The Garden Ecology Lab’s Pollinator Plant PR Campaign Presents….. Oregon Sunshine! ☀️
The Garden Ecology Lab is releasing a series of plant profiles of the top 10 Oregon native plants for pollinators, based on Aaron Anderson’s 2017-2019 field trials of 23 Oregon native plants. We will feature one plant per week for 10 weeks, this is week 2! Profiles will include photos, planting information, and will highlight common pollinators of each plant.
- Scientific Name: Eriophyllum lanatum
- Other names: Common woolly sunflower
- Life Cycle: Perennial
- Foliage: grey, woolly lobed leaves
- Growth Habit: Upright, spreading, “shrubby”; typically 12-14″ in height, may need to be cut back if it becomes too leggy to maintain upright flowers.
- Bloom Duration: June – September
- Hardiness Zone: 5-10; can tolerate cold up to -15 F
- Special Traits: Drought tolerant
- When to plant: Starts can be planted in the spring or fall, seeds should be sown in the fall.
- Oregon Sunshine provides both nectar and pollen to its insect visitors.
- Oregon Sunshine was found to be associated with one species of bee in Aaron’s research: Panurginus atriceps, the black-tipped miner bee.
- Oregon sunshine is a host plant to 7 moths: the Gernaium Plume Moth, Orange Tortrix Moth, the Lupine Ghost Moth, and three moths without common names: Telethusia ovalis, Phalonidia latipunctata, and Phtheochroa aegrana.
- Butterflies including orange sulfurs, red admirals, commas, and skippers are also often attracted to Oregon Sunshine.
Oregon Sunshine‘s Native Range in Oregon
Oregon Sunshine commonly grows on both sides of the Cascades as well as through Southern Washington and California, and has at least 6 different varieties present across the state of Oregon (slide 2). Maps and legend acquired from the Oregon Flora Project, with Imagery Sourced from Google. Copyright 2021© TerraMetrics
Oregon Sunshine as a pollinator plant
Oregon Sunshine is a widespread perennial in the sunflower family (Asteraceae). It provides resources to a great diversity of pollinators, including bees, butterflies, moths, and caterpillars. This native sunflower is a great late summer nectar plant with wide yellow flowers (sometimes up to 2″ across) that allow pollinators easy access to their nectaries!
Infographics developed by LeAnn Locher, Aaron Anderson, and Gail Langellotto.
Abundance and Diversity Calculations. Bee abundance was calculated using estimated marginal means of bee visitation to each of our study plants from 5-minute observations conducted from Aaron's 2017-2019 field seasons. Estimated marginal means (EM Means) were assigned to categorical values and averaged across years to yield the following categories: 0% = Very Low =EM mean below 0.49; 25% = Low = EM mean of 0.50 to 0.99; 50% = Moderate = EM mean of 1 to 1.49; 75% = High = EM mean of 1.50 to 1.99; and 100% = Very high = EM mean above 2.0. Bee diversity was based on the total sum of species collected on each of our study plants from 2017 to 2019. A Chao 2 Estimator was used to estimate total expected species richness for each plant; Chao 2 estimates were then used to create categorical values, as follows: 0% = Very Low = 9.99 or lower; 25% = Low = 10 to 14.99; 50% = Moderate = 15 to 19.99; 75% = High = 20 to 24.99; 100% = Very high = 25 or higher.
Did you know?
The white-grey trichomes (the little hairs on the stems and leaves) add a lovely color to gardens but is also act as an important adaptation for this drought-tolerant plant. The trichomes help Oregon Sunshine conserve water by both reflecting heat and reducing the amount of air that moves across a leaf’s surface. Though this trait helps Oregon Sunshine endure intense, dry landscapes, it can also explain why it might not do well in the gardens of those with a tendency to “kill with kindness”… this plant does not want a lot of water! It should be watered no more than once a month once established, so over-waterers beware!
Photos from the field
Tune in next week for the next edition of our Pollinator Plant PR Campaign.
The Garden Ecology Lab’s Pollinator Plant PR Campaign Presents….. Yarrow!
The Garden Ecology Lab is releasing a series of plant profiles of the top 10 Oregon native plants for pollinators, based on Aaron Anderson’s 2017-2019 field trials of 23 Oregon native plants. We will feature one plant per week for 10 weeks, this is week 1! Profiles will include photos, planting information, and will highlight common pollinators of each plant.
- Scientific Name: Achillea millefolium
- Life Cycle: Perennial
- Growth Habit: Upright, spreading
- Bloom Duration: June – October
- Hardiness Zone: 3-7
- Special Traits: Drought tolerant, deer resistant
- When to plant: Starts can be planted in the spring or fall.
- Yarrow provides both nectar and pollen to its insect visitors.
- Yarrow was found to be associated with two species of Andrena in Aaron’s research (Andrena cerasifolii, A. candida).
- Andrena is a genus of early summer mining bees!
- Other common visitors to yarrow include sweat bees, nomad bees, and butterflies!
- Yarrow inflorescences provide a great “landing pad” for pollinators- they can rest directly on the plant while they forage.
Yarrow’s Native Range in Oregon
In Oregon, we have our own native variety of yarrow: Achillea millefolium var. occidentalis. Western yarrow's native range covers the entire state of Oregon. Map acquired from USDA Plants Database. Copyright 2014 © ESRI
Yarrow as a pollinator plant
Yarrow is a ubiquitous North American native plant: its range extends from Alaska to Florida and every state and province in between! Though it commonly appears on pollinator planting lists, many people are not convinced that it’s a great bee plant, because it is not typically buzzing with activity like we may see on Goldenrod or Douglas Aster. Instead of hosting an abundance of visitors, yarrow supports a high diversity of insect visitors.
Infographics developed by LeAnn Locher, Aaron Anderson, and Gail Langellotto.
Abundance and Diversity Calculations. Bee abundance was calculated using estimated marginal means of bee visitation to each of our study plants from 5-minute observations conducted from Aaron's 2017-2019 field seasons. Estimated marginal means (EM Means) were assigned categorical values and averaged across years to yield the following categories: 0% = Very Low =EM mean below 0.49; 25% = Low = EM mean of 0.50 to 0.99; 50% = Moderate = EM mean of 1 to 1.49; 75% = High = EM mean of 1.50 to 1.99; and 100% = Very high = EM mean above 2.0. Bee diversity was based on the total sum of species collected on each of our study plants from 2017 to 2019. A Chao 2 Estimator was used to estimate total expected species richness for each plant; Chao 2 estimates were then used to create categorical values, as follows: 0% = Very Low = 9.99 or lower; 25% = Low = 10 to 14.99; 50% = Moderate = 15 to 19.99; 75% = High = 20 to 24.99; 100% = Very high = 25 or higher.
Although yarrow doesn’t buzz with activity like some pollinator plants, it’s certainly not a flower to ignore! Yarrow is a hardy and low maintenance perennial that establishes and spreads readily in gardens. It’s a beautiful cut flower and can also be dried to include in longer lasting floral arrangements; its foliage that maintains its aromatic scent even after drying. Yarrow is additionally a wonderful plant medicine that has been used for centuries.
Did you know?
Yarrow has naturally-occurring pink variants! It can vary from pale pink (left), to deeply magenta (right). These plants were started from seeds collected from wild populations of yarrow, so we can be certain it is indeed a natural variation, rather than a true hybrid or cultivar! Another fun fact: "millefolium" translates to "thousand-leaved", which is a reference to its dissected leaves!
Photos from the field
Tune in next week for the next edition of our Pollinator Plant PR Campaign.
My name is Nicole Bell, and I’m a first-year master’s student in the Garden Ecology Lab. I was born and raised in Oregon, and I’d like to think that part of the reason I’ve ended up in the field of horticulture/entomology is because I was surrounded by bugs and flowering plants growing up. My childhood backyard was filled with plants, bugs, wild bunnies, and raccoons (and our yellow lab, Bella). It was hard not to be fascinated by all the life that’s possible in just one space.
I completed my H.B.S. in Environmental Sciences here at Oregon State University in 2020. I chose to study environmental sciences because when I was entering college, I knew I cared about science and climate change, but I wasn’t sure what exactly I was interested in. It was an overwhelming decision to try and narrow down a field of study when I wasn’t even sure what the options were yet. I’m grateful that the summer before my freshman year of undergrad, my mom encouraged me to get a job… and there was an opening at Dr. Sagili’s Honey Bee Lab in the Horticulture Department. I had never worked or even thought much about bees/pollinators before, let alone considered making pollinators my focus. Long story short, I got the job as an undergraduate worker in the lab, and I learned so much about both lab and field work.
I worked at the Honey Bee Lab for over 4 years. Towards the end of my freshman year, though, I wondered what working with native pollinators would be like. I found a project offered through the URSA Engage program at OSU: studying the impacts of wildfire severity on offspring food provisions for a native bee (the blue orchard mason bee, Osmia lignaria) at the Forest Animal Ecology Lab in the Forestry Department with Dr. James Rivers. I designed an experiment and wrote my undergraduate thesis about mason bees, and I am grateful for my experience there, as I got to learn about the integration of bees and their environment. When I finished and defended my thesis, I was approaching graduation. I knew I wanted to take some time off school to enjoy reading and learning about topics that interested me outside of a classroom setting.
Science communication has become a big passion of mine. While most of my undergraduate experience (in the Honey Bee Lab and Forest Animal Ecology Lab) was hard science, either in the field or in the lab, I craved combining my passion for writing with my interest in expressing the implications of science to the public. My mom found a job posting (again… thanks mom!) for an agricultural science writing position at Washington State University, specifically the Center for Sustaining Agriculture and Natural Resources (CSANR). I worked with an amazingly supportive and intelligent group of scientists: they gave me publications to write blog posts about, and they helped me to edit the pieces into works I am proud of. The collaboration that the team members at CSANR have is inspiring and only bolstered my interest in communication and teamwork. While none of my articles on AgClimate were specific to pollinators, the knowledge I gained about agriculture in general and how to put together a synthesized blog post about a complex study was invaluable.
I met with several different potential graduate advisors, and I was amazed with Dr. Gail Langellotto’s knowledge and passion for native pollinators and their urban habitats. Dr. Langellotto also had projects that piqued my interests and would allow me to curate a thesis that blends science and communication. While I’m just now beginning work on the methods for my thesis, I’ll be conducting a comprehensive literature review on bee communities in urban and community gardens. Additionally, I will create an iNaturalist guide on native bees in the Portland, Oregon, area.
One of my favorite things about native pollinators is just how many species are out there. I feel like I haven’t even scratched the surface with my current knowledge about these ecosystems and how they function, so I couldn’t be more excited to learn from other members of the lab and from my research.
What I love most about bugs, bees, and insects alike may be this: there’s a whole world underneath us and above us that we can so easily miss if we don’t look for it.
Field season wrap up is underway in the butterfly bush plot, and there is so much to reflect on this year! The team has had a very productive summer, and as these bushes are better established and have reached their full spread and height, they have become more attractive to pollinators. As a reminder, the butterfly bush (Buddleja spp.) test plot consists of 34 butterfly bush cultivars of ranging fertility, habit, and breeding complexity. We have 6 -9 replicates of each individual cultivar, totaling 222 plants in the complete replicated block. The plot represents all the past and present (yes, we have some experimental cultivars) breeding that has been conducted to reduce fertility and hopefully invasiveness of Buddleja davidii. Much of that breeding centers around interspecific hybridization (breeding between 2 or more species in the same genus), so our plot represents hybridization of 7 different Buddleja species!
This summer we conducted pollinator observations the same as last year. This consisted of 5-minute timed counts at each location in full flower (we are calling full flower 50% or more of the buds or flowers on the individual plant are fully open) each week. During the timed count, we identify all visitors to morphology- which is simply differentiating between honeybees, bumblebees, butterflies, and other morphotypes. This presented new challenges this year because of the sheer mass some of our plants have reached! Though they were spaced 8 feet apart on all sides at planting, some have grown in together, making access an occasional issue. Many of the full-sized cultivars also reach well over my head, presenting more challenges in accurate counting. The team pushed through these difficulties, and by the end of the season we had counted 7,597 individual visitations on the plot. This is over 2,000 more than last year! You can view overall visitations by cultivar for both the 2020 and 2021 seasons below.
Though all the cultivars were most frequently visited by honeybee cultivars in 2020, three cultivars in 2021 were most frequently visited by bumblebees. Most notably the cultivar ‘Honeycomb’ attracted far and away more bumblebees than any other cultivar, and most of the visitors were male. Not only does ‘Honeycomb’ seem to be very attractive while sampling, it has an extremely long bloom season in comparison to the other cultivars in the study. It will bloom steadily from mid-June until the first deep frost of the season. Generally, there is an uptick in visitation across all the cultivars in 2021 as compared to 2020. Keep in mind the plants were substantially larger this season compared to last, meaning larger floral displays which are more attractive to pollinators.
In addition to pollinator observations, we collected nectar volume data for all 34 cultivars and attempted to collect pollen from a low and high fertility cultivar respectively. Tyler and Mallory were instrumental in getting nectar volume estimates collected, you can see them pictured below probing individual flowers with microcapillary tubes. Pollen collection turned out to be a very time-consuming process because there wasn’t a good alternative to good old hand collection. After about 80 hours of labor on the project, we were still a ways off of our mark, so we needed to reassess our methodology. More to report on that next year I’m sure.
Svea Bruslind and Jen Hayes also helped me take filtered photos of all my cultivars this season. You can read more about Svea’s excellent photography skills in her post ‘A Bee’s Eye View: UV photography and bee vision‘ but I’m sure the photographs she took of my cultivars in ‘Bee Vision’ will prove useful in understanding patterns of attraction out on the plot. Scroll through the pictures below to see examples of Svea’s work, in order of pollinator attraction in the 2021 field season.
This time of year, focus returns to the relative fertility portion of my study. This means time in the greenhouse monitoring controlled crosses I made over the summer, sowing seeds from the field and counting respective seedlings. This robust dataset will allow us to calculate relative fecundity of all our cultivars in both male and female roles, important information in assessing invasive species legislation.
I have been so grateful for the opportunity to assist Jen Hayes with her nativar research project. For the past year and a half, I have learned so much in the world of plant and pollinator relationships. One of the most valuable things I have learned, which I use every day in my own garden, is how to quickly identify bees. In the field, we observe each flower plot for five minutes and record the different things that visit. Being able to identify a fly from a bee, or a bee from a wasp is very important in order to obtain accurate data. I wanted to share the process we use to quickly identify bees in the field and hopefully answer some questions you may have had about what was buzzing in your garden.
Once the sun has risen and the chill of the morning has left, bees begin their foraging routine. Male bumblebees, out foraging too late, emerge from the layers of Zinnia flowers. Hundreds of bees possibly pass through your garden in a single day, from flower to flower, collecting pollen and nectar. But what are they? Are they native? Are they helpful in the garden? These are all questions I have whenever I see something buzzing on the mint, exploring the flower patch, or pollinating the tomatoes.
The first things I always look for are the antennae and the number of wings. The flies that are most often confused with bees have short, almost non-existent antennae, whereas bees will have noticeable, segmented antennae. The wings are also something to look: flies only have one pair of wings and bees have two, the forewings and hindwings. Be sure to look closely! There are flies known as hoverflies or syrphid flies that have incredible mimicry adaptations. Look at these two insects on this butterfly bush. Although almost identical, you can see the top insect does not have noticeable antennae. That’s because it is a honey bee mimic!
If you have established that it is a bee and not a fly, there are other things to look for to identify the bee to a more specific taxonomic level. The coloration of the bee could help if it is green or red, but there are many bees that have different variations of black and white. What I like to look for next is the pollen baskets, also known as the corbiculae. Megachilidae bees carry the pollen on the underside of their abdomen, like bright yellow furry bellies. Another distinguishing factor for Megachilidae bees is how they fly. The abdomen of the bee will usually curl upwards while in flight. Mellisodes bees carry the pollen on their hind legs but the baskets are dramatically bigger than honeybees or bumbles. We like to think of them as pollen pants! Mellisodes bees are also known as long-horn bees because of their disproportionately long antennae.
If the bee does not have any special coloration or noticeably different corbiculae, it could be one of many other genera we have in Oregon. Halictidae bees range in size from the tip of a pen to the size of a penny. They are usually black or black and white and are VERY difficult to distinguish in the field. There are details we have to look for in the lab such as the number of “panels” in the wings or if they have one versus two sub-antennal sutures.
The other bees we see while doing research include wasps, honeybees, and bumblebees. There are so many variations of Bombus here in Oregon it is almost like a scavenger hunt. Because of all the color and striping variations, we use the PNW Bumblebee Atlas to help us identify species in the field.
Our second field season studying pollinator visitation to Oregon native plants and native cultivars spanned from April to late September of 2021, although if Douglas Aster had any say in the matter, we would likely still be sampling. The densely blooming Symphyotrichum subspicatum continued to produce a smattering of new flowers through November of last year, and we predict it will do the same this year, too!
Our field crew this summer included Tyler, Svea, Mallory and I. Together, we sampled on 33 different dates across the growing season, allowing us to collect around 2000 physical pollinator specimens, and observe 6,225 unique interactions between pollinators and our study plants! This season we conducted floral trait measurements (including the dimensions of flowers), took multispectral photos, and additionally collected pollen from a subset of our study plants.
From left to right: Mallory vacuum-sampling off of Douglas Aster 'Sauvie Snow', Tyler shaking a farewell-to-spring flower to get pollen off of it, and Svea photographing Baby Blue Eyes 'Penny Black'.
This year, we introduced a third cultivar for California poppy (Eschscholzia californica ‘Purple Gleam’), yarrow (Achillea millefolium ‘Moonshine’), and farewell-to-spring (Clarkia amoena ‘Scarlet’). The new cultivars were established in the spring, which resulted in a late bloom for the annuals, so we expect to see them blooming during their typical period in 2022. The Achillea ‘Moonshine’ replaced Achillea ‘Salmon Beauty’ in being the most abundant yarrow cultivar; it began blooming almost immediately as it was planted into our field site and is still continuing to push out blooms through October alongside the Douglas Asters.
The plant groups in our study: the larger circles with orange text are the native plants, and the smaller circles and turquoise text are the cultivars. The top row contain the perennials yarrow, western red columbine, great camas, and Douglas aster. The bottom row shows the three annuals farewell-to-spring, California poppy, and baby blue eyes.
In addition to watching new plants bloom in the study garden, we had the opportunity to observe many incredible pollinators in the field this summer. We saw a hummingbird visit the Western Red Columbine, we tried to capture videos of leaf-cutter bees snipping little petal pieces off of farewell-to-spring, and at a neighboring plot we observed a male wool-carder bee section off an entire patch of Salvia for a female bee.
On the left: Farewell-to-spring 'Scarlet' with crescents cut out of the petals by leafcutter bees. Top right: A female wool-carder bee (Anthidium manicatum) collecting trichomes from Yarrow 'Calistoga'. Middle right: A leafcutter bee with a piece of petal from Farewell-to-spring 'Dwarf White'. Bottom right: A leaf cutter bee removing a piece of petal from Farewell-to-spring 'Aurora'.
We were also able to take a couple educational field trips this field season in order to learn about pollinator studies ongoing outside of Oak Creek. In June, we went up to the North Willamette Research and Extension Center in Aurora, OR to listen to three talks about pollinators at the Blueberry Field Day. We learned how to score the productivity of honeybee hives, how to properly don a the top of a bee suit, about blueberry’s best pollinators, and blueberry research projects at the University of Washington.
In August, we made a trip to Bend for a different kind of study… an artistic one! We travelled to the High Desert Museum in order to visit Jasna Guy and Lincoln Best’s exhibit “In Time’s Hum…”. Jasna is a brilliant artist inspired by pollinators, which translates into the subject of her pieces as well as her artistic media. Many of her pieces are made using encaustic (a method of painting using wax, bee’s wax in her case!), dipped directly into bee’s wax, or involve pollinators in some other format, including her color study of pollen, which attempts to replicate the colors of fresh pollen as well as the colors after bees have mixed them with nectar. In the center of exhibit were two cases filled with bees collected and identified by Linc, surrounding some of the dried plant specimens they forage on.
These field trips were a wonderful way to see what other pollinator work is happening in our broader community and to inspire future studies. It was especially exciting to see how Jasna and Linc combined art and science with their exhibit, which is something many of us in the Garden Ecology Lab are interested in.
1. Mallory, Svea, and Jen at the blueberry Field Day. 2. Svea, Jen, Mallory, and Tyler at the High Desert Museum. 3. A panorama of the "... In Time's Hum ... " exhibit. 4-5. Art on the outside of the exhibit. 6. A snapshot of two pollen samples from Jasna Guy's pollen color study.
While we cannot make conclusions until we complete our final field season, we are excited to report some of the variation in visitation between native plants and native cultivars that we have observed in our first two field seasons. In the first field season, our observations of native bees foraging on the study plants revealed three plant groups to have variable amounts of visitation. Yarrow, farewell-to-spring, and California poppy all had at least one cultivar that received substantially less native bee visits than the native type. In our second year, all three of farewell-to-spring’s cultivars received less visitation than the native Clarkia amoena. Poppy had only one cultivar with less native bee activity than the native (Purple Gleam), and in the case of Douglas Aster, both of the cultivars actually had more visitation by native bees than the native.
Figure 1: Average Abundance of Foraging Native Bees during 5-Min Observations in 2021. Individual plants are color-coded by genus. The naming scheme combines the first three letters of the genus and specific epithet; cultivars are denoted by an underscore and a 1-2 letter code to identify them. For example, AQUFOR is the native Aquilegia formosa, and AQUFOR_XT is Aquilegia x ‘XeraTones’.
Today, Tyler successfully defended his undergraduate research thesis, entitled ‘Invest in Vegetables: A Cost and Benefit Analysis of Container Grown Roma Tomatoes (Solanum lycopersicum cv. ‘Roma’) and Italian Basil (Ocimum basilicum cv. ‘Italian’)‘.
His research was inspired by the rush to vegetable gardening, that many households made during the start of the COVID-19 pandemic. Research has shown that there are many benefits to vegetable gardening, including social, emotional, physical, and financial. However, those in rental housing, or otherwise without easy access to land, were largely locked out of accessing these benefits.
Although previous research has shown that in-ground and raised bed vegetable gardening can yield positive economic benefits, to date, no studies (that we know of) have quantified the financial costs and benefits of growing vegetables in containers. Tyler thus set up a system of 5-gallon and 3-gallon bucket gardens, planted with Roma tomatoes, or Roma tomatoes plus Italian basil. He kept careful track of the cost of materials, and the time he spent gardening. He also kept careful track of the harvest he pulled off of each container.
Over the course of his study, he successfully learned about and fought back Septoria leaf spot, and blossom end rot. We learned that Roma tomatoes, in particular, are susceptible to blossom end rot. On top of these horticultural plant problems, Tyler’s research was abruptly halted by the late summer wildfires of 2020, that made air quality unsafe for him and others to continue their work, outdoors.
Despite these challenges, he was able to glean enough data from his project, to share some interesting findings:
- None of the containers netted a positive economic benefit, in the first year of gardening, largely because the cost of materials outweighed the financial benefits of the harvest.
- If the project were continued into year two, he projects that he would have had a positive financial outcome for the tomatoes grown with basil, in the 5-gallon containers.
- Across the course of the season, he only spent 30 minutes tending to each container. Because he had few garden maintenance tasks, the time invested in container gardens was minimal. This is an important finding, for folks who may shy away from gardening because of lack of time.
- As expected, the 5-gallon containers yielded more than the 3-gallon tomatoes. The 3-gallon containers stunted plant growth too much, to recommend them as a viable container gardening system. [As a side note, we were given the 3-gallon containers, for free, which is why we included them in the study.]
- The fair market value of Roma tomatoes was fairly low (~$1.00 per pound). Thus, the net economic benefit of growing Roma tomatoes was also low. Basil, on the other hand, was a high value specialty crop that helped to raise the overall economic value of crops harvested from the buckets.
If you are interested in seeing Tyler’s thesis defense presentation (~30 minutes), you can do so, at the link below.
Tyler will be graduating in a few days, with a degree in BioResource Research from OSU! He’s worked in our lab group for two years, and has been an absolute joy to learn and work with. We wish him the very best on the next adventures that await him.
Flowers and bees have one of the most well-known symbiotic relationships ever formed. Flowers rely on bees for pollination, and bees rely on flowers for nectar and pollen. It is generally understood that flowers act as advertisements to attract bees. However, less is known about what exactly bees are seeing and how that can change once humans get involved. This project is focused on the changes that can arise after a plant is cultivated, and how these changes can affect pollinator preference of a flower.
While changes made by breeders might not seem all that drastic to our eyes, we have little idea if that is the case for bees. Often breeders will change flowers for aesthetic purposes. This can have unknown consequences. These changes might not seem like such a big issue since the flowers are still colorful. However, bee vision is very different from humans, with bees having the ability to see into the UV spectrum. This means that while we might think we are only changing the bloom size or the color, we could also be unintentionally changing UV messaging visible only to the bees.
The purpose of this study is to use UV photography to explore these invisible differences between the native and cultivar. We also want to determine if the differences have a tangible impact on pollinator preference. This study is ongoing, but the images so far have shown a few native/cultivar sets that have a marked difference in UV markers between native and cultivars. While the study has only just started, our excitement and curiosity have not abated. This is an entirely new foray into pollinator relationships and mechanisms and could open up the world of bees and flowers in a brand new way.
This article is the third in a five part series that I am writing for the Hardy Plant Society of Oregon (HPSO) Quarterly Magazine. I am grateful to the team at HPSO for their editorial skills and feedback. Part 1 (overview, and gardens as ‘islands’ in an urban ‘ocean’), and Part 2 (putting a price on nature), and Part 3 (Wild Bees > Honey Bees) of this series can be found in earlier blog posts.
This study was published shortly after the first edition of Doug Tallamy’s book, Bringing Nature Home: How Native Plants Sustain Wildlife in Our Gardens.[ii] After decades of studying host plant records of butterfly and moth species, Tallamy was convinced that native plants were critically important to wildlife conservation. About half of all insects are herbivores, and about 70 percent of all herbivores are specialists that are only capable of feeding on a narrow range of plants (see Schoonhoven et al. 2005, Chapter 2, pages 5-9). Specialist insects have developed, over time, the ability to feed on plants that have physical or chemical deterrents that keep generalist insects at bay. Although specialist insects can feed on plants that can be toxic to other insects, they can’t easily switch to feed on novel, non-native plants.
Burghardt and Tallamy’s Study of Native Plants and Caterpillars
Tallamy was Karin Burghardt’s master’s degree advisor and one of her co-authors on the 2009 paper. In their study, they selected six pairs of suburban gardens in central Pennsylvania. Gardens were paired by size and proximity. One garden in each pair featured the conventional landscaping for this region: large lawns, Asian shrubs, Asian understory trees, and native canopy trees. The other garden was landscaped with native ornamentals at each vegetative layer: grasses, shrubs, understory trees, and canopy trees.
They counted the number of caterpillars at 12 points within each garden. Since caterpillars are herbivores, and most insect herbivores are specialists that do best on native plants, they hypothesized that they would find more caterpillars in the native plant gardens. Indeed, this is what they found. Caterpillar abundance was four times greater, and caterpillar species diversity was three times greater, in the native gardens versus the conventional gardens. In addition, Burghardt found that native plant gardens harbored more birds. In fact, native plant gardens had 55 percent more birds and 73 percent more bird species, compared to conventional gardens!
This study demonstrated that gardeners’ choices matter and can clearly influence ecological food chains. Food chains are organized into what are known as trophic levels. Organisms on the same trophic level share the same ecological function and nutritional distance from the sun. Photosynthetic plants are on the first trophic level. Herbivores, or organisms that eat plants, are on the second trophic level. Organisms that eat herbivores, such as birds, are on the third trophic level.
Burghardt and Tallamy demonstrated that what you decide to plant in your garden not only determines the structure of the first trophic level but can also cascade up to affect the second and third trophic levels. As an entomologist, I was not surprised that gardeners’ plant selections could influence the second trophic level. However, I was blown away that these decisions could cascade up to strongly influence the third trophic level.
Garden Ecology Lab Studies of Native Plants and Bees
In the Oregon State University Garden Ecology Lab, we study relationships between native garden plants and native bees. To be honest, I did not expect that native bees would prefer native plants. Whereas the leaves and other vegetative parts of a plant include an array of chemical and physical defenses to protect the plant from insect herbivores, flowers have few such defenses. In fact, flowers function to attract pollinators to a plant.
Thus I was somewhat surprised when Ph.D. student, Aaron Anderson, found that most of the native plants in his study attracted more native bees and more species of native bees than his non-native comparison plants. For example, non-native lavender ‘Grosso’ attracted a large number of bees, but most of these bees were non-native honey bees. By and large, the native plants were better for bee abundance and bee diversity, compared to the non-native comparison plants. In particular, Globe Gilia, Farewell to Spring, Oregon Sunshine, Douglas Aster, and California Poppy were all particularly attractive to native, wild bees in Aaron’s study.
Why might native bees prefer native plants, when flowers don’t have the same chemical and physical deterrents that herbivores must contend with? One hypothesis is that the nectar and pollen in native plants might provide better nutrition to native bees. Another hypothesis is that pollinators are keenly tied into the visual display of native plants. Flower color, size, shape, and ultraviolet markings are all important signals that flowers use to attract the attention of various pollinators. If there are changes in any aspect of this visual display, pollinators may no longer recognize a flowering plant as a good source of pollen or nectar.
Another OSU Ph.D. student, Jen Hayes, is trying to understand why native plants seem to be preferred by native pollinators. As part of her Ph.D. work in the Garden Ecology Lab, Jen is collaborating with an OSU photography student, Svea Bruslind. Svea uses different filters to take photographs of native plants and native cultivars in visible light, ultraviolet light, and in “bee vision” light. We are just getting started on this study, but look forward to reporting our findings in the near future.
[i] Burghardt et al. 2009. Impact of native plants on bird and butterfly biodiversity in suburban landscapes. Conservation Biology 23:219–224.
[ii] Updated and expanded version published as Bringing Nature Home: How You Can Sustain Wildlife with Natives Plants.
Your garden soil contains millions to billions of individual microorganisms, including bacteria, fungi, viruses, and archaea, representing tens of thousands of different microbial species. Humans evolved for millenia in the presence of these environmental microbes associated with vegetation, soil, water, and wildlife. Our immune systems are not only adapted to coexist with the majority of these microbes, but may even require that interaction to function properly. Emerging scientific evidence suggests that exposure to soil microbes trains the immune system, reduces inflammation, and improves mental health (Rook, 2013). For example, the common soil bacterium Mycobacterium vaccae has been found to have positive impacts on stress tolerance and mental health (Matthews and Jenks, 2013), while other research has shown that children exposed to greater microbial diversity, such as that encountered in farming environments, tend to have lower prevalence of autoimmune disorders, including allergies and asthma, than their urban counterparts (Hanski et al., 2012).
The primary goal of the Garden(er) Microbiome Project was to understand how much microbial transfer from soil to skin occurs during gardening activities, what types of microorganisms are transferred, and how long they can persist on the skin. We are also interested in exploring how soil microbial communities vary with different management practices (e.g., organic vs. conventional) and geographic locations, as we know that microbes play critical roles in soil nutrient cycling, carbon sequestration, pollutant degradation, and, of course, crop health.
To accomplish this study, we recruited 40 gardeners to collect microbial samples from their garden soil and from the surface of their skin (hands). All samples were collected in July–September, 2020, and were equally distributed between the Willamette Valley and High Desert regions, as well as between self-reported organic and non-organic management practices. Each volunteer was asked to collect soil samples from three different garden beds and skin microbiome swabs before, after, ~12 hours after, and 24 hours after gardening (Figure 1). To identify bacterial taxa (different types of bacteria) present in the samples, we used Earth Microbiome Project protocols to sequence the V4 region of the bacterial 16S rRNA gene.
In garden soil samples, we observed over 8.5 million individual bacteria, representing about 45,000 different bacterial species. In skin microbiome samples, we observed over 6 million individual bacteria, representing almost 13,000 different bacterial species. Of all these bacterial species, there were just over 7,500 that were shared between garden soils and gardeners’ skin microbiomes over the course of the study (Figure 2).
Our initial hypothesis was that skin microbiome samples would be more similar to soil samples immediately after gardening, due to microbial transfer from soil to skin during direct contact. We also expected that the skin microbiome would return to baseline (before gardening) after a period of time, depending on individual behaviors, such as washing hands and bathing. It turned out that soil microbial communities were very different than those found on skin. Interestingly, skin microbiome samples tended to be dominated by a small number of taxa, though they were not always the same taxa at different sampling times. For many of the study participants, we did indeed see an increase in shared taxa for the skin samples collected immediately after gardening (Figure 3). However, soil microbes were generally transient on the skin and were no longer present after 12 hours. We note that the COVID-19 pandemic may have influenced hand-washing behaviors and use of hand sanitizers, which could have had additional unexpected impacts on the skin microbiome.
Though it was beyond the scope of the project to describe life history details about every type of bacteria that was found, we did investigate a handful of taxa that were highly abundant in many samples. In garden soil, many of the most abundant bacteria belonged to the genus Pseudomonas. In a recent paper, Sah and Singh (2016) state, “The genus Pseudomonas encompasses arguably one of the most complex, diverse, and ecologically significant group of bacteria on the planet. Members of the genus are found in large numbers in all the major natural environments (terrestrial, freshwater, and marine) and also form intimate associations with plants and animals.” Importantly for gardens, several species of Pseudomonas are able to promote plant growth, while others are well-known plant pathogens. Members of the genus Sphingomonas were also common soil inhabitants found in this study. Sphingomonads are broadly distributed in the environment, including soil, water, air, and plant leaves. Only one species of Sphingomonas is known to cause disease in humans, typically in hospital-acquired infections (Balkwill et al., 2006). A third genus of interest from garden soils was Streptomyces. This is a large genus with over 500 members that are ubiquitous in soils. They are known to form symbiotic relationships with plants and animals, and they are responsible for the production of over 2/3 of all known antibiotics (Antoraz et al., 2015). Streptomyces also produce the chemical compound geosmin, which gives soil its earthy smell (Seipke et al., 2012).
The composition of skin microbiome samples in this study varied wildly from individual to individual, and sometimes even for the same individual at different time points. Among the most abundant taxa we found were members of the genera Pantoea, Acinetobacter, Bacillus, and Klebsiella, as well as Pseudomonas, which was described above. Generally speaking, these are very diverse genera and are widespread in many environments, including soil and human skin. Some Pantoea species produce antimicrobial compounds that can help control fire blight in fruit trees (Walterson and Stavrinides, 2015). The genus Acinetobacter contains two species of interest for health reasons—A. baumannii is typically found in wet environments and is a notable opportunistic pathogen associated with hospital-acquired infections (Howard et al., 2012), whereas exposure to environmental sources of A. lwoffii is thought to protect against development of allergies, although it can also cause infection in immunocompromised individuals (Debarry et al., 2007). Members of the genus Bacillus have been explored for potential probiotics (Elshaghabee et al., 2017), and the genus Klebsiella is somewhat notorious for its human pathogenic members. However, Klebsiella, Pantoea, and several other members of the Enterobacteriaceae family have highly similar DNA sequences in the region that we targeted, so these composition results should be interpreted cautiously.
This study represents one of the very first investigations of garden soil microbiomes and, to our knowledge, the only one that explores the ability of soil microbes to transfer and persist on human skin after typical gardening activities. Overall, we found that garden soils tend to have far greater bacterial diversity than skin microbiome samples. Bacterial community composition was largely similar across different garden beds, whereas skin microbiome composition varied dramatically. Some soil microbes appeared to transfer onto skin during direct contact with soil, but they were generally gone within 12 hours, suggesting a low ability to permanently colonize skin. However, a daily gardening routine with repeated and extended contact with soil likely reinoculates the skin such that soil microbes are like a regular visitor during the growing season.
The specific ecological role of most microbes, both in soil and on skin, is a relatively new area of investigation garnering intense interest. However, few, if any, concrete recommendations are currently available to guide actions towards improving plant and human health. A primary goal of this study is to gather baseline data for future studies, which are needed to further explore the impact of daily soil contact over longer time periods (e.g. entire growing season), how changes in gardeners’ skin microbiomes compare with non-gardeners, and whether consumption of fresh garden produce affects the gut microbiome.