An Update on Native Plant Studies from The Garden Ecology Lab at Oregon State University

Posted on February 17, 2025 by Gail Langellotto

A version of this article was originally written for the ‘Growing Knowledge‘ section of Digger Magazine, published by the Oregon Association of Nurseries.

The Garden Ecology Lab was founded in 2017 to advance an understanding of how to plan, plant, and manage garden systems to promote environmental and human health. It is one of two labs in the United States, and the only one in the Western US, to specifically focus on studies of garden ecology.

In this article, I provide an update on our native plant studies, with a focus on results that may be of particular interest to nursery owners. Brief summaries of many of our lab’s studies can be found on the ‘For Gardeners’ page of our lab website. Some nurseries have printed out copies of these lab briefs, so that their customers can see the ecological benefits of various plants. More briefs are planned for this year. Periodically visit our website for updates.

Native Plants in Garden Retail Centers

Interest in native plant gardening has drastically grown in recent years, but many native plants remain difficult to find for purchase. In the April 2019 issue of The Digger, Dr. Aaron Anderson highlighted three barriers that gardeners face, when trying to purchase native plants: 1) lack of advertising by native plant nurseries or gardeners’ lack of familiarity with these nurseries, 2) variation in nursery stock among native plant growers, and 3) geographic distance that gardeners might have to travel to find the plants they are looking for. These specific barriers were ones that Aaron faced when he was setting up his field study of insect communities associated with 23 species of Pacific Northwest Native plants.

Aaron used the Oregon Flora’s gardening resource page to locate where he could buy his study plants. He ultimately ended up purchasing plants from two retail nurseries (one in Corvallis and the other in Forest Grove) and two pop up native plant sales (one in Corvallis and one in Portland). He also worked with two wholesale nurseries that were generous enough to sell or donate study plants or seed in the small quantities he was seeking (one in Salem and one in Silverton). Because he has been asked this question, often, Aaron also wrote a blog post on ‘Where to Buy Native Plants in Oregon‘.

After a three-year field study, Aaron was able to identify 10 native plants which support a diversity of bee species. We developed an infographic to share this information with gardeners, and include lavender in the image, since many gardeners perceive lavender to be a pollinator-friendly plant (Bennett 2019).

Image 1: The number of estimated bee species associated with PNW native plants is shown in a yellow circle, above each bar. Lavender is shown as a comparison, since it is recognized as a pollinator-friendly plant by many gardeners.

Today, Oregon Flora’s garden resource page lists 10 nurseries where gardeners can find and purchase native plants (Oregon Flora 2025). I used their plant-finding tool, to see whether I could find the 10 native plants that we recommend to gardeners. None of the nurseries were listed as carrying all of these recommended plants: two nurseries were listed as carrying 6 species, three nurseries carried 5, two nurseries carried 4, and three nurseries carried 2. All of the 10 nurseries were listed as carrying Oregon sunshine (Eriophyllum lanatum). None were listed as carrying Farewell-to-spring (Clarkia amoena), varileaf phacelia (Phacelia heterophylla), or common madia (Madia elegans).

Farewell-to-Spring, a promising native nursery plant

The absence of farewell-to-spring from nursery shelves is particularly disappointing, because it has become a favorite in our lab group. Its native range spans the Bay Area of California, north through Oregon and Washington and into British Columbia. In Oregon, it grows west of the Cascades to the coast and is found in a variety of habitats including coastal prairie, grasslands and forested areas. It is an easy-to-grow annual plant with erect stems (5.4” maximum height), thin, green leaves and bright pink flowers. In our study plots, first bloom occurred anywhere between early June and early July and lasting through early August through late October, depending upon seasonal weather patterns and supplemental irrigation.

Farewell-to-spring attracts a diversity of beneficial insects. Aaron collected 14 bee species, 15 predatory insect taxa, and 12 parasitoid taxa from this wildflower (Anderson 2022, Anderson et al. 2022) documenting its ecological value for attracting pollinators, as well as natural enemies that promote the biological control of insect pests. In a separate, but related field study, Jen Hayes looked at the pollinator assemblages on eight species of wild-type native plants and 1-3 of their cultivars. Jen provided an overview of this study in the October 2020 issue of The Digger (Hayes and Langellotto 2020), and the full report of this study was recently published (Hayes et al. 2025) for folks wanting more detailed information.

Farewell-to-spring was one of the native plants in her field study of pollinators on native plants and native cultivars. The cultivars she used were ‘Aurora’ (dark pink blossoms with a cream center), ‘Dwarf White’ (white blossoms), and ‘Scarlet’ (red blossoms with a light pink center). She documented 32 total pollinator species from the wild-type plant (with an estimated 104 total pollinator species), 17 pollinators on ‘Aurora’ (28 species estimated), 23 pollinators on ‘Dwarf White’ (24 species estimated), and 9 pollinators on ‘Scarlet’ (13 species estimated). Furthermore, she found that specialist bees, which are picky about where they collect pollen, were either exclusively found on wild-type native plants (two species, Megachile gravita and Melissodes microstictus), or were found in higher abundance on wild-type plants compared to cultivars (two species, Melissodes lupinus and Melissodes clarkiae). Because specialist bees have relatively narrow diet preferences, including their preferred forage plants is an easy way to attract these unique bees into a garden, and to locally increase pollinator biodiversity.

In addition to the importance of wild-type Farewell-to-spring as a forage plant, Jen worked with Mallory Mead (a former undergraduate student in our lab) to document its importance for bee nest material. Many leafcutter bee species use leaves, mud, resin, sticks, pebbles, or petals when they build their nests. Jen documented two species of petal-cutting bees in her study plot, each of which had a significant association with Farewell-to-spring and its cultivars. Megachile montivaga had significant associations with the wild type native and ‘Dwarf White’. Megachile brevis was significantly associated with the wild type native, ‘Dwarf White’, and ‘Aurora’.

Image 2. A and B: Leafcutter bees cut discs from petals of a cultivar. C: A leafcutter bee carries a petal disc to its nest. D: A leafcutter bee nest in a sunflower stalk. Credits: Svea Bruslind (A), Devon Johnson (B), Mallory Mead (C), Heidi Nordijk (D), © Oregon State University

Although Jen found evidence that the leafcutting bees were significantly associated with two of the three cultivars she included in her study, Mallory documented a very strong preference for the wild-type native over the cultivars, when she documented foraging for nesting material. Because leafcutting bees leave a characteristic crescent cut in petals, Mallory could document foraging for nesting material by counting the number of petal cuts from each plant. Wild type native plants had 3-4X as many petal cuts than cultivars. Even when we controlled for bloom count per plant, the wild type native was significantly preferred over the cultivars.

Image 3: Number of petal cuts by bees on wild-type Farewell-to-spring, and 3 cultivars.

Native Cultivars Are Often Easier to Find and Buy

Given the high abundance and diversity of beneficial insects associated with Farewell-to-spring, as well as its unique association with specialist foragers and petal-cutting bees, we enthusiastically recommend this plant to ecologically-minded gardeners. However, the average gardener shopping for this species is more likely to encounter cultivars than wild-type plants. This is partly because the plethora of Farewell-to-spring cultivars are on the market. In addition to the three included in Jen’s study, gardeners can find ‘Double Azalea’ (pink, purple, red, white flowers), ‘Lilac’ (pink petals with dark red center spots), ‘Pink to Red’ (red petals with light pink edges), ‘White’ (white flowers), ‘Pink’ (light pink flowers with no other markings); and ‘Sugarplum’ (semi-double flowers, light pink with rose-colored center markings, dwarf, somewhat bushy).

As noted earlier, native plants can be difficult to source in the retail marketplace. Offerings may not reflect the regional species pool of plants (Zinnen and Matthews 2022), and in some areas, 77% of the native plants on market shelves are actually hybrids or cultivars (Coombs et al. 2020). However, multiple studies have found that gardeners are willing to pay higher prices for native plants and locally sourced plant materials.

Somewhat unexpectedly, in a recent survey of 719 gardeners (Hayes et al. in preparation), 81% report that they buy their native plants at pop-up plant sales hosted by Soil and Water Conservation Districts, Master Gardener groups, or other non-profits. A comparable percentage of gardeners (78%) said that they buy their native plants at retail plant nurseries. However, given the transient nature of pop-up plant sales, it was surprising to us that they were as or more popular than brick-and-mortar stores for native plant purchases. I think this speaks to the difficulty many gardeners have finding the plants they are seeking, and how non-profit plant sales are filling a market void. It also points to a market opportunity for the nursery industry, in general.

References:

Anderson, A. 2019. Native plant production and marketing. The Digger, April Issue, pp 33-36.

Anderson, A. (2022). Evaluating the Attractiveness of Pacific Northwest Native Plants to Insects and Gardeners [Dissertation submitted in partial fulfillment of Ph.D.] Oregon State University.

Anderson, A. G., Costner, L., Best, L., & Langellotto, G. A. (2022). The bee fauna associated with Pacific Northwest (USA) native plants for gardens. Conservation Science and Practice, 4(10), e12801.

Bennett L. 2019. Examining the gap between interest and understanding of provisioning for bees: A capstone project to support urban bee conservation [Thesis submitted in partial fulfillment of M.N.R.]. Oregon State University.

Coombs, G., Gilchrist, D., & Watson, P. (2020). An assessment of the native and invasive horticultural plants sold in the mid-Atlantic region. Native Plants Journal, 21(1), 74-82.

Hayes, J., Langellotto, G. 2020. Pollinator plant trials: researchers test the value of Willamette Valley natives and nativars. The Digger, October Issue, pp 33-37.

Hayes JJ-M, Bell NCS, Best LR, et al. 2025. Pacific Northwest native plants and native cultivars Part I: Pollinator visitation. Environ. Entomol. https://doi.org/10.1093/ee/nvae126.

Oregon Flora. 2025. Gardening with natives. https://oregonflora.org/garden/index.php, accessed January 29, 2025.

Zinnen, J., Matthews, J. W. 2022. Native species richness of commercial plant vendors in the Midwestern United States. Native Plants Journal, 23 (1) 4-15.

Year-round Alternatives to “No Mow May”

Posted on October 16, 2023 by Signe Danler

In the recent blog post “The Controversy Surrounding ‘No Mow May”, Dr. Langellotto explores the lack of good science supporting the idea of giving your lawn a month-long break from being mowed. Despite the scientific controversy, “No-mow May” is an idea that has taken off. It is simple and makes people feel good about helping pollinators, while also doing less yard work. At its best, it may indeed work in some places, for some people, to help some pollinators for a month…but what about the rest of the year?

A month of neglecting your lawn might allow flowers to bloom, depending on what grows in your lawn besides grass. These may well attract pollinators – but the untended expanse may also fool various creatures into thinking they have a safe place to nest, pupate, and burrow. What happens to them when the mowing starts again? Bees and butterflies can fly away to other flowers, but less-mobile creatures may be killed or displaced.

It’s also questionable whether this method reduces yard work at all. A lawn grown long and lush in peak growing season – and which may be wet from spring rains as well – will be very difficult to mow after a month. So at best, “No-mow May” provides a very short-term benefit, and may cause more problems than it solves.

Are there other routes to a low-maintenance pollinator paradise?
Definitely! As Gail concluded, a pollinator garden provides year-round support to pollinators, without the disruption of intermittent mowing. If you want detailed information on creating a pollinator garden in the PNW, and what to plant in it, here’s a good resource to get you started: “Enhancing Urban and Suburban Landscapes to Protect Pollinators”, https://extension.oregonstate.edu/catalog/pub/em-9289-enhancing-urban-suburban-landscapes-protect-pollinators.

But maybe you aren’t able to devote a whole garden to pollinators. Maybe you just have a little bit of space. How about planting just a few strategic plants?

Garlic chives, a white Allium) next to purple Douglas aster — Garlic chives (Allium) with Douglas aster (dwarfed by tight location) in fall

Certain types of plants are pollinator powerhouses. They tend to attract a wide variety of pollinators. Some are food plants for many different native butterfly and moth caterpillars. The best bloom for a long time, offering their bounty for up to several months. To extend the bloom season even more, plant several varieties of the same species, with varying bloom times, or multiple related species.

Include a few of these in any landscape and you will benefit many pollinators. Choose natives when you can, and choose at least one species from each family or general category.

Syrphid fly on Douglas Aster — It’s not just bees: Syrphid fly on Douglas aster

Pollinator Powerhouse starter list
In western Oregon, you could do worse than start with the Garden Ecology Lab’s Top 10 Oregon Native Plants for Pollinators (https://blogs.oregonstate.edu/gardenecologylab/category/top-10-plants-for-pollinators/) and their relatives. (Top-10 are in bold below).

Aster family (Asteraceae) – Daisies or Composites.
A huge family with many pollinator favorites. Here are just a few.
Achillea millefolium (yarrow)
Anaphalis margaritacea (pearly everlasting) NOT for a well-fed and watered area, or it can become invasive
Eriophyllum lanatum (Common woolly sunflower)
Solidago spp. (goldenrod) – Plant Native S. canadensis (Canada goldenrod), miniature S. ‘Little Lemon’, and late and showy S. ‘Fireworks’ for a really long season of bloom! Be aware that most tend to spread by seed, and the birds won’t eat all the seed. Seedlings are easy to pull, though, if you don’t want too many.
Symphyotrichum/Aster – Tall native S. subspicatum (Douglas aster) or short native S. hallii (Hall’s aster), miniature S. ‘Woods Blue’, and many others.
Also: Echinacea (coneflower), Erigeron (fleabane), Helenium (sneezeweed – for treating sneezes, not causing them), Helianthus (perennial sunflowers), Inula, and many more.

Mint family (Lamiaceae)
Another really big family almost universally attractive to pollinators. Includes Agastache spp. (anise hyssop, hummingbird mint), Calamintha nepeta (calamint), Caryopteris x incana (bluebeard – a small shrub), Monarda didyma (bee balm), Salvias, and herbs rosemary, mint, basil, oregano, and thyme, among others.

Calamintha and Alliums in midsummer (Wisconsin)

Sedum/Hylotelephium (stonecrops)
Both the low groundcover Sedums and the tall, fall-blooming Hylotelephiums like ‘Autumn Joy’ are pollinator magnets , though often you will only see honeybees mobbing them.

Alliums – Any kind
There are spring, summer and fall bloomers – plant some of each, mixed in with other pollinator plants. Late spring to summer is the main Allium season, with dozens of kinds available. For late summer and fall try Allium tuberosum (Garlic Chives), Allium cernuum (nodding onion), a NW native, and Allium thunbergii ‘Ozawa’ (Ozawa Japanese onion) for the very end of autumn.

Self-sowing annuals
Many annuals will bloom straight through the season until frost.
Alyssum, Clarkia amoena (Farewell-to-spring), Eschscholzia californica (California poppy) (mostly annual), Fagopyrum esculentum (Buckwheat) – a great cover crop, pollinators love it, and you can harvest the seeds to eat or let it self-sow; Gilia capitata (globe gilia), Limnanthes douglasii (NW native), Madia elegans (common madia), Phacelia heterophylla (Varileaf phacelia).

Late summer: *Crocosmia*, *Agastache, Solidago* (left to right)

To make sure your pollinator powerhouse plants thrive and bloom for a long time, make sure to give them good growing conditions.
• Soil should be reasonably good (though not excessively fertilized, which can cause pest-attracting lush growth and fewer flowers).
• They should have full to half-day sun in most areas.
• Even native plants appreciate some water during dry summer months, otherwise they will go dormant.
• Grouping these plants together can make care easier – voila, a pollinator garden! – but they can be tucked into any available spot as long as their needs are met. Even a vegetable garden!

Gardeners Needed for a Native Plant Survey!

Posted on October 9, 2023 by Jen Hayes

Study: Native Plants & Native Cultivars: Understanding Pollinator Preference for Native Plants and their Cultivated Counterparts in the Pacific Northwest

Thank you for your interest our survey! We are done collecting survey responses at this time. If you previously took the survey and have any questions, please direct them to Gail.Langellotto@oregonstate.edu and/or Jen.Hayes@oregonstate.edu.

Petal-cutting Bees!

Posted on January 27, 2023 by Mallory Mead

A study of leafcutter bees and a PNW native flower, through the lens of iNaturalist.

The Clarkia Project team: Mallory Mead, Jen Hayes, Sarah Erskine, and Ali Filipovic

If you are a subscriber to our blog, you have likely seen our photos and videos of one of our favorite plant-pollinator interactions: the petals of Farewell-to-Spring (Clarkia amoena) being harvested by leafcutter bees!

After observing this eccentric harvest behavior in the research garden, we got curious about the bees behind the petal-nest craft, and how we could study this interaction further.

Leafcutter bee mid-petal-harvest! Photo by Devon Johnson.

Crescent-shaped petal-cuts left behind by leafcutter bees.

iNaturalist is a popular community-supported biodiversity database that the Garden Ecology Lab has been experimenting with in recent years. Jen realized that the leafcutter bees’ distinct crescent-shaped mark are visible in many iNaturalist observations of Clarkia amoena. She wondered how we could use the already sizeable iNaturalist database of Clarkia amoena observations to study the interaction over a wider geographic and chronological scale than that of the research garden. Jen and Gail agreed to mentor me in producing an undergraduate research thesis on this subject.

The study’s objective is to use iNaturalist’s data on Clarkia amoena to see if there is a difference in leafcutter bee usage of Clarkia amoena petals based on whether the flower is a native versus a cultivar type, and whether the flower is found in an urban or non-urban environment.

In this process we have found that iNaturalist is easy for anyone to contribute to, but the information it provides is limited compared to the wealth of contextual information gained when being in the actual, living presence of a specimen. So, to get a greater feel for the intricacies of this flower, I embarked on what we called “Ground-Truthing Field Trips” to check out some Clarkia amoena populations in the “real world”.

I went out during peak pollinator season, following the coordinates of recently posted iNaturalist observations. Each specimen I visited was incredibly different from the next. I found the delicate blossoms in natural areas, the borders of farmland, restoration sites, and gardens.

Data from these trips will not be published in my thesis because the contexts are not exactly comparable, and my sampling was exploratory rather than precise. Nonetheless, I gained contextual insight and inspiration watching diverse pollinator assemblages in beautiful meadows of pink.

Mallory at a meadow restoration site near Corvallis with *Clarkia amoena* and tarweed (*Madia* elegans).

The field trips have helped us more clearly see through the window of iNaturalist and have informed the methodology we use.

For example, I saw examples of hybridization between two species of Clarkia in a seeded restoration site, and cultivar-hybrid escapees in natural areas. It’s been important to navigate identification of cultivars and hybrids in iNaturalist.

In a restoration prairie seeded with two different Clarkia species, pollinators cross-pollinate them, giving rise to sterile hybrids (Lewis & Raven, 1958). Note the malformed stigma and anthers.

Simultaneously, our field crew recorded petal-cutting behavior on the Clarkia amoena natives and nativars at Jen’s research garden this summer. Below are the three cultivars in the garden, and if you look closely you can see “petal-cuts” which we counted and recorded weekly. We will analyze the difference in leafcutter usage between the cultivars and native type.

This hot pink, stripy *Clarkia* doesn’t look like either the native or cultivars we had planted!

Clarkia amoena is an annual that reseeds itself effectively, so last year’s seeds gave rise to this season’s blooms. To our surprise, however, Clarkia amoena of all different colors started popping up in our research plots this Spring! Last season’s bees had combined pollen from the garden’s varieties bringing rise to all sorts of intermediate forms.

Clarkia amoena is prone to hybridization between members of the species or cultivars in the same proximity. These intraspecific hybrids are fertile. We seek to explore how cultivar genetics may be moving into natural populations.

Through the winter, our team is working with the iNaturalist data to quantify leafcutter bee petal usage. We expect to share our results in June 2023, so stick around to hear about our findings!

Work Cited:

Lewis, H., & Raven, P. H. (1958). Rapid Evolution in Clarkia. Society for the Study of Evolution, 12(3), 319–336.

2022 Field Update: Native plants & native cultivars

Posted on December 26, 2022 by Jen Hayes

This summer we completed our third and final field season surveying pollinator visitation to native plants and native cultivars! We will maintain our experimental garden for one additional season, to finish up some plant measurements and data collection missed in our initial three seasons. This post will serve as a 2022 field update in addition to summarizing some of our preliminary results from our field observations!

Study Plants (2020-2022)

*Discontinued in 2021 due to lack of vigor and availability of replacement plants
**Added in 2021 to replace removed plants
*******Discontinued after 2020 due to taxonomic inconsistencies

Scientific Name	Common Name	Plant Type
Achillea millefolium	Yarrow	Native
Achillea millefolium ‘Calistoga’*	Yarrow	Cultivar
Achillea millefolium ‘Salmon Beauty’	Yarrow	Cultivar
Achillea millefolium ‘Moonshine’**	Yarrow	Cultivar
Aquilegia formosa	Western Red Columbine	Native
Aquilegia x ‘XeraTones’		Cultivar (hybrid)
Camassia leichtlinii	Great Camas	Native
Camassia leichtlinii ‘Caerulea Blue Heaven’	Great Camas	Cultivar
Camassia leichtlinii ‘Sacajawea’	Great Camas	Cultivar
Symphyotrichum subspicatum	Douglas’ Aster	Native
S. subspicatum ‘Sauvie Sky’	Douglas’ Aster	Cultivar
S. subspicatum ‘Sauvie Snow’	Douglas’ Aster	Cultivar
Clarkia amoena	Farewell-to-spring	Native
Clarkia amoena ‘Aurora’	Farewell-to-spring	Cultivar
Clarkia amoena ‘Dwarf White’	Farewell-to-spring	Cultivar
Clarkia amoena ‘Scarlet’**	Farewell-to-spring	Cultivar
Eschscholzia californica	California Poppy	Native
E. californica ‘Mikado’	California Poppy	Cultivar
E. californica ‘White’	California Poppy	Cultivar
E. californica ‘Purple Gleam’**	California Poppy	Cultivar
Nemophila menziesii	Baby Blue Eyes	Native (California)
N. menziesii ‘Penny black’	Baby Black Eyes	Cultivar
N. menziesii ‘Snow White’	Baby Blue Eyes	Cultivar
Sidalcea asprella ssp. virgata*******	Rosy checkermallow	Native
Sidalcea malviflora ‘Purpetta’*******		Cultivar
Sidalcea malviflora ‘Party Girl’*******		Cultivar

We conducted 5-minute visual observations on our study plants over three seasons. During these observations, we recorded all insects that interacted with a plant. These interactions included foraging, resting, basking, mating, etc. We recorded insect IDs to morphological group levels, as many bees are hard to identify to species in the field! We were able to identify common bumble bees, honey bees, butterflies, and a few other insects to the species level, but many were identified to groups for ease (e.g. ‘green bees’, ‘black bees’, ‘leafcutter bees’).

Field Season Stats

Year	# Sample Dates	# Collected Pollinators	# Observed Pollinators
2020	28	2159	6238
2021	33	2471	6225
2022	29	~2000	~4700

Number of sampling dates, total number of collected pollinator specimen (via insect vacuum), and cumulative pollinators observed during 5-minute observations for each of our three field seasons.

Is there a difference in native bee visitation to native plants and their cultivars?

Graphs of cumulative and mean foraging native bees from 5-minute observations conducted over three field seasons. Plant Type (y-axis) is abbreviated with a 6 letter code, e.g. “SYMSUB” = *Symphyotrichum subspicatum* = Douglas’ Aster. Natives have a box around each bar, and cultivars can be identified by an underscore followed by 1-2 letters, e.g., SYMSUB_SN = *Symphyotrichum subspicatum* ‘Sauvie Snow’ = a native cultivar of Douglas’ Aster with white petals.

Our initial graphs show a subtle preference for native types by native bees. Douglas’ Aster, California Poppy, Farewell to Spring, and Columbine (4/7) have higher visitation by native bees when looking at cumulative and mean counts. The difference is marginal for Douglas’ Aster, but trends for the other three plants are strong. The remaining three species (Yarrow, Baby Blue Eyes, Camas) are difficult to assess, based on these figures alone.

Across these seven species, we do see differences in visitation between natives (wild types) and native cultivars. Whether these differences are statistically significant, and whether there is a trend across all plant groups, remains to be seen!!!

Subscribe to the Garden Ecology Blog to receive future updates on native-cultivar research and more news from the lab.

I want to recognize my amazing Bee Team this year, as this field season would not have been possible without them! I am grateful for all of their hard work and their success in managing this project while I was away numerous times this season. They are thoughtful, inquisitive, and resourceful students, all of whom would make amazing lab or field technicians upon their graduation this spring! Nicole is not pictured below, but also deserves recognition for all her contributions to this project. Thank you all

Svea working on her ultraviolet photography

Top 10 Oregon Native Plants for Pollinators: WEEK 10!!

Posted on January 24, 2022 by Jen Hayes

The Garden Ecology Lab’s Pollinator Plant PR Campaign Presents….. Douglas Aster!

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 10, which marks the end of our 10-week series! Profiles will include photos, planting information, and will highlight common pollinators of each plant.

Melissodes visits Douglas Aster. Photo by Tyler Spofford.

Plant Facts

Scientific Name: Symphyotrichum subspicatum
Life Cycle: Perennial
Growth Habit: Vigorous spreader, spreads through underground rhizomes
Bloom Duration: July-November
Hardiness Zone: 6-9
Special Traits: Drought tolerant, deer resistant
When to plant: Starts can be planted in the spring or early fall.

Pollinator Facts

Douglas aster provides both nectar and pollen to its insect visitors.
Aaron’s research found three species of long-horned bees (Melissodes robustior, M. lupinus, and M. microstictus) and three species of bees from the family Halictidae (Halictus ligatus, Agapostemon texanus angelicus and A. virescens) to be associated with Douglas aster.
Other common visitors to Douglas aster include syrphid flies and northern checkerspot butterflies! Douglas aster may also be a larval host to 8 different month species¹.

Photo by © mandamasprime, some rights reserved (CC-BY-NC).

Douglas Aster‘s Native Range in Oregon

Douglas aster is native to Northwestern Oregon and most of the coast.

Maps and legend acquired from the Oregon Flora Project, with Imagery Sourced from Google. Copyright 2022© TerraMetrics

Douglas Aster as a pollinator plant

Douglas aster is native to Western North American with a range extending from Alaska to California. It has an impressive ability to spread and a high volume of flowers that buzz with pollinator activity throughout its long bloom season. Hosting a high abundance and diversity of bee visitors, Douglas aster is a pollinator plant superstar. It is particularly valuable as a late-season pollinator plant, able to provide both nectar and pollen to its visitors when these resources may otherwise be scarce in the landscape.

People often have strong reactions towards Douglas Aster – they either love it, or find it to be “weedy” in appearance. We hope that this highlight may help some people change their opinions about it! We in the Garden Ecology Lab love Douglas Aster for its abundant blooms in varying shades of purple and for its great capacity for supporting wildlife. In the late summer, we love watching the diversity of pollinators bouncing from one flower to the next! Some common visitors to Douglas Aster that we see at Oak Creek Center for Urban Horticulture include bumblebees, green bees, long-horned bees, small sweat bees, and butterflies, including the woodland skipper (pictured below) and the occasional grey hairstreak (Strymon melinus).

Here, we see a woodland skipper (Ochlodes sylvanoides) foraging from Douglas Aster!

Infographics developed by LeAnn Locher, Aaron Anderson, and Gail Langellotto.

Did you know?

By mid to late summer, Douglas aster is quite the frenzied pollinator feeding ground, making the Oak Creek team’s sampling effort always a bit of a challenge. These photos are from 2 years after these plants were established, so you can see just how full these young plants can get when grown in favorable conditions!

At Oak Creek, we started all of our Douglas Aster plots with 4x 4″ pots, planted in the spring of 2020. As you can see in the photos below, they easily filled up their 1×1 meter beds! If you’re worried about Douglas Aster taking over your garden, consider starting with a single plant and observe it over the season to see how it reacts to your garden environment. Aggressive spreaders can be used to fill spaces such as borders with forest edges or along fences where low maintenance plants are key. If you want to contain your asters, consider planting some in a large pot or in an area where you can easily control the spread of their underground rhizomes. The purple flowers contrast beautifully with other late season natives, such as goldenrod and Madia.

Jen standing next to her Douglas Aster experimental plots. Photo by Tyler Spofford.

Tyler vacuum sampling bees off of a Douglas Aster plot. Photo by Jen Hayes.

Photos from the field

A yellow-faced Bumblebee visits a Douglas Aster flower
A woodland skipper enjoying some nectar
The baby Douglas Aster plants we introduced into the field in 2020
Douglas Aster still blooming strong on October 3, 2020
The native Douglas Aster has beautiful purple rhizomes!
Douglas Aster cultivars are even more vigorous, look at all these new shoots we removed from a neighboring plot!
Douglas Aster 1 year after planting, with last season’s biomass removed
A sweat bee enjoying some pollen!

Thanks for tuning in to the last posting of our Pollinator Plant PR Campaign! We hope you try growing some of these fantastic pollinators plants.

Top 10 Oregon Native Plants for Pollinators: Week 9

Posted on January 17, 2022 by Mallory Mead

The Garden Ecology Lab’s Pollinator Plant PR Campaign Presents….. California Poppy!

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

Plant Facts

Scientific Name: Eschscholzia californica
Life Cycle: Annual/Perennial
Growth Habit: Clumping, sprawling
Bloom Duration: Early Spring to Late Summer depending on seeding date.
Hardiness Zone: 7-10
Special Traits: Drought-tolerant, deer and rabbit resistant.
When to plant: Seed in Fall for a Spring bloom, or seed in Spring for a mid-summer bloom.

Pollinator Facts

California poppy only provides pollen to its insect visitors, but provides it in an abundance!
Aaron’s study found California poppy to be associated with 4 species of sweat bees: Halictus farinosus, H. tripartitus, Lasioglossum dialictus sp. 5, L. olympiae, and a bumblebee: Bombus vosnesenskii.
Other common visitors to California poppy include butterflies, specifically, acmon blue and mormon metalmark.

Sweat bee leaving a California poppy. Photo by Jen Hayes

California Poppy’s Native Range in Oregon

Oregon's populations of California poppy are primarily found in the Willamette Valley and the Klamath Mountains as well as some parts of the Columbia River Gorge and the Coast Range.

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

California poppy as a pollinator plant

California poppy’s range extends from Washington to northwest Baja California and east towards Arizona and southwest New Mexico. A popular flower for roadside plantings, California poppy survives well in average to poor soil that is well-draining. It survives mild-winters as an herbaceous perennial and reseeds itself readily. California poppy is an all-around easy pollinator plant to grow, and growing it pays off, as it attracts an incredible diversity and abundance of bees with its remarkable volumes of pollen.

Infographics developed by LeAnn Locher, Aaron Anderson, and Gail Langellotto.

Did you know?

California poppy’s petals are responsive to light! In the absence of light (at night and on cloudy days) petals spiral around each other and tighten to a close. In the presence of light, cells in the petals expand in response to the plant growth hormone auxin. This mechanism opens the petals allowing pollinators to access the flower’s pollen — although in the field we watch impatient bumblebees force their way into closed California poppy flowers to get to the pollen anyways.

Petals close tight during the night and remain so on overcast days. Photo by iNaturalist user metacom CC some rights reserved

Poppies in various stages of opening and poppy buds enclosed in pinkish-green calyxes. Photo by iNaturalist user Daniel Das C C some rights reserved

Photos from the field

Sweat bee traversing stamen. Photo by Jen Hayes
The underside of a sweat bee with pollen on its abdomen and hind legs. Photo by Jen Hayes
Photo by iNaturalist user baileylemkau CC Some rights reserved.
Jen’s California poppy research plot. Photo by Jen Hayes

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

Top 10 Oregon Native Plants for Pollinators: Week 8

Posted on January 10, 2022 by Jen Hayes

The Garden Ecology Lab’s Pollinator Plant PR Campaign Presents….. Globe Gilia!

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

Photo by iNaturalist user © slewiiis,
some rights reserved

Plant Facts

Scientific Name: Gilia capitata
Life Cycle: Annual
Growth Habit: Erect, clusters
Bloom Duration: May – June
Hardiness Zone: 7-10
Light requirements: full sun
Special Traits: Drought tolerant, tolerant to various soil types.
When to plant: Seeds can be sewn directly in the fall, or can be stratified indoors over the winter before planting out in the spring.

Pollinator Facts

Globe Gilia provides both nectar and pollen to its insect visitors.
Gilia was found to be associated with the yellow-faced bumble bee, Bombus vosnesenskii in Aaron’s research.
Globe Gilia is also a larval host for at least one moth species, Adela singulella, but possibly four others as well.
In addition to insect visitors, Gilia is can be an occasional nectar source for hummingbirds¹, which love its tubular flowers!

Photo by iNaturalist user © mudcitymelissa,
some rights reserved

Globe Gilia‘s Native Range in Oregon

Gilia Complex: Distribution of all Oregon Gilia capitata
Blue Field Gilia: Distribution of Gilia capitata ssp. capitata
Blue Field Gilia: Gilia capitata ssp. capitata. Photo (C) Kier Morse, courtesy of Oregon Flora
Pacific Gilia: Distribution of Gilia capitata ssp. pacifica
Pacific Gilia: Gilia capitata ssp. pacifica. Photo (C) iNaturalist user Wyattd.
Dune Gilia: Distribution of Gilia capitata ssp. chamissonis
Dune Gilia: Gilia capitata ssp. chamissonis, photo (C) iNaturalist user sennesand.

There are three subspecies of Gilia capitata in Oregon: Bluefield Gilia (ssp. capitata), Dune Gilia (ssp. chamissonis), and Pacific Gilia (ssp. pacifica). Dune Gilia and Pacific Gilia are considered to be rare plants in California (rare, threated, or endangered, rank 1B).

Distribution maps acquired from Oregon Flora with imagery from Google. Copyright 2022.

Globe Gilia as a pollinator plant

Globe Gilia may have only been associated with a single bee species in Aaron’s native plant research, but it is truly a powerhouse of an annual plant: it supports a highly diverse and abundant community of native bees! Gilia’s globe of flower heads provide pollinators with plenty of foraging spots to choose from, and the dense mass also allows easy access for both small and large pollinators, by acting as a nice landing pad. From their comfortable perch, butterflies and larger-bodied bees can dip their proboscis (tongue) into the nectar-rich blossoms. Smaller bees may need to crawl in to the individual flowers to access the nectaries.

Gilia is a great annual plant option to include in pollinator mixes and in meadows. It’s an easy to care for plant, requiring minimal water during the growing season. It grows up to three feet in height with lovely lavender – dark purple – blue flower heads, lacy foliage, and surprising blue pollen! The flowers contrast wonderfully with many other mid-summer blooms, such as poppies, Oregon sunshine, asters, and Clarkia.

Infographics developed by LeAnn Locher, Aaron Anderson, and Gail Langellotto.

Abundance 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.

Diversity Calculations. 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?

When you think about pollen, one color tends to come to mind: yellow. Perhaps you conjure up an image of a bumblebee in a field of clover, weighed down by some giant orange-toned pollen baskets as well. Many of us might stop there, and conclude that pollen must be either yellow or orange, as those are the predominant pollen colors we see in the plant world. The absolutely exciting news is that, like flower colors, pollen also comes in a rainbow of colors. Globe Gilia, for example, has pollen that comes in shades of blue!

A spotlight on pollen colors

As some of you may remember from my (Jen’s) 2021 field update, last summer, a few of us from the Garden Ecology lab had the wonderful opportunity to visit Jasna Guy and Lincoln Best’s exhibit ‘In Time’s Humm’ at the High Desert Museum in Bend. Part of this display was a pollen color study, showing Jasna’s recreations of pollen colors using pastels. We saw pollen in shades of yellows, oranges, red, pink, purple, white, and even green. Color can truly be found anywhere if you look closely enough! Perhaps it should be no surprise then, that even nectar may come in various colors, too… If you’re excited about pollen colors like we are, you might see if your local library has a copy of this book, and you might enjoy looking at pollen colors through the seasons, put together by the North Shropshire Beekeepers’ Association.

Now back to Globe Gilia: Photos from the field

Blue Field Gilia: Gilia capitata ssp. capitata. Photo (C) Kier Morse, courtesy of Oregon Flora
Dune Gilia: Gilia capitata ssp. chamissonis, photo (C) iNaturalist user sennesand.
Pacific Gilia: Gilia capitata ssp. pacifica. Photo (C) iNaturalist user Wyattd.

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

Top 10 Oregon Native Plants for Pollinators: Week 7

Posted on January 3, 2022 by Mallory Mead

The Garden Ecology Lab’s Pollinator Plant PR Campaign Presents….. Farewell-to-Spring!

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

Plant Facts

Scientific Name: Clarkia amoena
Life Cycle: Annual
Growth Habit: Upright, clumping
Bloom Duration: June – September
Hardiness Zone: 1-11
Special Traits: Drought tolerant, deer resistant
When to plant: For best results, direct seed in Fall or early Spring. Seeds can also be sown in containers or cold frames in the winter.

Pollinator Facts

Farewell-to-Spring was found to be associated with Megachile brevis, a species of leafcutter bee.

Other common bee visitors include long-horned bees of the genus Eucerini and other species of leafcutter bees.

Farewell-to-Spring also hosts some butterflies and moths including the White-Lined Sphinx, Pacific Green Sphinx Moth, and Clark’s Day Sphinx Moth.

Farewell-to-Spring provides both nectar and pollen to its insect visitors.

Although pollen is easily accessed on the protruding stamen, bees must dive into the flower to reach the nectar that is produced beneath the petals. This is because nectar is produced at the base of the ovary, and Farewell-to-Spring has an “inferior ovary” meaning the ovary is positioned below the sepals and petals.

A male bumble bee dives into a Farewell-to-Spring flower to reach its nectar. Photo by Jen Hayes.

Farewell-to-Spring’s nectaries are found beneath the stamen and petals. Photo © Stephanie Hazen.
some rights reserved

Farewell-to-Spring’s Native Range in Oregon

Farewell-to-Spring is found throughout Western Oregon from the Coast through the Cascades. Oregon is home to 4 subspecies of Clarkia amoena.

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

Farewell-to-Spring as a pollinator plant

Farewell-to-Spring hosts a moderate abundance of bee visitors, but the diversity of bees it hosts is among the highest found in the study! With a long flowering season, Farewell-to-Spring blooms when spring wildflowers are beginning to turn brown. Bloom duration can be lengthened by occasional watering over the summer, although Farewell-to-Spring are drought-tolerant and survive with minimal summer irrigation. This flower is an annual, but will reseed itself readily.

Infographics developed by LeAnn Locher, Aaron Anderson, and Gail Langellotto.

Did you know?

Leaf cutters forage for pollen, nectar, and one more surprising resource: petal clippings! Using their mandibles, the bees cut out a piece of a petal (often in the shape of a crescent), clasp the piece of petal under their abdomens, and fly away to use the petal as building material in their nests. If you keep a mason bee or leafcutter bee house in your yard and grow Farewell-to-Spring, look for nest holes that are plugged with pink petals instead of mud or leaves.

The tips of some of this flower’s petals have been harvested from by leafcutter bees:

Leafcutters in Action

In each of Jen’s two field seasons, she has set a challenge for student technicians: obtain a video of a leafcutter harvesting a piece of petal from Clarkia. Students that win the challenge are rewarded with baked goods!! This past summer, Mallory succeeded in capturing not one, but two videos of leafcutters in action (below). Leafcutters can be particularly difficult to capture on video because they cut the petal pieces very quickly, and often fly even faster! If you have Clarkia growing in your garden, look to see if your flowers bear any crescent-shaped cuts. If they do, you too might be able to spot some special bees flying away with their floral confetti.

Videos by Mallory Mead, summer 2021.

Photos from the field

Photo by Jen Hayes.
A bee from the genus Agopostemon visits blossom. Photo by Mallory Mead.
A bee from the genus Megachile rests in blossom. Photo by Mallory Mead.
A queen bumble bee reaches for nectar. Photo by Jen Hayes.
A long-horned bee mid-flight above Farewell-to-Spring. Photo by Mallory Mead.

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

Top 10 Oregon Native Plants for Pollinators: Week 6

Posted on December 27, 2021 by Jen Hayes

The Garden Ecology Lab’s Pollinator Plant PR Campaign Presents….. Common Madia (AKA Tarweed)!

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

Plant Facts

Scientific Name: Madia elegans
Life Cycle: Annual
Growth Habit: Erect, slender
Bloom Duration: July – September
Hardiness Zone: 1-11
Light requirements: Prefers full sun, will tolerate partial shade.
Special Traits: Drought tolerant, deer resistant, seeds valued by birds, adaptable to many soil types and textures.
When to plant: Seeds can be sown directly in the fall, or sown in containers or cold frames in the winter. Stratify seeds if growing indoors.

Pollinator Facts

Common madia provides both nectar and pollen to its insect visitors and blooms during a period where foraging resources are often scarce (late summer – early fall).
Madia was found to be associated with two bee species in Aaron’s research: the Bi-colored Sweat Bee (Agapostemon virescens) and Titus’s Sweat Bee (Lasioglossum titusi)
Madia is also the larval host for three moth species: the Spotted Straw Sun Moth (Heliothis phloxiphada), the Small Heliothodes Moth (Heliothodes diminutivus), and an Epiblema moth (Epiblema deverrae)¹.

Common Madia‘s Native Range in Oregon

Madia elegans is native to most of Western Oregon. Although it's native range does not extend east of the Cascades, it is a hardy annual that may do well in Central- and Eastern- Oregon gardens.

Map acquired from Oregon Flora with imagery sourced from Google.

Common Madia as a pollinator plant

Common Madia is an ideal plant for pollinator gardens due to its long bloom duration and attractiveness to bees, caterpillars, and butterflies. Madia was found to attract both a high abundance and a high diversity of bee visitors, which further speaks to its use as a great pollinator plant! Due to it’s late-summer bloom period, Madia can act as a great source of forage for it’s various visitors when there may not be many other plants flowering in the landscape. Madia flowers, which close at dusk and reopen in the morning, may also come with a fun surprise if you catch them before the sun has finished its ascent: if you’re lucky, you may be able to find male long-horned-bees sleeping in groups within the flowers².

Infographics developed by LeAnn Locher, Aaron Anderson, and Gail Langellotto.

A syrphid fly visiting a *Madia* flower. Photo by Signe Danler.

Did you know?

The other common name for Madia, “Tarweed”, comes from its foliage. It’s covered in stiff trichomes (hairs) and stalked glands which emit a tar-like scent. Common Madia is not the only species with this nickname, it applies to plants in the entire genus! For example, Madia glomerata, “Mountain Tarplant”, is a species of Madia native to the Northeast United States.

Common Madia‘s fruits are flattened achenes, which are valued by small mammals and birds as a food source. The achenes were also used by Indigenous groups, including the Pomo, Miwok, and Hupa and as a staple food source³. The fruits were often roasted with hot coals and then ground into flour.

Photos from the field

Madia in a garden, photo by Signe Danler
A syrphid fly visits Madia in a garden, photo by Signe Danler

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

Garden Ecology Lab

Socio-ecological research in urban and suburban garden systems

Category Archives: Native Plants

An Update on Native Plant Studies from The Garden Ecology Lab at Oregon State University

Year-round Alternatives to “No Mow May”

Gardeners Needed for a Native Plant Survey!

Petal-cutting Bees!

2022 Field Update: Native plants & native cultivars

Study Plants (2020-2022)

Field Season Stats

Is there a difference in native bee visitation to native plants and their cultivars?

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Top 10 Oregon Native Plants for Pollinators: WEEK 10!!

Douglas Aster‘s Native Range in Oregon

Did you know?

Photos from the field

Top 10 Oregon Native Plants for Pollinators: Week 9

California Poppy’s Native Range in Oregon

Did you know?

Photos from the field

Top 10 Oregon Native Plants for Pollinators: Week 8

Globe Gilia‘s Native Range in Oregon

Did you know?

Now back to Globe Gilia: Photos from the field

Top 10 Oregon Native Plants for Pollinators: Week 7

Farewell-to-Spring’s Native Range in Oregon

Did you know?

Leafcutters in Action

Photos from the field

Top 10 Oregon Native Plants for Pollinators: Week 6

Common Madia‘s Native Range in Oregon

Did you know?

Photos from the field