Pickled nasturtium seeds are a bit unusual, but they offer a nice little pop of flavor and are a good substitute for capers.
Wash nasturtium seeds thoroughly, remove any remaining stems, and break the seed pods apart. Place seeds in a wide mouth quarter-pint jar.
Dissolve salt in water to make brine; pour brine over nasturtium seeds to cover. Refrigerate remaining brine. Place a glass weight on top of seeds to prevent floating and to keep seeds submerged.
Use the Fermentools airlock system---it fits right onto any wide mouth jar---to prevent accidental overflows and to keep out the fruit flies. (I'm loving how easy fermenting is with this system!) After about three days, open the jar and you will likely smell a bit of a sulphur odor.
Drain seeds, cover with reserved brine, and put the airlock back in place. Allow to sit at room temperature for another three days or so, then give them the old taste test.
Water: Municipal tap water contains chlorine, which can inhibit fermentation. Use spring or distilled water instead.
Salt: Salt with iodine or anti-caking agents can inhibit fermentation.
No nasturtiums handy? Check out this recipe for dandelion capers.