Bumble Bee Abundance in New York City Community Gardens: Implications for Urban Agriculture

A variety of crops are grown in New York City community gardens. Although the production of many crops benefits from pollination by bees, little is known about bee abundance in urban community gardens or which crops are specifically dependent on bee pollination. In 2005, we compiled a list of crop plants grown within 19 community gardens in New York City and classified these plants according to their dependence on bee pollination. In addition, using mark-recapture methods, we estimated the abundance of a potentially important pollinator within New York City urban gardens, the common eastern bumble bee (Bombus impatiens). This species is currently recognized as a valuable commercial pollinator of greenhouse crops. However, wild populations of B. impatiens are abundant throughout its range, including in New York City community gardens, where it is the most abundant native bee species present and where it has been observed visiting a variety of crop flowers. We conservatively counted 25 species of crop plants in 19 surveyed gardens. The literature suggests that 92% of these crops are dependent, to some degree, on bee pollination in order to set fruit or seed. Bombus impatiens workers were observed visiting flowers of 78% of these pollination-dependent crops. Estimates of the number of B. impatiens workers visiting individual gardens during the study period ranged from 3 to 15 bees per 100m2 of total garden area and 6 to 29 bees per 100m2 of garden floral area. Of 229 B. impatiens workers marked, all recaptured individuals (45%) were found in gardens where they were initially marked. These results indicate an abundance of B. impatiens workers within New York City community gardens and suggest that, at least for certain time periods, many individual workers forage within single gardens. Both findings suggest that B. impatiens may be an especially important pollinator of several common crops grown within community gardens and other urban green spaces that are used for agricultural production. Studies of other pollinating insect species in urban habitats as well as the relationship between pollen movement and seed or fruit set will complement the findings of this study

The Influence of Garden Size and Floral Cover on Pollen Deposition in Urban Community Gardens

Many cucurbits, such as cucumbers, squashes and pumpkins, depend on pollinating bees in order to set fruit. However, fruit yield and progeny vigor in these plants generally decreases as heterospecific pollen deposition increases. We studied how the spatial area dedicated to cucumbers (Cucumis sativis), versus other flowering plants, influenced the deposition of conspecific and heterospecific pollen on cucumber plants in New York City community gardens. We also examined the effect of garden size on conspecific and heterospecific pollen deposition on cucumber plants. Female flowers were collected from potted cucumber plants that had been experimentally placed into the gardens, specifically for this study, or that were established in raised beds by members of the community garden. In the laboratory, pollen grains were isolated from the flower by acetolysis, and the number of heterospecific and conspecific cucumber pollen grains were quantified. Conspecific pollen deposition was positively and significantly associated with the size of a community garden, as well as with the area of each garden dedicated to non-cucumber, flowering plants (i.e. floral cover) and the area of each garden dedicated to cucumber plants (i.e. cucumber cover). Although floral cover explained a greater proportion of the variance, cucumber cover had the strongest effect on conspecific pollen deposition. Heterospecific pollen deposition was positively and significantly related to garden area. However, no significant relationship was found between heterospecific pollen deposition and floral cover or cucumber cover. Based upon these results, we hypothesize that floral cover positively impacts conspecific pollen deposition by attracting a greater number of pollinators into an urban garden, and that total cucumber area positively impacts conspecific pollen deposition when pollinators are locally foraging within a garden. We suggest that the arrangement of plants within a garden can positively influence yield in fruit and vegetable-producing plants within urban community gardens. Due to the low availability of fruits and vegetables within the stores of the neighborhoods where this study was conducted, developing a better understanding of those factors that constrain or foster fruit and vegetable production are important to increasing food security and public health

Assessing five decades of garden bee studies

Urban garden spaces are potentially important habitats for bee conservation. Gardens can host diverse flora, which provide floral resources across foraging seasons for bee species. Recent reviews have focused on the impacts of cityscapes on urban bee assemblages in different green spaces. Urban gardens are distinct from other urban green spaces, and bee communities in urban spaces have been an increasing topic of study over the past few decades. We reviewed 28 urban garden bee studies spanning five decades and 14 countries to compile an original metadataset of bee species' functional traits to understand the conservation value of gardens, identify gaps in bee sampling efforts, and summarize the calls to action included by their authors. Studies of urban garden bees have documented between 674 (conservative count, excluding morphospecies) and 830 (liberal count, including morphospecies) bee species. Urban garden bee communities were taxonomically and functionally diverse, although bee species that were non-eusocial, ground-nesting, generalist foragers, and native were most common in garden habitats. The proportion of parasitic bee species and specialist foragers found in urban gardens was comparable to proportions for global bee taxa. This suggests that gardens contain the hosts and forage needed to support bees with specialized life history requirements, and thus represent high quality habitat for a subset of bee communities. Garden bee research was strongly biased toward the northern hemisphere, which signifies a large gap in our understanding of garden bee communities in other regions. The variety of, and non-standard sampling methods in garden bee research makes it difficult to directly compare results between studies. In addition, both intentional low taxonomic resolution and a lack of collaboration with taxonomists constrains our understanding of bee diversity. Our analyses highlight both successes of past urban garden bee studies, and areas of opportunity for future research as we move into a sixth decade of garden bee research

Bottom-Up Forces Mediate Natural-Enemy Impact in a Phytophagous Insect Community

We employed a combination of factorial experiments in the field and laboratory to investigate the relative magnitude and degree of interaction of bottom-up factors (two levels each of host-plant nutrition and vegetation complexity) and top-down forces (two levels of wolf-spider predation) on the population growth of Prokelisia planthoppers (P. dolus and P. marginata), the dominant insect herbivores on Spartina cordgrass throughout the intertidal marshes of North America. Treatments were designed to mimic combinations of plant characteristics and predator densities that occur naturally across habitats in the field. There were complex interactive effects between plant resources and spider predation on the population growth of planthoppers. The degree that spiders suppressed planthoppers depended on both plant nutrition and vegetation complexity, an interaction that was demonstrated both in the field and laboratory. Laboratory results showed that spiders checked planthopper populations most effectively on poor-quality Spartina with an associated matrix of thatch, all characteristics of high-marsh meadow habitats. It was also this combination of plant resources in concert with spiders that promoted the smallest populations of planthoppers in our field experiment. Planthopper populations were most likely to escape the suppressing effects of predation on nutritious plants without thatch, a combination of factors associated with observed planthopper outbreaks in low-marsh habitats in the field. Thus, there is important spatial variation in the relative strength of forces with bottom-up factors dominating under low-marsh conditions and top-down forces increasing in strength at higher elevations on the marsh. Enhancing host-plant biomass and nutrition did not strengthen top-down effects on planthoppers, even though nitrogen-rich plants supported higher densities of wolf spiders and other invertebrate predators in the field. Rather, planthopper populations, particularly those of Prokelisia marginata, escaped predator restraint on high-quality plants, a result we attribute to its mobile life history, enhanced colonizing ability, and rapid growth rate. Thus, our results for Prokelisia planthoppers suggest that the life history strategy of a species is an important mediator of top-down and bottom-up impacts. In laboratory mesocosms, enhancing plant biomass and nutrition resulted in increased spider reproduction, a cascading effect associated with planthopper increases on high-quality plants. Although the adverse effects of spider predation on planthoppers cascaded down and fostered increased plant biomass in laboratory mesocosms, this result did not occur in the field where top-down effects attenuated. We attributed this outcome in part to the intraguild predation of other planthopper predators by wolf spiders. Overall, the general paradigm in this system is for bottom-up forces to dominate, and when predators do exert a significant suppressing effect on planthoppers, their impact is generally legislated by vegetation characteristics

An introduction to being a Master Gardener volunteer

The Oregon State University Extension Service Master Gardener Program is a voluntary educational program designed to meet the community’s gardening needs. This publication provides an introduction to the program and the Master Gardener position.Published January 2010. Please look for up-to-date information in the OSU Extension Catalog: http://extension.oregonstate.edu/catalogKeywords: volunteer, plant clinic, pest control, gardeningKeywords: volunteer, plant clinic, pest control, gardenin

Growing your own

A publication containing advice on a wide range of gardening topics, including composting, container gardens, fall/winter gardens, fertilizing, insect pests, plant diseases, planting guidelines, raised beds, site selection, slugs, soil improvement, tilling, warm-season crops, watering, and weeds. Includes regional tips for various parts of Oregon.Published April 2011. Replaces GROW. Facts and recommendations in this publication may no longer be valid. Please look for up-to-date information in the OSU Extension Catalog: http://extension.oregonstate.edu/catalogKeywords: soil preparation, gardening, pest control, Oregon, vegetable

Gardener Perceptions of Native Pollinator Plants

Native plantings are used in urban areas to improve pollinator habitat. To achieve wide adoption, these plant choices must be attractive to home gardeners as well as to pollinators. We distributed two surveys to identify native Willamette Valley pollinator plants that are aesthetically pleasing to home gardeners. The first survey sought to ascertain baseline attractiveness, and asked gardeners to rank the attractiveness of 23 wildflowers on a 1-5 Likert scale. In second survey, we were interested in how sharing information on the benefits of these plants impacts perceived attractiveness. We asked gardeners to rate the attractiveness of a subset of 11 of these 23 wildflowers both before, and after, being shared information on each flower’s attractiveness to bees. Both surveys also included space for open-ended comments. We found a high level of acceptance of native wildflowers by gardeners (over half had mean attractiveness scores of 4.0 or above), and gardeners found native plants significantly more attractive after learning about the bees that visit each plant. Gardeners who identified as “native plant gardeners” found all of the study plants significantly more attractive than non-“native plant gardeners”. In the open-ended comments, gardeners stated that they were most negatively concerned with the aesthetics and aggressive growth of flowers. Gardeners felt positively about flower aesthetics and beneficial ecological traits (e.g. pollinator attractiveness, drought tolerance). We identify five species of native wildflowers that Pacific Northwest nurseries might consider marketing as pollinator plants (Gilia capitata, Clarkia amoena, Eschscholzia californica, Madia elegans, and Sidalcea asprella ssp. virgata)

Garden bees of Portland

Gardens are known to contain a diverse and abundant community of bees, which suggests the value of gardens for bee conservation. To date, we do not have a species-level bee list for Oregon gardens. We thus sampled 24 Portland Metro area gardens for bees, in the summer of 2017-2018. Thus far, the 2017 bees have been identified to species. The 2018 samples are still being curated in the lab. The ecological characteristics of each bee species will be determined from an array of natural history resources, and the area of each garden allocated to turf/hardscape/flower beds has been estimated, to glean insights about the quality of habitat offered by Portland area gardens. We will sample gardens once more in 2019, and will perform more detailed analyses of within-garden and landscape level characteristics

Garden Bees of Portland

Gardens can provide forage and habitat to a diverse and abundant assemblage of garden bees. Although the garden bee assemblage has been described in several U.S. cities, a comprehensive accounting of Portland area garden bees has yet to be published. Each summer, from 2017-2019, we collected garden bees from 25 Portland area gardens using a combination of pan traps and hand-collection. With our 2017 and 2018 bees identified, we have collected 65 species or morphospecies. In this poster, we consider the ecological characteristics of these garden bees in the context of the resources that gardens may or may not provision for various native bee species

Bee Abundance and Richness in Portland-area Home Gardens

Research has demonstrated that urban gardens support diverse, abundant, and intact bee communities in New York, California. Ohio, and the United Kingdom. In fact, the abundance and diversity of bees visiting urban gardens has been observed to approach, and even exceed, numbers in nearby natural and/or agricultural systems. To date, no comprehensive study has yet to be conducted of Oregon’s garden bees. We thus sampled 24 residential gardens in the Portland Metropolitan region, to document the abundance and richness of Portland’s garden bees. We used a combination of pan trapping and hand collection to sample bees. Study sites varied in their composition (i.e. pollinator garden, perennial plant garden, edible garden, lawn-dominated garden, etc.), and were located in one of three landscape contexts: (1) Urban Core: gardens located within Portland, in highly populated neighborhoods, (2) Forest Edge: gardens located within Portland, located adjacent to Forest Park, and (3) Portland Suburbs: gardens located outside of Portland, in a peri-urban landscape. This presentation will review the diversity of bees that we have collected and identified, and explore the ecological characteristics of Portland’s garden bees