University of California Professor Dr. Gordon Frankie and the UCB Urban Bee Lab have been studying relationships between California’s diverse native bees and their favorite flowering plants at the University’s Oxford Tract Bee Evaluation Garden (UCB Bee Evaluation Garden) in Berkeley. Dr. Frankie, a bee ecologist who studies plant-pollinator relationships in Costa Rica, established the Garden to learn about native bee-flower relationships in California.
UCB Bee evaluation Garden and its Bees
In the summer of 2003, the Garden was planted with a handful of plant types that Dr. Frankie observed attracting native bees in gardens around Berkeley. By the end of the first year Dr. Frankie and the Urban Bee Lab recorded 25 bee species visiting the garden. Now, in its eleventh year, the garden is home to about 150 different plant species, varieties, and cultivars, with more added each year. With the help of UC Davis entomologist Robbin Thorp, nearly 60 bee species have been identified in the garden to date.
California is home to over 1,600 species of native bees; however, many people are familiar with only a few types of bees. The European honeybee (Apis mellifera) is a well-known and highly successful introduced species. Bumble bees (Bombus species) and carpenter bees (Xylocopa species) are familiar natives to gardeners across the state, but the wide variety of other native bee species often go unnoticed or are mistaken for other insects. From the startling colors of the ultra-green sweat bee (Agapostemontexanus) and the metallic blue orchard bee (Osmialignaria propinqua) to the tiny yellow-faced bee, (Hylaeus species) to the enormous teddy bear bee (Xylocopavaripuncta), California’s native bees are as diverse as the plants they pollinate.
The UCB Bee Evaluation Garden has evolved over the last decade to include non-native plants, which comprise about 30% of the garden, in addition to a broad variety of native species. Native bees generally prefer native plants, but many species will visit a substantial number of non-native plants. Because most California gardeners use many non-natives in their plantings, it is important to study the relationships of these plants with native California bees. Ornamental plants from other areas of North America, Asia, and the Mediterranean region are often good resources for native California bees; plants native to North and South Africa, Central and South America, Australia, and New Zealand are generally not attractive. Working with limited space at this urban location, the plant palette at the bee garden is ever changing. When enough information has been gathered about a specific bee-flower relationship, the plant will often be removed to make room for new plant types to be evaluated.
Statewide Bee-Plant evaluations
Information collected at the UCB Bee Evaluation Garden is evaluated and compared with data collected at other gardens across the state. Inland locations including Sacramento and Sonoma, coastal locales like Santa Cruz and San Luis Obispo, and southern sites such as Descanso Gardens near Pasadena, are studied and compared for a variety of elements, including the adaptability of bee-attracting plants to coastal and inland environments. Results of these statewide evaluations provide a knowledge base that is applied to constructing bee habitat gardens with relatively predictable out- comes. Based on ten years of conducting thousands of visitation counts, reasonable predictions can be made about which plant types will most frequently attract certain bee taxa in a given region of the state.
The knowledge that emerges from garden research is applied to other studies such as the Urban Bee Lab’s “Farming for Native Bees” project being conducted in Brentwood, California. Having learned of Dr. Frankie’s extensive research on bee-flower relationships in urban areas, the United States Department of Agriculture— Natural Resources Conservation Service (USDA-NRCS) and farmers like Al Courchesne at Frog Hollow Farm, invited the researchers to apply this knowledge to study native pollinators in fruit orchards. The importance of pollinators is well understood in the agricultural community and given the precipitous decline of honeybee populations due to Colony Collapse Disorder (CCD), farmers are interested in attracting native bees to their farms. This research seeks to understand how native pollinators might supplement pollination by honeybees.
Plant selections for Bees
The Urban Bee Lab’s research includes learning about growth and management of plants so that they will produce prolific, vigorous blooms. The Lab commonly experiments with deadheading and pruning methods, watering regimes, and the use of a variety of organic fertilizers and soil amendments to enhance growth.
Invite native bees into your garden by providing pollen and nectar resources, nesting space, and a diverse plant palette. You’ll find a list of plants that have been identified as attractive to California native bees on the Urban Bee Lab website. Plant each plant type in large patches—1 meter wide or larger—to encourage bees to forage for longer periods of time in your garden. Use at least 20 different plant species and include plants that flower successively throughout California’s very long growing season. Doing so will provide pollen and nectar resources for diverse bee species in all seasons. Like plants, bees have different seasons and every season in your garden will welcome a different group of bees (see graph left). Many native bees are ground-nesting and require exposed soil where their nests will not be disturbed. Bee nest boxes may be provided but are not necessary for creating a successful native bee garden. Pesticides should be avoided, because no insecticides are safe for bees.
UC Berkeley Bee evaluation Garden
The garden is primarily a research facility, but it is also a tool for local outreach. The research team invites grade schools, garden groups, native plant groups, nurseries, and university classes to visit the garden and learn about native bees and their plant associations. The UCB Bee Evaluation Garden is open to the public as part of the “Bringing Back the Natives” annual garden tour held on the first Sunday in May (www.bringingbackthenatives.net).