Top 10 Oregon Native Plants for Pollinators: Week 4

The Garden Ecology Lab’s Pollinator Plant PR Campaign Presents….. Varileaf Phacelia!

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 4! Profiles will include photos, planting information, and will highlight common pollinators of each plant.

Photo by iNaturalist user Leslie Flint.
CC Some rights reserved.

Plant Facts

  • Scientific Name: Phacelia heterophylla
  • Life Cycle: Biennial/ annual, typically grown as an annual in Oregon
  • Growth Habit: Upright, mounding
  • Bloom Duration: April – July
  • Hardiness Zone: 3-7
  • Special Traits: Shade tolerant, drought tolerant
  • Light requirements: Full sun to part shade
  • When to plant: Seeds should be sown in the fall, starts may be planted in the fall or spring after the last chance of frost.

Pollinator Facts

  • Varileaf Phacelia provides both nectar and pollen to its insect visitors.
  • Phacelia was found to be associated with five bee species in Aaron’s research: the obscure bumblebee (Bombus caliginosus), Edward’s long-horned bee (Eucera edwardsii), the fuzzy-horned bumblebee (Bombus mixtus), the confluent miner bee (Panurginus atriceps), and the yellow-faced bumblebee (Bombus vosnesenskii).
  • Phacelia is also a larval host for 4 moths: the Bilobed Looper Moth (Megalographa biloba), the Geranium Plume Moth (Amblyptilia pica), the Orange Tortrix Moth (Argyrotaenia franciscana) and Clepsis fucana1.

Photo by Aaron Anderson

Varileaf Phacelia‘s Native Range in Oregon

Phacelia heterophylla is native to most of the Western United States – From Washington to California, east to Montana and south to New Mexico. It is additionally native to Canada, where it is currently considered “imperiled” by the IUCN red list2.

Varileaf Phacelia's native range covers nearly the entire state of Oregon! It's native habitat includes moist conifer forests, riparian areas, sagebrush, mountain brush, as well as in aspen and fir communities3.
Maps and legend acquired from the Oregon Flora Project, with Imagery Sourced from Google.

Varileaf Phacelia as a pollinator plant

A female long-horned bee (Eucera sp.) searches for some leftover forage on a spent Phacelia heterophylla inflorescence. Photo by Aaron Anderson.

Varileaf Phacelia is the epitome of an underappreciated pollinator plant! This annual with petite white flowers attracts both an abundance and diversity of insect visitors. With stamen that stick out of the corolla, it heavily advertises its nutritious rewards, attracting plenty of busy bees. In fact, it commonly hosted 5 different bee species in Aaron’s field surveys, including three charismatic bumblebee species, one of which is currently listed as “vulnerable” on the IUCN Red List: Bombus caliginosus, the obscure bumblebee4.


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.


In a survey of gardeners conducted by Aaron and the Garden Ecology Lab, Phacelia heterophylla ranked last among 23 native plants scored for their aesthetic appeal. It may appear “weedy” to some gardeners, but as an annual, it could easily be interspersed with more attractive annual face flowers (such as California poppy, meadowfoam, farewell to spring, or baby blue eyes) to create a colorful and nutritious pollinator garden. Varileaf Phacelia is also a great native annual to include in dryland pollinator gardens, considering it is drought tolerant and able to grow in both nutrient poor and rocky soils.

Did you know?

Photo by iNaturalist user jwlipe. CC Some rights reserved.

Varileaf Phacelia also has the common name "Variegate Scorpionweed", and the pictures above can show you exactly why! It's flowers are borne on elongated stems which are tightly curled, similar to a fiddlehead from a fern! The flowers bloom from the base to the apex of the stem, and the "scorpion tail" slowly unravels as the blooms travel up the stem.

Photos from the field

Of all of the plants we highlight in this 10-week series, Varileaf Phacelia is the one plant that Gail regularly says is in great need of it's own public relations (PR) team. The goal of these plant profiles is to share information and photos of these plants that might convince readers to love this plant as much as we (and the bees) do! 

Let us know which plants have caught your eye, or those that may still take some convincing, by leaving a comment below! 🐝

Tune in next week for the next edition of our Pollinator Plant PR Campaign.

Top 10 Oregon Native Plants for Pollinators: Week 3

The Garden Ecology Lab’s Pollinator Plant PR Campaign Presents….. Pearly Everlasting!

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 3! Profiles will include photos, planting information, and will highlight common pollinators of each plant.

Photo by Patrick Perish

Plant Facts

  • Scientific Name: Anaphalis margaritacea
  • Life Cycle: Perennial
  • Growth Habit: Upright, clumping
  • Bloom Duration: June – October
  • Hardiness Zone: 3-8
  • Special Traits: Drought tolerant, deer resistant
  • Light requirements: Prefers full sun but will grow in partial shade
  • When to plant: Plant starts in the Spring, or sow seeds directly in the Fall.

Pollinator Facts

  • Pearly everlasting was found to be associated with two species of mining bees in Aaron’s research: Andrena cerasifolii, Andrena candida.
  • Other common visitors to Pearly Everlasting are American Lady butterflies, Painted Lady butterflies, Everlasting Tebenna moth, and Sweat bees.
  • Female and male flowers are generally found on separate Pearly Everlasting plants. This means that male plants provide nectar and pollen to insect visitors while female flowers just provide nectar.
Andrena visiting Pearly Everlasting. Photo by Aaron Anderson

Pearly Everlasting’s Native Range in Oregon

Oregon is home to three varieties of Pearly Everlasting whose native ranges extend the Cascade range, Western Oregon and parts of northeastern Oregon.

Maps and legend acquired from the Oregon Flora Project, with Imagery Sourced from Google. Copyright 2021© TerraMetrics

Pearly Everlasting as a pollinator plant

Pearly Everlasting is an herbaceous perennial commonly seen in open meadows, burned areas, rocky flats and along roadsides in dry, sun-exposed soils. Native throughout the United States, except for the Southwest, Pearly everlasting is an excellent nectar resource for pollinators, and is especially attractive to many butterfly and moth species. It makes an important larval host plant for American Lady and Painted Lady Butterflies whose seasonal feeding can leave Pearly Everlasting foliage slightly tattered, but nothing that the plant can’t recover from.

Pearly Everlasting hosts a moderate abundance and a relatively low diversity of insect visitors, but is a key host plant for its associated pollinators.

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?

As a plant that thrives in high light and very dry conditions, Pearly Everlasting is one of the first plants to colonize recently burned forests. When rain comes after a fire-season, Pearly Everlasting sends out rhizomes that allow the plant to spread rapidly across nutrient-rich areas. Similarly in a garden setting, Pearly Everlasting has low moisture and nutrient needs but when heavily watered and fertilized, it can quickly take over.

Established Pearly Everlasting should not be irrigated more than twice per month in the summer months. The white, petal-like bracts of Pearly Everlasting flowers retain a fresh appearance after being dried, so gardeners that allow aboveground growth to dry out in the summer months will be rewarded with dried flowers perfect for floral arrangements.

Photos from the field

Tune in next week for the next edition of our Pollinator Plant PR Campaign.

Top 10 Oregon Native Plants for Pollinators: Week 2

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.

Plant Facts

  • 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.

Pollinator Facts

  • 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 and 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.

Top 10 Oregon Native Plants for Pollinators: Week 1

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.

Plant Facts

  • 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.

Pollinator Facts

  • 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.

2021 Butterfly Bush Update

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.

‘Honeycomb’ in full bloom…on October 29th, 2021

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. 

2021 Field Update: Natives & Nativars

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’.

Spring with the Mason Bees

Written by Mallory Mead

My name is Mallory Mead, and I am new to the Garden Ecology Lab! I am an undergrad studying Horticulture and minoring in Entomology, and I started a few weeks ago as an assistant to Jen Hayes on her study of pollinator attraction to native plants and nativars.

I enrolled in Oregon State’s URSA Engage program, which gives undergrads a taste of research experience in the Winter and Spring of their first year, and joined a project studying how mason bees might be impacted by climate change with Dr. Jim Rivers of the department of Forest Ecosystems and Society. The study seeks to examine the effects of warming temperatures on mason bee behavior and the development of brood.

The Western US’s native species of mason bee, the Blue Orchard Bee (BOB) is known to be an excellent orchard pollinator. On many orchard crops they are more efficient at pollination than honey bees on a per individual basis, and so the commercial management of BOBs is being explored as honey bee colonies suffer management challenges and colony losses in recent years.

A mason bee nest within a reed. “DSC_0082” by tpjunier is licensed under CC BY 2.0.

Mason bees have a short lifespan of 4 to 6 weeks. Emerging in the early spring, males die shortly after mating, while females build nests in holes in wood or reeds. They forage for pollen and nectar to form provision masses in which they lay their eggs. They also collect mud to form partitions between each provision mass and to cap the nest once it is full. Their offspring will feed on the provisions and metamorphose into cocooned adults to overwinter in their cells and emerge the following spring.

To ensure the bees had ample nutrient resources, the project was conducted next to the organic cherry orchard at OSU’s Lewis Brown Farm. Before the cherries bloomed, 6 nest structures were designed and constructed by Jim, Ron Spendal (a mason bee house conisuerrier) and Aaron Moore of Revolution Robotics.

Nest structures, solar panels, and camcorders at Lewis Brown Farm.

Each structure has 3 shelves with 16 nest holes each, lined with paper straws so that the nests can be easily removed and examined. The structures are solar powered, and each shelf is heated to a different increment above the ambient temperature i.e. + 0°C , + 2°C, + 4°C, + 6°C, + 8°C, + 10 °C, and + 12°C. These differentials represent many potential warming outcomes of climate change.

Nest Structure Number 2 with labelled component parts. A. The Electronics control box. B. Cocoon-release box. C. Shelves sandwiched by heating pads, and lined with paper nesting straws

Our Hypotheses

  • We predicted that female mason bees will select the warmer nests first, and that females will leave nests earlier in the morning to begin foraging because they will reach the critical internal temperature necessary for flight sooner.
  • If heated bees have a greater window of foraging time, then we predict they’ll be able to construct nests at a faster rate in the warmer nests.
  • With greater nest construction will come a greater production of offspring from the bees in the warmed nests.

But…

  • In terms of offspring quality, we predict that offspring of heated nests will emerge as weak individuals and mortality will be the highest for the heated brood.

…and we are pretty confident about this last prediction.

Insects are poikilothermic meaning their internal temperatures are determined by the environment. Past studies by researchers Bosch and Kemp have reported that mason bees who are overwintered at warm temperatures will “use up their metabolic reserves and are likely to die during the winter”. And a more recent study by researchers at the University of Arizona found that mason bees subjected to heating resulted in reduced body mass, fat content and high mortality of the mason bee offspring.

Data Collection

One of the latest male mason bees to emerge, surrounded by empty cocoons in the release box.

Our mason bees started hatching from cocoons in mid-April and began to colonize the nest structures. I captured video footage of the bees as they emerged in the morning to forage. If bees from heated nest sites emerge earlier, this will support our hypotheses that they reach their critical-for-flight temperature earlier, and get a leg-up on foraging compared to their neighbors.

I also conducted “nest checks” to track the rate of nest construction along with two other research assistants.

In the fall, the nest tubes will be extracted to examine the reproductive output, and in the following spring, offspring will be assessed for rates of mortality, offspring mass, and fat content.

Obstacles

Some of the challenges along the way have included dealing with insect pests. Spiders were easygoing inhabitants of the nest straws, for they only nested in empty straws, so we’d swap them out for a clean one. The earwigs were much more pervasive, and went for the already inhabited nests. As generalist foragers, the earwigs took advantage of provision balls of nectar and pollen that had not yet been sealed off by mud. Once I read that earwigs will indeed eat the mason bee eggs that are laid into the provision masses, I knew it was crucial to remove the earwigs from all nests, but these feisty creatures proved determined to stay. We ordered some tanglefoot, a sticky substance to trap the earwigs on their way up the structure post, and meanwhile I coaxed earwigs out with tiny pieces of grass. Jabbing them repeatedly would eventually provoke them to charge at the blade of grass and fall out from the straw.

Yellowjackets were another opportunistic nester. They’d sneak into the cocoon boxes to build nests, and always gave me a start when opening the tiny boxes. I removed their nests with an extended grabber tool and would destroy them in any way I could. I feel immensely lucky not to have been stung through this process.

The most terrifying surprise during the project was a fat snake that was living in the solar panel battery box. It popped out at me hissing while I conducted a routine check. Alas, I was too spooked to take on this unexpected visitor and let it leave on its own time.

Preliminary Findings & Observations

By mid-May, a pretty clear pattern was emerging. At each structure, the control shelf’s nests (+ 0 °C) were full and capped with mud, while the hottest shelves were almost completely empty. We will analyze nest check data to confirm that these patterns are not just arising by chance, but a study that was released this past April showed another species of mason bee in Poland following the same pattern of nest site preference and selection for cooler nest sites.

The mason bees’ unexpected behavior of avoiding the heated chambers may lead to trouble during the second part of the experiment because this means our sample size for heated offspring has become so tiny, but here it is important to note that this is mason bee project is a pilot study and so the data collected this year will simply influence more specific future research.

these preliminary findings make me think that mason bees have an ingrained sense to avoid warm nests, which might show mason bees’ adaptability in the face of climate change, that is, if they can manage to continue finding cool nests. People managing mason bees find that nests facing the morning sun are the most attractive to the bees, but I wonder how long it will be before temperatures rise and mason bees start avoiding these sunny nests.

Moving Forward

By the end of May, I’d only see a few the mason bees per visit, so the season was clearly coming to an end. I wrapped up data collection and am now spending the summer extracting data from the video footage, and checking up on the bees to ensure they are safe and sound until Fall inspections.

I am wishing the best to both the wild bees in our region and those in our study, as the temperatures skyrocket this week but with this summer’s heat wave, I don’t think we need to simulate climate change; it is right here before us. Even though it is practically inevitable that temperatures will rise to dangerous heights in my generation’s lifetime, there is so much life to be saved, and there is no time to waste.

“Blue Orchard Bee, Osmia lignaria” by SeabrookeLeckie.com is licensed under CC BY-NC-ND 2.0″

Garden Ecology Lab Year in Review: COVID Edition

This past year presented challenge and change to the Garden Ecology Lab. COVID locked us out of the lab and out of the field for a period of time. We said goodbye to two lab members (Angelee graduated! Cliff decided to move on from graduate school), and said hello to new lab mates (Cara took over Cliff’s project; Gwynne started her post-doc; Tyler, Jay, and Max all joined the lab as undergraduate researchers and research assistants). In addition to COVID and personnel changes, I had orthopedic surgery that took me away from work for a little under a month.

But somehow, despite the challenges and changes, we managed to make progress on several research projects. Below, I present a partial reporting of the Garden Ecology Lab year in review for 2020. Besides each project heading is the name of the project lead(s).

1) Garden Bees of Portland (Gail & Isabella): Jason Gibbs’ group from the University of Manitoba provided final determinations for a particularly difficult group of bees to identify: the Lasioglossum sweat bees. In addition, Lincoln (Linc) Best provided determinations for garden bees collected in 2019. Isabella is entering in some of our last remaining specimens, and I am working through the database of over 2,700 collected specimens to ‘clean’ the data and double check data entry against specimens in hand. There are a few specimens that need to be re-examined by Linc, now that we have determinations from the University of Manitoba, the American Museum of Natural History (Sarah Kornbluth), and a graduate of Jim River’s lab (Gabe Foote).

Altogether, we collected between 76 and 84 species of bee across a combined acreage of 13.2 acres (sum total acreage of 25 gardens). The low end estimate conservatively assumes that each unique morphospecies (i.e. Sphecodes sp. 1 and Sphecodes sp. 2) are a single species, whereas the high end estimate assumes that each is a unique species. A few noteworthy specimens:

  • We collected one specimen of Pseudoanthidum nanum, which is a non-native species to our area, which seems to be establishing and spreading in Portland. Stefanie Steele from Portland State University is writing a note on this apparent introduction, and is using data associated with our single specimen in her paper.
  • We collected one specimen of Lasioglossum nr. cordleyi which might or might not be a new species. The notation nr. cordleyi means that this specimen looks similar to L. cordleyi, but that the morphology of this specimen is different enough than the normal ‘type’ for this species, that it catches your attention. Jason Gibbs’ group is retaining that specimen. Further study will be needed to determine if it is indeed a new species, or not.
  • Some of the species we collected (as well as their ecological characteristics) suggest that gardens might be healthy habitat for bees. For example, we collected 72 specimens of Panurginus atriceps, which is a ground-nesting, spring-flying bee. Previous studies of garden bee fauna found ground-nesting and spring-flying bees to be relatively rare. We found them to be surprisingly (but relatively) common in our collections. We also collected seven putative species and 23 specimens of Sphecodes bees. This type of bee is a social parasite that does not collect nectar or pollen or construct a nest for their brood. Instead, they take advantage of the hard work of other bee species, by laying their eggs in the nest of another female. Parasitic bees are often used as bioindicators of habitat health. They would not be present on a site, unless the site also supported their obligate hosts.
  • We collected two species of bee that are listed on the IUCN red list for threatened and endangered species: Bombus fervidus (18 specimens) and Bombus caliginosus (10 specimens). I am not yet sure if their presence in urban gardens suggests that these species are recovering, that these species might be urban-associates that would be expected to thrive in urban gardens, and/or if gardens might represent particularly good habitat for these species.

In 2021, I *hope* that I can complete gathering data for this study, so that I can begin to analyze data and write. I hope to make it out to every garden, one last time, to finalize garden maps that will be used to calculate the area allotted to ornamental plants, edible plants, hardscape, and unmanaged areas. Aaron has already mapped out the landscape surrounding each garden at radii of 500 and 1000 meters. Together, these data will be used to understand whether/how garden composition and the surrounding landscape interact to influence bee species richness.

2) Native Plants and Pollinators (Aaron Anderson): In February, Aaron successfully defended his dissertation proposal and passed his oral examination, and thus advanced to Ph.D. candidacy!! Since that time, he has been busy sorting, identifying, and counting three years’ of insect samples from his 140 study plots, representing five replicates plots of 23 native plants, four ornamental plants, and a control ~ a task that he finished two weeks ago! His bees have been identified to species by Linc. Aaron has identified the thousands of other insects in his samples to the taxonomic level of family. He is working through analysis of his massive data set, and is simultaneously working on two manuscripts: one focused on just the bees and the other covering all other insects. We plan to turn the key points of these two chapters into an infographic that can be used by gardeners and green industry professionals, to select native plants that support an abundant and diverse assemblage of beneficial insects.

Aaron recently submitted the first paper from his dissertation for publication consideration, to the journal HortTechnology ~ and it was accepted, pending revisions! This paper reports on his survey of gardeners’ impressions of the aesthetic value of his study plants, and includes five specific recommendations for native wildflowers that Pacific Northwest nurseries might consider growing and marketing as pollinator plants (e.g. Gilia capitata, Clarkia amoena, Eschscholzia californica, Madia elegans, and Sidalcea asprella virgata). These plants all fell within the ‘sweet spot’ of being attractive to both pollinators and to gardeners.

Aaron’s plots at the NWREC station remain in place. Although we are through collecting data for Aaron’s study, I am applying for grant funding to study how plant traits ~ both the reward that plants offer pollinators and the displays that they use to attract pollinators ~ change with plant breeding for specific aesthetic traits, and whether/how these changes affect pollinator visitation. We also hope to study how highly attractive pollinator plants function in mixed plantings and in garden settings.

3) Bees on Native Plants and Native Cultivars (Jen Hayes):

Jen successfully completed her first field season of research, which is a monumental accomplishment during this time of COVID restrictions on our work. In early 2020, Jen finalized her list of study plants, which included one native species and 1-2 hybrids or native cultivars. This, in and of itself, was a huge accomplishment. Although we started with a much broader list of potential study plants, so many native plants did not have native cultivars or appropriate hybrids available for sale.

Jen’s study plants, which include one native (top photo in each group) and 1-2 native cultivars or native hybrids.

Once Jen and her crew put the plants in the ground, a new set of challenges emerged. For example the native yarrow emerged with pink flowers, which was a clear signal that these plants were not true natives. In addition, the Sidalcea cultivars that Jen and her crew planted came up looking different than the Sidalcea native. This sent Jen on a journey to the OSU Herbarium, where she learned that the Willamette Valley’s native Sidalcea malviflora has been reclassified as Sidalcea asprella, and that the cultivars we purchased were hybrids of Sidalcea malviflora (native to SW Oregon and California). This all suggests a need to work with local nurseries and/or growers of native plants, to see whether or not there needs to be or can be standards for sale of native plants. Should native species and native cultivars be verified or share provenance? Should gardeners be asking for this information? I don’t know, but I think that they’re important questions to consider.

With one field season’s worth of data in hand, the native cultivars were more attractive to all bees (with overall patterns being driven by the abundance of the European honey bee) for all floral sets, except California poppy. When we excluded honey bees from the analysis, to look at (mostly) native bees, no clear pattern of visitation on native plants versus native cultivars emerged. Native California poppy was most attractive to native bees. But, native cultivars of Sidalcea were more attractive to native bees (keeping in mind that in 2020, our native cultivars were not cultivars of our regionally appropriate native plant). For all other plants, there was no difference. We look forward to collecting additional data in 2021 and 2022, to see if the lack of difference in bee visits to native plants versus native cultivars holds up. Particularly for the perennials, we are finding that bee visits change so much from year to year, as the plant becomes established.

4) Garden Microbes in Soil and on Skin (Dr. Gwynne Mhuireach): Dr. Mhuireach successfully recruited 40 gardeners to participate in this study: 20 from western Oregon and 20 from the high desert. She has received and processed all soil samples and all skin swab samples for PCR (genotyping), which will be used to infer the diversity and identity of the soil microbial community in garden soils and on gardeners’ skin. She has also received survey responses from all study participants, so that she can characterize gardeners’ crop types, time in the garden, and gardening practices (e.g. organic, conventional, or mixed).

Dr. Mhuireach then sent me the soil samples, so that I could process them for submission to OSU’s Soil Health Lab. The Soil Health Lab is currently performing the chemical and physical analyses on each soil sample, so that we can determine if there is any relationship between soil characteristics, gardening region (e.g. western Oregon or high desert), crop choices, management practices, and the microbes that can be found in garden soils and/or on gardeners’ skin. Gwynne just received the first data back from the PCR analyses ~ and we can’t wait to share some of the intriguing findings with you, after we’ve had some time to process and digest the data!

Because of COVID-19 lab closures, we are a bit behind where we had hoped to be at this point. We anticipate receiving all data from each service lab by the end of January or in early February. You can read more about Gwynne’s project, here.

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Beyond these four studies, Tyler started his BioResource Research project (costs and yield of container grown and intercropped tomotoes), and Isabella worked on her thesis (parasitoids in Portland area gardens). We also collaborated with OSU Computer Science students to turn a database of first frost / last freeze dates that Angelee compiled, into a web-based app (the app is still in beta-testing, but we hope to release it, soon!). I will detail those studies, in another post. But for now, I’m getting excited for the smell of carnitas that is filling the house, and that will go on top of the New Years’ nachos that will help us ring in 2021! I hope that you all have a very Happy New Year, and that 2021 brings health, and happiness, and joy to all.

The Gardens of Piet Oudolf: Pollinator Paradise?

Flower-filled garden in Oudolf style
Oudolf-designed garden at Pensthorpe, Fakenham, UK. https://www.fiveseasonsmovie.com/gallery/

As part of Master Gardener Week at the end of October, I had the opportunity to view “Five Seasons: The Gardens of Piet Oudolf” and participate in a discussion afterwards. This recently-released film has brought renewed attention to the gardens and landscapes created by this internationally-renowned designer. His popular public garden designs, and several books, have had a profound impact on the design of public spaces, as well as private gardens.

Oudolf’s gardens have been described as spontaneous, immersive and naturalistic, and rely heavily on grasses and structural perennials to maintain visual interest well into the winter. They evoke flower-filled meadows and prairies, and seem at first glance like places that could, indeed, have occurred spontaneously. Oudolf himself acknowledges, though, that they require a certain amount of “interference”, and his design process is comprehensive and very specific. He has a palette of plants that he has tested over time for durability and effect.

During the bloom season, one imagines these gardens will be buzzing with pollinators, and be places of lively, hungry activity. When it comes to pollinators, it seems, almost any garden is better than no garden at all, and a garden doesn’t need to be designed especially for pollinators in order to offer benefits to them. As research in this lab has shown, though, a garden designed specifically to be pollinator friendly has an outsized impact.

So I wondered, how pollinator-friendly are Oudolf’s naturalistic gardens, really?
On the positive side:
• Lots of flowers. From early season to late, things are blooming. Plants are left standing well into winter, providing seed and shelter.
• Little or no use of pesticides.
• Native plants are often included, though there is no particular emphasis on them.

Pollinator friendly flowers
Pollinator-friendly flowers in Oudolf Field, Hauser & Wirth, Somerset, Bruton, UK. https://www.fiveseasonsmovie.com/gallery/

On the negative side:
• Maintenance involves cutting everything to the ground in late winter. This destroys the winter homes of cavity-nesting bees that use the stems. At the Lurie garden in Chicago, this problem was recognized and steps were taken to leave some stems standing.
• Lack of layering. The iconic Oudolf garden is composed almost entirely of herbaceous perennials, with trees and large shrubs lacking. This limits the provision of food and habitat for a variety of creatures.


I believe pollinators could be better supported by Oudolf-style gardens with three simple changes.
• Keep mowed areas to a minimum. Group plants with good winter nesting stems, and leave them standing until they are covered by new growth.
• Include and group small groups of larger plants such as suitable small trees and shrubs.
• Prioritize native plants where possible.

Mowed brown winter garden with a section left standing
Lurie Garden with selected areas left standing for pollinators.
https://www.luriegarden.org/2019/03/15/cutting-back-on-the-cut-back/

If you would like to know more about Piet Oudolf’s gardens, plant choices, and design process, here are some reference materials. And if you get the chance, watch the film “Five Seasons: The Gardens of Piet Oudolf”.

Dream Plants for the Natural Garden by Henk Gerritsen and Piet Oudolf, Timber Press 2000
Essentially a catalog (although not all plants are pictured) of plants that Oudolf has culled to be “reliable plants that, over the years, can be maintained in an average garden without too much in the way of artificial props and bolstering”. Many of them “look good dead”, too. These are the plants he uses in his designs. They are divided into categories of Tough Perennials (the longest section by far), Playful Biennials and Annuals, Troublesome Invasive Plants, and Troublesome Capricious Plants – hardly the usual categories!
If you are an experienced gardener and want an invaluable reference for plants that will enhance your natural garden without requiring loads of work, this book is for you.

Planting Design: Gardens in Time and Space by Piet Oudolf and Noel Kingsbury, Timber Press 2005
On the other hand, if you are not an experienced gardener, this book might be a better place to start. It is a thrifty introduction to the concepts of how gardens fit into nature, and vice versa, and how plants can be used through space – and time! – to create the desired outcomes. There are many lists of plants for specific purposes, such as Small Trees to combine with perennials, and Biennials for self-sowing, and a short but useful section on how to prepare for, implement, and maintain a planting of this sort.

Planting: A New Perspective by Piet Oudolf and Noel Kingsbury, Timber Press 2013
This book builds on the previous two, offering a detailed look at the techniques and philosophy Oudolf uses to design his gardens, as well as specific ways in which he uses plants in them. A season-by-season guide dissects various effects and combinations, and a chart towards the end concisely organizes many of the plants used. One of the most interesting concepts is that of matrix planting.

Several Piet Oudolf books
Several of Piet Oudolf’s books

For more detail on the creation of specific gardens by Piet Oudolf, there are also books on Hummelo, the High Line, and Durslade Farm.

The Self-Sustaining Garden by Peter Thompson, Timber Press 2007
In this book matrix planting is presented in great detail. This is an effective and efficient way of designing intermingled plantings without having to specify the location of each and every plant. The matrix (often grasses) may be made up of several plant species, and serves as a stage for other, showier compatible plants embedded in it.

Dramatic Effects with Architectural Plants by Noel Kingsbury, Overlook Press, 1997
Oudolf’s chief writing partner has produced many noteworthy books himself. As the title describes, this book focuses on plants with strong and dramatic architecture. Having some of these in the mix is a key technique that makes Oudolf’s designs work.

Naturalistic Planting Design by Nigel Dunnett, filbert press 2019
With a foreword by, who else, Piet Oudolf, this is one of the most recent entries in the category of books focusing on natural or naturalistic design. It’s a dense book with at least as much text as photography, covering garden lore from historic, through contemporary, and looking to the future. Basic design principles, as they pertain to a naturalistic design, are also presented, along with a series of case studies illustrated by seasonal photos.

Gardening with Native Plants of the Pacific Northwest
by Arthur Kruckeberg and Linda Chalker-Scott, University of Washington Press, 2019.
And finally, if you want to use PNW native plants to achieve Oudolf-like effects in your garden, this recent book is an accessible, thorough, well-illustrated guide to those plants. You will find it easy to browse through for plants that have the look you want. Symbols by each photo give a hint as to each plant’s cultural requirements.

Other resources:
The blog Gardenista has several lovely entries on aspects of Oudolf’s designs. https://www.gardenista.com/posts/?t=oudolf#search
Piet talks about current projects in this recent interview: https://www.hauserwirth.com/ursula/29413-attached-world-piet-oudolf-garden-life

If you want LOTS of pictures to look at, try Piet Oudolf’s Flickr photostream, https://www.flickr.com/photos/10470961@N03/

Or his own website https://oudolf.com/