compatibility lists. Growers with old orchard blocks of single varieties sometimes provide bouquets of crabapple blossoms in drums or pails in the orchard for pollenizers. Home growers with a single tree and no other variety in the neighborhood can do the same on a smaller scale. During the bloom each season, commercial apple growers usually provide pollinators to carry the pollen. Honeybee hives are most commonly used in the United States, and arrangements may be made with a commercial beekeeper who supply hives for a fee. Honeybees of the genus Apis are the most common pollinator for apple trees, although members of the genera Andrena, Bombus, Halictus, and Osmia pollinate apple trees in the wild. Solitary bees or wild bees such as ground-nesting mining bees (Andrena) may play a far bigger role in pollination than at one time suspected, and are alternative pollinators in orchards. Bumble bees are sometimes present in orchards, but not usually in enough quantity to be significant pollinators; in the home garden with only a few trees, their role may be much greater. Apple growers also rely on several species of wild bees for pollination in their orchard. Increasingly Orchard bees (spring mason bees, genus Osmia) are being used in fruit tree pollination. According to British writer Christopher O'Toole in his book The Red Mason Bee, Osmia rufa is a much more efficient pollinator of orchard crops (in Europe) than honey bees. Both O. rufa and O. cornuta are used in Europe, while in western North America, the "Blue Orchard Bee" (Osmia lignaria, more black than blue in color) is a proven orchard pollinator. In Japan, the Japanese Orchard Bee—the hornfaced bee, Osmia cornifrons—provides up to 80% of the apple pollination. Beyond Japan, Osmia cornifrons is also used increasingly in the eastern US, because like other mason bees it is up to 100 times more efficient than the honeybee—a mere 600 hornfaced bees being required per hectare, as opposed to tens of thousands of honeybees. Home growers may find these more acceptable in suburban locations because they rarely sting. Symptoms of inadequate pollination are small and misshapen apples, and slowness to ripen. The seeds can be counted to evaluate pollination. Well-pollinated apples have best quality, and will have seven to ten seeds. Apples with fewer than three seeds will usually not mature and will drop from the trees in the early summer. Inadequate pollination can result