Growing peas for seed is not very different from growing them for food. But if you want to also have a crop for eating, it is best to plant a completely separate row. The peas grown for seed will need to stay on the plant until the pods are ripe and dry. It is also best not to harvest any peas for eating from the plants grown for seed. So if you have two separate rows, you’ll know exactly which vines you can eat from and which ones you can’t.
Direct sow the seeds as soon as the ground can be worked in the spring. Carve a small furrow in the row and scatter the seeds in the furrow. Cover with about an inch of fertile, well-drained soil, and keep watered until the seeds sprout. Peas like to grow in full sun.
Peas are self-pollinating, which means that the individual flowers are pollinated before they open, so there is very little danger the different varieties will cross-pollinate. Still, it is best to separate different varieties by at least 10 feet if possible.
Most pea varieties will require support in the form of a trellis. This can be easily constructed out of saplings or metal stakes with a cross beam over the top. You can use chicken wire to give the vines something to climb on, or use some commercial pea trellis which is often available through seed catalogues. Sometimes the vines will also need to be tied up with extra support to prevent them from flopping over.
Allow the pods to dry out completely on the vine before harvesting them. Pick them as they mature. With some varieties this happens all at once, with others it will happen over time and you’ll need to harvest dry pods over several days. Arrange the harvested pods in shallow layers in flats so they can continue to dry in a well-ventilated spot out of direct sunlight. Completely dry pods will be easier to thresh. If you have a small harvest, you can thresh by opening each pod individually. This lets you check the pods for weevils and immediately discard any pods that have signs of the insect. After all the seeds are threshed, allow them to continue to dry in a well-ventilated spot at room temperature out of direct sunlight for at least two weeks before packing for storage.
Store seeds in a cool, dark, dry place, and they will remain viable for at least 5 years.