The Garden Ecology Lab’s Pollinator Plant PR Campaign Presents….. Yarrow!
The Garden Ecology Lab is releasing a series of plant profiles of the top 10 Oregon native plants for pollinators, based on Aaron Anderson’s 2017-2019 field trials of 23 Oregon native plants. We will feature one plant per week for 10 weeks, this is week 1! Profiles will include photos, planting information, and will highlight common pollinators of each plant.
Scientific Name: Achillea millefolium
Life Cycle: Perennial
Growth Habit: Upright, spreading
Bloom Duration: June – October
Hardiness Zone: 3-7
Special Traits: Drought tolerant, deer resistant
When to plant: Starts can be planted in the spring or fall.
Yarrow provides both nectar and pollen to its insect visitors.
Yarrow was found to be associated with two species of Andrena in Aaron’s research (Andrena cerasifolii, A. candida).
Andrena is a genus of early summer mining bees!
Other common visitors to yarrow include sweat bees, nomad bees, and butterflies!
Yarrow inflorescences provide a great “landing pad” for pollinators- they can rest directly on the plant while they forage.
Yarrow is a ubiquitous North American native plant: its range extends from Alaska to Florida and every state and province in between! Though it commonly appears on pollinator planting lists, many people are not convinced that it’s a great bee plant, because it is not typically buzzing with activity like we may see on Goldenrod or Douglas Aster. Instead of hosting an abundance of visitors, yarrow supports a high diversity of insect visitors.
Infographics developed by LeAnn Locher, Aaron Anderson, and Gail Langellotto.
Abundance and Diversity Calculations. Bee abundance was calculated using estimated marginal means of bee visitation to each of our study plants from 5-minute observations conducted from Aaron's 2017-2019 field seasons. Estimated marginal means (EM Means) were assigned categorical values and averaged across years to yield the following categories: 0% = Very Low =EM mean below 0.49; 25% = Low = EM mean of 0.50 to 0.99; 50% = Moderate = EM mean of 1 to 1.49; 75% = High = EM mean of 1.50 to 1.99; and 100% = Very high = EM mean above 2.0.
Bee diversity was based on the total sum of species collected on each of our study plants from 2017 to 2019. A Chao 2 Estimator was used to estimate total expected species richness for each plant; Chao 2 estimates were then used to create categorical values, as follows: 0% = Very Low = 9.99 or lower; 25% = Low = 10 to 14.99; 50% = Moderate = 15 to 19.99; 75% = High = 20 to 24.99; 100% = Very high = 25 or higher.
Although yarrow doesn’t buzz with activity like some pollinator plants, it’s certainly not a flower to ignore! Yarrow is a hardy and low maintenance perennial that establishes and spreads readily in gardens. It’s a beautiful cut flower and can also be dried to include in longer lasting floral arrangements; its foliage that maintains its aromatic scent even after drying. Yarrow is additionally a wonderful plant medicine that has been used for centuries.
Did you know?
Yarrow has naturally-occurring pink variants! It can vary from pale pink (left), to deeply magenta (right). These plants were started from seeds collected from wild populations of yarrow, so we can be certain it is indeed a natural variation, rather than a true hybrid or cultivar!
Another fun fact: "millefolium" translates to "thousand-leaved", which is a reference to its dissected leaves!
Photos from the field
Tune in next week for the next edition of our Pollinator Plant PR Campaign.
Field season wrap up is underway in the butterfly bush plot, and there is so much to reflect on this year! The team has had a very productive summer, and as these bushes are better established and have reached their full spread and height, they have become more attractive to pollinators. As a reminder, the butterfly bush (Buddleja spp.) test plot consists of 34 butterfly bush cultivars of ranging fertility, habit, and breeding complexity. We have 6 -9 replicates of each individual cultivar, totaling 222 plants in the complete replicated block. The plot represents all the past and present (yes, we have some experimental cultivars) breeding that has been conducted to reduce fertility and hopefully invasiveness of Buddleja davidii. Much of that breeding centers around interspecific hybridization (breeding between 2 or more species in the same genus), so our plot represents hybridization of 7 different Buddleja species!
This summer we conducted pollinator observations the same as last year. This consisted of 5-minute timed counts at each location in full flower (we are calling full flower 50% or more of the buds or flowers on the individual plant are fully open) each week. During the timed count, we identify all visitors to morphology- which is simply differentiating between honeybees, bumblebees, butterflies, and other morphotypes. This presented new challenges this year because of the sheer mass some of our plants have reached! Though they were spaced 8 feet apart on all sides at planting, some have grown in together, making access an occasional issue. Many of the full-sized cultivars also reach well over my head, presenting more challenges in accurate counting. The team pushed through these difficulties, and by the end of the season we had counted 7,597 individual visitations on the plot. This is over 2,000 more than last year! You can view overall visitations by cultivar for both the 2020 and 2021 seasons below.
Though all the cultivars were most frequently visited by honeybee cultivars in 2020, three cultivars in 2021 were most frequently visited by bumblebees. Most notably the cultivar ‘Honeycomb’ attracted far and away more bumblebees than any other cultivar, and most of the visitors were male. Not only does ‘Honeycomb’ seem to be very attractive while sampling, it has an extremely long bloom season in comparison to the other cultivars in the study. It will bloom steadily from mid-June until the first deep frost of the season. Generally, there is an uptick in visitation across all the cultivars in 2021 as compared to 2020. Keep in mind the plants were substantially larger this season compared to last, meaning larger floral displays which are more attractive to pollinators.
In addition to pollinator observations, we collected nectar volume data for all 34 cultivars and attempted to collect pollen from a low and high fertility cultivar respectively. Tyler and Mallory were instrumental in getting nectar volume estimates collected, you can see them pictured below probing individual flowers with microcapillary tubes. Pollen collection turned out to be a very time-consuming process because there wasn’t a good alternative to good old hand collection. After about 80 hours of labor on the project, we were still a ways off of our mark, so we needed to reassess our methodology. More to report on that next year I’m sure.
Svea Bruslind and Jen Hayes also helped me take filtered photos of all my cultivars this season. You can read more about Svea’s excellent photography skills in her post ‘A Bee’s Eye View: UV photography and bee vision‘ but I’m sure the photographs she took of my cultivars in ‘Bee Vision’ will prove useful in understanding patterns of attraction out on the plot. Scroll through the pictures below to see examples of Svea’s work, in order of pollinator attraction in the 2021 field season.
This time of year, focus returns to the relative fertility portion of my study. This means time in the greenhouse monitoring controlled crosses I made over the summer, sowing seeds from the field and counting respective seedlings. This robust dataset will allow us to calculate relative fecundity of all our cultivars in both male and female roles, important information in assessing invasive species legislation.
Flowers and bees have one of the most well-known symbiotic relationships ever formed. Flowers rely on bees for pollination, and bees rely on flowers for nectar and pollen. It is generally understood that flowers act as advertisements to attract bees. However, less is known about what exactly bees are seeing and how that can change once humans get involved. This project is focused on the changes that can arise after a plant is cultivated, and how these changes can affect pollinator preference of a flower.
While changes made by breeders might not seem all that drastic to our eyes, we have little idea if that is the case for bees. Often breeders will change flowers for aesthetic purposes. This can have unknown consequences. These changes might not seem like such a big issue since the flowers are still colorful. However, bee vision is very different from humans, with bees having the ability to see into the UV spectrum. This means that while we might think we are only changing the bloom size or the color, we could also be unintentionally changing UV messaging visible only to the bees.
The purpose of this study is to use UV photography to explore these invisible differences between the native and cultivar. We also want to determine if the differences have a tangible impact on pollinator preference. This study is ongoing, but the images so far have shown a few native/cultivar sets that have a marked difference in UV markers between native and cultivars. While the study has only just started, our excitement and curiosity have not abated. This is an entirely new foray into pollinator relationships and mechanisms and could open up the world of bees and flowers in a brand new way.
In this post, I cover the 2009 paper, “Impact of native plants on bird and butterfly biodiversity in suburban landscapes,” by Karin Burghardt, et al.[i]
This study was published shortly after the first edition of Doug Tallamy’s book, Bringing Nature Home: How Native Plants Sustain Wildlife in Our Gardens.[ii] After decades of studying host plant records of butterfly and moth species, Tallamy was convinced that native plants were critically important to wildlife conservation. About half of all insects are herbivores, and about 70 percent of all herbivores are specialists that are only capable of feeding on a narrow range of plants (see Schoonhoven et al. 2005, Chapter 2, pages 5-9). Specialist insects have developed, over time, the ability to feed on plants that have physical or chemical deterrents that keep generalist insects at bay. Although specialist insects can feed on plants that can be toxic to other insects, they can’t easily switch to feed on novel, non-native plants.
Burghardt and Tallamy’s Study of Native Plants and Caterpillars
Tallamy was Karin Burghardt’s master’s degree advisor and one of her co-authors on the 2009 paper. In their study, they selected six pairs of suburban gardens in central Pennsylvania. Gardens were paired by size and proximity. One garden in each pair featured the conventional landscaping for this region: large lawns, Asian shrubs, Asian understory trees, and native canopy trees. The other garden was landscaped with native ornamentals at each vegetative layer: grasses, shrubs, understory trees, and canopy trees.
They counted the number of caterpillars at 12 points within each garden. Since caterpillars are herbivores, and most insect herbivores are specialists that do best on native plants, they hypothesized that they would find more caterpillars in the native plant gardens. Indeed, this is what they found. Caterpillar abundance was four times greater, and caterpillar species diversity was three times greater, in the native gardens versus the conventional gardens. In addition, Burghardt found that native plant gardens harbored more birds. In fact, native plant gardens had 55 percent more birds and 73 percent more bird species, compared to conventional gardens!
This study demonstrated that gardeners’ choices matter and can clearly influence ecological food chains. Food chains are organized into what are known as trophic levels. Organisms on the same trophic level share the same ecological function and nutritional distance from the sun. Photosynthetic plants are on the first trophic level. Herbivores, or organisms that eat plants, are on the second trophic level. Organisms that eat herbivores, such as birds, are on the third trophic level.
Burghardt and Tallamy demonstrated that what you decide to plant in your garden not only determines the structure of the first trophic level but can also cascade up to affect the second and third trophic levels. As an entomologist, I was not surprised that gardeners’ plant selections could influence the second trophic level. However, I was blown away that these decisions could cascade up to strongly influence the third trophic level.
Garden Ecology Lab Studies of Native Plants and Bees
In the Oregon State University Garden Ecology Lab, we study relationships between native garden plants and native bees. To be honest, I did not expect that native bees would prefer native plants. Whereas the leaves and other vegetative parts of a plant include an array of chemical and physical defenses to protect the plant from insect herbivores, flowers have few such defenses. In fact, flowers function to attract pollinators to a plant.
Thus I was somewhat surprised when Ph.D. student, Aaron Anderson, found that most of the native plants in his study attracted more native bees and more species of native bees than his non-native comparison plants. For example, non-native lavender ‘Grosso’ attracted a large number of bees, but most of these bees were non-native honey bees. By and large, the native plants were better for bee abundance and bee diversity, compared to the non-native comparison plants. In particular, Globe Gilia, Farewell to Spring, Oregon Sunshine, Douglas Aster, and California Poppy were all particularly attractive to native, wild bees in Aaron’s study.
Why might native bees prefer native plants, when flowers don’t have the same chemical and physical deterrents that herbivores must contend with? One hypothesis is that the nectar and pollen in native plants might provide better nutrition to native bees. Another hypothesis is that pollinators are keenly tied into the visual display of native plants. Flower color, size, shape, and ultraviolet markings are all important signals that flowers use to attract the attention of various pollinators. If there are changes in any aspect of this visual display, pollinators may no longer recognize a flowering plant as a good source of pollen or nectar.
Another OSU Ph.D. student, Jen Hayes, is trying to understand why native plants seem to be preferred by native pollinators. As part of her Ph.D. work in the Garden Ecology Lab, Jen is collaborating with an OSU photography student, Svea Bruslind. Svea uses different filters to take photographs of native plants and native cultivars in visible light, ultraviolet light, and in “bee vision” light. We are just getting started on this study, but look forward to reporting our findings in the near future.
[i]Burghardt et al. 2009. Impact of native plants on bird and butterfly biodiversity in suburban landscapes. Conservation Biology 23:219–224.
[ii] Updated and expanded version published as Bringing Nature Home: How You Can Sustain Wildlife with Natives Plants.
I’m pleased to present the work of my very first field season as a master’s student here at OSU. My project centers around presumptive sterile cultivars of Buddleja, or butterfly bush. Over the next few years, I will be studying how breeding for sterility affects pollinator attraction, pollinator nutrition, and if this breeding is truly effective in slowing the invasiveness of this particular plant. The hope is that this research will be able to serve as a framework for assessing putative sterile varieties of other potentially economically lucrative, but invasive, ornamentals.
Buddleja davidii was designated as a B-list noxious weed in 2004, and was placed in quarantine in conjunction with this designation. Since then, the ODA (Oregon Department of Agriculture) has begun to allow sale of B. davidii cultivars that display a 98% reduction in fertility in comparison to fully fertile ‘old school’ cultivars such as ‘Black Knight’ or ‘Nanho Blue’. At the moment, 14 cultivars of Buddleja davidii are legal to sell, propagate, transport or import in Oregon though no science has been conducted to assess how a reduction in fertility actually translates to reduced weediness.
The other questions I am researching are how pollinators behave around these new, ‘sterile’ cultivars in comparison to how they interact with fertile ones, and what kind of nutrition pollinators can obtain from sterile varieties. These are ever more important questions as we continue to put pollinator health at the forefront of plant selection decisions. To that end the team has been conducting timed pollinator counts through the summer in the test plot.
The test plot is located at Lewis-Brown Horticulture Farm, in the beautiful countryside surrounding Corvallis, Oregon. There, we have randomly allocated six to nine replicant plantings of six fertile cultivars and 28 putative sterile cultivars. Working in this gorgeously fragranced field (seriously-think notes of honey, spice, and fruit) has been a true delight all summer. Cultivars of Buddleja run the gambit in terms of color, plant habit, and floriferousness. There is everything from Buddleja ‘Purple Haze’, a prostrate variety with blue-violet flowers, to my personal favorite, Buddleja x weyeriana ‘Honeycomb’, an absolutely uprightly enormous variety with unique yellow blooms.
Once a week, I go to the field and determine which of the 204 plants are at maximum flower. These plants are slated for our weekly pollinator counts. To conduct a pollinator count, we simply set a timer for 5 minutes and watch the plant for visitors. These visitors are identified to morpho-type in the field (i.e. Honeybee, Bumblebee, Syrphid fly, Butterfly…). Here are the full counts for this season:
You may notice that there are less than 34 cultivars on this graphic! That is because we are in possession of several cultivars that have yet to be released to the general public, so unfortunately, I cannot share them here with you today. It does seem clear, for this season at least, that honeybees are the most prevalent visitor of butterfly bush. Though we can’t draw conclusions from this season’s data alone, we hope that with a few more seasons of data we will be able to identify patterns of attraction and biodiversity. Until then I will be back in classes and working on other aspects of my research-looking forward, of course, to next field season.
Our colleague, Brooke Edmunds, was kind enough to shoot and edit this short video on two of our current lab projects: Jen Hayes’ study of native plants and nativars and Tyler Spofford’s study of the economic costs and benefits of growing vegetables in bucket gardens.
As we near the end of our 2020 field season, stay tuned for research updates.
[Preface: For the past few years, I have written a column for the Hardy Plant Society of Oregon’s (HPSO) Quarterly Magazine. It has been a wonderful experience, as the HPSO provides excellent editorial assistance. Below, I share my most recent article for the HPSO Quarterly, and thank Eloise Morgan and her team for helping to improve and elevate my writing.]
I spend my nights thinking about gardens: not about the plants that I want to purchase or the crops that I want to plant. Instead, I puzzle over how to study a system that is incredibly variable (from person to person, or even in the same person’s garden from year to year) and complex (with more plant species than just about any other system that has been studied). Gardens are both wild and managed, and unlike other systems I have worked, it is impossible to divorce human behavior from the ecology and evolution of the garden.
In this series, I wanted to share five scientific studies that have had a large role in shaping how I think about gardens. Because of space limitations, I will share the first study in this article. I will wrap up the remaining four studies, in subsequent issues. The five studies are:
Simberloff and Wilson (1969). This study commenced 54 years ago, and yet remains a ‘must read’ for any ecology student. In 1966, Dan Simberloff and Ed Wilson selected six small mangrove islands off the coast of Florida. The islands varied in distance from the mainland coast, from near to far (Figure 1a), as well as size, from small to large (Figure 1b)
Simberloff and Wilson constructed a scaffold that encircled the edge of each island, covered the scaffold with a tarp, and then proceeded to ‘defaunate’ each island with methyl bromide pesticide. In other words, they killed every arthropod on the islands. After removing their ‘death tents’, and over the course of the next year, they carefully monitored, cataloged, and counted every arthropod that arrived and survived on each island. What they discovered was formulated into the ‘Theory of Island Biogeography’, or a theory about how organisms colonize new habitat, and assemble into a biological community.
They found that islands that were closer to the mainland coast of Florida were colonized earlier, and accumulated species faster, compared to islands that were farther (Figure 2). They also found that species would accumulate on each island, over time, until a maximum peak is reached (not shown). Then, the number of species would begin to drop, as ecological interactions (such as competition for food) would allow some species to prosper, while others went locally extinct. They found that smaller islands were more prone to species extinctions, than larger islands (Figure 2).
Size, distance, age: those are the three things that Simberloff and Wilson predicted would govern the diversity and assembly of organisms within a habitat.
My first faculty position was at Fordham University in New York City, where I studied pollinators in 18 community gardens in Harlem and in the Bronx. During the course of this study, I was inspired by Simberloff and Wilson. I could not help but see the 600+ community gardens that dot the landscape of New York City as islands of green in a sea of concrete.
We expected that gardens that had been long-established would have more pollinator species than newer gardens. We expected that larger gardens would host more pollinator species than smaller gardens. And, we expected that gardens that were closer to ‘mainland’ sources of pollinators, such as Central Park or the New York Botanical Garden, would have more species of pollinator than those that were distant.
We were wrong on two out of three predictions (Matteson and Langellotto 2010). Larger gardens had more pollinator species than smaller gardens, but neither distance nor age had any impact. I was so disappointed that we did not find an effect of distance, or of garden age. I had visions of ‘revitalizing’ the Theory of Island Biogegraphy for urban landscapes, but it was not to be. If anything, our study suggested that the ‘sea of concrete’ was not exactly a wasteland, afterall. The street trees, potted plants, windowsill gardens, and patio gardens all provided resources for urban pollinators, even in one of the most densely populated and heavily developed cities in the world.
This study showed me that it will be much more difficult to track pollinator movements among urban gardens, than I had hoped. We tried to use a traditional mark-recpture approach (see Matteson and Langellotto 2012), but out of 476 marked butterflies we only found four in a garden other than which it was marked and released. We were searching for the ‘needle’ of small butterflies in the ‘haystack’ of the New York City landscape. My students tried to follow pollinators as they left our study gardens, and almost got hit by a car, as they were running across the street. We played around with the molecular markers of a few bumblebees (see Morath 2007), to see if there was evidence of genetic differentiation, but were stymied by a lack of reliable primers that could help us look for any genetic differences in bees from different gardens. And then I moved to the Willamette Valley, where gardens are islands of green in an ocean of green. Understanding what draws pollinators to particular gardens will be even more difficult in this landscape, where pollinators have so many other choices for finding nectar and pollen.
Based upon our initial results from our Portland Garden study (2017-2019), I think I have a new hypothesis as to what might draw pollinators to home and community gardens. Our second study year (2018) was characterized by a hot and dry summer. Our first sampling season was also dry, but the spring months were wet, and the summer was cooler. In 2018, we collected far more bees (abundance) and more types of bees (species) than we collected in 2017 or 2019. In 2018, the landscape of the Willamette Valley was toast! Almost all flowering plant materials seems to shut down photosynthesis, so that they could conserve pressure water that would otherwise escape through open stomates. In this type of situation, bees seemed to concentrate in home gardens, which seemed to be one of the few places where they could reliably find nectar and pollen.
If this is the case, gardens aren’t necessarily going to be an important source of floral resources across all years. In a good year, there should be other plants in bloom in the greater landscape that bees can use. But in a hot, dry year, gardens may become an even more important refuge for bees. Most gardeners provide irrigation, which extends the bloom season beyond what is natural in the valley. Or, gardeners select plants that can prosper and bloom without supplemental irrigation, such as goldenrod or Douglas aster. It’s important to note that, even in the hot, dry weather of 2018, we still collected more bees from gardens that used drip irrigation, rather than overhead sprinklers. I think that the overhead irrigation physically blocks bees from navigating through a garden, which lessens their abundance and diversity.
Ultimately, I hope that our studies can lead us to a more predictive model of the resource value of home gardens to pollinators. The goal isn’t necessarily to understand what gardeners should do to attract pollinators, but to describe the conditions where gardens become increasingly important to pollinator conservation. In addition, I’d love to describe the value of gardens, relative to other habitat types, to pollinators. And finally, I hope to better understand the direction and movement of pollinators between gardens and other habitat types.
Ever since I was a child, I have been fascinated by and loved nature. I used to try and catch lightning bugs, and put them in a mason jar, hoping to catch so many that I could make a lantern. Today, when I visit my folks near my childhood home, nary a lightning bug can be found. Scientists suspect that increased landscape development has removed the open field habitats and forests that the lightning bugs depend upon to display their mating signals and to live. Light pollution likely also plays a role.
My time in college was my first real exposure to nature. I worked at Patuxent Wildlife Research Center, supporting the work of James Wagner when he was a graduate student at UMBC. He was studying wolf spiders, and I fell in love with these amazing creatures. Did you know that wolf spider mommas carry their young on their back ~ at least for the first few days of a baby spider’s life? Did you know that to collect wolf spiders, you go out at night with a flashlight . . . shining the flashlight into the forest floor litter, to find eight tiny glowing eyes staring back at you? Wolf spider eyes glow, as an adaptation to capture more light (enabling them to see better) when hunting at night. Like a cat’s eye, wolf spiders have a tapetum at the back of their eye . . . a mirror that re-reflects light back out, and lets the spider’s eyes have a second shot at capturing that light. My time working with James was magical. For the first time in my life, I gained the skills to identify trees, and wildflowers, and birds, and insects. I tell people that it was as if a scrim had been lifted from my eyes, and I saw the world in an entirely different light. I was forever changed, by this newfound knowledge that allowed me to ‘read’ the natural world in a different way.
As a graduate student, I studied salt marsh insects on the New Jersey coastline. I had never been to a salt marsh before, despite living within an hour of the ribbon of salt marsh that hugs the eastern seaboard. I saw horseshoe crabs for the very first time. I saw the fishing spiders in the genus Dolomedes that I had read about in books. I went bird watching and butterfly hunting with scientists who were generous with their time and knowledge, most notably, my advisor, Robert Denno. Now, so much of that ribbon of coastline has been destroyed. What remains is at risk due to increased nutrient pollution from fertlizers and run-off.
My post-doctoral work was spent in California on many projects, including studying the food webs of cotton fields that were using organic or conventional production practices. From talking to the farmers and stakeholders, I learned that there are not insurmountable impediments to growing organic cotton. The problem was that there was a limited market for organic cotton, grown in the United States. Growers who would plant organic cotton faced an uncertain market and reduced yields. Often, reduced yields might be compensated for with a premium price for organic products. But not in the case of US-grown organic cotton. This is when I first started to realize that science can not work in a silo, but that an understanding of economics and the social sciences is critical to promoting more sustainable solutions.
I came to OSU in 2007, for the opportunity to work with about 30 faculty and staff and between 3,000-4,000 volunteers who were dedicated to sustainable gardening. Coming from a teaching and research position to an Extension position was initially a challenge for me. I recognized importance of bringing good science to Extension and outreach work, but I didn’t know exactly how I would or could contribute. In 2016, I started the Garden Ecology Lab at OSU, mostly because I was more convinced than ever, that having good science to guide garden design and management decisions can truly make a positive difference in this world. I sometimes talk about ‘how gardening will save the world’, which is a lofty and aspirational goal. But, I truly believe (and science backs up this belief), that the decisions that we make on the small parcels of land that we might have access to in a community or home garden matter. These design and management decisions can either improve our environment (by provisioning habitat for pollinators and other wildlife) or harm our environment (by contributing to nutrient runoff in our waterways, or by wasting water when irrigation systems fall on the sidewalk more than on our plants).
This is one reason that I stand in awe of the Master Gardener Program. When I was purely a researcher, rarely interacting with the public, I doubt that many people were able to take our research findings and apply them in their own yard. When I was initially struggling with my new Extension position, I went to my former Department Head at the University of Maryland entomology deparment, Mike Raupp.Mike had a lot of experience with Extension and outreach, in addition to being a world-reknown researcher and a super-nice person. I remember him saying ‘Gail, when you publish a research paper, you’re lucky if 20 eggheads will read it. When you talk to the Master Gardeners, you have the opportunity to make real change in this world.’
And together with the Master Gardeners, I hope that is what we have done. I hope that is what we will continue to do. I hope that we find new and novel ways to discover how folks can manage pests without pesticides, to reduce water use in the home garden, and to build pollinator- and bird-friendly habitat. And then I hope that we will reach and teach our neigbhors and friends how to appreciate the biodiversity in their own back yard, and the small changes that they can make to improve the garden environment that they tend. I hope that we can instill a wonder for the natural world in the next generations, and to preserve or improve the natural world, so that our kids, and grandkids, and subsequent generations can hunt for lightning bugs, or spiders, or butterflies.
And I want to do it with you, dear gardeners. Together, we truly can make a difference.
In the Garden Ecology Lab,
researchers are studying specific pieces of the garden ecology puzzle,
including soil nutrient levels, pollinators, and native plants. But what
exactly is “garden ecology”, and why is studying it important?
Let’s start by defining our
terms. If you hear the word “garden”, some pretty specific pictures may come to
mind, but it is really a very broad term, encompassing anything from pots on a
patio to acres of arboretum. A garden is by definition a human-influenced system
involving plants, but there are many human-influenced landscapes that are not
considered gardens, such as agricultural fields (though gardens may grow food),
golf courses (though a garden could include a putting green), tree farms
(though many gardens have trees), and parks (though ornamental plants may grow in
Brittanica defines a garden as a “Plot of ground where herbs, fruits, flowers, vegetables, or trees are cultivated.” This suggests that the keys are variety and control. A garden is typically composed of a variety of different plants and types of spaces…not unlike a natural ecosystem! In addition, there is the element of control (cultivation). Human choice and aesthetic sensibilities strongly influence what plants grow in a garden. Even a very naturalistic garden has some human-imposed order in it, or it wouldn’t be a garden.
we get to “ecology”. Ecology is a relatively new natural science, with
beginnings in the early 1900’s, when scientists in Europe and the U.S. began to
study plant communities. At first animal and plant communities were studied
separately, but eventually American biologists began to emphasize the interrelatedness
of both communities.1
word Ecology (originally oekologie) comes from the Greek oikos, meaning “household,” “home,” or “place to live”,
so ecology is the study of the relations and interactions between organisms and
their environment – the place they live. Brittanica further clarifies that “These
interactions between individuals, between populations, and between organisms
and their environment form ecological systems, or ecosystems.”
of ecology most often takes place in natural, or near-natural, areas, such as a
forest, meadow or mountain. Ecologists study these wilderness environments,
searching for guidance on how to restore degraded ones. This reinforces the common
concept of nature as being “out there”, far away from where most people live.
ecology studies parks, greenbelts, and forest preserves – the large, public
green spaces of a city. But garden ecology? Can something as small as most
gardens have an ecology at all? And why should we care?
Well, if you have a garden, and spend much time caring for it, then you are a part of the ecology of that place. Every person who manages a plot of land, however small, is part of the ecology of that land, and all of them together, along with the other people and parts of a city, form the ecology of that city. What is done on those small plots, what grows and lives (or doesn’t) on each one, multiplied by hundreds or thousands or hundreds of thousands of individual plots, has the potential to influence the ecosystem – and the health – of the entire city.
deeply-entrenched American reverence for lawns means that, at present, the
relatively barren landscape of manicured, often chemical-soaked turf is the
dominant ecosystem in most cities. Ecologically speaking, such sites don’t
contribute much to the local ecosystem.
But that is changing, as more people become aware that a diverse, densely-planted landscape can support a diverse cast of fauna and provide many ecosystem services, including carbon sequestration. This enriches the local ecosystem immeasurably. If this stewardship ethic can be multiplied by even a fraction of the yards in a city, we will begin to see that “garden ecology” is another name for OUR ecology. It is the interrelationship of we humans to the plants and animals, stones and streams, among which we make our homes. It is part of understanding that nature is not just far away, in pristine wilderness. Nature is right here, sipping nectar from your flowers, nesting in your trees, burrowing under your feet and buzzing past your nose.
You know about butterflies, about bees, beetles, and ladybugs, all of our favorite garden critters – but do you know about the parasitic wasp? Alias: The Parasitoid. Not quite a parasite and not quite a predator, they are the zombie-creating hymenopterans that make your garden their home and hunting ground. Unlike a true parasite, the parasitoid will eventually kill its host, but unlike a true predator, there is a gap between parasitism and host death. The Parasitoid is truly one of a kind, but with thousands of species in over 40 families, there are many of that kind. They prey by laying their eggs in or on the bodies and eggs of other arthropods, growing, aging, and getting stronger as their unknowing host provides their executioner food and shelter until the parasitoid is ready to attack.
As menacing as their way of life may seem, parasitic wasps are actually one of the most effective biological pest control agents available to home gardeners, and can be an excellent indicator of habitat health for ecologists. As biocontrol agents, parasitoids can effectively manage a very wide variety of pests from aphids and sawflies to weevils and mites, along with many more. They occur naturally if their hosts/prey and habitable conditions are present and it costs little to nothing to maintain their populations. If pest outbreaks are not completely out of control and the site is habitable, parasitoids can safely, easily, cost-effectively, and naturally bring pest populations below economic injury thresholds. Know any pesticides that check all those boxes? In terms of habitat health, parasitoids can drive biodiversity and positively influence ecosystem functions. As such, their diversity and abundance can act as an indicator for the overall health and functionality of an ecosystem – such as your home garden.
Is it starting to seem like parasitic wasps could be an area of research for say. . .a garden
ecology lab? Certainly seems like that to me. That’s why this upcoming year I will be taking on an undergraduate research project to assess the parasitoid populations present in the Portland home gardens Gail and I have collected bees from for the last 3 years. Thanks to our sampling methods, we already have lots of parasitoid data to perform this analysis with, so there won’t be any more soapy bowls in your gardens this summer. This is the first of hopefully many blog posts that will accompany this research, so stay tuned as the year progresses to learn more about your new flying friends!