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.
COVID-19 has impacted our research in many different ways, including making it more difficult to find time to provide research updates on a regular basis. Despite the long silence, we have many projects up and running this summer! In fact, we’re launching four new projects, finishing up three long-term projects, and writing up another two projects.
In this blog post, I give a brief overview of the four new Garden Ecology Lab projects that launched this summer.
Microbiome of Garden Soils and Gardeners: Dr. Gwynne Mhuireach’s project has been spotlighted in a recent blog post and webinar. She has selected the 40 gardeners that will be included in her study: 20 high desert and 20 Willamette Valley gardeners, half of whom are organic and half of whom are conventional gardeners. Soon, these gardeners will be sending in their soil and skin swab samples. And then, the long process of analysis will begin.
She’s studying the microbe community in garden soils, and how those might differ according to garden region (Willamette Valley or high desert) and gardening practices (organic versus conventional soil managmeent). She’s also studying whether garden soil microbes transfer to gardeners’ skin during the act of gardening, and if so, how long those microbes persist on the skin.
Jen’s field site is located at the Oak Creek Center for Urban Horticulture at OSU, which makes it so much easier for undergraduate student researchers to participate in this project. She samples pollinators on Tuesdays and Fridays. She takes 5-minute observations of pollinator visits on Mondays and Thursdays. In between, lots of time is spent weeding and watering plots, counting flowers, and measuring floral traits.
Cost / Benefit Analysis of Growing Edible Plants in Containers: Tyler Spofford is a new lab member, who is completing his undergraduate degree in the BioResource Research program at OSU. He is working to develop a ‘budget’ for growing food in low-cost containers. I’ve summarized this ‘budget’ data for growing food in standard vegetable gardens, but no data yet exists (that I can find) for containerized vegetable gardens. Tyler is growing 40 tomato plants across two sizes of containers (3 gallons and 5 gallons), as single plants and in combination with basil. He’s keeping track of all of the costs (both money and time spent to grow food). When he harvests food, he’ll weigh his harvest, and track the economic benefit of his efforts, and how container size and planting configuration (one or two crops per container) influences harvest. I’ve set up a Flickr album for his study, to host project photos.
Tyler’s project grew out of my concern that, even though 18,000+ people enrolled in a free, online vegetable gardening course (over 40,000, at last count) ~ that the people who might be most at risk for food insecurity may not be benefitting from Extension Master Gardener resources and information. Tyler’s project is one component of a larger effort to develop more support for renters who might want to grow their own food.
Below is an excerpt from a concept paper I’m writing on the topic:
We know that the COVID-19 pandemic is exerting stress on multiple pressure points related to the economic and food security of U.S. households: more people are in need of food aid and more people are concerned about food access. The U.S. has a long history of gardening in times of national emergency (e.g. Victory Garden of WW I and WWI II, ‘recession gardens’ of 2008). The benefits of gardening as a tool of economic security and resilience are well-established. However, research suggests that these benefits are largely restricted to homeowners. Currently, most state and local laws afford no legal right to renters who want to grow their own food. Community gardens might offer renters opportunities to grow their own food, except that these gardens are often associated with gentrification. To promote public health in the face of economic and health risks of COVID-19 and future pandemics, it is critical to support the food gardening efforts of the most vulnerable. Those in rental housing have been found to be most vulnerable to food insecurity, as well as the food and economic insecurity associated with natural disasters.
Pollinators on Buddleja Cultivars: Cara Still is studying how breeding butterfly bush (Buddleja davidii cultivars) for sterilty impacts the pollinator community that visits Buddleja blossoms. Buddleja davidii and some fertile varieties of this plant are considered noxious weeds in Oregon, and many other places. Normally, noxious weed status would make it illegal to sell or trade butterfly bush in Oregon. However, the Oregon Department of Agriculture allows exceptions for non-sterile cultivars and interspecific hybrids.
Cara is studying whether or not the plants that are allowed for sale, under the exceptions, still pose a risk of invasion. Our group is working with Cara to document the abundance and diversity of pollinators that visit eight fertile Buddleja cultivars with 16 cultivars that have been bred for sterility.
When I was initially approached to participate in this project, I thought that it should be obvious that sterile cultivars would not attract pollinators. Afterall, sterile cultivars don’t produce pollen, or produce very little pollen. Without pollen, I doubted that bees would visit the plants. But, it is possible that sterile plants would still produce nectar. And, many pollinators ~ such as butterflies and moths ~ visit plants to consume nectar, rather than pollen.
The more I looked into the literature, I realized that no one has yet studied how breeding for sterility might affect a plant’s attractiveness to pollinators. Would sterile forms of butterfly bush no longer attract butterflies? Would sterile varieties attract syrphid flies that visit blossoms for nectar, and not pollen? We’ll let you know what we find, in about a two years. In the meantime, you may want to visit the Flickr album of photos I set up for Cara’s study.