allow bean pods to ripen on the vine until the pods wither and turn yellow or brown. Pods may be soft, but will stiffen as they dry.
Clip the vine into 12-inch sections so bean pods remain attached to the vine. Gather into a bundle of five or six vines and tie the stems together with garden twine, or secure with elastics.
Hang the vines in a dry, well-ventilated area until the pods become brittle and the beans rattle in the pod when shaken. Drying time varies from one to several weeks, depending on the moisture content of the beans, humidity level and air temperature.
Break the pods open with your hands and remove the seeds. Store seeds in a glass jar in a cool, dry place until spring. Replant bean seeds in the spring after all danger of frost has passed in your area.