Gordon Frankie is a Professor in the Department of Environmental Science, Policy and Management at UC Berkeley. He has been studying the preferences of bees in northern California for over 20 years. In 2002 he published an article in Fremontia, the journal of the California Native Plant Society, reporting on the preliminary results of his study.*
First, a word about the methods used in his study. His research team visited the residential gardens of north Berkeley and Albany twice per week for three years, 1999 to 2002. In the first stage of the study, the team identified the plants that were being visited by bees. In the third year, they focused on counting the number of visits made to the identified “bee plants” by each species of bee.
The plants of Berkeley
Frankie’s team reports having identified 600-700 different varieties of non-native plants in the study area. Native plants were defined as those that occur historically only in northern California. Only 50 species of native plants were identified in the study area.
The bees of Berkeley
Frankie was surprised by the diversity of the bee population found by his research team. They report having identified 74 different species of bees (updated on his website to 81). Of those, only two were non-native bees (the European honeybee and the leaf cutting alfalfa bee). Putting these numbers into perspective, there are approximately 1,600 species of bees in California and about 4,000 known to occur in the U.S. Frankie reported that the population of European honeybees in the study area has declined significantly in the past 10 to 15 years.
What do the bees of Berkeley want?
The bees were observed visiting a small number of the total number of flowering plants available to them. Only 72 species of flowering plants were visited by bees often enough to be counted by this study as “bee plants,” about 10% of the total number of flowering plants available to them. Fifty-three of the “bee plants” were non-native and 19 were natives.
While the bees of Berkeley are using a higher percentage of the available native plants (38%) than they are of non-native plants (8%), the percentage of non-native plants they are using is nearly 75% of all the flowers they are using. Clearly, the non-native plants are important to the bees of Berkeley.
Frankie explains that many non-native plants are not useful to bees because they have been cultivated for looks, rather than for the nectar and pollen needed by the bees. However, on his website, he updates his research with some strong recommendations to include both natives and non-natives in our gardens both for the benefit of the bees and the benefit of native plants.
Non-native plants extend the blooming period in our gardens, which provides food to the bees for a longer period of time:
“California native [plants] tend to flower in early spring and summer, while non-native ornamentals bloom mainly in late summer to fall, so a combination of both would be ideal for attracting the highest potential density of bees.”
Also, when our gardens attract more bees, all the plants in our gardens benefit from their pollination services, which will also benefit the native plants in our gardens:
“If your priority is a healthy garden, it makes good ecological sense to consider your plants’ bee-attractiveness, rather than focusing exclusively on whether one hundred percent of your plants are natives. Even if your priority is to have a native garden, it can be highly advantageous to include even a couple of exotic plants on the basis of their bee-attractiveness. The bees they attract will help your natives thrive.”
Frankie reminds us that the bees don’t care about the nativity of the plants that they use.
“Insects and other wild animals make no distinction between weeds and plants we put in our gardens. From the perspective of the bee, any plant that provides quality pollen and nectar is attractive. For the short period they are in bloom, weeds such as dandelions and white clover provide bees with good sources of pollen and nectar.”
Opening our minds to the benefits of non-native plants
The bees of Berkeley remind us that the obsession with native plants is a human hang up that is not shared by animals. They consider the nativity of the plants that are useful to them to be irrelevant. So should we.
* Gordon Frankie, et al, “Bees in Berkeley,” Fremontia, July/October 2002