Even when the flowers seem perfect in all respects they often in the cultivated fruits seem incapable of self-pollination. This is not confined to the individual flower or to the flowers of a single tree or a large block of trees. As a rule, large blocks of a single variety of the orchard fruits have not proven productive. As Bailey says: "We chiefly know that the most productive orchards are usually those of many varieties, and that some varieties sometimes refuse to fertilize themselves." The concensus of opinion at this time of those with most experience and extended observation is that it is best to mingle varieties of the cultivated fruits and nuts in planting for profit or home use.