Whether you call them string beans, snap beans, or haricots verts, green beans are a great addition to any backyard garden, and because they're easy to grow and harvest, they can be a good gateway crop for beginning gardeners.
Green beans come in a wide variety of sizes, shapes, and colors, and two distinctly different growing habits, so they can be grown to suit just about any garden space in most climates. And in addition to being a tasty garden treat, green beans can improve soil fertility by fixing nitrogen with their roots.
The biggest distinction that you'll need to know about before running out and buying seeds to grow your own green beans is their growth habits, which can be either pole beans (climbing vines) or bush beans (compact plants that don't need support). Pole beans are well suited to trellises, bean tipis, or along fences, as they really do need to climb up a pole of some sort, without which they sprawl on the ground and quickly become a tangled jungle that isn't conducive to optimal growing or harvesting of the beans. Bush beans, on the other hand, are much shorter plants that can stand alone without support, are often quicker to mature than pole beans, and could be grown in a container garden.
How to grow green beans:
Most green beans should be planted after the soil warms and the danger of frost is gone, and need to be planted about an inch deep (and as deep as two inches, especially in arid climates). As a rule of thumb for planting, plan for about 10 to 15 green bean plants for each person in your household. Once planted, the beds should be watered to stay evenly moist until all of the seedlings emerge from the ground, at which point the surface of the soil can be allowed to dry out between watering. Green beans will do best in fertile soil that is rich in organic matter, and digging some finished compost into the garden beds will help them thrive. Once the green bean seedlings have several true leaves, cover the garden beds with several inches of mulch to conserve moisture, keep soil temperatures cooler, and keep weed seeds from germinating.
For growing pole beans, choose a garden bed that has full sun and good drainage, and build a bean tipi or trellis before planting them (one simple method for a trellis is to put a t-post at the middle of each end of the bed, and then attach chickenwire or other wire fence to the posts). Pole beans can be planted close together and then thinned to about 6 to 10 inches apart after germination, or sown at that distance to begin with (which yields more green bean plants per packet, as none of them will need to be removed for thinning). Pole beans tend to produce continuously throughout the season (about 60 days after planting, depending on the variety), up until the first frost of fall, and can end up yielding more green beans per plant than bush beans.
For growing bush beans, which also require full sun and well-drained soil, plant the seeds about 3 to 6 inches apart (or plant more densely and then thin to that distance once germinated), with about 1 to 2 feet between rows, depending on the size and shape of the garden bed. Because they don't require any support (although they could use it if grown in an open area that tends to be windy), bush beans can be planted without building any sort of trellis for them, and their shorter height is more conducive to fitting them into areas of the garden that wouldn't work for pole beans. Bush beans tend to produce a crop over a single period of about two weeks or so (about 50 days after planting, depending on the variety), but to have a continuous harvest throughout the summer, do several succession plantings a couple of weeks apart for the biggest yields.
The soil for both types of green bean plants should be kept moist during flowering and fruiting, as hot and dry conditions can make them drop their flowers or young beans before they're big enough to harvest. A thick mulch under the plants will keep soil moister and cooler in the middle of summer, as well as serving to feed the earthworms and other soil life.
To harvest pole beans, begin harvesting them when the pods are still small and tender, using two hands to pick them to keep from ripping the vines (although with practice, green beans can be harvested with one hand with a little twist and pull action). Pole beans should be picked every few days to keep the plants flowering and producing new bean pods, but the green beans can be allowed to grow to a larger size before harvesting them.
To harvest bush beans, which should also be picked regularly, use two hands to twist or snap them off of the plant (or try the one-handed approach, which uses the thumb and finger to pinch the stem of the bean). Both varieties of green beans should be picked before they get tough, unless you're saving some to dry for cooking or for next year's seed. Green beans are self-pollinating, so different cultivars can be grown next to each other, although to minimize the possibility of cross-pollination for next year's seed crop, the different varieties should be grown in beds that are widely separated from each other.
Growing green beans is a great activity for children, as the seeds are large and easy to plant, and growing pole beans over a tipi or other trellis can produce a fun shady spot for kids to play in the garden. Pole beans can also be grown in front of, and over, sunny windows, to help keep your home cooler during the hot days of summer.