Green beans refer to any bean, whether a climbing or bush variety, whose pods are harvested and cooked along with the beans themselves while still young and tender. Beans are “legumes,” plants that spread their seed via seed pods that split in half and deposit the seeds on the ground when mature. Like the majority of bean types, green beans can be devastated by even a mild frost and should not be planted outside unprotected until the danger of frost has passed.
Soak green bean seeds for up to 24 hours before planting to increase the speed of germination. Soaking softens the testa, which is the hard, outer layer of the seed that provides protection during the seed’s dormant stage. Plant seeds at a depth of 1 to 1 ½ inches. As water enters via the micropyle (tiny hole in the testa, located on the indent of the seed), the embryo begins to develop. The embryo consists of two halves; the radicle, which is the first root, and the plumule--the first two leaves. The radicle begins to descend, pushing through the micropyle and into the soil below. Once the radicle has begun its descent, the plumule ascends, splitting the testa and growing toward the light.
When the plumule, cotyledons (two large halves of the seed) and hypocotyl (part of the stem between the roots and the cotyledon) emerge, they are folded over. They then begin phototropism, the process of straightening and growing towards sunlight. The seedling takes its nutrients from the cotyledons until the root system matures and is able to support the young plant. As the nutrients are consumed by the seedling, the cotyledons wither.
After the root system is mature and able to sustain the plant, green beans experience a four to six-week period of intense foliage growth. Most green bean varieties flower after this growth spurt. After pollination, the flowers die and fall, and very small, green bean pods appear.
Fruit Production and Harvest
To use as green beans (cooking and eating the pods as well as the seeds), beans must be harvested while still young. If left on the plant for too long, the pods become tough and “stringy” with an unpleasant texture. The pods should be pale and smooth when harvested. Over-matured pods can be identified by a lumpy, gnarled appearance, and have thick, rough edges.
Green beans rarely cross-pollinate with other varieties, and so seed can be readily saved. Leave some pods on the plants until the pods are completely dry and develop a papery texture. Once dried, remove the pods and shell them, leaving the beans to air-dry in a secure, rodent-proof area. Use these dried beans as seed for next year’s bean crop.