There's a good chance you wouldn't recognize a mason bee if you saw one, because many in the species don't look anything like what we think a bee looks like. Some are all black. Many are iridescent blue or green, and if weren't for their jointed bodies and long wings, you could mistake them for flies.
Mason bees are in the Osmia family, and there are 140 species native to North America. Approximately the same size as a honeybee, they are becoming ever more important as honeybee populations decline.
While the native orchard mason bee (Osmia lignaria) doesn't make honey, it excels at pollination and is an especially efficient pollinator of fruit trees, hence the name. How efficient? It is said that one mason bee can do the pollination work of 60 honeybees. Professional beekeepers even raise orchard mason bees and rent them out to almond and fruit tree farmers to aid in pollination, just as honeybee keepers do.
They are called mason bees because they create a paste of mortar-like mud to seal the nests where they lay eggs. They usually nest in holes in the ground, though they will use the deserted nests of carpenter and other bees, as well as hollow tubes and voids in stone. They do not excavate holes themselves.
Each bee builds her own "nursery," lays her own eggs, and tends to her brood. There are no queens or worker bees. These are solitary bees, though they are not territorial and will nest near each other. They have a gentle disposition and are not aggressive.
In early spring, male bees emerge from the nest first and wait for the females to appear. After mating, the males die and the females start collecting pollen, building nests and laying eggs. Each egg sits on a ball of nectar and pollen to feed on as it grows. A bee will lay five to eight eggs per tube, each one separated from the next by a plug of mud. A final, thicker plug seals the entrance, and the bee begins again in a new location. Over the winter the eggs pupate, and the new adult bees emerge from holes the following spring.
Their readiness to use available nest spots makes "keeping" mason bees easy, much easier than keeping honeybees. You can buy bees, but there's no need to. Create habitat and they will find you. Buy or make nest boxes of hollow reeds or tubes in varying diameters arranged in a box with a roof to protect the tubes from rain. The different sizes of tubes will attract different species of mason bees. Nesting boxes made from blocks of wood are popular, but are difficult to clean and over time can harbor disease.
Hang the nest box at least five feet off the ground, ideally protected under the eaves of a house or garage and sheltered from wind. The box should face south or southeast where it can get sun.
To feed the bees, plant a variety of flowers so there's something in bloom all season. Mason bees are not picky about the flowers they visit, though it's a good idea to include plants native to North America, since the bees have co-evolved with them.
Whether you grow fruit, flowers, vegetables or all three, mason bees will improve your garden by enhancing pollination, thereby improving crop yields, and maintaining the genetic diversity of plant species.
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