When the heads are the size of a quarter, pull a few leaves over them and secure with a rubber band (blanching). This will shade the heads from the sun and prevent them from turning yellow.
Environmental stress during transplant can negatively affect the development of cauliflower heads. “Buttoning” is a term to describe heads that stop developing beyond one-inch in diameter. Temperature fluctuations, inconsistent moisture, nutrient deficiencies and root bound transplants can all be susceptible to this condition. Row covers can be used to help regulate air and soil temperature as well as reduce infestations of insects.
Heads will be ready for harvest when they are five to six inches in diameter and still tight. As the head begins to separate, the flavor and texture declines significantly.