Fermentation is not necessary. Allow the tomatillos to ripen for a week or longer after picking, then remove the husks, and select the ripest for seed.

Add water to a blender, leaving room for the fruits to be processed. I have found that this works best if the fruits make up no more than 1/4 of the volume... more than that, and too many seeds will be trapped in the debris. Add halved tomatillos (cut larger ones into quarters), and blend at lowest speed only until the seeds have broken loose. The seeds are very hard, and few will be harmed.

The good seeds are heavier than water, and will sink to the bottom - the pulp & bad seeds will float to the top. You might need to stir the top gently to allow some seeds caught in the pulp to sink. Add water slowly, then pour off about 1/2 of the water & pulp. Re-fill with water to the top, stir, and repeat the process until only the seed at the bottom remains.

Pour the water & seed through a fine strainer, set it on a towel to wick out excess moisture, and pour the seeds out onto a hard non-porous surface to dry. A fan is helpful for at least the first hour or two. DO NOT dry them in the sun. Break up clumps to allow faster drying.

Ensure that the seed is fully dry before storing in any air-tight container.

This method also works for ground cherries, and for eggplant. But for eggplant, the fruits should be allowed to ripen on the plant until they begin to soften, then the end with the seeds cut into cubes or thin slices prior to processing.

I simply picked the seeds out when I sliced them and then dried them. They came up fine the following year.

I just got some Purple Tomatillos this year from my local seed exchange and I am so excited to try growing them. Thanks for the tips on saving the seeds. Cheers

how do i save to plant next year

I actually extraxted fresh seeds and put them directly inro a warm pod to start growing. Ill get back to you on what happens.