If using the starter culture, place 1 cup of water in a glass measuring cup and add the culture, stirring until dissolved. Let the mixture sit while you prepare the celery — anywhere between 5 and 15 minutes. If using kefir whey, add it when the recipe calls for culture in step 3.
Place the celery spears to fit securely in your jars. Leave 2 inches of space at the top of the jar.
Add the ginger and culture to the jar.
Fill up the rest of the jar with filtered water, leaving 2 inches of headspace to let the celery expand as it ferments.
Seal the jar and let it sit on your kitchen counter, out of direct sunlight, for 3 days.
After 3 days, place in the refrigerator.