Spring with the Mason Bees

Written by Mallory Mead

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

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

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

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

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

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

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

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

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

Our Hypotheses

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

But…

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

…and we are pretty confident about this last prediction.

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

Data Collection

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

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

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

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

Obstacles

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

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

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

Preliminary Findings & Observations

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

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

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

Moving Forward

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

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

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

Garden Ecology Lab Year in Review: COVID Edition

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

The Gardens of Piet Oudolf: Pollinator Paradise?

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

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

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

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

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

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

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


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

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

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

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

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

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

Several Piet Oudolf books
Several of Piet Oudolf’s books

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

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

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

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

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

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

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

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