Photo is of the second heads from my cabbages planted in early fall. Note quarter for scale. Some are huge brussel sprout size and others are perfect to cut in half and fit into a small crock pot for boiled cabbage. When the second set of heads are harvested, the entire plant is pulled and composted. In addition to these smaller heads, we have a second planting of cabbage that is just now coming in with full sized heads.
With our approaching hot days, I expect the cabbages to start cracking. They crack because they are "going to seed" plus we actually got a bit of rain and the heads are swelling. If I am not ready to harvest the full sized heads and they start to crack, I twist the cabbage so the roots twist in the ground. This slows the cracking, however the second crop will either not happen or be very small. This time of year, with 90ºs approaching, I know I will not get a second crop from this "cold crop" and have no problem twisting them.