Archives For Plant Science & Conservation

Conserving plants is one of the most significant challenges of our time—and a major focus at the Chicago Botanic Garden. From studying soil to banking seeds, from restoring habitats and protecting endangered plant species to developing new ones, Garden scientists are fighting plant extinction, pollution, and climate change through diverse and exciting research.

In honor of Black History Month, I would like to call attention to a botanist who would have fit in very well at the Chicago Botanic Garden: George Washington Carver. He was a gardener, a soil scientist, an inventor, a genius, and a good guy.

George Washington Carver (1864–1943)

George Washington Carver (1864–1943)

You probably know Carver as the famous black scientist who invented dozens of products for peanuts. What’s most important about his story is why he devoted so much time and ingenuity to peanuts and how he did so much more than make a high protein sandwich spread and cooking oil.

I’m not a historian or biographer, so this story will omit details about Carver’s life—being born into slavery,  studying agriculture in an era of racial discrimination, and becoming a botany professor at Tuskegee University. While these details are interesting and definitely worth learning, you can read about all that in other places. Instead, this snapshot is devoted to celebrating how one humble scientist used his botanical superpowers to solve a real-world problem. It is a story about successfully tackling agricultural sustainability and economic stability at the same time.

Carver grew up in the south and he knew the agricultural conditions very well. Soil in the southern states is fine and dry. Summers are long and hot. These are suitable conditions for growing cotton, a profitable cash crop. The problem is that cotton needs a lot of nitrogen. Several years of growing cotton on the same patch depletes the soil, making the crop yield less and less over time. In the late nineteenth century, commercial fertilizer was not available—and even if it had been, the poor people who worked the land couldn’t have afforded it. To make things worse, in 1892 a little pest called the boll weevil moved northward from Mexico and began invading and destroying cotton crops. The boll weevil population spread and plagued the south through the 1920s and ’30s, making the life of a cotton farmer even harder and less rewarding.

Peanut plant (Arachis hypogaea)

Peanut plant (Arachis hypogaea)
Photo by Biswarup Ganguly [GFDL or CC BY 3.0], via Wikimedia Commons

A cotton boll weevil (Anthonomus grandis)

A cotton boll weevil (Anthonomus grandis)

Freshly harvested peanuts, still attached to the roots of the plant.

Freshly harvested peanuts
Photo by Pollinator [GFDL or CC-BY-SA-3.0], via Wikimedia Commons

Carver knew this life because he had lived it, and he wanted to make it better. He worked to teach farmers about crop rotation. Legumes (like peanuts and soybeans) and sweet potatoes have the ability to convert nitrogen from the air to a form that plants can absorb from the soil. Planting what is called a “cover crop” of peanuts instead of cotton for a year restores the nitrogen in the soil so the cotton grows better the next year. As an added benefit, diversifying crops by growing peanuts and other plants that the weevils do not eat helps reduce their population so there are fewer to harm the cotton crops. Sounds like the answer to all of their problems, right? So of course, farmers changed their practices right away, and lived happily and sustainably ever after.

Not quite.

You see, at that time peanuts were only used as cheap feed for livestock, and nobody was buying a lot of them. A farmer could not earn as much money growing peanuts as he could from his dwindling crop of cotton, so changing crops was financially risky, even as the cotton was failing. Carver realized he had to solve the market problem or farmers were never going to plant cover crops. THAT is why he set out to invent more than 100 uses for peanuts from 1915 to 1923. 

Products that were developed by George Washington Carver and made available commercially.

Products that were developed by George Washington Carver and made available commercially. Photo via the National Park Service Legends of Tuskegee exhibition.

He didn’t stop there, He also worked to promote his inventions to businessmen and investors in order to create a demand for peanuts, because, as we all learned in high school economics, when the demand goes up so does the price. Then—and only then—did the sustainable practice of crop rotation take hold.

But wait, there’s more.

The increased demand for peanut products also led to an increase in peanuts imported from other countries. In 1921, Carver spoke to Congress to advocate for a tariff on foreign peanuts so American farmers would be protected from the competition. Though it was highly unusual for a black man to speak to Congress in those days, his appeal won over the legislators and tariffs were imposed.

Peanut flower (Arachis species)

Peanut flower (Arachis sp.)

George Washington Carver did not seek wealth or fame for his work. He found personal satisfaction in scientific discovery and using his talents to make the world a better place for farmers and everyone. I believe if he were alive today, he would have embraced the challenge of researching and teaching people about sustainable urban agriculture to improve the health, nutrition, and livelihood of low-income city dwellers just as he did for rural farmers 100 years ago, and I believe programs like our Windy City Harvest grow out of that same spirit and desire to help people make a better living for themselves.


©2018 Chicago Botanic Garden and my.chicagobotanic.org

Pop quiz: What kind of natural habitat is increasing in urban areas? This is not a trick question. Rather, the answer offers a slice of good news on a planet that has been increasingly turning from green to gray.

Green roofs are on the rise in cities, according to Kelly Ksiazek-Mikenas, Ph.D., who has a newly minted doctorate degree from the Chicago Botanic Garden and Northwestern University’s graduate program in plant biology and conservation. In Illinois, where more than 99 percent of native prairie has been lost since the 1800s, this is especially good news. 

Kelly Ksiazek-Mikenas in the Plant Science Lab

Kelly Ksiazek-Mikenas, Ph.D., in the Plant Science Lab

Dr. Ksiazek-Mikenas, a former biology teacher, spent six years studying these engineered habitats and their potential to support biodiversity.

The plant scientist is now eager to share her findings: When started carefully and with a long-term plan in mind, these sites do grow up to support species, natural communities, and genetic diversity.

“When you have these three pieces working, you have a good foundation that should sustain plant life over long periods of time and live through environmental changes, and that look and function like a diverse prairie,” she said.

Dr. Ksiazek-Mikenas examined shallow (up to six inches of soil depth), low-moisture roofs from Glencoe, Illinois, to Neubrandenburg, Germany, before reaching that conclusion. While the roofs within the United States are generally younger, some in her German sites were up to 93 years old, providing a mix of data about green roofs at all ages. She also studied data sets and conducted shorter-term experiments to clarify the qualities green roofs need to succeed.

Setting up insect traps in 2013 on a green roof on top of the Berliner Wasserbetriebe building in downtown Berlin

Dr. Ksiazek-Mikenas sets up insect traps in 2013 on a green roof in downtown Berlin.

Her work had its ups and downs. She arrived in Germany looking for similarities, expecting the insect and plant species on one roof to mirror that on the others. Rather, she found differences between roof gardens. After a deep dive into data, she found the secret. Although the plant species differed between gardens, those that grew well shared the traits of being stress-tolerant and adept at establishing themselves in new areas.

She was concerned by the lack of diversity on individual roof gardens both in Germany and in her study sites in Chicago.

Back at the Chicago Botanic Garden, she set up an experiment to test how different soil types would affect which plants were successful, and whether she could create a more diverse community on one rooftop by planting both rock and sand prairies.

She planted her experimental plots on the Josephine P. & John J. Louis Foundation Green Roof Garden North on the Daniel F. and Ada L. Rice Plant Conservation Science Center and monitored activity over three years. She found success in growing a more diverse habitat. In related work at the same site, she confirmed that native plantings, rather than the common sedum plant mix used on roof tops, offered benefits similar to a native prairie when it comes to storing rainwater, for example.

The Plant Science Center’s Green Roof Garden is an important resource. Planted in 2009, it serves as a living laboratory, classroom, research site, and a source of inspiration to visitors.

The north side of the green roof of the Chicago Botanic Garden Plant Science Center in 2015, including a blooming population Penstemon hirsutus used in one of Dr. Ksiazek-Mikenas' experiments

A blooming population of Penstemon hirsutus was part of  Dr. Ksiazek-Mikenas’ experiments.

She then expanded to include plots on the Ellis Goodman Family Foundation Green Roof Garden South to study genetic diversity. She compared the genetic diversity of populations established from nursery stock to natural populations, finding more diversity in the natural populations grown from wild collected seed.

On the heels of that finding, she studied populations on green roofs in Chicago near Lake Michigan to find out if the plants were able to share their genetic material with plants on neighboring roofs through pollination. She was thrilled to confirm that they did, as the exchange of diverse genetic material is essential for the long-term health of a species.

Although there are limitations to green roof gardens, mainly due to the lack of soil depth and disconnected setting, Dr. Ksiazek-Mikenas is optimistic about their ability to sustain native species. She has presented her work at numerous conferences across the globe to academics and those in the landscaping industry.

Two prairie species in Dr. Ksiazek-Mikenas' experimental plots blooming on a green roof on the Peggy Notebaert Nature Museum in Chicago

Two prairie species in Dr. Ksiazek-Mikenas’ experimental plots—Ratibida pinnata (foreground, right) and Lespedeza capitata (background, left)—bloom on a green roof on the Peggy Notebaert Nature Museum in Chicago.

“In the future, I hope that green roofs can continue to provide ecosystem services to people but also increasingly support a wide variety of urban biodiversity,” she said.

The motivated researcher is ready to move ahead with her career and intends to continue to bring her unique perspective to future students and to the development of more green infrastructure in this growing world.


©2018 Chicago Botanic Garden and my.chicagobotanic.org

Why did five Midwestern horticulturists hike through the oak-hickory forests of the Missouri Ozarks? And why did we need a desiderata? The first question is easy—we were on the trail of specific wildflowers and woody plants to preserve and add to our collections.

Collections trip horticulturists Mike Jesiolowski, Tom Weaver, Josh Schultes, Kelly Norris, and Steve McNamara

Collections trip horticulturists Michael Jesiolowski, Tom Weaver, Josh Schultes, Kelly Norris, and Steve McNamara (left to right)

In a trip funded by the Plant Collecting Collaborative (PCC), a consortium of public gardens, Tom Weaver (horticulturist, Dwarf Conifer Garden) and I (senior horticulturist, Entrance Gardens) joined Kelly Norris (the trip leader) and Josh Schultes of the Greater Des Moines Botanical Garden, along with Steve McNamara of the Minnesota Landscape Arboretum. Before we left, our desiderata—or essential list of desirable plants we would target—was developed, based on what plants our gardens deemed important for conservation, to fill a gap in our collections, or add beauty to our display gardens. And of course, we had the proper state and federal permits in hand for seed collecting. The six areas that we explored were typically oak-hickory forests, which opened up to rocky-soiled glades and provided for plentiful opportunity for collecting wildflowers. With an eye for distinct plant material and genetic diversity, we roamed through the uneven Ozarks terrain, but we weren’t tied to our wish list—we also found a couple of surprises.

Glade opening at Roaring River State Park

Glade opening at Roaring River State Park

Since seed-grown plants are reproduced sexually through pollination, via wind or insects/animals, they are genetically variable. A variety of genes can give each plant the best chance to exhibit a specific phenotype, or physical appearance, and better adaptability to survive pests and diseases. Where seeds are collected could have significant implications on whether a plant can survive in a given environment or not. For instance, we collected seeds of Echinacea paradoxa (yellow coneflower) from its northern most growing region, in Ha Ha Tonka State Park in Missouri. Selecting seeds of Missouri provenance gives this wildflower a better chance of survival in our region, rather than if the seeds had been collected in Texas. Plants that have a different phenotype from what we commonly observe in northern Illinois were of special interest to us. Fruit from Diospyros virginiana (common persimmon) was collected on a 4-foot-tall tree in Mark Twain National Forest because it is unusual to see fruit on a tree of such short stature. In a similar fashion, Symphoricarpos orbiculatus (coralberry), was collected from the Big Buffalo Creek Conservation Area, after we all remarked at the stunning ornamental quality of the fruit display.  

Yellow coneflower (Echinacea paradoxa)

Yellow coneflower (Echinacea paradoxa)

Persimmon (Diospyros virginiana)

Persimmon (Diospyros virginiana)

Josh Schultes examines some holly (Ilex decidua) for collection.

Josh Schultes examines possumhaw holly for collection.

In some cases, we came across desirable plants, but they had already dropped their seed for the year, or simply didn’t produce any due to drought-induced stress. With the aid of GPS, we marked these areas so future explorers to the Ozarks are aware of these plants for their potential collections. For example, Boyce Tankersley, the Chicago Botanic Garden’s director of living plant documentation, was a part of a team that collected in many of these same areas in 2005; their field data was helpful in our search.

Dotted blazingstar (Liatris punctata)

Dotted blazingstar (Liatris punctata)

Although the Ozarks region experienced a late-summer drought that negatively impacted seed production in some instances, we were still able to make 71 collections from October 12 to 16. Our seeds will be grown in our plant production greenhouses. Once they achieve a certain size, they will be distributed to PCC members and planted in the Garden. I am ecstatic to cross Liatris punctata (dotted blazingstar) off the desiderata for use in my gravel garden project in parking lot 1. The seeds we collected should be ready to plant in these beds in two years.


©2017 Chicago Botanic Garden and my.chicagobotanic.org

Powering Up the Prairie

Undercover Science

Julianne Beck —  July 26, 2017 — Leave a comment

Home gardeners can sympathize: not every seed that is planted grows.

This truth extends to restored prairies that are grown from seed mixes, according to Rebecca Barak, Ph.D., who completed research this year examining the success of individual species within seed mixes, and their combined potential to power up to the diversity level found in remnant prairies. 

A healthy, diverse prairie

A healthy, diverse prairie

Urban and agricultural development has left us with less than one-tenth of one percent of prairieland, which is vital part of our ecosystem. Today, the prairie can be found only in small patches, and scientists at the Chicago Botanic Garden study prairie plants and their chance for survival amid changing climates and landscapes. For Dr. Barak, a key question is what restored plant communities will look like. 

Restored prairies can and do grow in all kinds of places, according to Barak, who conducted fieldwork at dozens of sites within an hour or two of Chicago. From a small playfield behind a nature center to the grounds of a temple to a large swath of acreage in the suburbs, she and her team visited each restored prairie site to compare the plant communities to the mix of seeds that were planted there initially. 

“I studied that on the ground—how do prairies differ, how do seed mixes become prairies, and how can we tweak those seed mixes to improve diversity outcomes for restored prairies,” explained Barak, who recently earned her doctoral degree from the Chicago Botanic Garden and Northwestern University and is now a post-doctoral researcher in a joint appointment between the Garden and Michigan State University.

To conduct her fieldwork, she outlined a 50-meter-long transect in each study prairie, and marked off a large circle every 5 meters along the way. Within the circle, she and her collaborators counted all the plant species they could find. They compared those notes to a walk-through of each site months later as bloom cycles changed.

A native of the Chicago suburbs, Barak made unofficial discoveries that warmed her prairie-loving heart.

Dr. Becky Barak

“I’ve lived here almost all my life and there were all these preserves that I didn’t know about,” she said. Small corners of the city were transformed into lush green spaces, such as the Burnham Wildlife Corridor. Suburban sites such as Orland Grassland were larger and more delightful each season than she anticipated.

After summer months spent documenting and counting, she compared the list of existing plants to the list of seeds that were planted from the original seed mix. She found that less than 50 percent of the species diversity survived from seed to plant. “A lot of species are lost along the way,” she noted.

The plant mix within the restored prairies was then compared to historical data from 41 remnant prairies across Illinois—sites that had never been altered for other purposes. In addition to her findings about the success rate of seeds planted in restored prairies, “I found that species in restored prairies are more closely related to one another than species in remnant prairies,” said Barak.

The David H. Smith Conservation Fellow is not only tuned in to the number of species found in each prairie, but also to how well they represent a variety of evolutionary threads. “We think about how spread out plants in the prairie are across the evolutionary tree of life. Maybe, if you are getting more branches on the tree, your community will function better, or differently,” she noted.

“When we look at remnant and restored prairies, we find that there are differences in biodiversity and there are opportunities to increase diversity of restored prairies. In order to do that we have to think about the seed mixes that are being used,” she added.

In doing so, Barak anticipates that a higher level of diversity will support more functions like serving as habitat for pollinators.

Her detailed findings will be published this August in the Journal of Applied Ecology.

Spiderwort (Tradescantia)

Spiderwort (Tradescantia)

In addition to the benefits of prairies—such as storing rainwater and carbon dioxide—they also provide opportunities we can all enjoy each time we visit, said the scientist and former teacher. “I think it’s about more than that [the ecological benefits]—it’s about teaching people our natural heritage, thinking about habitats that are unique and special to our area, getting people to notice biodiversity, and recognizing that it can even happen in the city or suburbs.” 


©2017 Chicago Botanic Garden and my.chicagobotanic.org

Imagine an episode of the Jerry Springer Show in which the paternity of a child will be determined. Now imagine that instead of human beings, the show is focused on plants, and the issue at hand is the paternity of seeds produced by a given flower.

Next, consider that instead of just two candidate dads, there are dozens or even hundreds of individuals that could have fathered those seeds. What would you expect to find out at the end of the episode?

New research by biologists at Chicago Botanic Garden and the University of Arizona brings such a scenario into reality, and the “big reveal,” while not quite as dramatic as what you’d typically see on the Springer show, offers new insights into plant mating. The paper, titled “Pollinator identity and spatial isolation influence multiple paternity in an annual plant,” was published online today in Molecular Ecology.

“Biologists have known for decades that multiple paternity is common in plants—that is, the seeds contained in a fruit will often have been fathered by many different individuals,” said Matt Rhodes, a Ph.D. student in ecology and evolutionary biology at the University of Arizona. “While we have long had a basic understanding of how multiple paternity occurs in plants, we wanted to explore how it might be influenced by some of the messier aspects of pollination ecology.”

Much of this messiness stems from the fact that plants are sessile: once they start growing, they’re stuck where they are. “One important consequence of this immobility is that plants can’t seek out mates on their own,” Rhodes explains. “Instead, most flowering plants entrust the mating process to animal pollinators that move pollen from flower to flower. On top of that, some individuals are surrounded by potential mates while others are spatially isolated. There are good reasons to expect both of those factors to influence multiple paternity, and that’s what motivated our study.”

In the video above, pollen is deposited on the proboscis and body as hawkmoths (Hyles lineata and Manduca quiquimaculata) visit flowers of Oenothera harringtonii. (Video: K. Skogen) View video on YouTube here.

To address these issues, Rhodes went to the grasslands of southeastern Colorado with Jeremie Fant and Krissa Skogen, conservation scientists at the Chicago Botanic Garden who co-authored the article. They studied a rare evening primrose species with a strange twist in its pollination ecology: its flowers are visited by large-bodied hawkmoths at night and comparably smaller-bodied bees during the morning. “Based on these differences in body size as well as some important differences in behavior, we predicted that flowers visited by hawkmoths would mate with a greater number of fathers than those visited by bees,” said Skogen. “Because these floral visitors are active at different times of day, we were able to test this prediction with a fairly simple experiment in which we limited different flowers on a plant to visits from either hawkmoths or bees. We also predicted that multiple paternity would be less likely for individuals that were farther away from potential mates.”

Hyles lineata visits an Oenothera harringtonii flower; note the pollen on the moth’s head and body. (Photo: S. Todd)

Hyles lineata visits an Oenothera harringtonii flower; note the pollen on the moth’s head and body.
(Photo: S. Todd)

A Lasioglossum bee collects pollen from the anthers of an Oenothera harringtonii flower without coming into contact with the stigma. (Photo: S. Todd)

A Lasioglossum bee collects pollen from the anthers of an Oenothera harringtonii flower without coming into contact with the stigma. (Photo: S. Todd)

After collecting the seeds from these plants, the researchers spent months examining seed DNA in the genetics lab. “By comparing the seeds’ DNA to the DNA of the maternal plants from which we collected them, we were able to figure out which parts of the DNA came from the father,” explains Fant. “We then screened that paternal DNA against all of the individuals in the population—which in our case included more than 300 plants spread across 2 square miles of the landscape—to find the most likely father for each of the seeds we collected.”

For the most part, the results were consistent with the researchers’ predictions. “We found that on average, flowers visited by hawkmoths mated with nearly twice as many different fathers as flowers visited by bees,” said Rhodes. “We also found that spatially isolated individuals were far less likely to mate with multiple different fathers. Overall, it looks as though plant ‘promiscuity’ depends both on what kind of animal visits the flowers, and how far away that individual is from potential mates.”

Scales from Hyles lineata were deposited on the stigma of an Oenothera harringtonii flower. (Photo: K. Skogen)

Scales from Hyles lineata were deposited on the stigma of an Oenothera harringtonii flower. (Photo: K. Skogen)

In addition to providing a more thorough account of factors that can influence multiple paternity in plants, the results also allow researchers to consider how plants might be affected by the loss of certain pollinators. “This study allows us to make predictions about how some plants may be affected if particular pollinators disappear. Hawkmoths play an important role in moving pollen from plant to plant; if they decline in large numbers or are lost completely, there may be cascading effects on the success of future generations of hawkmoth-pollinated plants” said Skogen.

Comanche National Grasslands, Colorado— the shortgrass prairie where the study was conducted. (Photo: K. Skogen)

Comanche National Grassland, Colorado— the shortgrass prairie where the study was conducted. (Photo: K. Skogen)

The field team in Colorado (left to right: Kelly Ksiazek, Matt Rhodes, Sadie Todd, Evan Hilpman, Krissa Skogen, and Jeremie Fant)

The field team in Colorado (left to right: Kelly Ksiazek, Matt Rhodes, Sadie Todd, Evan Hilpman, Krissa Skogen, and Jeremie Fant)


©2017 Chicago Botanic Garden and my.chicagobotanic.org