Willow Pruning in the Malott Japanese Garden

If you took advantage of the warm weather last Tuesday and decided to visit the Chicago Botanic Garden, you may have noticed something unusual, especially if you wandered over to the Elizabeth Hubert Malott Japanese Garden.

The Zigzag Bridge was closed for public safety until we could finish pruning.

The sight of horticulturists walking on water was not a hallucination.
In spite of the 60-degree weather, the lake was still frozen and we took advantage of the situation to finish some winter pruning.

The arborists, equipped with the proper safety equipment, are busy pruning the small willow branches.

 Though this willow pruning appears very intense, even harsh, it provides airflow into the tree and gives young branches more room to grow. Some of the large, more upright branches are left to provide height. From an aesthetic point of view, this pruning gives the tree significantly more texture, creating clumps that flow into thin weeping branches. As willows can become quite large, pruning also prevents the tree from becoming disproportionately so.

Benjamin Carroll stands on the ice to prune and provide direction to the arborists.

For the past four years, Benjamin Carroll, the senior horticulturist who maintains the Japanese Garden, has been working with arborists from the area to shape up his trees to give them a more traditional appearance. This style first emerged in Japan.

Seba on the Kisokaido by Utagawa Hiroshige shows the style we are trying to emulate.

Before this style of pruning was implemented, the willows were pruned to appear mounded. For the first three years of this pruning style, many large branches were cut to drastically change the appearance of the trees. This past year we were able to focus on smaller branches.

A willow prior to pruning this year.
A willow looks different before it was pruned this year.

January is the best time for us to do this because the trees are dormant and the sheet of ice on the lake is fairly thick. Tree dormancy is very important when pruning because nutrient flow is minimal and the wounds made by winter pruning will heal quickly in the spring.

Cleanliness is very important to us, it looks good and reduces debris that could promote disease.
While the arborists cut branches with pole saws and chainsaws, I moved branches off the ice.

 The thickness of the ice is also helpful to us because it simplifies cleanup.

After the branches are moved to shore, they’re loaded onto a club car and taken to the mulch pile.

Cleanliness is very important to us because it not only keeps the Garden looking its best but it also reduces debris that could cause disease problems in the future.

Though we look fairly confident walking on the ice, it is important to remember that ice is always dangerous. We always have seasoned professionals and the proper safety equipment nearby.

©2013 Chicago Botanic Garden and my.chicagobotanic.org

Finding the Perfect Match

PHOTO: Norm Wickett looks at moss.
Dr. Wickett looks for liverworts growing under the cover of other vegetation on a previous research trip to Costa Rica.

In the deep green landscape of Vancouver, British Columbia, Norm Wickett stood spellbound.  As an undergraduate biology major at the University of British Columbia, he was enchanted by the seemingly endless ribbons of moss wrapped around the region’s natural areas.

“My heart is in mosses,” he shared during our recent conversation in his office at the Chicago Botanic Garden. “My first love in biology is mosses.”

Many of us non-scientists might consider this common plant—often seen lurking in shadowed, damp areas, to be a turnoff. But to Wickett, Ph.D., now a conservation scientist at the Garden, it presents an irresistible puzzle. How did this plant, likely one of the first to have lived on land, evolve from relatively few species during the Jurassic period to the 15,000 species living today? How did it adapt to all of the environmental changes that occurred?

“I’m attracted to more primitive plants,” said Wickett. He enjoys observing early species in the Garden’s Dwarf Conifer Garden.

As the recipient of a new grant from the National Science Foundation, Dr. Wickett is working to put the pieces together. “This grant is going to allow me to get back into mosses and it’s a great opportunity,” he said.

Part of the National Science Foundation initiative called “Assembling the Tree of Life,” Wickett’s project is one of many branches of study the organization is funding to explore how all life is related.

His work, he believes, will answer important questions about the evolution of all plants from mosses to the conifers and flowering foliage that ensued. Also, it will allow him to identify the ways in which past environmental events, such as climate change, influenced the evolution of mosses, other plants, and animals. This type of knowledge will help researchers predict how plants could respond to future environmental changes.

The spore-bearing capsules of a species of Dicranum moss drew Wickett’s attention while he climbed to a high elevation in Costa Rica.

Wickett’s research process begins in growth chambers in the Garden’s Daniel F. and Ada L. Rice Plant Conservation Science Center. There, he nurtures plants for study. He then takes samples of them to capture the many strands of RNA, or genes, in each species. An expert in plant genetics, he uses new computerized technology to compare the genes of many species of moss and look for patterns.

Why are genetic patterns important? They draw a mazelike course scientists can follow to answer vital questions. Wickett will trace them from species to species in order to see which mosses share RNA and are therefore related. He will also use this information to determine when new species, which share some genes with earlier moss species but also carry some slightly different genes, emerged and what the environmental conditions were at the time that allowed them to thrive.

Timing is everything. He explained that the arrival of new genes must happen at the same time as a complimentary environmental condition for a new species to endure. For example, a plant which developed the ability to hold more water would have been successful during a drought, while it may not have survived during a flood.

Wickett noticed this patch of Sphagnum moss in Costa Rica at a high elevation.

The genetic change can only last, according to Wickett, if it occurs at a time when it gives the plant a benefit in its environment. “It’s a combination of genetic changes in the moss and changes in the climate and finding the change that is most successful,” said Wickett. “For all these things the first step is that there has to be a change in the genes.” Then, he said, “we can go back in time using computer modeling to see what caused the changes.”  These are the pieces Wickett plans to assemble into a bigger picture of evolution during the next three years of his research project.

It is too early to predict where his discoveries may take him, but for now, at least, it is clear that his heart is in the right place.


Look for liverworts, a relative of moss, growing in the Greenhouses on your next visit!

©2013 Chicago Botanic Garden and my.chicagobotanic.org

How to Train Your Plant

Since it’s winter, and we’re all stuck looking at leafless plants outside, why not try growing some plants indoors? Better still, why not experiment with your plants to understand them better?

In this activity, you will confuse a bean sprout and train it to grow in any direction you want. Sound like fun?

You will need:

  • a gallon-size zip-top bag
  • paper towels, preferably 2-ply (if they are single-ply, double them)
  • a pinto, lima, or kidney bean (try whatever you have) soaked in water overnight
  • a stapler
  • water
  • tape

Lay the paper towel flat inside the plastic bag. If it doesn’t fit exactly, fold the edge of the paper towel.

Put a staple in the middle of the bag, and place the bean just over the staple. Add two staples that are separated by more than the length of the bean. 


The staples hold the bean in place, but should give enough room for the bean to grow between the staples. Watch to see how the bean grows and needs the space. Add just enough water to the bag to wet the paper towel. Take care not to have a pool of excess water in the bag.

Now tape the bag to a wall, or your refrigerator, or a window if it’s not cold. That’s right, put it right on a vertical surface. Don’t close the bag, because it’s good to allow water and air to move in and out. The picture shows you what it should look like. (Ignore the four staples, only put three on yours. I discovered that four staples trap the seed and ruin the activity.)


As soon as your plant has grown a root and a stem that is 1-2 inches long, turn the bag one quarter turn and put it back. You may have to wait a week – less if your bean is warm, more if your bean is in a cooler location, like my office.

This is what it may look like at this stage after I turned it.


Now wait. When the sprout has grown another inch or so, turn the bag again in the same direction. Since the opening of your bag will now be on the bottom, you should seal it. Then wait.

Yes, I know, you have to wait a while to get results. The timing will depend on the level of light and the temperature. That’s the way it goes with growing plants. Horticulturists – the people who grow plants – are some of the most patient people you will ever meet!

Here are the results of one bag I started in early January, about three weeks ago. Since I turned the bag clockwise, the roots and stem appear to be going around counter-clockwise.


From here on it’s up to you.  Let the plant grow and turn the bag when you want to change the direction of growth, let it go for as long as you like.  Can you make it grow in a full circle around the middle of the bag? 

What is Going On Here?

Plants are affected by the gravitational pull of the earth. When you turn the bag, you change the direction of the force and the plant responds by changing direction of growth. This phenomenon is called geotropism. A tropism describes an organism’s response to a stimulus. In this case, the “geo” refers to the Earth, and it is the scientific way of saying that the earth makes leaves grow up and roots grow down. This phenomenon may also be called gravitropism.

The Garden’s horticulturists play with gravitropism. Look at this picture of the Visitor Center bridge in fall. Notice the gorgeous pink mums hanging from the trellis.


Left alone, the stems of these plants would naturally grow up like the mums planted on the sides of the bridge. Our horticulturists train the stems to grow down, cascading over the sides of their container, by tying small weights on the stems while the plants are growing in the greenhouses. They actually use metal nuts from a hardware store! The weights are removed before the planters go on display, and they look fabulous, thanks to the horticulturists’ success in playing with the plant’s response to gravity.

©2013 Chicago Botanic Garden and my.chicagobotanic.org