Scarlet runner beans (Phaseolus coccineus) are a distinctive and rewarding crop, providing both ornamental beauty and a generous harvest of edible beans and pods. These climbing plants are native to the mountains of Central America. Known for their striking, vibrant red flowers, the scarlet runner bean serves a dual purpose, making it an excellent choice for maximizing visual appeal and productivity. This guide details the specific steps required to successfully cultivate these unique legumes from seed to harvest.
Site Selection and Soil Preparation
Scarlet runner beans thrive in full sun, requiring a location that receives at least six hours of direct sunlight daily. Planting them in a sheltered spot helps protect the dense, leafy vines from strong winds later in the season. Planting should only occur after the last anticipated spring frost has passed and when night temperatures consistently remain above 50°F (10°C).
The soil must be rich in organic matter, well-draining, and maintain a slightly acidic to neutral pH range of 6.0 to 7.0. Amending the planting area with aged compost or manure before sowing provides the fertile base necessary for growth. While the seeds can germinate in soil as cool as 50°F (10°C), warmer soil, ideally around 60°F (16°C), is preferred to ensure quick, healthy establishment and reduce the risk of seed rot.
Planting and Initial Spacing
Direct sowing outdoors is the preferred method for scarlet runner beans, as their roots are sensitive and do not tolerate transplanting well. If a head start is necessary in shorter growing seasons, seeds can be started indoors in biodegradable pots four to six weeks before the last frost. Unlike common beans, scarlet runner beans exhibit hypogeal germination, meaning the cotyledons remain below the soil surface, which offers them some protection.
Sow seeds 1 to 2 inches deep in the prepared soil, spacing them 6 to 8 inches between each seed along the support structure. Soaking the seeds before planting is generally unnecessary and can sometimes lead to rot, but ensuring the soil is consistently moist will encourage germination within one to two weeks. If direct sowing results in too many seedlings, thin them to the suggested spacing once the first true leaves appear to prevent overcrowding.
Providing Support and Ongoing Maintenance
Because scarlet runner beans are robust climbers that can reach heights of 10 to 15 feet, a sturdy support system is necessary for successful cultivation. Structures like trellises, netting, or a teepee made of bamboo poles should be installed before planting to avoid disturbing the young plant’s root system. The vines naturally twine clockwise, making it easy to train the young plants onto the support.
Consistent soil moisture is important, especially once the vines begin to flower and set pods, as irregular watering can cause flowers to drop. Applying an organic mulch layer around the base of the plants helps maintain even moisture levels, keep the soil cool, and suppress weeds. Fertilization should be managed carefully; as legumes, these plants fix atmospheric nitrogen, so excessive nitrogen application promotes lush foliage growth at the expense of flower and bean production. Aphids are a common pest, and small infestations can be managed by spraying the affected areas with a strong jet of water or using insecticidal soap.
Harvesting and Culinary Uses
The scarlet runner bean allows for harvest at multiple stages, each offering a different culinary experience. The bright red flowers are edible and possess a mild, sweet, bean-like flavor, making them an excellent garnish for salads.
For use as a young green vegetable, pods should be picked when they are still slender and tender, typically around 6 to 8 inches long, before the seeds inside fully develop and the pod becomes fibrous. Regular picking of these young pods encourages the plant to produce more flowers, extending the harvest season.
If left on the vine, the pods will swell, and the large, colorful seeds can be harvested as “shelling beans” for fresh use once the pod is fully plump. Allowing the pods to fully mature and dry on the vine until they turn brittle signals that the speckled beans inside are ready to be collected and stored as dried beans for winter use. Note that mature, raw beans contain a substance called phytohaemagglutinin, making cooking necessary before consumption.