Archives For Nature in View

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

Autumn Scents

Barbara Brotman —  October 15, 2016 — Leave a comment

“What’s that smell?”

It’s what I’ve been asking myself in recent weeks. Not in a bad way; it’s an entrancing scent that’s been wafting through the air, at the Garden and in gardens I walk by in my neighborhood—but one I couldn’t quite place. I’ve been walking around, nose in the air, happy but perplexed.

Every spring we marvel at the sweet smells in the air. But perfumed breezes in autumn? And what an unusual perfume. Cilantro? With a hint of honey? What could it be?

“You’re smelling something that’s reminiscent of coriander, maybe cilantro?” said Jacob Burns, the Garden’s curator of herbaceous perennial plants.  “You’re probably smelling Sporobolus heterolepis. Prairie dropseed.”

Welcome to a signature scent of late summer and early fall: the scent of prairie dropseed, a native grass.

PHOTO: A single panicle of prairie dropseed.

A single panicle of prairie dropseed

Prairie dropseed (Sporobolus heterolepis)

Prairie dropseed (Sporobolus heterolepis)

Never mind the sweet scents of spring; this season’s plant aroma is in a class of its own. And it’s almost indescribable. I thought of cilantro partly because of the scent, but also because I couldn’t quite place it or compare it to anything else—like cilantro.

“Some people think it smells like buttered popcorn,” said Garden horticulturist Liz Rex, who cares for the Native Plant Garden.

The scent comes from the flowers, feathery panicles that bloom in late summer. I’ve smelled it walking by gardens where people have planted a few native prairie species.

Rex has been surrounded by it in places where it is planted en masse.

“The first year I was in the Native Plant Garden, it was almost overwhelming,” she said. “But now I really enjoy it and look forward to it.”

You can smell it in various spots in the Garden, Rex said—the Native Plant Garden, the restored prairie, the Kleinman Family Cove near the new Regenstein Learning Campus, the Regenstein Fruit & Vegetable Garden; and the rainwater glen outside the Daniel F. and Ada L. Rice Plant Conservation Science Center.

You can smell it in remnant prairies, said Joan O’Shaughnessy, prairie and river ecologist at the Garden—and if you do, that means the prairie is of high quality.

But you can also smell it in ordinary gardens. Native species are increasingly popular in front and back yards, and prairie dropseed (it gets its common name because of the way its mature seeds drop to the ground in autumn) is a Chicago-area superstar.

“It’s a wonderful garden plant because its growth form is low, which people like; it has this fountain-like look to the vegetation; and you can keep it over winter for appeal,” O’Shaughnessy said.

It can grow in both wettish and dry soil. Like many native plants of this region, it can tolerate drought. It can grow in that bane of the Chicago gardener’s existence, heavy clay soil. “It’s just a great plant,” she said.

It isn’t the only source of fall fragrance in the Garden. There is also the katsura tree (Cercidiphyllum japonicum).

PHOTO: In early fall, the gold outline of katsura tree leaves is particularly visible as they begin to change color.

In early fall, the gold outline of katsura tree leaves is particularly visible as they begin to change color.

PHOTO: The late fall foliage of the katsura tree.

The late fall foliage of the katsura tree
Photo by Amy Campion

“The leaves turn a really pretty fall yellow, and once they drop, they release a sugary aroma that smells like cotton candy,” Burns said. “Some liken it to caramel or even brown sugar.”

You can find a katsura on Evening Island by the trellis bridge, he said, and also in the Krasberg Rose Garden.

So while fall’s colors are rightfully beloved, it turns out that the season appeals to another sense, too. Go ahead and enjoy looking at the annual show of autumn colors—but don’t forget the autumn scents.

©2016 Chicago Botanic Garden and

When someone first hears the name of the red-bellied woodpecker, it doesn’t make sense. The bird has a bright red crown and nape, but where’s the red belly? Actually, there is a small pinkish tinge on the bird’s stomach, but it’s difficult to see unless you look for it with binoculars (and if it’s not covered with gray feathers).

PHOTO: A red-bellied woodpecker looking for food. Photo by Carol Freeman.

A red-bellied woodpecker looking for food. Its eclectic diet consists of nuts, berries, seeds, insects, and suet from feeders. Photo © Carol Freeman

Unfortunately, the name “red-headed woodpecker” was already taken by another bird—incidentally, much rarer in northern Illinois—so ornithologists named this common, year-round bird the red-bellied woodpecker.

The red-bellied woodpecker (Melanerpes carolinus) has creamy-to-white underparts, and a black-and-white, zebra-patterned back. The male’s forehead is red; the female’s is creamy white. (By contrast, the red-headed woodpecker’s entire head is blood red, and its back is solid black with white patches on the wings.) The red-bellied woodpecker’s preferred year-round habitat is woodlands, and the oak, pine hardwood, and maple forests of the eastern United States. Occasionally, it can be found in wooded suburban neighborhoods.

Woodpeckers have long, barbed tongues. A woodpecker’s tongue is so long that when it is not extending it to grab a meal deep within a crevice, it pulls it in, and wraps it around the inside back wall of its skull, almost to its nostril holes. Because they can get food from deep within a tree instead of relying on what is readily available, they are well-suited to spend winter in northern Illinois, when other insect-eating birds need to move south.  

PHOTO: Female red-bellied woodpecker.

Female red-bellied woodpecker by [CC BY 3.0], via Wikimedia Commons

If a red-bellied woodpecker visits your yard, you may be able to observe some interesting behavior: the woodpecker puts a nut into the crevice of tree bark, then hits the nut with its beak to get to the yummy morsel inside. It also may store the food there to eat later.

The woodpecker makes its presence known in woodlands and yards or at feeders by calling “querr” or “cherr-cherr” several times, or giving various chattering sounds. Its boisterous noises and colorful plumage add cheer to a cold winter’s day.

In February or March, the male red-bellied woodpecker begins seeking places to excavate cylindrical cavities—in dead trees or dead limbs of trees—and enticing a female to mate and lay eggs, which happens in late March and early April.

As with many birds, red-bellied woodpeckers will nest in the same location year after year. The male typically builds a new cavity—often in the same tree, near the old one—each season. The nest cavity is from 10 to 14 inches deep and usually built on a limb (as opposed to the trunk). The female lays four to five white eggs each season, and both parents incubate the eggs for about 12 days and take care of the nestlings, which fledge in another 24 to 27 days.

Numbers of this beautiful, common bird have grown across most of its range over the past 50 years, according to the North American Breeding Bird Survey. Once most common and found mostly in central and southern Illinois, it has expanded its range northward in the state in the past century, including into northern Illinois, where it had been decidedly rare in the early twentieth century.

The red-bellied woodpecker is the November bird species highlighted by the Forest Preserves of Cook County. Come #birdthepreserves with the Forest Preserves; view the list of upcoming events for free events near you.

©2016 Chicago Botanic Garden and Additional photos by Ken Thomas and Tom Friedel.

Black-Capped Chickadees Are Preparing for Winter

Year-round resident bird adds cheer to coming winter days

Sheryl DeVore Bailey —  September 14, 2016 — Leave a comment


Most people recognize that familiar call of the black-capped chickadee. It’s often heard in late summer and fall as chickadees gather in family groups and small feeding flocks to prepare for the winter.

The chickadee’s song—translated as “Hey, sweetie,” (though you can’t often hear the third syllable)—is reserved for late winter, spring, and summer, when the bird is courting and nesting. Nothing brightens a mid-February day more than when a chickadee sings because to those who hear it, the song signals spring’s arrival.

PHOTO: Black-capped chickadee (Poecile atricapillus). Photo © Carol Freeman.

Because of its curiosity and propensity to visit feeders, the black-capped chickadee (Poecile atricapillus) can often introduce youngsters and adults to bird-watching. Its telltale black cap and throat with white cheeks makes it easy to identify. Photo © Carol Freeman

The black-capped chickadee is the September bird species highlighted by the Forest Preserves of Cook County. Come #birdthepreserves with the FPDCC; there is a free walk at the Garden on September 17, 7:30 to 9 a.m.

The black-capped chickadee is considered a non-migratory species—it can survive the harsh winters of northern Illinois. These birds can lower their body temperature when sleeping at night, which protects them from freezing.

While some birds need to leave the region in fall because insects and other food will soon become difficult to find, chickadees know how to find insect larvae overwintering in tree bark (although flocks of chickadees do make small geographic movements, depending on food availability in colder months).

They also stash seeds to eat later, and unlike squirrels, they remember where they put them. Chickadees eat berries and animal fat in winter, and they readily come to feeders feasting on seeds and suet. Supplemental food, especially sunflower seed from feeders has been shown to help these little balls of feather and hollow bones survive when it gets really cold and wet outside. Those who feed birds can observe an interesting behavior in chickadees—they form a hierarchy, meaning the top chickadee gets to eat at the feeder first—it snatches a seed and leaves, then the second in command gets its turn.

PHOTO: A chickadee enjoys a plentiful and tasty treat in early February: berries.

A black-capped chickadee enjoys a plentiful and tasty treat in early February: berries.

In February, chickadees begin singing and looking for a cavity hole in which to nest—and there’s a wide variety of homes they’ll find suitable. They’ll choose abandoned woodpecker cavities and man-made nest boxes, or excavate their own small, natural cavities. Chickadees will nest in rotted, old wooden fence posts and abandoned mailboxes, and a pair once built a nest in an old shoe hanging from a line.

The female builds a cup-shaped nest with moss for the foundation, lining it with rabbit fur or other soft material. She has one brood each year, laying an average of seven to eight eggs. After 12 days of incubation, the young hatch, then remain in the nest for another 16 days. When they fledge, they continue to follow their parents, calling and begging for food. Come winter, they travel in small feeding groups, often with nuthatches, titmice, and other small songbirds.

West Nile, which came to the U.S. about 17 years ago, likely may not have affected black-capped chickadees as much as some thought, according to a recent study.

Though people were seeing fewer chickadees in their backyards and in woodlands when the virus came to the region, a 2015 study showed that overall black-capped chickadee numbers have not been affected by the mosquito-borne disease, especially compared with other species. Studies will continue on how the virus is affecting bird populations—but one thing is for certain—when the virus struck, it reminded humans not to take for granted the common birds they enjoy. And the black-capped chickadee is certainly a species that humans enjoy watching and hearing.

©2016 Chicago Botanic Garden and

In August, when the jewelweed and cardinal flowers bloom, the ruby-throated hummingbird is migrating. It’s perfect timing, because the hummingbirds get energy for their journey southward by sipping nectar from the blossoms of these plants native to northern Illinois.

Ruby-throated Hummingbird photo © Carol Freeman

Ruby-throated hummingbird © Carol Freeman

The ruby-throated hummingbird is the August bird species highlighted by the Forest Preserves of Cook County. Come #birdthepreserves with the FPDCC; there are two free upcoming walks at the Garden.

PHOTO: A female ruby-throated hummingbird (males have the ruby coloring) enjoys a sip of salvia nectar in Circle Garden in summer.

A female ruby-throated hummingbird (males have the ruby coloring) enjoys a sip of salvia nectar in the Circle Garden in summer.

The ruby-throat is the only hummingbird to breed in eastern North America, and these tiny jewels are somewhat common nesters in Cook County woodlands. They become more numerous in late summer and fall, as those that nested farther north pass through on their way to their winter homes in Mexico and Central America.

The ruby-throated hummingbird (Archilochus colubris) wears emerald green on its back and crown, and in good light, the male reveals an iridescent red throat. (During fall migration, you’ll see males as well as females and young, both of which lack the ruby throat.)

They return to Illinois in April and May, seeking nectar from early blooming trees and shrubs as well as insects and spiders.

It’s at this time you might get lucky enough to observe the courting male as he flies in a U-shape and also buzzes in front of a perched female. Buzzes? Yes! Hummingbirds aren’t silent—you can hear their wings buzz and vocalizations from their throats when they’re defending feeding territory or seeking a mate.

The female builds a thimble-sized cup nest on a horizontal branch, adding grasses and spider webs, lining it with plant down and then covering the outside with lichens and dead leaves. The young hatch in about 15 days, and remain in the nest for another 20 days or so as the female brings them insects.

An aerial wonder, the ruby-throated hummingbird, can beat its wings 53 times per second, and can fly backward and upside down.

You can attract ruby-throated hummingbirds to your yard by planting the flowers they love—tubular and brightly colored in red hues—and by putting up feeders. Hummingbirds are fun to watch at feeders as they have spats in flight trying to hoard the food to themselves. 

To make hummingbird food, add ¼ cup white sugar to 1 cup boiled distilled water. Stir to dissolve, then cool before you put it into the feeder. It’s not necessary to put red food coloring in the water. Use a red feeder to attract the hummers. Hang out of direct sunlight, and clean and refill often.

Most ruby-throated hummingbirds are gone by the end of October in this area. You can put your feeders back up in April when they return.

©2016 Chicago Botanic Garden and