It is easy to save seed from your achocha (Cyclanthera pedata, also commonly known as caigua) plants, although you might wonder at what stage they are ready to harvest. These instructions will also work for the closely related Cyclanthera brachystachya and probably for other Cyclantheras as well.
I had been trying to time things so that I could both eat the achocha pod and keep the seeds. In my experience, this is not a good compromise. Achocha fruits don’t taste that good by the time they have produced reasonably mature seeds. If you are determined and quick, you can find a point when the pods are suitable for use in recipes where they are cooked and stuffed and when the largest of the seeds in the pods are probably germinable, but since achocha is such a big plant and sets so many pods, it doesn’t really seem to be worth the trouble. I prefer to each achocha raw and it tastes best when the pods are small and haven’t really begun to form seeds yet.
If the seeds are light brown and require some work to separate from the pith, they really aren’t ready yet, although some of them will germinate even at this stage. Basically, if you need a knife to get at the seeds, then they aren’t ready yet. When they’re ready, you can just pull a pod open with your fingers. They will have changed color from green to a more yellow color as well.
The best solution is to leave some of your early fruits on the vine until they have started to go mushy. At this point, most of the pith will have broken down and you will basically have a sack full of hard, black seeds. Eight to twelve seems to be about the range in number of seeds in the smaller varieties, but the larger varieties may contain up to 24. Keep an eye on them because birds like to try for the seeds once the pods have become soft enough.
Just leave enough ripening to give you the number of seeds that you want and eat the rest when they are fresh and green. If only every plant made it this easy to save seeds! If you live in a climate where frost threatens before the pods are fully mature, you can just pick the ones that are farthest along and bring them inside to ripen. The number of mature seeds will probably be lower, but you ususally get something for your trouble,
Since they are big seeds, you’ll want to give them sufficient drying time. I leave ours on paper towels for a couple of weeks before bagging them for storage.