A good number of people are not crazy about commercial grapefruit, mainly because they are pick early, at or near the 11,000 heat unit time period. Of course commercial growers want to harvest as soon as possible for economic reasons. The 11,000 heat unites is assumed to be acceptable for harvest. This measure was set some times back. In recent times many new varieties, especially reds, have come into existence. I am not sure what the heat unit number is for each individual cultivar. However, it is also known that the longer a grapefruit hangs on the tree, the the better the quality becomes. Of all the people that I personally know, the one person with the highest level of intelligence on the science concerning the production of citrus, Dr. Malcolm Manners PhD, (Florida Southern University) once told me that grapefruit left hanging on the tree until March produces the most fantastic tasting grapefruit possible. He further stated that of all the different grapefruit cultivars, the white fleshed Marsh grapefruit is the best of the best (at least in his estimation.) - Millet