the seed should be black and shiny when ready. Wait until about ten
days after the flower has completely dried up. You can check their
progress by sacrificing a few flowers. The seeds will probably go brown
or beige before blackening. Store in a ziploc bag the freezer until
next spring.
Keep in mind that one sage plant can grow quite large, typically one
will be enough for a family. I have two, and each is two feet tall.