Just tried this, though following the recipe through to the originator, a baker in Alaska, she says to rinse the cabbage leaf and use the water for making the starter. It worked, but I found the pineapple juice method to be 1 day faster in getting a starter going from nothing...amazingly easy. Here's my twitter summary:
100% Flour 100% Pineapple Juice. Discard 50% next day, feed 100 x100, after 2 days, switch to filtered water. 3rd or 4th day you should be good to make your mother starter/levain/biga/etc.