How do we know what flowers bees like?

Posted on March 14, 2020 by Jen Hayes

Pollinator Syndromes

Pollinator syndromes are the characteristics or traits of a flower that appeal to a particular pollinator. These traits often help pollinators locate flowers and the resources (e.g. pollen or nectar) that the flowers have to offer.

Syndromes include bloom color, the presence of nectar guides, scents, nectar, pollen, and flower shapes. We can use these traits to predict what pollinators might be attracted to certain flowers or we can use these tools to guide us to pick the right plant for the right pollinator!

Bees, for example, are most attracted to flowers that have white, yellow, blue, or ultra-violet blooms.

Male long-horned bee on a white bindweed flower

Orange bumblebee (*Bombus sp*.) on a sunflower

Pollinator Syndromes for Bees & Butterflies

Table adapted from the North American Pollinator Protection Campaign

Trait	Bees	Butterflies
Color	White, yellow, blue, UV	Red, purple
Nectar Guides	Present	Present
Odor	Fresh, mild, pleasant	Faint but fresh
Nectar	Usually present	Ample, deeply hidden
Pollen	Limited; often sticky or scented	Limited
Flower Shape	Shallow; with landing platform, tubular	Narrow tube with long spur; wide landing pad

What are nectar guides?

Nectar guides are visual cues, such as patterns or darker colors in the center of a flower, that lead pollinators to nectar or pollen. These cues are beneficial to plants and their pollinators because they can reduce flower handling time, which allows bees to visit more flowers and transfer more pollen in a shorter amount of time.

Northern Blue Flag Iris (Iris versicolor).

The petals (yellow arrow) and sepals (red arrow) both have dark purple nectar guides. The yellow portion of the sepals may also be a nectar guide!

Image courtesy of Mike LeValley and the Isabella Conservation District Environmental Education Program

While the iris’s nectar guides are visible to humans and their pollinators, this is not always the case. Some flowers have nectar guides only visible in ultra-violet light. The video below shows how different flowers look to us (visible light), and simulates what the flowers look like to butterflies (red, green blue, and UV) and to bees (green, blue, UV).

What about pinks and purples?

Red-flowering currant (Ribes sanguineum)

It’s not uncommon to see bees visiting flowers that are colors outside of their typical pollinator syndromes. In the spring in Oregon, we see bees visiting red-flowering currants, many pink and magenta rhododendrons, plum blossoms, and cherry blossoms. Lavender, catnip, and other mint-family plants too are common on pollinator planting lists, but tend to have purple flowers.

Pollinator syndromes can help us understand these anomalies. These flowers may appear differently in ultraviolet light or may have strong nectar guides that encourage bees to visit them, despite how they look to us. Alternatively, these flowers might have rich reserves of pollen and nectar that draw bee visits.

How else do we know if a flower is a good choice for bees?

Many people have developed plant lists based on personal observations, so there are many pollinator plant lists available to choose plants from. Many nurseries include pollinator attraction information with their planting guidelines too. While these are often based on anecdotal evidence, many researchers (including Aaron and I) are working to provide empirical evidence for plant selections.

To find native plants to attract bees and other pollinators, I recommend starting your plant selections by checking out your local NRCS Plant Materials program.

Many extension programs may also have regionally-appropriate plant selections! Here is the link to Oregon State’s list of native pollinator plants for home gardens in Western Oregon.

When you’re ready to buy some plants, make sure to check out this blogpost by Aaron.

Where to buy native plants in Oregon?

Posted on March 6, 2020 by andeaaro

As an ecologist who studies garden systems, the increasing use of native plants in urban and suburban landscaping is exciting to me (see lab member Signe Danler’s great blog post on “ecological gardening”). Unfortunately, there are still many challenges associated with growing the adoption of native plants by home gardeners, with the largest barrier simply being the lack of availability of these species. I have noticed this barrier when giving talks to the public – many home gardeners are interested in gardening with high-ecological value native plants, but don’t know where to purchase them. These anecdotal observations are backed up by peer-reviewed literature, as several studies that have investigated the use of native plants in urban landscapes identified availability as one of the major barriers to adoption.

So, if you are a gardener in Oregon interested in gardening with native plants, where do you start? The good news is that native plants are available! Most big box stores (like Home Depot) have few to no native plants. One option is to go to a large, diverse nursery, like Portland Nursery or Garland Nursery in Corvallis. Besides perusing the selection of native plants they do stock, you can always ask them if they are able to stock a native plant you are interested in. These nurseries generally have contacts with a variety of growers, and demonstrating demand for native plants may lead to nurseries stocking more of these species on the shelf.

But what if you don’t have a specific native plant in mind, or what if you are new to the native plant world? Your best bet is to go to a specialty native plant nursery. Luckily, in Oregon there are a variety of native plant growers throughout the state. Below is a (non-comprehensive) list of some of the retail options. Keep in mind that some of these nurseries grow/stock a wide variety of species, while others specialize in plants of a certain region of the state or in a certain type of plant (think trees, or shrubs). I did not include nurseries that are primarily wholesale operations.

Portland Region:

Bosky Dell Natives

Echo Valley Natives

Livingscape Nursery

Sauvie Island Natives

Sparrowhawk Native Plants

Xera Plants

Columbia Gorge:

Humble Roots Farm and Nursery

Salem to Eugene

Willamette Gardens

Willamette Wildings

Doak Creek Native Plant Nursery

Southern Oregon:

Shooting Star Nursery

Althouse Nursery

Bunyard’s Barnyard Specialty Nursery

Eastern Oregon

Clearwater Native Plant Nursery

CTUIR Tribal Native Plant Nursery

WinterCreek Nursery

There are a few sources of native seed in the region. These can be easily ordered online!

Silver Falls Seed Company

Willamette Wildlings

You can find more information on the Oregon Flora Project’s website, where they have a tool that lists Oregon native plant nurseries, as well as a list of what each grower stocks.

http://www.oregonflora.org/gardening.php

Finally, another great source of native plants are native plant sales! Many Master Gardener chapters and many soil and water conservation districts put on native plant sales in the spring. Here are a few, but check with these organizations in your county and see if they have sales scheduled!

Benton Soil and Water Conservation District

East Multnomah Soil and Water Conservation District

Marion Soil and Water Conservation District

Yamhill Soil and Water Conservation District

Ethnobotany of Oregon Wildflowers

Posted on February 25, 2020 by Isabella Messer

As many of you may know at this point, Aaron Anderson and Jen Hayes are conducting some amazing research regarding Oregon native plants and their pollinator attractiveness. If you haven’t had the chance to read about their research yet, check out Aaron’s here and Jens here. While those two are producing data to determine the ecological benefits derived from some of our wildflowers, I chose to go down a more selfish route and see what our native plants can do for me. . .forget the bees. Below I have compiled a list of ethnobotanical uses for 6 of the 23 Willamette Valley wildflowers included in Aarons research – California Poppy, Camas, Pearly Everlasting, Oregon Iris, Western Red Columbine, and Goldenrod (my favorite).

Before you read any further, be aware that I am not an expert in wildcraft, ethnobotany, or herbalism. Never ingest the parts of any plant without being absolutely sure of its effects on the human body. Think of this more as a jumping-off point for your own research rather than any sort of guide or expert recommendation.

California Poppy – Escholzia californica:

The California Poppy – the ubiquitous orange herald of summer can do significantly more for you than just adding a pop of color to your yard or garden. E. californica can also be used as a medicine or candy! The flower itself is high in carotenoids and slightly sweet, the whole thing can be eaten raw as a candy-like treat. The ground roots and sap of the plant can be made into tinctures or infusions and be taken as a sedative, pain reliever, and muscle relaxer. California Poppy has been used by herbal practitioners as a “safe and gentle sedative for hyperactive children”. Maybe because they had too much poppy candy earlier in the day.

Camas – Camassia leichtlinii:

Camas is perhaps one of the best known plants on this list for its very popular edible bulb. The bulb is the most useful part of the plant and can be prepared in a few different ways. The two most popular are roasting and steaming. The roasted bulb gives off a flavor similar to a potato with a little hint of sweetness. Frying or mashing the bulb after the roasting are also common options to expand the flavor. Steaming camas bulbs is another popular practice which results in a food not unlike an onion. They are gelatinous and rich in complex carbohydrates, a fully browned camas bulb is just as delicious as any caramelized onion.

Pearly Everlasting – Anaphalis margaritacea:

Pearly Everlasting, a sweet little flower that has always reminded me a bit of a brilliant white star with a bright yellow center. These little flowers could also be a star of your ethnobotanical handbook considering how useful they are! The slender green leaves can be eaten as a normal green once they have been cooked a bit, perhaps by way of steaming or sautéing. A. margaritacea also offers a whole pallet of dyes all from one plant, depending on the concentration of each, it can provide shades of yellow, green, and brown. Pearly Everlasting can be employed as treatment for a whole range of ailments. The whole plant is filled with metabolites which can act as an anodyne, antiseptic, and sedative. Internally, it can also be used to treat diarrhea, dysentery, and some pulmonary affiliations. Externally, a poultice of the whole plant can be used to alleviate pain from burns, sores, ulcers, and bruises.

Oregon Iris – Iris tenax:

Oregon Iris is well known and celebrated for its floral beauty, but its grass-like leaves are often overlooked despite their usefulness. The long and immensely durable leaves can be used to make ropes or baskets. The 19th century botanist David Douglas once described Iris tenax’s leaves as “. . .in point of strength it will hold the strongest bullock and is not thicker than the little finger”. Like any craft, basket-weaving requires practice and learning, however the unique texture and color of the leaves are bound to make the product stand out among the rest.

Western Red Columbine – Aquilegia formosa:

The number of uses associated with Aquilegia formosa practically matches the number of bright red petals surrounding its cascading stamens. In terms of edibility, Western Red Columbine boasts edible leaves when boiled and a sweet nectary treat from the flowers themselves, but you have to share with the hummingbirds. Medicinally, treatments can be found from the roots, seeds, and leaves. The mashed roots can be used to relieve aching pains, for diarrhea, to counteract dizziness, and stomachaches. The chewed leaves can be used to alleviate sore throats and calm and upset stomach. Finally, a paste made from mashed seeds can be applied to the scalp to kill lice!

Goldenrod – Solidago canadensis:

Although sometimes considered cumbersome due to its amazing ability to spread, Goldenrod is one of the Pacific Northwest’s most diversely useful plants. It offers medicinal properties from its internal metabolites, edible roots and seeds, and of course Goldenrod’s signature pigmentation can be harnessed for dying. Infusions made from the flowers can offer relief from a variety of ailments, fever, flu, diarrhea, and sore throats are just some. Roots are commonly eaten smoked and seeds can be eaten roasted or raw. Finally, the flowers can bring a beautiful golden hue to any natural fiber that needs dying, just with a simple soak in warm water.

Further reading –

California Poppy:

https://plants.usda.gov/plantguide/pdf/pg_esca2.pdf

https://ethnobotany.csusm.edu/search_details.php?plant_id=9

Camas:

http://naeb.brit.org/uses/species/699/ http://arcadianabe.blogspot.com/2012/06/how-to-cook-camas.html

https://www.nrcs.usda.gov/Internet/FSE_PLANTMATERIALS/publications/orpmcpg13213.pdf

https://honest-food.net/cooking-blue-camas/

Pearly Everlasting:

https://practicalplants.org/wiki/Anaphalis_margaritacea

Oregon Iris:

https://www.mountpisgaharboretum.com/habitats-and-ecology/plant-list-at-mount-pisgah-arboretum/iris-tenax/

http://naeb.brit.org/uses/18060/

Western Red Columbine:

http://naeb.brit.org/uses/species/303/

https://www.sutrostewards.org/single-post/2017/07/25/Columbine-A-Flower-of-Meanings

Goldenrod:

http://naeb.brit.org/uses/species/3734/

https://plants.usda.gov/plantguide/pdf/pg_soca6.pdf

Setting up a native plant and native cultivar study

Posted on January 8, 2020 by Jen Hayes

Natives Plants & Native Cultivars Recent studies report an increase in consumer demand for native plants, largely due to their benefits to bees and other pollinators. This interest has provided the nursery industry with an interesting labelling opportunity. If you walk into a large garden center, you find many plant pots labelled as “native” or “pollinator friendly”. Some of these plants include cultivated varieties of wild native plant species, or native cultivars, sometimes referred to as “nativars”. While many studies confirm the value of native plants to pollinators, we do not yet understand if native cultivars provide the same resources to their visitors.

Echinacea purpurea

Photo Source: Moxfyre – Own work, CC BY-SA 3.0,

E. purpurea ‘Maxima’

Photo Source: Ulf Eliasson – Own work, CC BY 2.5,

E. purpurea ‘Secret Passion’

Photo source: National Guarden Bureau

An Echinacea Example Above are three purple cone flower (Echinacea purpurea) plants: on the top is the wild type, in the middle is a native cultivar ‘Maxima’, and on the bottom is another native cultivar ‘Secret Passion’. In some cases, like ‘Secret Passion’s double flower, there is an obvious difference between a native cultivar and a wild type that might make it less attractive to insect visitors. Since we can’t see the disc flowers (the tiny flowers in the center of daisy family plants), we might assume that ‘Secret Passion’ may be more difficult for pollinators to visit. The floral traits displayed by ‘Maxima’ seem similar to the wild type, but it might produce less pollen or nectar, causing bees to pass over it.

Unless we observe pollinator visitation and measure floral traits and nectar, we can’t assume that native plants and native cultivars are equal in their value to pollinators.

Native Cultivar Research One study looking at the difference between native species and their cultivar counterparts has come out of the University of Vermont (my alma mater!). A citizen science effort started by the Chicago Botanic Garden is also currently ongoing. My Master’s thesis will be the first to use a sample of plants specific to the Pacific Northwest. We have selected 8 plants that are native to Oregon’s Willamette Valley and had 1-2 native cultivars available. These plants have shown a range of attractiveness to pollinators (low, medium, or high) based on Aaron’s research. We are including plants with low attractiveness because it’s possible that a native cultivar may have a characteristic that makes it more attractive, such as a larger flower or higher nectar content.

This example of a Randomized Complete Block design shows 2 garden beds containing a native species (California Poppy and Camas) and their cultivar pairs (a yellow poppy cultivar and a white Camas cultivar).

Experimental Design We have four garden beds in our study, and each bed contains at least one planting of each native species and their cultivar counterpart(s). This kind of design is called a “Randomized Complete Block” (RCB). The RCB has two main components: “blocks”, which in our case are garden beds, and “treatments”, which are our different plant species. Above I have drawn a simplified RCB using two of our plants: Camas and California poppy. The bamboo stakes outline each plot and have attached metal tags that label the plants.

We planted our seeds and bulbs in November and will plant out 4″ starts of the other plants in early Spring. Look out for my spring and summer updates to see how these plots progress from mulch and bamboo stakes to four garden beds full of flowers and buzzing insects!

Reference articles: https://www.asla.org/NewsReleaseDetails.aspx?id=53135 http://www.gardenmediagroup.com/garden-media-releases-2019-garden-trends-report

How attractive are native wildflowers to gardeners?

Posted on December 26, 2019 by andeaaro

For my dissertation research, I am studying which native Willamette Valley wildflowers are most visited by pollinators and natural enemies for use in home gardens and urban landscaping. I’ve previously shared preliminary results from my field study on our blog, namely pollinator abundance and richness. For a refresher, here are summaries from 2017, 2018, and 2019.

Initial survey

Determining which of these flowers are most attractive to insects is only half of the equation — I also want flowers that are attractive to gardeners. To investigate this I developed two surveys — thanks to anyone reading who took them! The first simply asked gardeners to rank the aesthetic appeal of my study plants, as well as how likely they would be to utilize them in their home gardens. This allowed me to get a baseline understanding of how appealing these flowers are for use in home gardens and landscaping.

As you can see in the figure below, many of the plants most visited by bees (highlighted in orange) were the least attractive to gardeners (Fig. 1), while plants gardeners liked the most (e.g. Iris, Columbine) were hardly visited by bees. However, its notable that many of these native wildflowers ranked around a four on a 1-5 scale, showing that these flowers do have a high potential appeal for use in landscaping!

Figure 1: Gardener ranked aesthetic appeal of study flowers on a scale of 1-5. Orange bars note plants that were consistently highly visited pollinator plants. N=587

Follow-up survey

The follow-up survey consisted of a subset of ten flowers most visited by bees, and again asked respondents to rank the aesthetic appeal and likelihood of planting for each of these flower species. Then, they were shown facts about and images of bees that visit each flower species, and asked whether they viewed each plant species more favorably, less favorably, or the same. Finally, they were asked to re-rank how attractive they found the flower species and how likely they would be to use the species in their garden, both on a scale of 1-5.

Gardener acceptance

This second survey showed a remarkable increase in gardener acceptance of pollinator friendly native plants after being educated on plant-pollinator associations. Over 80% of respondents stated that they viewed Clarkia amoena as more attractive after gain, and over 60% of respondents viewed Phacelia heterophylla, Madia elegans, and Gilia capitata as more attractive (Fig. 2).

Figure 2: Percent of respondents viewing flower species as more attractive after learning about pollinator associations. N=184.

Likelihood of planting

After learning about the benefits these flowers provide to pollinators, gardeners were also more likely to plant all ten flower species (Fig. 3). Notably, they were 40% more likely to plant Phacelia heterophylla, (a species that ranked as the least aesthetically appealing overall in the first survey). As a whole, they were also over 20% more likely to plant Solidago canadensis, Clarkia amoena. Similar increases were also observed in likelihood of planting Oreganum vulgare and Nepeta cataria. Many of the plants that showed a smaller percent change are species that started out with a higher aesthetic appeal (e.g. Gillia capitata, Lavendula intermedia, Aster subspicatus), meaning gardeners were already very likely to include these plants in their home garden before learning about the ecological benefits they provide.

Figure 3: Percent change in respondent’s likelihood of planting each top pollinator flower after learning about the pollinators associated with each. N=184

Ecological beauty

What does this all mean? This suggests that although native plants are frequently denounced as being less attractive than showy garden species, many home gardeners are still willing to use native flowers in their landscaping. Additionally, this lends credence to the concept of “ecological beauty” – that many gardeners are willing to utilize plants that will increase the habitat value and wildlife diversity in their yards.

From the Lab to Your Laptop: Getting Research to the Public

Posted on November 26, 2019 by Signe Danler

The members of the Garden Ecology lab spend much of their time on research into subjects that affect, what else, the ecology of home gardens. Pollinators and their relations with native and non-native plants, bee variety and abundance in gardens, and soil nutrient levels, are among the topics they are delving into.

One of the challenges for the lab members – and for all scientists – is how to get the results of their research into the hands of people who can use it. Scientific papers are the traditional way, but not many people actually read those, and it can take a long time for research to trickle out from papers to the general public. If you read this blog, you’ve discovered one of the ways current research is disseminated quickly, and you’re learning new ideas that you may be able to implement in your own research or gardening.

Another way research gets to the public is through teaching. Lab members present new data in lectures, interviews, presentations, workshops and classes, including OSU Extension’s Online Master Gardener training, which I teach. Each year the course reaches around 40 Oregon MG trainees, plus another 60 or so horticulturally-minded people who take the course simply to improve their garden knowledge. In addition, our single-subject Short Courses are accessed by several thousand people per year. So any new research I can include in these courses can potentially reach hundreds or thousands (depending on the subject) of gardeners per year, who in turn may influence other gardeners.

With this in mind, I have cited Mykl Nelson’s research on excessive nutrient levels in managed vegetable garden soils to caution students about the perils of over-fertilizing. In 2020, my new module on Gardening with Pacific Northwest Native Plants will be influenced by Aaron’s data on the native flowers most favored by native pollinators. His research, plus other research taking place elsewhere, is showing that just planting a garden of pollinator-attracting plants may not be the best tactic to help native pollinators. A garden full of bees is often, really, a garden full of honey bees. What about all the native bees that are less visible, but at least as important? Aaron Anderson’s research into which plant species attract which bee species is beginning to show that the plants most attractive to honey bees are generally not the same as those most attractive to native bees.

The takeaway? Gardeners who want to support pollinators can take the extra step of searching out and growing native plants that are especially attractive to native bees, in addition to the many flowers that honey bees frequent. This is what I will be teaching my Master Gardener trainees in Oregon, and the rest of my students all over the country; many of them will in turn teach other people. Bit by bit the new information gets out there, and more native bees may find the flowers they need to thrive.

2019 Native Plant Field Season Update

Posted on November 4, 2019 by andeaaro

I’m thrilled to announce that this summer I completed the third field season of my study. This is slightly bittersweet – while I’m excited that we are done with hot fieldwork, I will miss chasing bees around the farm and the view of Mt. Hood. I’m incredibly thankful for this third season of data, as it will help account for some of the temporal variation inherent in ecological studies. In fact, pollinator communities in particular tend to be highly variable both within and across field seasons. Having three seasons of data will hopefully allow us to identify more reliable patterns of pollinator visitation between my study plants.

Lots of lab work remains, as I’m tackling the insect samples that we collected with the bee vacuum. With the help of a dissecting scope, I’m attempting to identify the each specimen to at least the taxonomic level of family to get a sense of the broader insect communities associated with each flower species in my study. It will be several months before I can share this species-richness data, but in the meantime I have bee abundance data to share with you!

Aaron and Lucas in the native plant study site, in 2017. You can see the 1m by 1 m plot in the foreground by Aaron, a second one near Lucas, and a few more in the distance.

As a refresher, we performed timed pollinator observations at each plot. This consisted of observing each blooming plot for five minutes and counting all the insects that landed on open flowers. Bees were sorted to “morpho-type” (honey bee, bumblebee, green bee, and other native bee). Though this doesn’t give us species-level information on the floral visitors, it allows us to understand which plants attracted the most pollinators overall, and allows us to detect any patterns of visitation between honey bees, bumblebees, and solitary native bees. Below is a summary of some of the highlights.

2019 overall bee abundance by plant species:

Origanum vulgare, Lavendula intermedia, and Eschscolzia californica were top five bee plants in 2019, just as they were in 2018.
In 2019, Phacelia heterophylla and Solidago canadensis jump into the top five, while Nepeta cataria and Gilia capitata fall out of the top five. It should be noted that Nepeta was the sixth most attractive plant, with about the same visitation level as Solidago.
Again, similar to 2018, it appears that honey bee visitation was driving the high visitation rates of the popular exotic garden species (marked with a red asterisk), while native wildflowers were being visited more frequently by native bees.
I’ve included the 2017 and 2018 overall abundance graphs as well, for comparison. You can see that the overall abundance was higher in 2019 for the two most popular plants, at about ~25 bees per observation period!

2017 overall bee abundance by plant species:

2018 overall bee abundance by plant species:

Since honey bee visitation drove the high abundance of many of the top pollinator plants, I took honey bee visits out of the data set and made a new graph, to compare which plants were most attractive to native bees.

2019 native bee abundance by plant species:

As you can see above, honey bees are excluded from the analysis, the top five most popular plant species completely reshuffles.

Native wildflowers Phacelia heterophylla, Eschscolzia californica, and Solidago candensis are still top pollinator plants, while Aster subspicatus and Anaphalis margaritacea jump into the top five.
The exotic garden plants fall in the rankings: Lavendula intermedia drops to the middle of the pack, while Nepeta cataria and Origanum vulgare hardly attracted any native bees at all (an average of only ~one bee per five minute observation).
Phacelia heterophylla, Lavendula intermedia, and Eschscolzia californica attracted the most bumblebee species.

I’ve included that 2017 and 2018 native bee abundance data below for comparison.

2017 native bee abundance by plant species:

2018 native bee abundance by plant species:

Please stay tuned for more updates on the bee species richness we collected in 2019, as well as data on the other insects (pests and natural enemies) that we collected!

Native Plants and Pollinator Survey

Posted on May 23, 2019 by Gail Langellotto

Aaron Anderson is repeating his original survey on native plants and pollinators. This time, he is trying to understand how knowledge of a plant’s ecological function may alter impressions of native plants.

The survey takes about 25-30 minutes to complete. Folks who have taken the survey thus far have commented on how much they learned from taking the time to answer the questions.

If your time and interest allows, we would be extremely grateful if you could take the time to respond to this survey. The direct link to the survey is:

http://oregonstate.qualtrics.com/jfe/form/SV_9Alhv961rZX8Vs9

If you have friends or acquaintances who also might be interested in taking the survey, please feel free to share it with them.

A syrphid fly pays a visit to a California poppy at the North Willamette Research and Extension Center.

A bee visiting one of the Canada goldenrod plots in our Native Plant study.

Gilia capitata

Lotus unifoliolatus

Native plants and pollinators – 2018 field update

Posted on November 12, 2018 by andeaaro

It’s been a while since I’ve posted a field update about my native plant – pollinator study, so this post will be a recap of the entire 2018 field season! Sampling this year was successful, though it was a much shorter bloom season for almost all the flowers species, perhaps due to a combination of the heat, low rainfall, and lack of supplemental irrigation. I performed some summary statistics on the data, and there are some intriguing results from this year.

Below is a summary of some of the highlights:

Visitation Data

Only two (Gilia capitata and Nepeta cataria) flowers made it into the top-five most attractive in 2017 and 2018. The full results can be visualized in the two histograms below.
Three of the non-native garden species were found in the top five in 2018 (though I noted this visitation seemed strongly driven by honey bees).

2017 overall bee abundance by plant species:

2018 overall bee abundance by plant species:

Because of this, I removed honey bees from the dataset and recreated the graphs.

The 2017 visitation data is largely unchanged (though Nepeta cataria is less attractive, and Eschscholzia californica jumps into the top-five).
When only native bees are considered, the top-five most visited 2018 plants are almost completely different. Eschscholzia californica, Aster subspicatus, and Phacelia heterophylla are the three most attractive flowers.
It seems like the native wildflowers are being visited more frequently by native bees.

2017 native bee abundance by plant species:

2018 native bee abundance by plant species:

Sampling Data
I also take vacuum samples from each plot so that we can identify pollinators (and other insects) to species. I’m excited that my 2017 and 2018 bees have been identified by taxonomist Lincoln Best!

Across those two years, we collected 36 bee species (from 540 samples, which doesn’t include all the honey bee individuals). You might ask – is this many bees, or only a few? Simply put – we don’t know! Without knowing how many bee species are found at our site at NWREC, its hard to tell what this number means. However, I was excited to find that we collected two bumblebees that are on the IUCN Red List, Bombus fervidus and Bombus calignosus.

Below are a two pollinator interaction matrices to visualize these data, but I should note that these are very preliminary – they are not scaled by number of sampling events but are still a neat way to visualize interactions and richness data. (Darker squares represent higher abundance; a white square means no bees were collected off that flower).

Bumblebee Richness and Abundance:

Other Native Bee Diversity and Abundance:

Its obvious from looking at these data that the answer to the question “which plants attract the most pollinators?” isn’t simple! Are we interested in certain suites of bee species – honey bees, or bumblebees? Are we interested in high overall abundance, or high species richness? Some species attract many individuals but few species, while other plants attract a higher species richness but fewer overall individual bees. Additionally, there are also seasonal changes in bee populations to consider, as well as seasonal changes in flower phenology and floral display.

Luckily we’re going to have a 2019 field season, which will help account for this temporal variation and allow us to acquire data for species that didn’t flower in one or both of the previous years.

Plant of the Week: Douglas Aster (Revisited)

Posted on October 30, 2018 by Lucas Costner

Image from: http://www.nwplants.com/

This entry is from Lucas Costner, an undergraduate horticulture major at Oregon State University. It highlights one of the plants that Aaron Anderson is using in his research.

Original “Plant of the Week: Douglas Aster” post available here: http://blogs.oregonstate.edu/gardenecologylab/2017/11/07/plant-week-doulgas-aster/

Last November I took a look at a Pacific Northwest favorite, the Douglas aster (Symphyotrichum subspicatum (1)). What I didn’t know then was just how popular this species would be with the bees we had been sampling in the field. It turns out that while surveyed gardeners ranked Douglas aster 14 out of 27 in terms of attractiveness, based on the 2017 data it boasted the third highest number of bees (2). This means that it is the most attractive native perennial species for bees that we sampled, and the 2018 data shows this as well (3). Based on the gardeners’ ranking, however, which placed it in the bottom 50% of all the species we sampled, it also looks as though the Douglas aster is in need of some public relations help.

It is my personal belief that it isn’t just the showiness of the blooms or the potential benefits to X, Y and Z that brings plants into our gardens, but rather the stories we tell about them. Familiarity after all is more than just recognition; it is also marked by appreciation and understanding. One of the stories we can tell through our work in the Garden Ecology Lab about Douglas aster is of its relationship with our native bees. As gardeners we are uniquely positioned to both benefit from and to be of service to these insects.

Here are some of their “faces”:

Long-horned Bees

Melissodes sp.

The most common genus of bees collected from Douglas aster in the field, Melissodes are true summer and fall flyers, easily recognizable by their long antennae. These bees are solitary ground nesters, although they have been observed forming nesting aggregations in the soil (4). While we collected potentially five species of Melissodes in total, one species in particular, Melissodes microsticta, was especially common. Many Melissodes species are generalists, but can usually be found visiting members of the Asteraceae family (such as sunflowers and our Doulgas aster) because of their late season blooms.

Image from: https://odabeeguide.weebly.com/melissodes.html

Yellow-faced Bumblebee

Bombus vosnesenskii

The second most commonly collected visitor of Douglas aster, the yellow-faced bumblebee is really a remarkable native pollinator. While many native bees are considered solitary, bumble bees are social insects, with a queen and workers (4). Like non-native honeybees, they have been investigated for their potential as commercial pollinators, being used in greenhouse production (5). Isabella Messer wrote a post for the “Pollinator of the Week” series highlighting these ubiquitous bees that can be found here: http://blogs.oregonstate.edu/gardenecologylab/2017/08/29/pollinator-week-yellow-faced-bumble-bee/

Image from: https://odabeeguide.weebly.com/bombus-sp.html

Ligated Furrow Bee

Halictus ligatus

The third most commonly collected visitor of Douglas aster is the ligated furrow bee. Found throughout North America, Halictus ligatus is special amongst native pollinators (like the yellow-faced bumblebee) for its social nature (4). Sociality is rare amongst native bees, as it is in nature in general, but amongst the Halictus the situation is even more unique. This is because, unlike other social species, Halictus have been seen to switch back and forth between solitary and social behaviors over time as environmental conditions differ (4). Isabella wrote a post about these bees a while back for the “Pollinator of the Week” series that can be read here: http://blogs.oregonstate.edu/gardenecologylab/2018/04/30/pollinator-week-mining-bee/

Image from: https://odabeeguide.weebly.com/halictus.html

Virescent Green Metallic Bee

Agapostemon virescens

The fourth most commonly collected visitor of the Douglas aster is none other than my personal favorite, the virescent green metallic bee. These stunning bees are communal soil nesters and are members of the Halictidae family, cousins of the ligated furrow bee introduced above (4). I wrote a post about them for the “Pollinator of the Week” series last November that can be found here: http://blogs.oregonstate.edu/gardenecologylab/2017/11/13/pollinator-week-virescent-green-metallic-bee/

Image from: https://odabeeguide.weebly.com/agapostemon.html

In addition to these bees, we also collected striped-sweat bees (Agapostemon texanus/angelicus), brown-winged furrow bees (Halictus farinosus), metallic sweat bees (Lasioglossum sp.), and common little leaf-cutter bees (Megachile brevis). We also collected with a number of long-horned bees (Melissodes) that have yet to be identified to species.

Walking the streets of Portland and seeing Douglas aster’s purple flowers still in bloom this late in October brings a smile to my face because it tells me that people are indeed planting this species. If only for its benefit to wildlife and pollinators in particular, that is still good news. As you may be able to tell from the information given above, we are still learning about these bee species while we are simultaneously working to save them — not just for future generations but for ourselves as well. Hopefully, by putting a “face” to the bees that visit and depend on these plants and our gardens, the bond that links us to them can be strengthened and our preference for them in our landscape enhanced.

Sources:

Geraldine A. Allen 2012, Symphyotrichum subspicatum, in Jepson Flora Project (eds.) Jepson eFlora, http://ucjeps.berkeley.edu/eflora/eflora_display.php?tid=88843, accessed on October 30, 2018.
Langellotto, G. (2018, September 12). Do Gardeners Like the Same Flowers as Bees? [Blog post]. Retrieved from http://blogs.oregonstate.edu/gardenecologylab/2018/09/12/do-gardeners-like-the-same-flowers-as-bees/
Anderson, A. (n.d.). First Look: Research Into Native Plants in the PNW Garden. Webinar. Retrieved from http://blogs.oregonstate.edu/gardenecologylab/2018/10/23/webinar-on-willamette-valley-native-plants-and-pollinators/
Wilson, J. S., & Messinger Carril, O. (2016). The Bees In Your Backyard. Princeton, NJ: Princeton University Press.
Dogterom, M. H., Matteoni, J. A., & Plowright, R. C. (1998). Pollination of Greenhouse Tomatoes by the North American Bombus vosnesenskii. Journal of Economic Entomology, 91(1), 71-75. doi:https://doi.org/10.1093/jee/91.1.71
Oregon Department of Agriculture: Bee Pollinators of Oregon. (2016). Retrieved October 30, 2018, from https://odabeeguide.weebly.com

Garden Ecology Lab

Socio-ecological research in urban and suburban garden systems

Category Archives: Native Plants