If plants will not establish by direct seeding despite following the above cultural directions, or if transplants become stunted and don't grow even if well-fertilized, the cause may be symphylans, which eat sprouting cole seeds before they emerge and chew off root hairs on cabbage family plants. The high ammonia content of fresh chicken manure may be the best "organic" symphylan control measure, especially for coles.
Early cauliflower varieties are based on two different breeding lines. The first is the alpha cauliflower varieties that were developed in Europe for early growth. The alpha varieties do well in cool weather. The other source for early maturity are the tropical genetics. These are used in the warmer production area and are generally considered more tolerant of hot weather. Snow Peak and Snow Crown are bred from tropical genetics.
These varieties are bred to mature during the cooler period at Summer's end and Autumn. If sown too early, curd formation may suffer from high heat . Use F1 types for May sowings. The autumn varieties below form a succession of maturity. Heavy frosts occurring during curd formation can cause browning, so the later varieties are bred to wrap and protect the head as much as possible.
These are the easiest class of cauliflowers to grow. Overwintering types are bred to form very well-wrapped heads that are protected from the cold and are unsurpassed in uniformity. Perhaps the most amazing aspect of these specimens is the fact that they are bred to mature at specific spring dates. These varieties should be sown between July 1st and August 1st. If transplanting, it is best done by the end of the first week in September. Small or no heads are usually the result of planting too late or low soil fertility. Non-headed plants will grow into monstrous plants that will usually form exhibition size heads the following spring.
The Walcherin types of cauliflowers are a Dutch breeding masterpiece. Most of the early varieties of cauliflower are based on tropical genetics to withstand Summer heat. The Walcherin varieties, however, are based on Northern European breeding and were the first varieties specifically developed for overwintering. Walcherin selections have the ability to withstand cold temperatures and show little damage down to 10 degrees. These varieties have the ability to tightly wrap their own heads with leaves to protect them from freezing temperatures. In England and Holland these varieties are extensively grown commercially and have been bred to produce a highly concentrated harvest. At one sowing date, the farmer plants his field into blocks of several varieties and then harvests the blocks completely as they mature.