When to Harvest Beans:
Pick snap beans (also known as green or string beans) before the seeds swell in the pods when they are no more than the diameter of a pencil. Smaller beans can be served as tender, baby snap beans.
Start your snap bean harvest about 2 to 3 weeks after the plants begin to bloom and continue to pick almost daily. Snap beans take about 50 to 60 days from sowing to reach harvest.
How to Harvest Beans:
Harvest beans by holding the stem with one hand and pulling pods with the other. Don’t jerk or yank beans from the plant; you will only break vines and branches and injure the plant.
By picking often, you encourage more blossoms and more beans. Each plant should produce two or three flushes of pods.
At a minimum, harvest pole beans every 2 days and bush beans at least once a week. Pole-type beans generally bear over a longer period than bush types.
When you quit picking and allow seeds in the pods to develop and mature, the plant will stop blossoming and producing pods; its life cycle will be complete.
Your bean harvest will end when temperatures drop below 40°F (4°C); then pods will become opaque and develop rust-colored spots.
How to Store Beans:
Store snap beans in a cool, moist place, 40°-50°F and 95 percent relative humidity. You can keep snap beans in the crisper section of the refrigerator in a perforated plastic bag; this will keep the beans from drying. (You can purchase perforated plastic bags or make your own by punching 20 holes in a medium-size bag; use a hole punch or sharp object.)
Snap beans will keep for 8 to 12 days in a cool, moist place.
Do not refrigerate snap beans at less than 40°F; beans are easily injured by cold developing opaque discoloration, rusty spots, and pitting.
Blanching and freezing is an easy way to preserve a larger snap bean harvest. Blanch whole beans in boiling water for 1 minute and then quickly cool them in ice water and freeze them. This process will brighten and fix the color while preserving the crisp texture of the pods.
More tips at: How to Grow Green or Snap Beans.