Melissodes or Longhorn Bees — The female gathers pollen and nectar while the male bees sleep. (Photos by Celeste Ets-Hokin).

The following article is an excerpt from a talk given in the Gardens at Lake Merritt by native bee advocate Celeste Ets-Hokin.

Eighty percent of the planet’s 250,000 flowering plants, including much of our food, depend on pollinating insects.  Bees are the most important pollinators for maintaining our food supply and keeping ecosystems alive.

Why are bees unique pollinators? Most insects, unlike bees, land on a flower to bask, find a mate, drink nectar or eat. Flower pollen adheres to them and brushes off on subsequent blooms they visit.

 Bees are different. The female bee deliberately collects pollen to provision her nest. In her quest for pollen, a female bee may visit hundreds of flowers during a single foraging trip.

There are approximately 4,000 native bee species in North America and some 1600 species in California. The honey bee, brought to North America in the 1600s by European settlers, is different from our native bees. Honey bees are highly social and live in colonies comprised primarily of female workers and a single egg-laying queen.  Native bees are mostly solitary. Each female bee builds and provisions a nest in which to lay her eggs.  These nests are mostly built in the ground or in a wood cavity.

The female bee lays a series of eggs in her tunnel nest, each one contained in an individual compartment or cell. Generally, each generation of offspring will include both males and females, with females laid at the back of the nest, and males occupying the cells nearest to the nest entrance.  She creates the partitions between the cells with materials collected from the environment, such as mud or leaves.

Solitary native bees are not aggressive, and many have only a mild sting. Male bees have no stinger whatsoever.  North American bees range widely in size, from tiny sweat bees measuring less than ¼” in length, to robust carpenter bees and bumble bee queens, often exceeding an inch. They also vary widely in colors and patterns — from metallic green or iridescent blue, to red, black, grey, brown, yellow, and even spotted.

Native bees are far more efficient than honey bees at pollinating crops such as apples, cherries, squash, watermelon, blueberries, cranberries and tomatoes. Native bees currently contribute some $3 billion each year in crop pollination serves. Recent research suggests that native bees can pollinate nearly all of our current crops if given sufficient habitat.

Natural bee habitat areas, however, are steadily diminishing making residential gardens increasingly important as habitat for many bee species. By following the three “build it and they will come”principles below, both gardeners and growers will enjoy the rewards of prodigious pollination services.

Plant a variety of bee-friendly plants with different bloom periods to ensure a continuous supply of pollen and nectar throughout the spring, summer and fall nesting seasons. Be sure to include a selection of native plants as these plants are best adapted to the region and therefore attract regional native bees. Native plants offer the additional advantages of generally requiring less water, little or no fertilizer, and providing habitat for other beneficial insects, birds and wildlife.  

Create nest sites by leaving areas of undisturbed, un-mulched soil and by offering wood nests. Bare soil will provide nesting opportunities for the 70% of our native bees that nest in the ground. Mulch prevents females from establishing their ground nests, and tilling can destroy existing ones. The remaining 30% of our native bees are wood-nesting, and will benefit from snags or stumps left in place, or by the placement of artificial tunnel nests around your property.

Avoid the use of pesticides and herbicides. Pesticides will harm not only our native bees, but a spectrum of beneficial insects that would otherwise naturally control garden and crop pests.

For information on selecting the best seasonal bee plants for California native bees, visit nature.berkeley.edu/urbanbeegardens.  For general information on native pollinators and how to attract them to your gardens, parks, open spaces and farms, visit the Xerces Society website at www.xerces.org.    

Celeste Ets-Hokin is dedicated to promoting awareness of native bees, their vital role in our ecosystems, and the measures required to ensure their conservation.  She is dedicated to fostering a transition to a more conservation based system of agriculture, which supports and depends on biodiversity.

Her North American Bee Calendars, created to assist gardeners in identifying and attracting native bees through photos and descriptions of distinguishing characteristics, emergence times, nesting habits and recommended floral resources for each featured bee genus, is a tremendous step forward in raising awareness of the critical role native bees play in the health and well being of the planet.

In addition, Celeste is collaborating with the Alameda County Master Gardeners in the Trials Garden located in the Gardens at Lake Merritt. She has created a native bee garden area including native bee attracting plants and nesting blocks for the habitat. It is a beautiful and buzzing area of the garden.

Celeste Ets-Hoskin can be reached at celeste.ets@comcast.net.

The highly informative talk was part of the Alameda County Master Gardeners 2011 Speaker Series.  The 2011 Series concluded in October 2011 and will resume in the summer of 2012.