Cauliflower plants need plenty of space. They need at least 1 foot between them to grow big. When they reach this size, they will bolt, which means the stems will begin to swell and start to turn yellow. This is a good thing, as it means the plants are ready to harvest.
The heads of cauliflower can be harvested in any stage of development. When they are small, the heads are quite mild and can be used for salads or steamed. As the heads grow larger, the flavor becomes more intense and the texture becomes firmer.