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 behaviorin the research garden, we got curious about the bees behind the petal-nest craft, and how we could study this interaction further.
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Data from these trips will not be published in my thesis because the contexts are not exactly comparable, and my sampling was exploratory rather than precise.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.
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.
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!
Lewis, H., & Raven, P. H. (1958). Rapid Evolution in Clarkia. Society for the Study of Evolution, 12(3), 319–336.
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)
Achillea millefolium ‘Calistoga’*
Achillea millefolium ‘Salmon Beauty’
Achillea millefolium ‘Moonshine’**
Western Red Columbine
Aquilegia x ‘XeraTones’
Camassia leichtlinii ‘Caerulea Blue Heaven’
Camassia leichtlinii ‘Sacajawea’
S. subspicatum ‘Sauvie Sky’
S. subspicatum ‘Sauvie Snow’
Clarkia amoena ‘Aurora’
Clarkia amoena ‘Dwarf White’
Clarkia amoena ‘Scarlet’**
E. californica ‘Mikado’
E. californica ‘White’
E. californica ‘Purple Gleam’**
Baby Blue Eyes
N. menziesii ‘Penny black’
Baby Black Eyes
N. menziesii ‘Snow White’
Baby Blue Eyes
Sidalcea asprella ssp. virgata***
Sidalcea malviflora ‘Purpetta’***
Sidalcea malviflora ‘Party Girl’***
*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
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
# Sample Dates
# Collected Pollinators
# Observed Pollinators
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?
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 🐝
We have been seeing syrphid flies (family: Syrphidae) in great abundance this summer over at the Garden Ecology lab’s research garden, so much so, that our field research team has begun to call it the year of the syrphids! These bee-mimicking, skittish pollinators have particularly loved the native and cultivar yarrow we have planted in our plots. Although their abundance has recently dipped–likely because Yarrow (Achillea millefolium) is done with its first round of bloom–we still see them buzzing around.
Syrphid flies, also known as flower flies or hover flies are a common visitor of gardens. You may see them buzzing around bright flowers or fighting mid air. They are important pollinators and feed off of nectar and pollen in their adult stage. Additionally, in their larval form, they are great at reducing aphid populations, but are extremely susceptible to pesticides.
The life cycle1 of syrphids start with the adults laying eggs in leaves of infested plants. After about three days, they hatch into their voracious, blind, larval stage.
The larvae feast on small pests like aphids, leafhoppers, scales, and thrips. The larvae do this by moving along plants, lifting their heads to try and seize and pierce their prey with their triple-pointed dart inside their mouth2. After slurping their prey dry, they will discard the exoskeleton.
Larvae will develop through a few instars and after 1 to 3 weeks will go into a pupal stage on the host plant or on the soil. After two weeks, an adult emerges.
In the pacific northwest, our common syrphid is Scaeva pyrastri. It is unique in that rather than overwintering as a larvae, S. Pyrastri overwinters as an adult. Three to seven generations occur in a year, with possibility for the higher counts depending on the region and species. Another species, originally native to Europe, the drone fly (Eristalis tenax3) is named after male honey bees because it is mimics them so well. Other mimics in Syrphidae lay their eggs in the nests of bumblebees or social wasps, where the larvae eat dead bees and detritus.
Their quick movements and bee-like appearance can make syrphid flies hard to identify.
To identify a flying insect as a syrphid, look for a single pair of wings. Flies (Order: diptera) do not have a second pair of wings like bees. Instead they have a vestige of hind wings called halteres that look like little nubs beneath their wings. These act like gyroscopes to help the fly balance during unique in-flight maneuvers. Also look for large, forward facing compound eyes typical of any dipterans. In our lab, we’ve see a wide range of size and different colors. Syrphids can be anywhere from a tenth of an inch to half an inch long, and have black or brown bodies with white or yellow spots and stripes. Fun fact: most hover fly mouths are extendable ‘sponges’ that mop up nectar and pollen.
Flower flies are extremely important to pest control and pollination, 40% of syrphid species larvae feast on the previously mentioned prey, and each larvae can eat up to 400 aphids during development!
Unfortunately, the larvae of syrphids are similar to many other species so are hard to identify. However, they are usually on pest infested plants and may be seen near adult syrphids. Look for their typical ‘stretching’ behavior while they are on the hunt. If you have a pest problem, avoid using pesticides or insecticides! These kill the syrphids that can help with pests. Instead, promoting syrphids or other pest eaters like ladybugs and lacewings by providing a variety of insectary plants can help you in the long run.
As previously mentioned, yarrow (Achillea millefolium) has been our most successful syrphid-attracting plant in our lab this year. Syrphid flower preference varies based on the subfamily, according to studies. The subfamily Eristalinae is attracted to white flowers, Pipizinae prefer white and yellow, and Syrphinae is more general. Link to an article going more in depth on syrphid flower preference here4.
Not coincidentally, native yarrow is primarily white, while our cultivars are yellow and pink. Observationally, syrphids visit yellow yarrow at a similar rate as they do the native, while our pink cultivar saw next to no syrphid visitors. We recommend planting yarrow as well as a variety of native flowering plants to support these pollinators. Leave leaf litter and debris around flowering plants, too. These provide protected overwintering sites which syrphids rely on7.
Currently, no syrphid species are on the U.S. Endangered Species Act lists, but like many insects, this underappreciated pollinator is understudied and biodiversity of this group is not well tracked. In Britain, however, some hoverflies have been placed on their Biodiversity Action Plan.6
Whether syrphids are endangered or not, we can help biodiversity by promoting native pollinators and planting native plants in our yards and gardens.
Lawns are perhaps one of the most controversial spaces when it comes to improving landscapes for wildlife. When I was in college, I threw myself head first into becoming more “green”, which for me meant being the best environmental and eco-friendly entomologist I could be. That meant changing not only my own habits, but those of my parents who, fortunately for me and maybe less fortunately for them, lived only thirty minutes away from my university.
It started with composting. After we got over the discussion about how to properly care for an indoor bin to avoid fruit flies AND my mom saw how much deliciously rich soil her dear friend yielded from her own bin, composting was a hit. My mom still tells me how amazed she is by how quickly the pile reduces every spring. I’m still surprised as to how easy of a practice it was for them to adopt.
The topics that came next were bees, buying local, what organic means, reusable everything, why you should check the insulation on the house before even thinking about buying solar panels, and then, after I took two landscape design courses, we approached the topic of grass. For this talk, which actually spanned months, I came prepared with books, quotations, and 3 or 4 finely detailed maps with elaborate plans for turning my parent’s yard into a pollinator sanctuary.
I began with dropping hints that this talk was coming. I would casually add “lawns should be like area rugs, not wall to wall carpeting” into a conversation, or post graphics like the one at the beginning of this blog on Facebook, and tag my parents in it. I even gave my dad Noah’s Garden: Restoring the Ecology of our Own Backyards by Sara Stein for Father’s Day. I knew this was a change that would take a lot more time than the compost.
Truthfully, I started with my mom. She’s the outdoor gardener, my dad is the houseplant guy. And, as anyone who has ever been a child knowns, there’s always one parent or guardian you go to first for the more difficult requests. For the most part, my mom was excited to see me become a budding naturalist. Around the house or on hikes I would point out plants I now knew the names of, and together we would assess the basal leaves of new garden growth, trying to figure out what in the world did she plant next to the lupine in the garden last year. When I got my wisdom teeth removed, she and the nurse patiently waited while I explained how to identify the red oak next to the car from other common oaks planted as street trees. I made it my mission to make my mom a budding naturalist, too.
When my landscape design class ended, I took my mom on a tour of her property, pointing out all of the potential diversity their landscape could support if they turned it into something beyond grass. I described the changes I recommended, I explained the benefits of the rain gardens, the swales, the terraced lowbush blueberries for the front yard, the beautiful meadow that would grow in the seasonal wet spot in the backyard and enhance the firefly populations we see glowing in the summer. I explained that though the initial transition would take a lot of work, the result would be significantly less maintenance for them, and they would sit atop the ecological design of my dreams. And there would be so much less lawn, err grass for them to mow.
Nearly 10 years later, I am reluctant to report that the quantity of grass covering my parents’ landscape remains relatively similar. The problem with my plan? I went too big. If mom was not ready to completely transform 3.5 acres, then dad certainly would not be either. Though they both appreciated and complemented my thoughtfulness and the rigor behind my design work when I reviewed it with them, my bold idea of turning the yard into a part pick your own blueberry farm and part pollinator paradise certainly scared them from asking my opinion on any further garden projects for a while.
I refused to let this setback alter my new found passion for increasing the value of my childhood home (to wildlife). I continue to share information with my parents, but in small doses rather than in huge design plans. My mom happily adds native plants we pick out together to her gardens and excitedly reports back about the bees she sees visiting them. They’ve added a small planting of mint outside the kitchen to keep the ants at bay, and when it comes to the lawn, they don’t mind leaving the dandelions and other wildflowers (“weeds”) for wildlife to snack on in the spring. And they’re not afraid of asking my advice on new plants or yard projects, though they don’t always utilize it.
Perhaps the most important result of my collegiate mission for Making the Hayes Family Eco-Conscious was helping my parents to see their yard differently, to help them see the potential that exists underneath all of the grass. I hope part two of this blog post might make you do just the same.
No mow May & reimagining our yards
No mow may is an initiative that started in the United Kingdom and has since spread to numerous other countries. To participate is relatively simple: don’t mow your lawn for the month of May. The goals of the initiative include increasing forage for pollinators and other wildlife, and creating awareness about the negative ecological impact of intensively managed lawns.
The practice of reducing mowing to promote diversity is supported by research. A meta-analysis of studies from North America and Europe found that both plant diversity and invertebrate diversity is higher in urban lawns with a lower mowing intensity. This increase in diversity was true regardless of mowing height or frequency, and the authors also found that weeds and invertebrate pests occurred in higher quantities with intensive mowing in many Northern regions.
In 2020, a study in Appleton, Wisconsin found that yards that went unmown in the month of May had more diverse flora, more abundant flora, 3x greater bee species richness (total number of species), and 5x greater bee abundance than regularly mown green spaces. Though the results of this study cannot entirely be attributed to No Mow May, it does highlight the potential for areas traditionally covered in lawn to be used as spaces for pollinator conservation.
In terms of surface area, the largest irrigated crop in the United States is lawn. Our idyllic front and backyard monocultures have been cultivated as such to meet the dominant neat and tidy aesthetic. This aesthetic has been so deeply wound into our culture that untidy yards are accused of being a sign of disrespect to one’s neighbors. The impact is such that if you choose to maintain a yard outside of this aesthetic, you have defend yourself against your neighbors with signage.
Perhaps some of this discomfort with weedy yards is due to misinformation- common wildflowers like dandelions, goldenrod, and even sneezeweed have poor reputations because they are thought to cause seasonal allergies. Insect-pollinated plants, which all three of these happen to be, actually shed very little pollen into the air. These plants have co-evolved with their insect pollinators, such that insect-collected pollen grains are actually often larger and/or heavier than those of wind-pollinated plants, and as a result, their pollen cannot easily drift into our respiratory tracts. Many tree species and grasses (which we in the Willamette Valley know all too well about) are more likely to be the culprit for seasonal pollen allergens.
Whether it’s the allergens, the HOA, city standards, your landlord, your own personal preference, or societal pressures that encourage you to keep your yard tidy, there are many small ways in which to increase the productivity and diversity in your landscape. One option is No Mow May- committing to the whole month, or even part of it, to increase the availability of flora to early emerging invertebrates. Reducing mowing frequency is another option, or mowing around weeds like hedge nettle, creeping Charlie, heal-all and others that you may find some insects foraging on. Or perhaps you can replace a small section of lawn a native plant garden, or butterfly garden, or plant some giant sunflowers for the birds.
I have compiled a few resources related to No Mow May below, in addition to some more “neighborly” ways you can begin changing your own yard’s aesthetic. If you decide to go No Mow May, we’d love to hear about your experience!
“A weed is a flower in the wrong place” – Ian Emberson
It’s early spring and the trees have begun leafing out. Colorful flowers are springing from the ground, and the landscape is slowly coming to life with insect activity. In this post, I’ll highlight some of Oregon’s ubiquitous spring bees, what they are up to, and how to easily recognize them.
Queen bumblebees are emerging from their winter burrows under leaf litter and forest duff. They zoom by with boisterous buzzes. Queen bumblebees are sturdy and furry, and can power through wind, rain and cold better than any other type of bee. Queens are much bigger than the workers that will come once the queens find nest sites and begin laying eggs. For now, they work alone, preparing to lay their first set of worker eggs.
If you see (or hear) any queen bumblebees this spring as they scan the sparsely blooming landscape, they are most likely looking for a proper nest site, finding nectar to energize this search, or, if one has already found her nest, she may be collecting pollen to feed her developing worker offspring.
Mason bees (Osmia lignaria) are a cherished Oregon spring bee active from March to early June. Look closely in a bee hotel for a chance to observe mason bees in action!
Male mason bees emerge first from their pupal cocoons. You might see them patrolling bee hotels waiting for a female to chase down. When the females emerge a little later, they mate and then begin their work provisioning nests with pollen balls and eggs. An individual female has a short lifespan living only about 20 days, but in this time, she may provision anywhere from 2 to 7 nest holes each containing many offspring cells.1 Quite the busy bee!
Andrena is a genus of mining bees that are some of the earliest risers when it comes to spring emergence. They are a diverse group of small, furry, ground-nesting bees that are only active for a few weeks out of the year. Andrena are solitary bees, but can be seen foraging and mating in droves on early blooming fruit trees like cherry, apple and pear. Last spring, I watched hundreds swarm this cherry tree to collect nectar and mate.
Spring Bee Quick ID:
Now, let’s identify some of the bees you may see out and about on sunny spring days when the wind is low. We’ll start with the most conspicuous group – the bumblebees. Bumblebees are the biggest and the loudest bees on the landscape, covered in a thick coat of fuzz. Here’s how to recognize the 3 most common species of bumblebees you’ll see in the Willamette Valley in early spring.
Bombus vosnesenskii or the “yellow-faced bumblebee” is by far the most common bumblebee in this region. It is recognized by the yellow fuzz on its face and yellow band near the distal end of its abdomen.
Bombus melanopygus, the “black-tailed bumble bee” is another of the earliest Bombus species to emerge. You can identify this bee by the orange band in the middle section of its abdomen!
Bombus mixtus, the “fuzzy-horned bumblebee”, tends to emerge a little later than the previous two species, and has orange hair on its lowest abdominal segments.
Mason bees can be recognized by their deep iridescent blue-green color, that sparkles in the sun. Males are distinguished from females by their small size and the yellow mustaches found on the front of their faces. Females lack the yellow tufts and are larger than the males but smaller than a honey bee. They carry pollen on the underside of their abdomen which is a trait unique to their bee family, Megachilidae.
Andrena are a diverse group that are tricky to identify. They can be distinguished from other small, furry bees by the presence of velvety hairs between their eyes and the middle of their face called “facial fovea”.2
They also carry pollen on their hind legs and on hairs between their abdomen and thorax, which distinguish them from bees in the Megachilidae family.
We hope this little guide will help you experience the native bees in your landscape this spring that make the pollen go round.
Thank you for joining us on this exploration of Oregon’s spring bees and what they are currently doing! We will release two more blog posts in this series, one for each of the four seasons. Blogs will be posted during their prospective seasons, so be sure to subscribe so you don’t miss the next in the series!
What… is it already time to think about spring cleaning?! It might still be winter, but spring will be here faster than we know it. Some quick cleaning is a great way to take care of a garden that we enjoy during the year!
If you’re wondering where to start, this blog post could be a way to jumpstart your cleaning. Here’s 5 tips on things to clean in the garden.
It’s a great feeling to see all types of birds using and enjoying your bird feeder. While they’re great, bird feeders can actually pose a major threat to bird health: excrement that is on the feeder perch can pass from bird to bird, spreading Salmonella and other diseases. Even if you don’t see dead birds around your bird feeder, birds that use your feeder could still be passing disease elsewhere, after they use it. Luckily, it’s a simple fix! How to clean a bird feeder: It’s best to clean your bird feeder regularly, say in between fills. Ideally, take it inside and wash it with soap and water. Then, soak it in a bleach solution (9:1 water to bleach) for 10 minutes. Rinse again to rid the feeder of any bleach solution. Make sure to wash your hands after touching the feeder! For more information, check out this link.
Bird baths: Algae isn’t fun to look at, but did you know it’s also dangerous for birds? Luckily, there’s simple fixes to keep bird baths clean and fresh for visitors! The easiest way to help keep your bird bath clean is to wash it out regularly (sometimes even every day, especially in the summer).
There are two other mixing solution options for doing a deep clean of your bird bath: vinegar or hydrogen peroxide. Each mixture is nine parts water and one part vinegar or hydrogen peroxide. Use a scrub brush to fully clean the bath and then ensure no cleaning mixture remains. Refill with water, and you’re good to go!
Tools help us take great care of the garden… let’s show the same level of care to our gardening tools! Cleaning gardening tools helps to extend their lifespan and can also help prevent the spread of disease.
How to clean gardening tools: Different options exist to clean gardening tools. For those tools that have metal, you can fill a 5 gallon bucket with sand and about a quart of car motor oil. After you’re done using the tools for the day, dip them in the sand and oil mixture. This mix helps to both clean the blade and coat it in a thin layer of oil. If you want to do a deep clean, you can wipe off any tools with a damp rag and some alcohol. If there’s sap or other buildup on your tools, try using sandpaper to get rid of it. Sandpaper is also a great way to refresh the wooden handle on tools (if you want to add a layer of oil after sanding wood, try mineral oil as a finish)!
Debris from diseased plants. Did you find black spot on any roses last year? How about other diseases on plants in the garden? Remove those diseased leaves or other debris from infected plants to prevent the spread of disease.
Stepping stones/moss slipping hazard. Moss is great! But if you have too much of it on your walkways, it can be a slipping hazard. Use your best judgment – if you’re worried about it being a potential hazard, it’s rather easy to select where you want to remove it on pathways/pavers. Mix a solution of bleach with water (up to 15% bleach) and use a scrub brush to agitate and remove the areas of concern.
Welcome to the Garden Ecology Lab’s “What are the bees doing” mini-series! This series will extend through the four seasons to shed some light on where bees are in their life cycle and what they may be doing during each of the four seasons. We begin with winter, and an overview of the overwintering and nesting strategies of common groups of bees in the Pacific Northwest.
As the seasons change, where do all the bees go? Different groups of bees utilize unique strategies to survive the cold of winter. In many cases, bees require cold temperatures to develop properly, and as spring rolls around, they rely on thermal cues to determine when to start their next phase of life.
We can divide bees into four broad categories based on their strategy to nest and survive the winter. There are the Ground Nesters – who find or dig in the ground to nest and lay eggs, Cavity Nesters – who nest in hollow reeds, canes, or in people’s backyard “bee hotels”, Bumblebees – whose new-born queens burrow into leaf litter, waiting to start a colony in spring…. and then there is the oddball: the European Honey Bees, who are not native to North America, but were brought here along with European colonizers and are now key players in modern agriculture. They do things pretty differently than our native bees, so we’ll start our discussion with them.
The European Honey Bee
European honey bees (Apis mellifera) survive the winter huddling in their hive! They are an example of a social insect and many consider a honey bee hive a superorganism. Fueled by their honey stores, the colony huddles together in a mass to thermoregulate at temperatures between 33 – 36°C (91.4 – 96.8°F).1 I love these words from the American Bee Journal:
"The honey bee is a cold blooded insect; but the honey bee colony is a warm blooded creature."1
We will see that honey bees are the only bee in our landscape to overwinter socially. The rest go it alone.
Bumblebees are social bees too, living in natural cavities most often in the ground, but in winter, the members of the colony die off except for the new-born queens. These queens will fly out of the hive on her maiden voyage to mate with a male bumblebee before finding a place to settle and overwinter alone.
Queens find a safe environment often a few inches deep under leaf litter or light soil. As temperatures decrease in Fall and early Winter, the queens do not thermoregulate. Instead, they enter diapause, which is a state of arrested development. An overwintering queen appears frozen in the soil until warmer temperatures wake her again. In the late Winter or Spring she will begin looking for a site to start her own colony.
Cavity Nesting Bees
About 30% of native bees are cavity nesters who build their nests inside cavities in wood or reeds.2 These bees avoid overwintering as adults, and instead, they lay their eggs in cavities and die before the winter temperatures come.
Female cavity nesting bees forage for pollen and nectar and nesting materials in the spring or summer and make balls of pollen and nectar (often called “bee bread”) as food for their offspring!
They lay eggs on the pollen balls, and then proceed to seal off compartments, one for each of the eggs, until the cavity nest is full. These eggs will hatch into larvae that consume the bee bread as winter approaches.
Here is a video of a small carpenter bee larva eating its bee bread, magnified under a microscope!
Once the larvae finish off their food store, they may spin themselves a cocoon in which they further develop into pupae. Cavity nesters spend the winter developing from pupae to young adults in their cocoons. These developing bees go into a state called torpor to survive the winter, where the bee is inactive and its body temperature drops, but it still goes through critical physiological processes and development.
These bees must experience low Winter temperatures natural to their region to undergo proper development. Mason bees, for example, have lower survival and vital rates when exposed to warm nest temperatures that simulate predicted climate change temperatures for their region.3
Mason bees (genus: Osmia) are cavity nesters that have become well known in garden and agriculture circles in recent years, but many other groups of bees fall into this category too including leafcutter bees (family: Megachilidae), small carpenter bees (genus: Ceratina), large carpenter bees (Genus: Xylocopa),and masked bees (family: Colletidae).
A friend of the lab, Olivia Honigman, conducted a brief research project on small carpenter bees in Vermont. Here are some photos from her study that showcase a tiny cavity nesting bee, from the genus Ceratina, nesting in raspberry canes.
Ground Nesting Bees
Last but certainly not least are the ground-nesting bees which make up about 70% of native bee species! Bees from the genera Andrena, Lasioglossum, and Halictus fall into this category.4 Ground-nesters have unassuming nests that are hard to spot, but under the soil, they are putting down bee loaves and laying eggs in a compartmentalized fashion, just like cavity-nesters!
Similarly, adult ground-nesters die after they finish provisioning their nests for their offspring. In the winter, the young bees of the new generation are developing from pupae into adults in their underground nests.
Left: exposed soil revealing tiny holes- could these be bee nests? Top right: A ground-nesting bee pokes its head out of its home. Bottom right: The entrance to a ground-nesting bee’s home.Photos by Gail Langellotto.
Although their nests are modest, some of Oregon’s showstopper bees fall in the ground-nesting category, such as the metallic green sweat bees (Agapostemon).
Long-horned bees from the genera Melisoddes and Eucera also flaunt unique forms with noticeably fluffy, feathery hair on their legs they use for collecting massive volumes of pollen!
To invite these bees to your garden, leave patches of earth free from wood mulch and instead mulch with compost! To avoid disturbing ground nests, avoid tilling when possible.4
Something remarkable about nesting in the ground is that, depending on nesting depth, ground nesters are more buffered from extreme temperatures than honey bees and cavity nesters whose homes may be in the direct sun. This may be a critical difference when it comes to surviving climate change.
Changing Climatic Norms…
With climate change upon us, native bees have experienced warmer than usual winter temperatures. These conditions may be suboptimal for their development and survival and encourage bees to emerge earlier in the season. Cavity and ground nesting bees require low temperatures with which they have evolved to reach physiological benchmarks for their development, and scientists worry that there will be phenological mismatches between plants and their pollinators in which bees emerge at different times than when their optimal food sources are in bloom as plants and insects will experience novel timing of thermal queues under climate change predictions.5
As bees and other pollinators face a multitude of challenges, we should support our local bees and appreciate them while we can!
Thank you for joining us on this exploration of what bees are doing during the winter! We will release three more blog posts in this series, one for each of the four seasons. Blogs will be posted during their prospective seasons, so be sure to subscribe so you don’t miss the next in the series!
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.
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.
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.
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).
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.
Photos from the field
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.
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.
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.
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!
Globe Gilia‘s Native Range in Oregon
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
Tune in next week for the next edition of our Pollinator Plant PR Campaign.
I’m sure many are familiar with the long treks that many pollinators make when winter begins to roll around. Monarch butterflies will travel thousands of miles to reach their final destination. Rufous hummingbirds will spend August swooping and diving in your backyards before moving Southward as September slowly drizzles it’s way into October. But not every pollinator decides to seek warmer climes as the temperature drops. Many opt to hunker down and wait out the cold weather, seeking shelter in any manner of burrow all around your gardens. This post is focused on several things that you, as caretakers of your gardens and friends of pollinators, can do to watch out for your hard working friends.
Leave the leaves
One of the most important things you can do to help overwintering pollinators is by doing nothing at all. By leaving the ground cover of leaves, sticks, and plant material you are also leaving the material that many pollinators use to make nests. Many pollinators will snuggle down into this protective layer, and be safe and sound during the colder months. By not raking up the leaves deposited by shedding trees, you are helping pollinators have a safer and more comfortable winter. If a little clean up is necessary, try not to completely remove the leaves or plant material, but instead, rake it onto beds or around shrubs so that it stays as part of the environment. Along with protecting pollinators, leaving this cover can help retain soil moisture, prevent weeds, return nutrients to the soil, and reduce waste entering landfills. So if and when possible, consider leaving the leaves.
Postpone pulling up dead stems, or moving old bark
Many pollinators will use dead stems or old bark as protection from the elements while they are overwintering. If possible, postpone pulling dead steams, or throwing out old branches, sticks or bark. Cavity dwelling pollinators will often seek shelter inside wood piles, old logs, or dead flower stalks. Several types of chrysalis’s have patterns similar to wood to blend into the environment while the pupa inside waits for spring. Butterflies that do not migrate will spend winter in varying life stages, some as eggs, some as caterpillars, some as a chrysalis, and some as adults. Therefore, it is best to leave as many forms of shelter as possible. Keep your eye on any bamboo posts in your garden, as many different types of bees will use these as bunkers during the cold. Be careful when moving or uprooting, and keep an eye out for pollinators hiding in crevices, cracks or crannies.
Leave your hummingbird feeder up
There are many different opinions on this advice. Many people will say that leaving your hummingbird feeder up during the winter will deter the hummingbirds from migrating. However, there is no easily found evidence that supports this. The Audubon Organization indicates that you can leave up your feeder for as long as you have hummingbirds, and having a feeder up as winter rolls around will not keep hummingbirds from migrating. Hummingbirds migrate due to genetics and other factors, not necessarily due to availability of food. However, not all hummingbirds migrate. Anna’s hummingbird, which can be found across the Northwest, Oregon included, is nonmigratory, and might be extra appreciative of feeders that are left up during the colder months. Adding extra sugar to keep the hummingbird food from freezing is not recommended, however, as this can dehydrate the birds. Keep the ratio of 1:4 parts sugar to water. Instead, to try and prevent freezing, you can take the feeder inside at night; hummingbirds don’t feed at night. You can also hang an incandescent bulb near the feeder, as this can generate enough heat to keep the feeder thawed.
While the three listed above are only a few steps to be taken to help overwintering pollinators, a little help can go a long way for our essential pollinator companions. They, like any of us, just want to stay warm and fed during the cold months, and I’m sure would greatly appreciate any help from you in helping them stay that way.