Botanical name: Phaseolus species; Vicia species; Vigna species; Glycine species.
Also known as: French beans, climbing beans, bush or dwarf beans; Runner beans; Tepary beans; Lima beans; Snake or yardlong beans; Cowpeas or Black-eyed beans/peas; Adzuki beans; Mung beans; Soybeans and Broadbeans.
Planting: What do we need to know before planting for seed production?
Before we start we need to be clear about what we mean by ‘beans’. It is a common name that gets used for a few different species. The name tells us it is a pod and they are generally used in the kitchen in similar ways – either we eat the whole pod or we eat the seeds that form in those pods, and sometimes we do both with particular varieties.
Beans come in lots of different forms: climbing and bush plant forms; flat or rounded pods; long or short pods; green, yellow, purple and mottled coloured pods; eaten fresh or as dried beans or even as sprouts.
Luckily we don’t need to worry too much about technical details like which species a particular bean belongs to because as seed savers we can treat them all the same, with three exceptions – Broadbeans, Runner beans and Lima beans.
All beans are self-pollinating which means their seed will come true-to-type. The flowers either pollinate the day before they open or do not provide easy access to insects. But Broadbeans, Runner beans and Lima beans are also capable of being pollinated by insects that might carry pollen from another nearby variety, so they need some special consideration. If you are not on the Australian mainland you may also want to check whether you have insects capable of cutting open the flowers and interfering in the self-pollination process for any variety.
Pollination method: Self-pollinating, except Broadbeans, Lima & Runner types.
Isolation distance: Try to keep different varieties 2 to 5m apart. Use the larger distance for vigorous climbers. Increase the distance to 50 to 150m for Broadbeans, Lima and Runner types. Caging or using insect netting is also a viable method of controlling potential cross-pollination instead of using distance.
Population size: You can get viable seed from just one plant. It is better practice to collect from 5 to 10 plants. Larger populations (10 to 25 plants) are required for long term propagation for Broadbeans, Lima and Runner beans and also Snake beans, Adzuki beans, and Mung beans.
Grow beans in the same way as for eating, there are no special cultivation requirements for seed saving. As the pods are left to mature on the plant the ground space is needed for slightly longer than when they are just grown for fresh eating.
When you are planning to grow them for food as well it is best to set aside the number of plants needed for seed and not harvest from them. We want all the energy from the plant to go into our seeds rather than our tummies. You will get much stronger seed this way than if you eat from the plants all season and just leave a few missed pods to mature at the end of the season.
Selection: What are we looking for in good seed plants?
You want to check that the plants you are harvesting your seed from are the correct plant form; flower colour; pod colour, shape and size; and seed colour and size for what is expected for that variety. Plants that vary from the variety being conserved should not have seed collected from them. We don’t often see variations but we should be aware they can happen.
Harvest: How and when do we harvest for seed?
Leave the pods on the plants until they have dried to crunchy, brown pods. Bush or dwarf varieties can be harvested when most of the pods have dried off by cutting the entire plant and placing it on a tarp to finish drying. Climbing varieties will likely need each pod to be hand picked from the trellis as it becomes dry enough.
Be vigilant and collect any dried pods before rain. Once dried on the plant significant rain very easily causes mold to grow on the pods and seeds and these should not then be saved for replanting
Processing: How do we separate the seed from the plant material?
Once the pods are dry they can be broken open to get the seeds out. This can be done by hand for each pod. Alternatively the usual methods of walking on or using a threshing machine can be tried. If the seed is dry it is difficult to damage it by threshing. Do not be tempted to try threshing or walking on the plant material before it is dried as the seed could be damaged while it is sill moist and soft.
Storage: What do we need to do to successfully store the seed?
After processing it is a good idea to keep the seed either spread out or in a paper bag in a dry location to ensure that any moisture being held in the seed has a chance to dry off. Beans are large seeds and can take a surprisingly long time to dry out fully internally.
Dryness can be tested by hitting a sample one with a hammer. If it shatters it is dry enough, if is squashes at all then it is still holding moisture. Have a look at our video on dryness if you need more help with this part.
There is a fair likelihood that insect pests will have laid their eggs in or on the seed. To stop them in their tracks one of the easiest methods of control is to freeze the seed for a few days. To do this the seed must be absolutely dry first. Seed will also store for longer if it is fully dry. It then must be placed in an airtight container – like a glass jar – before going into the freezer for 48 to 72 hours to kill pests and their eggs.
Seed is best stored in an airtight container where it is dark, cool and dry.
Contributors: Liz Worth, Julie Davies