Just pulled out a dozen garlic bulbs (out of 90) which had rot around the bulbs. What are the causes ? any idea what to do about the soil? how to avoid repeating problems next year? I have been growing garlic for 15 years, rotating each year, and never had any problem. I replant my own cloves from the biggest harvested ones. last year, I had 3 bulbs with rot which I discarded.