Archives For Behind the Scenes

An uncommon look at how the Chicago Botanic Garden’s beauty is created and cultivated.

What’s black and white and spread all over? Zebra mussels—but they’re no joke.

If you noticed more aquatic “weeds” and algae growing in the Garden Lakes this year—or that our beloved Smith Fountain was MIA after mid-summer—read on to find out why.

Invasive plants and the problems they pose have been the topic of frequent postings here on the Chicago Botanic Garden’s blog. Now we have another invasive species to tell you about—and this time, it’s an animal: zebra mussels.

PHOTO: Adult zebra mussel (Dreissena polymorpha).

Adult zebra mussels (Dreissena polymorpha) are about the size of your thumbnail.

Like many invasive plants and animals, zebra mussels’ native range is a faraway place; in this case, eastern Europe and western Russia. In the past 200 years, they have spread throughout all of Europe and Asia. Here in North America, the first account of an established population was in 1988 in Lake St. Clair (located between Lakes Huron and Erie), likely arriving here as tiny hitchhikers in the ballast water of a single commercial cargo ship traveling from the north shore of the Black Sea.

Somewhat remarkably, over the next two years they had spread throughout the entire Great Lakes. Just a year later in 1991, zebra mussels had escaped the Great Lakes and begun their march across North America’s inland waters. (Watch an animation of their spread). Today they are found in at least 29 states.

A zebra mussel may live up to five years and produce up to one million eggs each year—that’s five million eggs over their lifetime. A freshwater species of mollusk, they prefer to live in lakes and rivers with relatively warm, calcium-rich water (to help support their shell development). They feed by filtering microscopic algae from the surrounding water, with each adult zebra mussel filtering up to one liter of water per day.

Though tiny in size (adults are typically ½ to 2 inches long), their ecological and economic impacts can be enormous. Adult zebra mussels prefer to attach to hard surfaces such as submerged rocks, boat hulls, and pier posts—but they also cling to water intake structures as well as the interior of most any pipe that has flowing water in it (such as drinking water supply and irrigation system piping). From an ecological perspective, zebra mussels’ removal of microscopic algae often causes the afflicted waterway to become much more “clear.” While this clearer water may otherwise seem like a good thing, the now-removed microscopic algae is an important food source for many native aquatic animals. The clearer water also allows sunlight to penetrate deeper into the water, thereby stimulating much more rooted aquatic plant growth.

Nearby, zebra mussels were first identified in 2000 at the Skokie Lagoons, just south of the Garden. In 2013 and again in 2014, just a few zebra mussel shells were found at the Garden on the intake screens for our irrigation system’s South Pumphouse. Since so few mussels were found, we were hoping that the Garden’s lakes were simply not a hospitable place for the zebra mussels to flourish. Unfortunately, that thinking all changed in 2015….

PHOTO: Waterfall Garden label covered in zebra mussels.

These zebra mussels, only a few months old at the time, completely covered this plant label that had inadvertently fallen to the bottom of the Waterfall Garden’s upper pool.

At our Waterfall Garden, 1,000 gallons per minute of lake water are pumped to the top of the garden, after which the water flows down through the garden’s channels and then back into the lake. When Garden staff drained the Waterfall Garden for cleaning in June 2015, there were no apparent zebra mussels present—but by September 2015, the entire bottom of the Waterfall Garden’s upper pool was completely encrusted with attached zebra mussels. Needless to say, we were more than a little alarmed.

Realizing that the Garden’s lakes could indeed support massive growth of zebra mussels, the Garden’s science, horticulture, and maintenance staff quickly came together to devise a remediation strategy that would protect two critical components of the Garden’s infrastructure from “clogging” by zebra mussels: our irrigation system (which utilizes lake water to irrigate nearly all of our outdoor plant collections) and our building cooling systems (three of our public buildings extract lake water to support their air conditioning systems).

PHOTO: One of the Garden's lake water filtration systems.

Automatic backwash filters like the ones pictured here will be added to each of the Garden’s three pumping stations that withdraw lake water to irrigate nearly all of our outdoor plant collections.

The Garden’s zebra mussel remediation team drew upon the best scientific expertise available in North America, which confirmed that there is no scientifically proven approach for removing all zebra mussels from a body of water. The team explored all potential options for eliminating zebra mussel impacts on our infrastructure, and ultimately settled on two approaches: first, the installation of automatic backwash filters to keep even the tiniest of zebra mussels from getting into our irrigation system (the youngest zebra mussels are about 70 microns in size, or about the width of a human hair), and second, the installation of conventional closed-loop “cooling towers” on the three Garden buildings that currently use lake water for air conditioning (thereby discontinuing all withdrawals of the lake water for building cooling). Final design of the backwash filtration systems and the cooling towers is currently underway, and our intent is to have everything installed and operational by spring 2017.

PHOTO: The Garden’s aquatic plant harvester cuts and removes excessive aquatic vegetation and algae from the Garden lakes.

The Garden’s aquatic plant harvester cuts and removes excessive aquatic vegetation and algae from the Garden lakes.

If you visited the Garden in 2016, you probably witnessed some of the zebra mussels’ ecological impacts to our lakes. Mid-summer lake water transparency in our lakes typically is about 3 to 4 feet—but in 2016, this increased dramatically to about 6 feet (likely due to the zebra mussels’ filtering abilities described earlier). This clearer water resulted in much great submerged aquatic plant growth in our lakes, and our aquatic plant harvester struggled to keep up. Many visitors commented that there was much more aquatic “weed” growth in the lakes this year—and they were correct.

In fact, there was so much aquatic plant growth in our lakes this summer that the water intake for Smith Fountain in the North Lake became clogged and the pump burned out. Look for a repaired Smith Fountain (with a more clog-resistant intake) to reappear next spring.

PHOTO: The Smith Fountain (which is illuminated at night) is an acclaimed feature in the North Lake.

The Smith Fountain (which is illuminated at night) is an acclaimed feature in the North Lake.

While there currently is no known way to eliminate zebra mussels from freshwater lakes and streams, Garden researchers intend to utilize the new aquatic research facilities in the emerging Kris Jarantoski Campus to explore experimental approaches, such as biological control agents, to potentially lessen the zebra mussels’ ecological impacts to our 60-acre system of lakes. Stay tuned.

©2016 Chicago Botanic Garden and

In the past year, more than 181 million people learned about Spike, Alice the Amorphophallus, and Sprout—the Chicago Botanic Garden’s titan arums (Amorphophallus titanum) that entered a bloom cycle—through various media sources.

Now even more people may have the chance to learn about the unique corpse flower from seedlings sowed at the Garden that have been shared throughout the United States.

It all began about 12 years ago when the Garden procured titan arum bulbs and seeds, which we carefully cultivated until they were ready to flower. With the bloom cycles of Alice and Sprout, we wanted to try to pollinate our plants. In nature, titan arums are pollinated by carrion beetles. Since such insects don’t exist at the Garden, we needed to do the work ourselves. As Spike, Alice, and Sprout are thought to be very closely related (with very similar genetic makeup), we speculated that fertilization with pollen from our first titan—Spike—to Alice would not occur: they were “self incompatible”—a term that often describes a plant species that is unable to be fertilized by its own pollen. So in addition to Spike’s pollen, we looked for genetically different pollen. Fortunately, the Denver Botanic Gardens also had a titan arum (“Stinky”) in bloom last year, and they sent us some of Stinky’s pollen, which we used to pollinate Alice.

After the pollination, Alice developed large, plump red fruits. These fruits were harvested and cleaned, and Deb Moore, part of the Garden’s plant production team, sowed the seeds. The result: about 40 quick-growing seedlings—each a single titan arum leaf

We decided to keep a few seedlings for our own uses, but we really wanted to share these young plants with the broader botanical community. We contacted institutions in the American Public Gardens Association to see if any would be interested in acquiring an Amorphophallus titanum.

We had great response. Seedlings were sent to 27 institutions (see Google map above), including the Cincinnati Zoo and Botanical Garden; the JC Raulston Arboretum at North Carolina State University; the Botanic Garden of Smith College in Northampton, Massachusetts; Ganna Walska Lotusland in Santa Barbara, California; the University of Idaho Arboretum and Botanical Garden in Moscow, Idaho; Smithsonian Gardens in Washington, D.C.; University of California-Davis Department of Plant Biology; and of course, three seedlings went to the Denver Botanic Gardens to grow alongside Stinky. 

©2016 Chicago Botanic Garden and

I have an update on Alice the Amorphophallus: Alice has been repotted and has a leaf sprout. Yes, Alice is alive and well, happily growing in the production greenhouses here at the Chicago Botanic Garden.

(Many of you might remember we successfully pollinated Alice with pollen from Stinky, donated to us from the Denver Botanic Gardens’ own Amorphophallus titanum.)

Alice followed a normal growth cycle—as it would have in its native habitat on the island of Sumatra, Indonesia—producing fruit and seeds. This past summer, the flower stalk with the remaining fruit began to wither and collapse as Alice went into dormancy. (We successfully sowed and germinated the seeds, and were rewarded with several dozen seedlings.) On Tuesday, September 13, we removed Alice from the wooden crate she had been living in for the past 24 months, pleased to observe a healthy corm—and a new leaf shoot emerging from the top! We loosened the corm below the soil surface in order to repot it and record its current measurements, and got a few pretty interesting photos. 

First, we washed the corm thoroughly so we could examine it better and get accurate measurements of the corm’s weight and size. We looked for areas of rot, if any, and pulled off any new bulblets that may have developed. (We removed and potted up two new small bulblets—mini-corms—from Alice at this repotting.)

PHOTO: Amorphophallus corm before repotting.

Here is Alice the Amorphophallus as removed from the crate, before washing.

PHOTO: The freshly washed titan arum corm awaits weighing.

The freshly washed titan arum corm awaits weighing.

One big observation was that the corm had actually decreased in size and weight. The big cracks seen in the images below are from the corm rapidly shrinking in size. This is from the large amount of energy (starch and sugars) used for Alice to bloom, and in the production of fruit and seeds. Rather than losing mass and becoming spongy, the post-bloom and fruiting corm is the same density, but smaller in size—both diameter and height—by several inches.

PHOTO: Titan arum corm with emerging leaf sprout and roots.

Splits in the titan arum’s corm are from its rapid decrease in size as energy was used up.

PHOTO: Closeup of a large split in the titan arum corm.

Close-up of a large split in the corm

Now Alice is getting ready to begin the life cycle all over again as a leaf. A ring of new roots at the top of the corm is to support the growth of the emerging leaf bud. The roots do not form or add to a new corm—new corms come from the main corm as bulblets on the side and bottom of the original corm.

The corm has been repotted in a mixture of peat, coir (coconut fiber), composted bark, and perlite, back in its original crate, which still has room to grow in it. 

PHOTO: Alice the Amorphophallus gets ready to leaf out, almost exactly a year after blooming.

Alice the Amorphophallus gets ready to leaf out, almost exactly a year after blooming.

Here are some interesting details on the corm: 

  • Corm size: 13 inches in diameter and 7.5 inches in height
  • Corm weight: 17.5 pounds (weight at last repotting in 2014 was 28.2 pounds)
  • Base of old stem (top growth plate): 4.75 inches in diameter
  • Bottom growth plate: 3.5 inches in diameter
  • New growth/leaf shoot: 2 inches tall (still underground) with a healthy rosette of new roots
  • Surface of the corm: very lumpy and warty looking

I can’t believe it has been a year since we all gathered in the Semitropical Greenhouse at the Chicago Botanic Garden to celebrate Alice’s bloom and stink. What an event that was! Alice will bloom another day, maybe three to five years from now; we will just have to wait and see. But in the meantime, it’s likely another one of the titan arums in our collection will bloom before then. 

©2016 Chicago Botanic Garden and

The opening celebration of the Chicago Botanic Garden’s Regenstein Learning Campus on September 10 and 11 is just the beginning of the fun at the Nature Play Garden. How about splashing in the runnel or running up and down the rolling hills?

Beyond those charms, the Nature Play Garden has another wonderful element: plants that were chosen specifically for this garden. There are plants that appeal to all five senses, and plants with funny names or those that exhibit extreme contrasts. One of the best ways to explore the new Learning Campus and its Nature Play Garden is through plants.

In the Garden’s 26 other gardens, plants are chosen, tended, and laid out to enhance the visitor experience. In this, the Garden’s 27th garden, plants are meant to be touched, smelled, and examined up close.

Plants that appeal to the senses:

PHOTO: Stachys byzantina 'Big Ears'

Stachys byzantina ‘Big Ears’

Sensory plants like lamb’s ear (Stachys byzantina ‘Big Ears’) feel soft to the touch.

PHOTO: Physostegia virginiana 'Miss Manners'

Physostegia virginiana ‘Miss Manners’

Obedient plant (Physostegia virginiana ‘Miss Manners’) has tubular flowers that remain in place if you move them.

PHOTO: Polemonium reptans 'Heaven Scent'

Polemonium reptans ‘Heaven Scent’
Photo courtesy of Intrinsic Perennial Gardens

Heaven Scent Jacob’s ladder (Polemonium reptans ‘Heaven Scent’) was chosen for its fragrance. Enjoy its bright bloom in the spring.

PHOTO: Bergenia cordifolia 'Winterglut'

Bergenia cordifolia ‘Winterglut’

Pigsqueak (Bergenia cordifolia ‘Winterglut’) has big, fleshy leaves that squeak when rubbing fingers over them.

PHOTO: Liquidambar styraciflua

Liquidambar styraciflua

Moraine American sweetgum (Liquidambar styraciflua ‘Moraine’) has star-shaped leaves and seedpods that are spiky; when dry, the seedpods are a great percussion instrument when shaken.

Plants that look cool:

PHOTO: Sedum 'T. Rex'

Sedum ‘T. Rex’

Autumn stonecrop (Sedum ‘T Rex’) was a cultivar we didn’t yet have in the Garden. The education staff likes these leaves because they can be filled with air.

PHOTO: Cercis canadensis 'Columbus Strain'

Cercis canadensis ‘Columbus Strain’

Columbus Strain redbud (Cercis Canadensis ‘Columbus Strain’) promise to put on a glorious color show each fall. You won’t have to look far to find these: more than 60 surround the McCormick Entry Plaza. 

PHOTO: Carpinus caroliniana 'JN Select'

Carpinus caroliniana ‘JN Select’

Johnson’s Select American hornbeam (Carpinus caroliniana ‘JN Select’), a cultivar of hornbeam that is recognized for its unusually smaller and upright stature, is ideal for smaller urban gardens with red and orange fall color. These create the Hornbeam Room in the Nature Play Garden.

PHOTO: Chelone obliqua 'Tiny Tortuga'

Chelone obliqua ‘Tiny Tortuga’

Tiny Tortuga turtlehead (Chelone obliqua ‘Tiny Tortuga’) has flower heads that look like turtles.

PHOTO: Alchemilla mollis 'Thriller'

Alchemilla mollis ‘Thriller’

Lady’s mantle (Alchemilla mollis ‘Thriller’) is best when it rains because the raindrops stay on the leaves.

And a few bonus plants with fun names:

PHOTO: Eupatorium perfoliatum 'Milk and Cookies'

Eupatorium perfoliatum ‘Milk and Cookies’

Milk and Cookies common boneset (Eupatorium perfoliatum ‘Milk and Cookies’) is unusually dark-leafed.

There’s also a mythical hero — Hercules coral bells (Heuchera ‘Hercules’) — and a princess — Cinderella anemone (Anemone × hybrida ‘Cinderella’).

PHOTO: Heuchera 'Hercules'

Heuchera ‘Hercules’

PHOTO: Anemone x hybrida 'Cinderella'

Anemone × hybrida ‘Cinderella’

The team of horticulturists and landscape designers who worked to choose and plant the elements of the Nature Play Garden looked for four-season interest and plants that would appeal to visitors of all ages and abilities. Our heavy clay soil didn’t work for everything, but the range of options was still enormous. Come to the Nature Play Garden and discover your own favorite plants.

Join us for the opening celebration of the Regenstein Learning Campus, Saturday and Sunday, September 10 & 11, from 10 a.m. – 4 p.m.

©2016 Chicago Botanic Garden and

Attention orchid fans: our vanilla orchid is blooming in the Tropical Greenhouse at the Chicago Botanic Garden. It’s a rare occurrence in the wild—and in a greenhouse. Wade Wheatley, assistant horticulturist, seized the moment to hand-pollinate the flower. 

Vanilla planifolia before pollination

Vanilla planifolia before pollination

Why hand pollinate? In hopes of producing a vanilla bean. Yes, the fruit of a vanilla orchid is used to make pure vanilla extract, which flavors many foods we enjoy.

Vanilla vines typically begin to flower at five years or older. Flowers are produced in clusters, with one flower opening each day in the morning. Stop by the Tropical Greenhouse soon to see what’s in bloom. 

©2016 Chicago Botanic Garden and