The Seed Garden (Seed Savers Exchange, 2015) by Micaela Colley & Jared Zystro and edited by Lee Buttala & Shanyn Siegel brings together decades of research and hands-on experience to teach both novice gardeners and seasoned horticulturists how to save the seeds of their favorite vegetable varieties.
You can purchase this book from the MOTHER EARTH NEWS store: The Seed Garden.
Common beans are one of the most popular garden crops from which to save seeds, because the task is so straightforward. This species includes a seemingly endless list of open-pollinated cultivars that are harvested both dry and fresh, including beans in a variety of shapes, sizes, and colors. Almost without exception, there is a variety suitable for cultivation—and seed saving— no matter where one lives. Saving common bean seeds can be as simple as collecting the mature beans left on the vines at the end of the season, shelling them, and storing them.
Phaseolus vulgaris varieties can be classified by their growth habit (bush, half-runner, or pole beans) and by the way they are consumed (dry, green, or shelling beans). Beyond these classifications, common beans are divided into broad market classes according to the size and color of the bean’s seed coat or the color, shape, and size of the pod. These categories include dry beans, such as turtle, cranberry, and pinto beans, and snap beans, such as green beans, wax beans, and the French varieties known as haricots verts.
Phaseolus vulgaris was most likely domesticated twice, once in the Andes around 8,000 years ago, and once in Central America around 7,500 years ago. Common beans were subsequently cultivated throughout South and North America. Common beans were brought to Europe from the Americas by the Spanish in the sixteenth century and then made their way to Africa and Asia. In Europe, common beans were selected to produce the edible immature pods that are now commonly known as green beans.
Growing Common Beans for Seed
Phaseolus vulgaris is an annual species that germinates and grows best when planted in warm, loose-textured soils. Ideally, dark-seeded beans should be planted when the soil temperature has reached at least 60°F (16°C), and light-seeded beans should be sown when the soil temperature is above 65°F (18°C). Typical garden spacing and trellising is appropriate when growing common beans for seed.
Saving seeds from a dry bean planting is as simple as setting aside and properly storing a portion of the harvested seeds, provided the variety was properly isolated. Green beans and shelling beans, on the other hand, must be grown past market maturity in order to produce viable seeds. Individual green beans that were missed at harvest can be left to mature as next season’s seeds if they have been properly isolated, or, since the plants do not take up too much space, a select number of plants can be grown expressly for seed saving.
Flowering, Pollination, and Seed Set
Common beans produce racemes of perfect flowers, and the blossoms range in color from white to shades of pink and purple. The perfect flowers self-pollinate, although insect-pollination occurs with some frequency, depending on the cultivar and climate. Following fertilization, each pod will develop three to eight seeds.
Phaseolus vulgaris is a self-pollinating species and requires only a short distance between varieties to ensure purity; a separation of 10 to 20 feet (3 to 6 m) between varieties is sufficient to prevent cross-pollination in many cultivars. However, the likelihood of cross-pollination by insects varies widely by variety, and some gardeners have found that greater distances provide more reliable isolation. If genetic preservation of a variety is the goal, the isolation distance should be increased to 100 feet (30 m).
When a sufficient isolation distance cannot be provided, caging is a reliable method for isolating this self-pollinating species, although it is only practical for compact, bush-type plants. The vining forms (half-runner and pole beans) are difficult to cage. Blossom bags can be placed over individual racemes, but this method is practical only if a gardener wishes to collect a small quantity of true-to-type seeds.
Inbreeding depression is not an issue for Phaseolus vulgaris. Viable seeds can be collected from just one plant, however, it is best to save seeds from more than one plant—especially if seeds will be shared with others. A population size of 5 to 10 plants is recommended to maintain the health of a variety over multiple generations. When the genetic preservation of a variety is a gardener’s goal, the recommended population size increases to 20 plants or more.
When roguing or selecting common beans, seed savers should consider important traits including growth habit; color of flowers, pods, and seeds; and pod shape and length.
Seed Maturity and Harvest
Beans can be harvested for seeds any time after the pods have begun to fade in color. Many recently developed bush-type green bean cultivars can be expected to reach seed maturity and be at the proper stage for harvesting approximately 45 to 60 days after pollination; heirloom and pole bean types may take longer to mature.
The fruits of bean plants, commonly referred to as pods but botanically classified as legumes, are dehiscent fruits—they split open at maturity. But in the garden, the pods of most varieties of common beans can be left on the plant to dry fully without fear of losing seeds to shattering.
Bean pods can be handpicked, or whole plants can be cut at the base. Most gardeners collect fruits from pole beans by hand as they mature, and even if entire bush bean plants are to be harvested only for seeds, handpicking pods is common on the home garden scale. If harvested prior to the pods turning tan and papery, the pods should be allowed to dry on screens or landscape fabric in a protected place until the seeds become too hard to dent with a fingernail.
Cleaning and Storage
Dry pods can be hand-shelled, eliminating the need for screening and winnowing. Alternatively, harvested material can be threshed by placing it into a sack, on a tarp, or into a container and treading lightly on it, provided there is sufficient plant material to buffer the force exerted on the seeds. Although there is a wide range of seed sizes among different Phaseolus vulgaris varieties, all varieties are large seeded, and the seeds separate easily from the chaff through screening and winnowing.
When stored under cool, dry conditions, common bean seeds can be expected to remain viable for three to four years.
LIFE CYCLE: Annual
SUGGESTED SPACING: Same as when grown for eating
OTHER REQUIREMENTS: None
FLOWER TYPE: Perfect, self-fertile flowers are produced
POLLINATION: Self-pollinated (autogamous), with
varying frequency of insect pollination depending on
MATING SYSTEM: Self-pollination is the primary mating
system, though cross-pollination is common in some
ADDITIONAL CROSS-POLLINATION CONCERNS: None
FRUIT TYPE: Dry, dehiscent fruit (legume)
SEED MATURITY: Seeds are mature when pods turn tan.
SCREEN SIZE: 11⁄64–34⁄64 inch (4.5–13.5 mm)
EXPECTED SEED LIFE: 3–4 years
ISOLATION DISTANCE: 10–20 feet (3–6 m)
For Viable Seeds: 1 plant
For Variety Maintenance: 5–10 plants
For Genetic Preservation: 20 plants
For more on seed saving, see our Seed Saving Guide.
Reprinted with permission from The Seed Garden, by Micaela Colley & Jared Zystro, edited by Lee Buttala & Shanyn Siegel and published by Seed Savers Exchange, 2015. Buy this book from our store: The Seed Garden.