So maybe we waited a -little- too long. All three cabbage were pulled today, and the green one was beginning to split. Some claim that such splitting indicates over-watering, or perhaps watering more than usual (extra rains). However, I think cabbages just do that when they've decided they're big enough. Perhaps both are true; quoting one web source: "Splitting is caused by the pressure of excessive water taken up after the heads are solid." One of the red cabbages looked a bit bigger than last week, but the other did not. It was time to harvest.