Answer: Allowing seed pods to develop will bring a halt to additional blossoming of your plants. If you're sure they've finished blooming you can allow seedpods to develop. If the plants are still developing flowering stems, cut the spent blooms off before they begin to produce seeds.
Towards the end of the flowering season, allow the seed pods to develop. When the pods are a tannish-brown, the seeds are ripe for harvest. The seeds should be a dark brown color, but still look plump. Cut the pods from the plants, open them up and allow the seeds to fall into a container. I use an old mason jar with a screw-type lid. When you're sure the seeds are fully dry, put the lid on the jar and store it in a cool, dark location, such as the bottom of a seldom used cupboard or on the closet floor.
In the spring, when the weather is warm, sow your saved seeds in a prepared garden bed. You can plant sweetpeas in the same location year after year without compromising their health.
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