I have grown some cabbages with perfect formed heads but after I harvested and cooked them, it was tough to eat. What causes this problem? Could it be the soil or weather? I look forward to hearing from you and thanks. Regards Serina
Environmental extremes could be a cause.
Harvesting at the proper times are important.
Also many gardeners I know swear by steaming the cabbage verses boiling it. If you do boil it use little water as possible and only cook for no more than 5 min.
Here is a link about harvesting.