Here are instructions for saving common bean seeds. What are common beans? snap beans, string beans, wax beans, shell/dry beans, kidney beans, and most garden beans.
If you are growing green beans or other garden beans, by now you may have some left on the vine that have gotten too big to enjoy eating. If you planted an open pollinated or heirloom variety and want to save the seeds to plant back next year, you’re in luck! Let those beans continue drying on the vine until they are dried out and you can hear them rattling inside the pods. Choose to save seed only from plants that have grown well all season and appear true-to-type.
The back of my truck, the day before frost
Setting out pods to sun dry after being picked from plant
If you are having an exceptionally wet fall or a frost is looming and your plants are still green, you could pull the plants and allow them to dry indoors by hanging them or laying them in a well ventilated area. If you lay them somewhere, turn them often. Hanging is preferred. Leaving the pods attached to the plant allows the pods to soak up energy from the plant for a few extra days, which will result in better quality seed. After a few days of hanging, you may remove the pods and continue to let them air dry, or leave them right on the vine.
Harvesting:
Once your seeds are dry and ready for harvesting, you need to remove them from the pods. This can be done in several ways – place them in a pillowcase and tie it shut, then throw it around the house like a hot potato with your kids. Or jog in place on it. Or beat it with a bat. Once the seed is dry, the pod will fall off in pieces with a light touch, so your goal here is to crush the pod so the seeds fall out. This doesn’t mean you need to drive over the pillowcase with a vehicle or anything extreme, as you might with trying to crack walnuts. To remove the broken pods, or chaff, you will want to set yourself up in the area of a light breeze outdoors or in front of a fan, and pour the pillow case contents into a bowl or container below. Ideally, with the right speed breeze, the chaff will float out and the seeds will fall into your container below. Do this as often as needed to clean the seed.
Another option that might save you the extra step of sorting the undesirable seeds from the bunch is to simply open each pod individually and drop the seeds into a bowl. You will get pretty good at determining what seeds can get dropped in, and what should be discarded. You will want to discard any seed that is not true-to-type – small, shriveled, or any with characteristics that differ from the rest.
Storage:
Store beans in a cool, dry, dark area. Common beans will retain 50% germination for four years.
A dry pod reading for processing 
Storing beans.
Remember…
- Always save seed from healthy plants that appear true-to-type and have produced a large harvest.
- Leave pods to dry on the vine as long as possible – ideally until completely dry.
- If you are unsure if the seeds are dry and ready for storage, place a few on a solid surface and strike with a hammer. If it/they shatter, they are dry.
- Don’t grow different varieties right next to each other. While beans often do not cross pollinate (it IS possible, but rare), having varieties separated will help give another layer of protection.