The central head is ready first. After it is harvested, side shoots develop, extending the harvest period for a month or more. Six to 12 plants are enough for most families unless you plan to can and freeze a lot. Usually, two or three plants of any one maturity group are adequate. Plant late varieties for storage.
Heads are usable when they are reasonably firm.
A plant remaining after the head is cut will sometimes produce several small, edible side heads and thus extend the harvest season. Cauliflower Early varieties may be harvested in about two months and late varieties in about three months. Snow Crown is an early variety. Curds exposed to light while forming tend to yellow, but this does not affect eating quality. You can obtain pure white curds by tying the leaves together as the curd develops.