Scarlet runner beans have been grown in the United States since frontier days. Here scarlet runner beans grow along the kitchen garden fence at the Pioneer Farm Museum in the Great Smokey Mountains National Park. Click to download a large (800x600) version of this image.
Runner beans are long, twining perennial vines that are usually grown as annuals for their showy flowers and their edible pods and seeds. They have thick stocky roots and their vines can reach 12 ft (0.3 m) or more. The leaves are trifoliate and each leaflet is broad-oval and 4-5 in (10-12.7 cm) long. The flowers in most cultivars are bright scarlet red, and shaped like typical bean family flowers with the two lowermost petals united into a "keel", the uppermost petal modified into a hoodlike "standard", and the lateral petals modified into spreading "wings." The flowers are about an inch long and clustered on many-flowered racemes to 10 in (25 cm) long. There can be as many as 20 flowers on a single flowering stalk. The legumes (pods) range from 6-12 in (15-30 cm) in length and the seeds are about an inch long, with 6-10 seeds per pod. The most well known cultivar is 'Scarlet Runner' which has red flowers and burgundy and black mottled seeds. 'Black Runner' has intense crimson flowers and jet black seeds. 'Painted Lady' has flowers with red standards and white wings and keels. 'White Dutch Runner' and 'Case Knife' have white flowers and white seeds. 'Butler' and Polestar' are new stringless cultivars with very long pods to 12 in (30.5 cm). 'Hammond's Dwarf' and 'Pickwick Dwarf' are non-climbing bush types that mature 2-3 weeks earlier than the running kinds.
scarlet runner beans
Runner beans are similar to green beans (P. vulgaris), but green beans are annuals with smaller flowers in smaller clusters and smaller seeds in smaller pods. Also, runner beans twine clockwise when viewed from above, whereas most other kinds of beans twine counterclockwise. Also, when runner beans emerge from the ground, the first growth you see is the stem and the first set of true leaves. The cotyledons (embryonic leaves or "seed halves") of runner beans remain underground. In most other beans the cotyledons emerge first, and the first set of true leaves develop soon after.
Runner beans are native to the high elevation mountains of Central America. They have been domesticated for more than 2000 years by natives of the region, but wild relatives of the runner bean still occur in Guatemala and Mexico, where they grow in cool, partially shaded valleys in mixed pine-oak forests.
Runner bean flowers are perfect. That means they have both male and female parts: pollen producing stamens and pollen receiving pistils. However they are unable to self-pollinate unless an insect "trips" the flower by alighting on the keel, causing the stamens to come in contact with the pistil. Hummingbirds, bumblebees and honeybees usually do the runner bean's bidding. Light: Full sun to partial shade. Moisture: Runner beans need abundant water during flowering and pod expansion. Hardiness: USDA Zones 7 - 11. Runner beans are evergreen in the tropics, and some cultivars don't flower until their second growing season. Where the ground does not freeze, runner beans are perennial, and can be expected to sprout back in spring from their tuberous roots. In colder regions, you can dig up the roots and store in cool, damp sand for replanting in spring. Plants that sprout back from their roots will flower much sooner than plants started from seed. Scarlet runner bean and other varieties commonly available in temperate regions are usually grown as warm season annuals and they will flower in a single growing season. Runner beans cannot tolerate frost at all, nor will they set fruit while temperatures are above 90ºF (32 ºC). Propagation: Runner beans are grown from seed sown in place. Space 4-8 in (10-20 cm) apart and plant 2-3 in (5-7.6 cm) deep. Be sure to provide a sturdy trellis, fence or pole teepee. Do not plant until soil temperature is at least 50ºF (10 ºC).
Scarlet runner bean flowers are brilliant and beautiful on their way to becoming bean pods.
Most American gardeners grow runner beans for their showy sprays of red or red and white flowers which are attractive to butterflies and hummingbirds. Use the twining vines to cover a trellis or arbor. Let them scramble with clematis, trumpet vines and morning glories.
Runner beans are more popular for food in Europe. The immature pods are used like green beans. Their texture is a little coarser than green beans and so they are usually sliced lengthwise before cooking. Some consider them more flavorful than green beans. The flowers are delicious in salads. Seeds in the shelly stage are good to eat, but the mature beans can be dry and mealy and are not generally consumed except by Native Americans in Central America. They eat the starchy roots, too.
Scarlet runner beans are perennial. After their first year, they will come up and flower earlier in the season. Plant some on a back fence or a trellis and enjoy the flowers and the hummingbirds year after year!