The UC Davis Arboretum Teaching Nursery is a Davis treasure. Tours, classes, family activities and the most wonderful plant sales are big attractions here. Last Saturday Robbin Thorpe professor emeritus of entomology, and Neal Williams, assistant professor of entomology, spoke to a chilly and windblown but enthusiastic group of gardeners about native pollinators and, in particular, native bees.
Despite the wind making it difficult to hear, the hour-plus talk covered numerous topics ranging from how to make bee houses to what type of bees are most likely in your garden to what to do about carpenter bees drilling into your trellises.
Many of us visualize bee hives when we think of bees but in reality the majority of the bees you see buzzing around your salvias are not hive dwellers but rather solitary, ground dwelling bees. Some of them even count on the cracks that form in unamended soil during the hot, dry months as a place to raise their young. With over 50 species of bees observed so far in the Häagen-Dazs Honey Bee Haven on campus there is a lot to learn about the habits and lifestyles of our local bees.
If you have been tempted by the mason bee houses sold in many gardening catalogs you might like to know that most of the holes in those houses are too large for our local bees and will remain unused. Instead, 4 inch deep blind-ended holes with diameters of 1/4 inch, 3/16 inch, or 5/16 inch are what our bees look for and it is easy to make these custom houses from untreated scrap wood. You might, however, need to purchase a long shafted drill bit as many standard bits will not drill a deep enough hole. Lining the holes with straws allows them to be easily cleaned so they can be reused with less concern about contamination buildup.
Since gardeners made up a large part of the audience some time was spent discussing the physical makeup of flowers and the floral preferences of those bees you hopefully see in your garden. Much hybridization work aims to produce fuller flowers with more petals. While this can be lovely those increased petals usually come at the expense of the pollen and nectar producing plant parts, an eye opening piece of information to many gardeners. Less pollen and nectar means your bee buffet might be passed by for one that has more to offer. Those simpler flowered native plants could be one secret to attracting more native pollinators, a goal for anyone growing food crops which need to be pollinated in order to produce those über-local fruits and vegetables.
Increasing the diversity of plants in your garden will also increase your dinner crowd. Some bees are specialists, feeding only on a particular plant such as squash or sunflowers. But don’t just go for a one-of-each type garden. Planting in drifts allows bees to locate their favorite meals more easily and is also, for many people, more pleasing to the eye.
For more information on native bees and other pollinators visit The Xerces Society resource page. Plant lists, pollinator identification guides, bee biology, and so much more can be found here.