Aaron Anderson is a Ph.D. student in Horticulture at Oregon State University, where he works in the Garden Ecology Lab.
Aaron’s project was inspired by the Garbuzov and Ratnieks paper entitled ‘Listmania: the strengths and weaknesses of lists of garden plants to help pollinators’. In this paper, the authors note that many pollinator plant lists were created with an absence of data. This is something I see in my own work, as the statewide Master Gardener coordinator in Oregon. Gardeners will swear that marigolds (Calendula spp.) are wonderful for bees, even though a two year study only found 141 bee visits to marigolds (Carreck and Williams 2002). Compared to the 12,759 bee visits to Phacelia or the 7,818 bee visits to Borage, marigolds just can’t compete (Carreck and Williams 2002).
Aaron is studying 23 species of Williamette Valley native plants. He is also studying bee visits to four non-native species that are known to be highly attractive to bees. These non-native plants (oregano, lavender, sage, catmint) can thus be used as ‘yardsticks’ against which he can compare bee visits to native plants. Aaron uses timed counts of bee visits to each flower, and also vacuum samples each plot.
In 2017, the top four species of plants for bee abundance were all natives (Gilia, Madia, Aster, Solidago). In 2018, the top four species of plants for been abundance were split between natives (Gilia and California poppy) and non-natives (oregano and lavender). However, when Aaron removed honey bees from consideration, the top four most attractive plants in 2017 (Gilia, Madia, Aster, California poppy) and 2018 (California poppy, Aster, Phacelia, and Goldenrod) were all native plants.
Aaron also looked at the bee richness on study plants in 2017. For bumble bees, three of the top four plants for bumble bee species richness were natives (Phacelia, Gilia, California Poppy). Lavender was also in the top four, and notably, was attractive to two species on the IUCN Redd list: Bombus fervidus and Bombus caliginosus.
Finally, Aaron asked gardeners to rate each of his study plants, based upon aesthetic beauty. Interestingly, he found that the flowering plants that were most attractive to gardeners were often the least attractive to the bees. One exception was Gilia capitata, which was ranked in the top five most attractive plants by home gardeners. Aaron then re-administered his survey to a different set of gardeners. This time, he asked to rate each plant, and then he told them what bee species were collected off of each plant, before asking them to re-rate each plant. When gardeners had information about the pollinators that could be found on plants, Aaron found that they increased their acceptance of a plant. In the case of Phacelia, a favorite of bees but ranked LAST by gardeners in his first survey, gardeners increased their ranking of this plant by 80%!
Aaron’s data is helping to change the way that gardeners think about their garden space. Aesthetic beauty is just one aspect to consider. Ecological beauty in the garden may very well be the next big thing. As evidence, this post came across my Facebook feed this week. This was posted by a gardener whose garden has been featured in Fine Gardening Magazine! Her willingness to install goldenrod, in particular (a much-maligned plant by gardeners, many of whom mistakenly think that it causes allergies) is such wonderful encouragement to and an endorsement of Aaron’s work.
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