Bees: The Pollinators

Bees are commonly thought of as a beneficial insect. However, most people are thinking of honey bees. While honey bees are, indeed, very beneficial, they are not the only bee that helps pollinate flowering plants in the garden. In addition to honey bees, bumble bees, mason bees and to a lesser extent, carpenter bees, help do this work.

Red Mason Bee

Honey bees have become the number one pollinator of crops in the United States, yet ironically, they are not native to North America. The honey bee was imported to America from Europe so that settlers could have the honey, beeswax, and other honey bee byproducts with which they were familiar in Europe.

Honey bees live in large nests or commercial hives holding between 20,000 and 80,000 bees. Their populations are higher during the summer months when pollen collecting is at its highest. The hive consists of one queen with the ability to reproduce, a few hundred male drone bees available to mate with a new queen; the rest are all female worker bees. The worker bee lives in the hive for up to 9 months during non-pollination times, but lives only 6 weeks during the heavy summer pollination period, working herself to death to support the hive.

Honey bees travel further than other types of bees in search of nectar. On average, a honey bee makes 12 trips to and from the hive each day and visits several thousands different flowers a day. On each trip, a honey bee will visit only one type of flower. It is estimated that honey bees are responsible for up to 80 percent of the pollination in crops, orchards, flower gardens and vegetable gardens.

Bumblebees are native to North America and there are at least 50 known species. While they make excellent pollinators, they are not commercially viable because they make only enough honey to support the small hive of 30 to 400 bees. Unlike honey bees whose queen can live several years and whose drones and workers can live several months, bumble bees die off with the approach of winter, leaving only the queen to start a new colony in the spring.

Being native to the colder northern climates, bumblebees are active in much cooler temperatures than honey bees and are particularly well suited to pollinating cool season crops. Their long tongues enable them to pollinate flowers with long corollas (necks) such as alfalfa, clover, and vetch which are all important crops for feeding livestock. Because of the small hive size, many greenhouse growers have turned to keeping a bumblebee hive within the greenhouse to pollinate plants in order to get away from labor intensive hand-pollinating. Bumblebees generally make hives in the ground, but are also attracted to bird houses, old flower pots, and other garden debris.

Mason bees, also called orchard mason bees, are solitary bees, often blue back in color though sometimes with golden hairs on their upper thorax similar to honey bees. These bees do not produce honey, but are very active pollinators. Mason bees make nests in existing holes in wood. The female bee will find a hole, collect mud to plaster into the hole and then begin collecting pollen. The female mason bee collects enough pollen for the larva to survive on, then lays an egg in the hole and seals up the hole with more mud. Each nest requires between 15 to 20 trips with nectar, often collected from several hundred flowers. The mason bee is able to build, collect and lay eggs in two nests each day for about a month. The larvae grows over the summer, pupating in the fall, but remains in the nest all winter, emerging again in the early spring.

Though they are only active for a month in the spring, the orchard mason bees are important pollinators because they emerge earlier than honey bees. Mason bees are active during the flowering of many fruit crops such as cherry, apple, apricot and grapes. While their nesting behaviors can be worrisome to homeowners, mason bees do not create holes in wood, but only seek out existing holes. They can be purchased and kept by the home gardener with much less investment of time and resources than honey bees and encouraged to nest in special boards.

Carpenter bees are large black solitary bees similar to bumblebees in size, but similar to mason bees in their nesting behavior. Unlike mason bees, however, they will create holes in wood to build a nest. Usually the nest is in a tree, but sometimes they nest in fences, patio furniture, wooden eaves, and siding. The carpenter bee is an important pollinator, flying in the early morning. They pollinate tomatoes, eggplants, and other early morning blooming plants. These bees can also have several generations in a season depending upon temperatures, making them helpful for a longer portion of the growing season. While carpenter bees are beneficial, care should be taken to seal any holes in siding to discourage them making nests on houses. While not commercially available in the U.S., they are used commercially in the Philippines to pollinate farm crops.

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Resources:

Galveston County Master Gardeners: Beneficials in the Garden Landscape: The Pollinators: Carpenter Bees
Washington State University Extension: Orchard Mason Bees
Backyard Beekeepers Association: Facts About Honeybees

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