There are over 100 varieties of tulips, each with different colours and shapes. A number of tulips are white or very pallid in colour. Among these tulip varieties, almost every variety flowers in early to mid-spring. White tulips are not in season in September.
When a flower is not in season, it can only be grown in a controlled, artificial indoor environment. This is more costly than outdoor growing, so out-of-season plants cost more at your local florist.
White tulips grow between 8 and 12 inches high. If you grow or purchase out-of-season tulips in September, they may be slightly stunted because of the artificial growing conditions.
Late-blooming white tulips are available into August in most regions. September tulips are technically out-of-season, but it is close enough to the normal growing season that you may not notice a dramatic price markup.