The surprising science behind hummingbirds and flowers

Fast and graceful, hummingbirds flit from flower to flower—but which ones and why? A Chicago Botanic Garden scientist and his collaborators recently made some unexpected findings on the subject.

It’s a common perception that plants are perfectly matched to their pollinators and that each pollinator has a specific flower type that they are attracted to. For hummingbirds, many gardeners and scientists alike have long assumed their flower type to be one that is strikingly red, tubular, and scentless.

Flowers that are often thought of as typical choices for hummingbirds:

Wyoming paintbrush (castilleja linariifolia)
Wyoming paintbrush
Castilleja linariifolia
Giant red paintbrush (castilleja miniata)
Giant red paintbrush
Castilleja miniata
Scarlet gilia (lpomopsis aggregata)
Scarlet gilia
Ipomopsis aggregata

It’s not hard to see why anyone might assume that hummingbirds and certain kinds of flowers are perfect matches. Hummingbird visits to flowers are visually striking, and many casual observations suggest a typical and consistent set of floral characteristics associated with this plant-pollinator interaction. The vibrant red or orange color of blooms appear as if they were designed specifically to attract the eye of hummingbirds. A hummingbird’s long bill appears perfectly matched for the extraction of nectar from the long, tubular flowers. But don’t be fooled—while it’s satisfying to organize flowers and pollinators and their interactions into clear-cut categories (known as pollination syndromes), these human constructs may mask what is really going on in nature.

Many “typical” hummingbird flowers belong to species that produce diluted nectar with lower sugar concentrations. Yet the hummingbird’s signature hovering flight burns massive amounts of calories. From the hummingbird’s perspective, it would therefore be much more efficient to drink from flowers with more concentrated nectars. Hummingbirds are also known to have acute color vision and show no innate preference for the color red—in other words, there is no reason for them to exclusively focus on red or orange flowers. And their long and slender bills are perfectly capable of extracting nectar from both long and shallow flowers. Finally, hummingbirds do have a sense of smell. So why would hummingbirds go out of their way to visit a limited selection of reddish, long-tubed, scentless flowers that produce cheaper nectar when they could feed from more suitable nearby sources in a diverse buffet of flowers?

Flowers that are “atypical,” or lacking the characteristics we associate with hummingbird-visited flowers (note that they vary in color, shape, odor, and nectar concentration):

Nuttall’s larkspur (delphinium nuttallianum)
Nuttall’s larkspur
Delphinium nuttallianum
Glacier lily (Erythronium grandiflorum)
Glacier lily
Erythronium grandiflorum
Ballhead waterleaf (Hydrophyllum capitatum)
Ballhead waterleaf
Hydrophyllum capitatum

The Garden’s  Paul CaraDonna, Ph.D., and his research collaborators Nickolas Waser, Ph.D., and Mary Price, Ph.D., of the Rocky Mountain Biological Laboratory, discovered that it all comes down to the basic economics that maximize energetic gain at minimal energetic cost. While camping and conducting research across the American Southwest, the three researchers kept observing something curious and unexpected: hummingbirds routinely visited flowers that lacked the expected typical characteristics of hummingbird flowers.

To make sense of these observations, the team dug back into their field notes from the past four decades and began to look more closely at the potential profitability of atypical vs. typical flowers for hummingbirds. Their field notes contained information on hummingbirds’ foraging rates at flowers and measurements of the nectar sugar concentrations; with this information, the team was able to calculate the energetic profits that could be gained by a hummingbird foraging at either type of flower.

How do hummingbirds choose flowers?
A broad-tailed hummingbird (Selasphorus platycercus) feeding from the so-called “atypical” flowers of pinedrops (Pterospora andromedea). Photo courtesy: Audrey Boag

What the team found was that typical and atypical flowers overlapped considerably in their energy content and profitability for hummingbirds. In other words, most typical flowers were no better than most atypical flowers and most atypical ones were no worse than most typical ones. Taken together, this research reveals that hummingbirds are making an energetic profit—not a mistake—when visiting these atypical flowers. In fact, atypical flowers may play a critical yet underappreciated role in supporting hummingbird migration, nesting, and populations in areas that seem to be lacking in suitable floral resources. The results of this research were recently published in the peer-reviewed scientific journal The American Naturalist. Neither typical nor atypical flowers are categorically better or worse than the other, and instead show considerable overlap in the energetic gain they offer to foraging hummingbirds.

Many hummingbird conservation efforts focus solely on typical flowers. Perhaps you have come across suggested hummingbird plant lists that are dominated by typical species. Now knowing that atypical plants can support the migration and residence of hummingbirds, we can consider more than just the typical plants as food resources in habitats and along migration routes.


Karen Wang

Guest blogger Karen Wang graduated with a B.S in ecology and evolutionary biology and a B.A in creative writing from the University of Arizona in 2017. She has worked as a research assistant on a variety of projects, mostly involving pollinators such as bees and moths. 


©2018 Chicago Botanic Garden and my.chicagobotanic.org

Wanted: Leaf Peepers for Science

Have you ever noticed the first crocuses poking out of the snow or the brilliant, changing colors of fall leaves? If so, we need your help with the critical work of studying how plants are affected by a changing climate.

Budburst, a project adopted by the Chicago Botanic Garden in 2017, brings together citizens, research scientists, educators, and horticulturists to study “phenology,” or the life-cycle events of plants. Wildflower phenology events, for example, are fairly simple: first flower, full flower, first fruit, and full fruiting. Deciduous trees, on the other hand, are more complex, with stages from first buds to leaf drop.

Sweetgum in the summer - Budburst
Sweetgum (Liquidambar styraciflua) seed in the summer.
Sweetgum in the fall - Budburst
Sweetgum (Liquidambar styraciflua) leaves in the fall.

Budburst builds on the basic human drive to notice this kind of changing nature around us and record the information to a database for scientists to review. As director of Budburst, I’m excited to hear about your observations on Fall into Phenology, a study on the autumnal changes you see in plants, or the Nativars Research Project, which looks at how bees, butterflies, and other pollinators react to cultivated varieties of native plants.

Budburst’s Fall into Phenology is not limited to just leaf color and seed; it is about observing plants in the fall. This will be my second autumn with Budburst and the Garden, and I’m looking forward to watching some my favorite plants go through their life-cycle changes. I’ll be keeping an eye on the sweetgum trees (Liquidambar styraciflua) underneath my window at the Regenstein Learning Campus, for instance. I can’t wait to see the beautiful shades of yellow or orange or…well, you just never know.


©2018 Chicago Botanic Garden and my.chicagobotanic.org

How to move plants to a new home

Quick poll: Does the word “moving” trigger your anxiety?

How about “moving more than 100 plants”?

Former Chicago Botanic Garden horticulturist Tom Weaver recently moved to Minnesota to start a new chapter. Along with his husband and dog, he brought his plant family, a love he has nurtured since childhood. “My mom makes fun of me because I knew the Latin names of plants before I could read,” he said.

Part of Weaver's houseplant collection, grown under grow lamps in his basement.
Part of Weaver’s houseplant collection, grown under grow lamps in his basement.

Now he’s a proud plant parent to more than 100 plants. The collection is impressive, to be sure. But just how does one transport a thriving plant collection?

As I prepared for my own move (only a few blocks away), I sat down with Weaver to learn how to make the transition happy and healthy for my green, leafy friends.

Weaver's dog, Pepin, isn't so sure about the monstera coming along for the move.
Weaver’s dog, Pepin, isn’t so sure about the monstera coming along for the move.
Weaver's trunk-load of houseplants.
Weaver’s trunk-load of houseplants.

  1. Research state restrictions for plants

    “First you have to consider—if you’re moving across state lines—whether you can even bring your plants,” said Weaver. “California, Florida, Arizona … pretty much any warm-climate state has strict rules about what you can and cannot bring because there are so many agricultural pests.” For a current listing, refer to the National Plant Board.

  2. Sort and purge

    Just as you might sell, donate, or trash unwanted clothes, take a good look at your plants. Toss any you don’t want to bring to your new home. “Why bring something if you’re just going to throw it away once you get there?” Weaver said. “Now is the time to get rid of anything disease or insect-infested.”

  3. Make cuttings of large plants you can’t move

    If you’re like Weaver, you may want to take only a cutting of large specimens like his 6-foot monstera or 8-foot dracaena. Decide whether you want to bring the whole plant, or save room in your moving truck by taking a cutting (and gifting the large plant to a friend). “The nice thing about aroid plants like monstera is the vines have roots growing all over the place,” said Weaver. “You can easily chop a leaf off and root it without really having to think about it.”

  4. Pack plants with care

    Make sure plants are packed snugly in boxes so they don’t move and break. Weaver recommends wrapping plants in newspaper so dirt won’t spill, and so that plants like cacti don’t poke holes in their plant buddies.

  5. Water plants before moving

    Plants can tolerate two to three days in a box without any major problems, said Weaver. Just be sure to water them before you leave, especially if you’re driving through intense heat. “If it’s going to be 100 degrees and you make pit stops along the way, your plants will get hot,” said Weaver. “You’ll want to water them enough to get them through the trip.”

  6. Be patient with the adjustment

    Getting used to a new home goes for your plants, too. “Once you get to your new place, they’ll go through some transport shock,” said Weaver. “They may lose a couple of leaves. With anything, adjusting takes time. It’s best to put your plants in a spot that is a similar environment to their old home.” Be patient with the learning curve.

 


©2018 Chicago Botanic Garden and my.chicagobotanic.org

Brushing Up on Broomcorn

Take a peek in your closet, and you might find a long wooden broom for sweeping up dust or offering rides to witches and wizards. For broom maker John Spannagel of Hidalgo, Illinois, brooms are more than just a pantry item. They’re a labor of love, made with a special ingredient: broomcorn.

Broom Corn Plants Growing at the Regenstein Fruit & Vegetable Garden

Broomcorn is a type of ornamental grass used to make specialty brooms, a passion Spannagel discovered nearly three years ago. The retired construction worker makes roughly 50 brooms a year and tours at local farm shows. As part of the Chicago Botanic Garden’s Harvest Weekend, September 29 to 30, Spannagel will bring his broom-making machines to the Garden to demonstrate broomcorn broom-making.

We caught up with Spannagel to learn a little about his craft:

What is broomcorn? (Spoiler: It’s not corn)

Broomcorn (Sorghum vulgare var. technicum) is an annual ornamental grass. It has no “ears” or “cobs,” and it can grow anywhere from 12 to 14 feet tall. Broomcorn seeds are planted in the early spring, and stalks are harvested in mid- to late August. The long woody stalks have tassels of flowers and seeds at the tips, which are removed during broom-making. You can find broomcorn growing in the Garden’s Regenstein Fruit & Vegetable Garden.

BroomcornWhere does broomcorn come from?

Broomcorn originated in central Africa, where it eventually spread to the Mediterranean. Benjamin Franklin is credited with first bringing broomcorn to the United States in the 1700s, says Spannagel. Commercial production of broomcorn flourished in Illinois, one of the leading producers of broomcorn in the 1860s. Nearly a century later, commercial broomcorn production slowed to a halt due to low demand and labor-intensive harvesting methods.

How do you make brooms with broomcorn?

Broomcorn broom-making is a lengthy process that starts with planting broomcorn seeds in the spring. When broomcorn is harvested, the stalks are run through a threshing machine to remove their seeds. The stalks are then laid on a broomcorn crib to dry for a few weeks. Once the stalks are dried, Spannagel uses broom-making equipment, including an antique kick-winder machine to wind straw around a broom stick; straw cutter; and broom press.

How much broomcorn is used to make a broom?

Spannagel orders his broomcorn from a supplier, and uses seven bundles of straw to make a broom. It takes about 45 minutes to make each broom. “Each of my brooms is a little different, and that’s okay,” says Spannagel.

So, what do you do with a broomcorn broom?

Most of the people who buy Spannagel’s brooms use them to sweep, but many others use them as decorations. Spannagel says as long as you take care of your broomcorn broom, it should last up to 15 years. Be sure to store them upside down or hang them so that that the bristles don’t bend. And always keep them dry; if the broom gets wet, let them air dry.

Broomcorn at Harvest Weekend

Hear more and see Spannagel’s broom-making in action at Harvest Weekend, September 29 to 30, at the Regenstein Fruit & Vegetable Garden.


©2018 Chicago Botanic Garden and my.chicagobotanic.org

Corpse flowers go on an excellent adventure

This is the story of a road trip I took with some corpse flowers, the rock stars of the plant world. One of the hallmarks of the Chicago Botanic Garden’s plant collection is the more than 70 species of Amorphophallus. In particular, Amorphophallus titanum, also called the titan arum or corpse flower, has gained attention because of its very large flower and pungent fragrance at bloom time—a hybrid of week-old gym socks and a rotting mouse that you just can’t seem to find in your kitchen.

The Garden began collecting titan arums, or corpse flowers, in 2003. There’s a worldwide conservation effort to preserve the species, as it is considered “vulnerable”—unless the circumstances threatening its survival and reproduction improve, the species is likely to become endangered.

Our titan arums began blooming about three years ago. The first one, Spike, failed to bloom, but shortly after, in September 2015, Alice the Amorphophallus bloomed in all of its stinky glory. At one point, we had two, Java and Sumatra, in their bloom cycle at the same time.

Titan Twins Java and Sumatra
Titan Twins Java and Sumatra

Over time, our family of titans has grown. Many of the Garden’s corpse flowers share the same lineage, and the Garden decided to share some of our titan wealth with other botanical institutions. It is important to build genetic diversity in our collection and at other botanical institutions and to understand more about these plants through genetic assessment work being conducted by Garden scientists.

All aboard the Titan Express!
All aboard the Titan Express!

I volunteered to captain the Titan Express, which would deliver the titan arums to their new homes: “Pat” to the New York Botanical Garden, “Sprout,” which bloomed in April 2016 at the Garden, to Longwood Gardens in Pennsylvania, and “Kris” to Chanticleer Garden in Pennsylvania.

We departed the Garden on August 17. All aboard the Titan Express!

My plan was to make it to the New York Botanical Garden by 2 p.m. the next day. Of course, I had several hundreds of miles and the George Washington Bridge to deal with. Even though I left Ohio at 4 a.m., I arrived at NYBG two hours late. Marc Hachadourian, director of the Nolen Greenhouses and curator of the Orchid Collection, graciously met me on a Saturday and more graciously waited two additional hours for my arrival.

Titan Road Trip - Marc_Hachadourian
Marc Hachadourian, director of the Nolen Greenhouses and curator of the Orchid Collection.
Titan Road Trip - Wawa Gas Station
The iconic Wawa convenience store—its coffee rivals Starbucks.

With Pat safe and sound, I headed to the New Jersey Turnpike. As much as Philadelphia and Pennsylvania are identified by the Phillies, Eagles, cheesesteaks, and the Liberty Bell, the iconic Wawa convenience store dots the landscape and its coffee rivals Starbucks.

Titan Road Trip - Deleware
Welcome to Delaware

Since I was back in my old “stomping grounds,” I tried to add in visits to see friends, family, and colleagues, as well as take care of some additional botanical business. I conducted a national collections review for the University of Delaware Botanic Gardens in Newark, Delaware.

Feeling weak after a long day of critical thinking about Styrax and Baptisia (two collections under consideration for a national status), I retreated to the regionally famous University of Delaware Creamery for some toffee-flavored sustenance.

Titan No. 2, Sprout, was destined just north of the Delaware border to the Longwood Gardens.

After Longwood, I headed to the beautiful Chanticleer Garden in Wayne, Pennsylvania. Intern Jack McCoy and grounds manager Jeff Lynch stand among some younger titans they received from the Chicago Botanic Garden a couple years ago.

Titan Road Trip - Chanticleer Garden
Andrew Bunting delivers Sprout to the Longwood Gardens.

While in the area, I had a chance to visit Doe Run, which was the famed garden of plantsman, Sir John Thouron, and which is now owned by the owner of Urban Outfitters, Richard Hayne. The estate sits in beautiful Chester County, which is rolling countryside with many equestrian-related activities. While Philadelphia and Wilmington, Delaware, create a significant megalopolis, there remains a reasonable amount of farmland and a very pastoral countryside.

Titan Road Trip - Doe Run
Chester County
Farmland in Pennsylvania
Farmland in Pennsylvania
Titan Road Trip - Andrews House
Bunting’s house, in Swarthmore

Wrapping up the few days on the Titan Express on the East Coast, I had to stop by the Scott Arboretum of Swarthmore College, where I worked for 27 years. And while in Swarthmore, I headed to my house, Belvidere, which I still own, but is rented to a horticulturist at the Scott Arboretum, Josh Coceano.

After several long days of titan tribulations and adventures, a stop at a Delaware drinking hole was in the cards.

I made one last stop to see my mom in Haddon Heights, New Jersey. She is an avid gardener and could appreciate my stories of Andrew’s Excellent Amorphophallus Adventure.

Titan Road Trip - Andrews Mom
Bunting’s mom in Haddon Heights, New Jersey

More than 1,000 miles later, the Titan Express made its last stop.

©2018 Chicago Botanic Garden and my.chicagobotanic.org