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For many bonsai tree species, early spring is the best time for repotting.

As the days get longer and the temperatures slowly increase, the roots of a bonsai gradually become active. During this time, the energy of the tree that was stored in the roots over the winter begins to move back up into the tree branches. As this happens, the dormant buds begin to swell. This swelling is the first sign that the tree is beginning to break dormancy. Over the next few weeks, the amount of energy from the roots to the branches increases, and the buds go through a transformation from dormant nub to a fully-opened leaf.

PHOTO: Dormant bud on bonsai.

Dormant bud

PHOTO: Swelling bud on bonsai.

Swelling bud

PHOTO: Extending bud on bonsai.

Extending bud

PHOTO: Opening bud on bonsai.

Opening bud

The best time to repot is generally in the middle of this process, when the roots are active, and the buds are in the swelling and extending stage. All repotting should be done by the time the trees are in the opening stage.

The tree set to be repotted today is this wonderful crape myrtle (Lagerstroemia indica). The first step is removing the tree from the pot.

PHOTO: Bonsai ready to be repotted.

Crape myrtle (Lagerstroemia indica)

Using the root hook and saw, we slowly and carefully create a gap between the root ball and the sides of the pot. Creating this space will allow us to safely remove the tree from the pot.

PHOTO: Loosening a bonsai from its pot with a root hook before repotting.

Use the root hook to carefully loosen the plant from the pot.

PHOTO: Use a root saw to carefully remove the bonsai from its pot.

Once a furrow has been created with the root hook, use the saw to free the bonsai from the pot.

This tree was certainly in need of being repotted! You can see the abundance of roots on the sides and the bottom of the root ball (below). You can even see where the roots started to grow down through the drainage holes in the pot. These “root plugs” prevent proper drainage, which is very important for tree health.

PHOTO: Root plugs—where the roots started to grow down through the drainage holes in the pot—prevent proper drainage.

Root plugs—where the roots started to grow down through the drainage holes in the pot—prevent proper drainage.

PHOTO: Bonsai drainage screen covered by root mat.

Drainage screen covered by root mat

The frequency of repotting is determined by a number of factors, including species, stage of development, and pot size. Vigorous root growers like maples need to be repotted and root pruned more frequently than pine trees of the same developmental stage (which grow roots more slowly). Though root pruning is important to bonsai health, it can be stressful to a tree if the roots are disturbed too frequently. Knowing the tree species you have and how it grows is important in making the decision of when to repot and root prune. 

PHOTO: Bonsai volunteer Ester Bannier assists in root trimming.

Volunteer Ester Bannier assists in root trimming.

PHOTO: Root hook working bonsai roots free.

Use a root hook to work roots free.

Using root hooks, scissors, and chopsticks, the roots are teased out and pruned as needed. Cutting the roots back removes large woody roots, allowing more space for fine feeder roots to grow. The woody roots act only as transporters of energy. Woody roots do not absorb water, food, or oxygen; only the fine feeder roots do that. Having primarily fine feeder roots in our pots is what allows us to keep bonsai in such shallow containers. If the woody roots take up too much space, then the tree cannot absorb enough water, food, and oxygen to support the large amounts of foliage they have, and the trees’ health will suffer.

PHOTO: The bonsai, carefully removed from its pot.

The bonsai, pre-trimming

PHOTO: The bonsai rootball after pruning.

The bonsai root ball after pruning

While the tree work is going on, the soil and pot are being prepared for its return.

Bonsai soil is one of the most important aspects of growing bonsai trees. There are many different soil mixes and combinations that can be used based upon your tree species, the region in which you live, the amount of time you have to water, and many other factors. No matter what mix you choose, a good bonsai soil should support vigorous root growth, a healthy microbe balance, and have good drainage. Here at the Chicago Botanic Garden, we use a variety of mixes based on tree species and stage of development. For this tree, we will be using our base mix of akadama (a clay-like material mined in Japan), pumice, and lava rock. Our soil mix is sifted to remove any small particles and dust that could clog up the drainage holes, decreasing drainage.

PHOTO: Soil mix of akadama, pumice and lava rock is used on this tree.

A soil mix of akadama, pumice, and lava rock is used on this tree.

PHOTO: Volunteer Dick Anderson sifts soil for repotting the bonsai collection.

Volunteer Dick Anderson sifts soil for repotting the bonsai collection.

Once the pot has been cleaned, screens have been secured over drainage holes, and tie-down wires have been added, a layer of lava rock is placed to aid with drainage. After the drainage layer is placed, a small amount of soil is added to bring the tree up to grade and help position it in place.

PHOTO: Bonsai pot prepped and ready for drainage.

Fresh mesh and tie-downs have been placed over drainage holes in the pot.

PHOTO: Bonsai pot with drainage layer.

Drainage has been added in a single layer.

 Once the tree is in place and secured, soil is added and chopsticks are used to push the soil into all the open spaces in and around the root system. Any open gaps left in the pot will result in dead space where roots will not grow. The soil should be firmly in place but not packed too tightly; otherwise, the drainage will be affected, and it will be difficult for roots to grow.

PHOTO: Adding soil to repotted bonsai.

Adding soil to repotted bonsai

PHOTO: Chopsticks are used to push soil into open spaces around roots.

Chopsticks are used to push soil into open spaces around roots.

When the soil is set, the tree is soaked in a tub of water and a liquid product called K-L-N, which promotes root growth and reduces stress from the repotting process.

After a good soaking, the tree is removed and allowed to drain, then returned to its bench in the greenhouse. It will remain there until it is warm enough to go outside on the benches. Not all trees are moved to the greenhouse after repotting; most will return to the over-wintering storage. However, this tree was stressed at the end of the growing season, and I wanted to give it a jump-start on the year and give it more time to recover and gain back some of its vigor.

PHOTO: Soaking the repotted bonsai in water and K-L-N.

Soaking the repotted bonsai in water and K-L-N

PHOTO: Bonsai "benched" in the greenhouse until spring.

Bonsai “benched” in the greenhouse until spring

In just a couple of weeks, the tree is fully leafed out, and has had a slight pruning to help balance the new growth throughout all the branches.

This tree is just the beginning of a busy repotting season here at the Bonsai Collection. We will most likely be repotting nearly 100 trees this year—nearly half the collection! Thanks for reading, and be sure to look out for more bonsai blogs to come in the months ahead.

PHOTO: A leafed-out bonsai, ready to display for the season.

A leafed-out bonsai, ready to display for the season

Upcoming bonsai events:

Tropical bonsai are installed in the Subtropical Greenhouse: Tuesday, March 31.

Trees return to the Regenstein Center’s two courtyards for the season: Tuesday, April 22.

Join us May 9 for World Bonsai Day demonstrations, and a tour of the courtyards.


©2015 Chicago Botanic Garden and my.chicagobotanic.org

Hail to the Queen of Flowers

A stroll through the Krasberg Rose Garden is a feast for the eyes and the nose.

Renee T. —  March 23, 2015 — Leave a comment

As the first day of summer approaches, the Krasberg Rose Garden begins a show of flowers like none other.

More than 5,000 roses begin to unfurl countless buds in myriad colors that gradually fill the air with delicate, sweet scents. Dedicated in 1985, the Rose Garden is home to 200 varieties of roses that include old garden roses (also called antique or heirloom roses), hybrid tea roses, floribundas, miniatures, grandifloras, climbers, shrubs, and several other types.

PHOTO: Singin' in the Rain floribunda rose (Rosa 'MACivy')

Singin’ in the Rain™ floribunda rose (Rosa ‘MACivy’)

A focal point among the roses is an impressive fountain designed in the shape of a Tudor rose (see lore, below). Amble along the curving path through the three-acre garden and you’ll discover some of the more than 34,000 other plants—trees, shrubs, and perennials—that enhance the Rose Garden’s overall design. Nearby (technically outside the parameters of the Rose Garden) is the History of Roses Bed, boasting a rose collection that spans antique varieties, from the earliest wild rose to modern hybrids. Newer All-America Rose Selections winners are also on display.

“I hope visitors view the garden for the aesthetic experience it is—the way it looks and smells,” said Tom Soulsby, the senior horticulturist who oversees the Rose Garden. “There’s probably a rose for everybody and every place.”

PHOTO: Walking on Sunshine floribunda rose (Rosa 'JACmcady')

Walking on Sunshine™ floribunda rose (Rosa ‘JACmcady’)

Besides their incredible beauty and an abundance of blossoms, many of the roses on display were chosen for their hardiness, disease and insect resistance, long period of bloom, and low maintenance requirements. “There’s not a lot to fear when it comes to growing roses,” said Soulsby. He aims to educate gardeners and demystify rose care.

Rose maintenance—pruning, removing spent blooms, mulching, and monitoring for disease and insects—is a collaboration among Soulsby, other garden staff, and volunteers. “We take the most environmentally friendly means of dealing with insects and disease, and sometimes that means doing nothing,” Soulsby said. “One of our objectives is to minimize the use of chemicals. The volunteers are trained to look for things that might need to be addressed. Sometimes it involves handpicking Japanese beetles to get rid of them or handpicking leaves with black spot if the problem is small. If fungus is prevalent, we’re careful about sanitizing our tools with disinfectants so it doesn’t spread from one plant to another.”

The roses receive a water-soluble fertilizer in summer, which is important because each plant spends a lot of energy creating blooms. Deadheading—removing the spent flowers—is also done during summer. “That encourages roses to repeat bloom. If you don’t deadhead them, they form hips,” Soulsby said. Hips are the rose fruits that contain seeds and they may be shades of red, orange, purple, or black. The colorful hips provide winter interest and are often enjoyed by wildlife.

Most of the roses are pruned after Thanksgiving, and the crowns of the plants are covered with 2 to 3 feet of composted horse manure (preferred over Styrofoam rose cones) for winter protection. The compost is removed in spring and used as mulch. “It’s a great soil amendment and we spread as much as we can,” Soulsby said.

PHOTO: Black Baccara hybrid tea (Rosa 'MEIdebenne')

Black Baccara hybrid tea (Rosa ‘MEIdebenne’)

Rose Scents
Although their fragrance is sometimes indescribable, many roses, especially old garden varieties grown before 1867, fill the air on warm summer mornings with a variety of scents.

Pop your nose into a rose blossom and you may discover a hint of cloves, anise, citrus, honey, or pears. Or, perhaps one flower reminds you of apricots, while another exudes a trace of lemon. When the tea roses are blooming, you might detect a trace of sweet orange pekoe tea in the air. Like fine wines, roses often feature a fascinating, complex collection of sweet smells.

Rose breeder William Radler is a consulting rosarian for the Krasberg Rose Garden. He developed the wildly popular KnockOut® series of shrub roses, which are also on display. “Will has been breeding roses for our area, along with other breeders, for a long time,” said Soulsby. The rosarian meets annually with Soulsby and other Garden staff to review the rose collection. This year, Radler will receive the 2015 Hutchinson Medal, which recognizes “outstanding leadership or professional accomplishment that has been significant in furthering horticulture, plant science, or conservation.”

Some of the roses have celebrated a 30-year reign since the Rose Garden opened, but others have been replaced over the years. “We constantly evaluate the rose garden; a plant may not perform to its full potential here. However, the need to change out roses is pretty minimal overall,” Soulsby said. 

Although it’s difficult for him to name favorites, the Mr. Lincoln rose (Rosa ‘Mr. Lincoln’) tops Soulsby’s list. “I tend to favor hybrid tea roses,” he admitted. “There’s also ‘Olympiad’ and ‘Peace’ [see lore, below], but my favorites? It depends on the day.”

Soulsby calls June and September the “rock star” months for the Krasberg Rose Garden. “The best viewing time is around Father’s Day for the first flush of major blooms, and then again in mid-September through early October.” But there’s almost always something interesting to see. Flowering can begin as early as April, and there are even a few blooms in November. Come winter, according to Soulsby, there’s a lot of structural interest with the conifers and shrub roses silhouetted against—or accented with—fallen snow.

Long may the queen of flowers reign!

PHOTO: The Krasberg Rose Garden in summer.

The Krasberg Rose Garden in summer

The Lore of the Roses

In ancient Greek mythology, the goddess Chloris (Roman counterpart: Flora) came upon the body of a lovely wood nymph one day, and asked other gods to help her change it into a flower. Aphrodite donated some of her beauty; the Three Graces bestowed qualities of brilliance, joy, and allure; and Dionysus provided fragrant nectar. When the nymph’s transformation into a flower was complete, Chloris proclaimed it the rose, queen of all flowers.

The rose was said to have bloomed without thorns in the Garden of Eden, but grew them after Adam and Eve were driven out of paradise as a reminder to man of his sinful nature. Inside and outside a religious sphere, roses have represented virginity and purity (white) and passion and martyrdom (red).

During the Middle Ages, the color of roses stood for different heraldic houses, such as the House of Lancaster (red) and the house of York (white), who fought in the War of the Roses (1455–85). At war’s end, after the houses were blended in marriage, a red-and-white striped Tudor rose became the national symbol of England and, eventually, its national flower.

The rose has long featured in literature, from Dante’s Inferno to the sonnets and plays of William Shakespeare, from William Faulkner’s short story A Rose for Emily to Umberto Eco’s novel The Name of the Rose, and many more.

Empress Josephine Bonaparte, wife of Napoleon, in the late eighteenth century sponsored the development of rose breeding at her gardens outside of Paris, where she reigned over more than 250 types of roses.

In World War II, while Americans grew victory gardens, the Peace rose (Rosa ‘Madame A. Meilland’) almost became a casualty when Nazis invaded the Lyon, France, home of breeder Francis Meilland. He smuggled the ivory-yellow hybrid tea rose out of Europe in 1940 to the protection of his business partner, Robert Pyle, of West Grove, Pennsylvania. Pyle continued its propagation, introducing the rose to the public at war’s end. The enduringly popular Peace rose is arguably the most popular in the world today.


This post was adapted from an article by Nina Koziol that appeared in the spring 2015 edition of Keep Growing, the member magazine of the Chicago Botanic Garden.

©2014 Chicago Botanic Garden and my.chicagobotanic.org

It may be 5 degrees Fahrenheit outside right now, but that’s not stopping the Dwarf Conifer Garden from shining.

In fact, many of the conifers are at their peak during the coldest weather.  While other plants have gone dormant for the winter, various conifers are lighting up the landscape in shades of blue, yellow, bronze, plum, and more.

PHOTO: Platycladus orientalis 'Elegantisima' and Thuja occidentalis 'Golden Globe' provide a burst of color with Picea pungens 'Montgomery' and other evergreens providing a calming backdrop.

Platycladus orientalis ‘Elegantisima’ and Thuja occidentalis ‘Golden Globe’ provide a burst of color with Picea pungens ‘Montgomery’ and other evergreens providing a calming backdrop.

Arborvitae (Thuja sp.) are among the best evergreens for bright winter color. Cultivars such as Thuja occidentalis ‘Golden Globe’ provide a burst of gold while other varieties turn shades of bronze or deep green.

Pines (Pinus sp.) also provide a winter show with species such as Pinus sosnowskyi and Pinus sylvestris showcasing powder blue needles and beautiful brown bark. Others, such as Pinus virginiana ‘Wate’s Golden’ turn to a soft yellow hue that lights up the garden.

PHOTO: The yellow foliage of this Thuja occidentalis 'Yellow Ribbons' brightens up dreary winter days.

The yellow foliage of this Thuja occidentalis ‘Yellow Ribbons’ brightens up dreary winter days.

PHOTO: Pinus sosnowskyi.

Pinus sosnowskyi

Among my favorite evergreens for winter interest are the firs (Abies sp.). Korean fir (Abies koreana) has needles that curl upward tightly, showing off silvery undersides and giving the plant a clean, tidy appearance. They also grow into a classic pyramid shape with little to no pruning, making them great for low-maintenance settings. Other firs have long, upturned needles that catch large amounts of snow. Some are the most clean, bright, silvery blue, and others have beautifully deep green foliage all winter long. 

PHOTO: The soft blue of this Picea glauca 'Pendula' brings out the glowing yellow tones of Thuja occidentalis 'Yellow Ribbons'.

The soft blue of this Picea glauca ‘Pendula’ brings out the glowing yellow tones of Thuja occidentalis ‘Yellow Ribbons’.

PHOTO: Douglas Fir have cones with interesting wings at the tip of each scale, such as those seen on this dwarf selection, Pseudotsuga menziesii 'Fletcheri'.

Douglas fir have cones with interesting wings at the tip of each scale, such as those seen on this dwarf selection, Pseudotsuga menziesii ‘Fletcheri’.

Other groups of conifers such as larch (Larix sp.), Douglas fir (Pseudotsuga sp.), yews (Taxus sp.), and more each have their own unique growth habits that provide valuable winter texture and create strong focal points. Some of them (such as larch), lose their needles for the winter, leaving you with skeletons of copper-colored branches, while others (such as Douglas fir), are laden with unique cones. Still others (such as yews), that spent all summer providing a nice green backdrop are suddenly a sturdy focal point where your eyes can rest as you view the landscape.

PHOTO: Contrasting textures and shapes keep the garden interesting even when snow is minimal.

Contrasting textures and shapes keep the garden interesting even when snow is minimal.

PHOTO: Fresh snow highlights the different textures found throughout the Garden.

Fresh snow highlights the different textures found throughout the garden.

The Dwarf Conifer Garden is full of dozens of varieties and species of conifers in all shapes and sizes. While the rest of the Chicago Botanic Garden slumbers under a thick layer of snow, this one is at its peak, waiting to show off shapes and colors that almost don’t seem real.


©2015 Chicago Botanic Garden and my.chicagobotanic.org

Creating Blooming Dish Gardens

Tim Pollak —  December 27, 2014 — 4 Comments

Create a miniature landscape in an open, shallow container: a dish garden! Gather small foliage and flowering plants together in a decorative container—like a basket or saucer—for a versatile display you can enjoy throughout the year. 

Dish gardens are easy to grow, very adaptable to most environments, and can be placed anywhere in the home. Even if you do not have a green thumb, you’ll find it difficult to kill a dish garden. They last much longer than fresh cut flower arrangements, although if you like, you can add fresh cut flowers—they will last up to a week or more. Once done blooming, the flowers can be easily removed or replaced, and the dish garden can be enjoyed for many more months.

Watch this video to learn more.

  • Choose the container: Your dish garden should be planted in a shallow container. The size depends only on how many plants you want to put into it. Almost anything can be used as a container—let your imagination be the judge. 
  • Provide drainage:  Adequate drainage is probably the most important rule to ensure the success of your dish garden. Be sure to remove excess water and avoid over-watering. Drainage holes on the bottom are best, but not mandatory. If drainage holes are not present, use a plastic liner or saucer in the container, or add a layer of gravel or pebbles on the bottom for drainage.
  • Choose the plants: Use small starter plants; 3-inch or 4-inch pots work best. Choose plants with the same general light and water requirements. Using seasonal flowering plants or interesting seasonal focal points—such as poinsettias for the holidays—and change them out throughout the year: replace your poinsettia with a flowering primrose or bulbs in the spring.
  • Dish garden themes: Be different! Try a cactus or desert garden, bulb garden, flowering annuals, African violets, or herb garden. Or try to spruce it up with special decorations for a holiday or event.
  • Planting and design: Always use a well-draining peat-based potting soil. Place the tallest plants in the center if the dish garden is to be viewed from several sides, or place them in the back of the container if viewed only from one side. Mix plants with contrasting foliage, colors, leaf sizes, and shapes. Top dress the soil with a layer of Spanish moss, gravel, or bark chips.
  • Care of your dish garden: Again, they are easy, needing only proper drainage, water, light, and an occasional dose of general fertilizer, and minor trimming if needed. They can last in the home for 1-2 years before repotting is needed.

©2014 Chicago Botanic Garden and my.chicagobotanic.org

The Gift of Bonsai

Chris Baker —  December 17, 2014 — 1 Comment

Thirteen years ago, when I was working as an exotic animal veterinary technician, I bought my friend a gift—a juniper bonsai—that would set me on a course that I never could have imagined.

I already had a yard full of tropical plants, succulents, and orchids, but once I added my first bonsai, I knew something had changed. It was the beginning of a journey that took me from Gainesville, Florida, to Washington, D.C., to Japan and finally here to the Chicago Botanic Garden, where I am the curator in charge of the Bonsai Collection, which is known as one of the best of its kind in the world.

PHOTO: Chris Baker pruning bonsai.

Tending this large bonsai is a delicate task.

Shortly after I purchased my first tree, I started learning about bonsai and joined a prominent bonsai club in Gainesville. In 2006, Gainesville (home of the Gators) hosted the State Bonsai Convention. That weekend was an eye-opening experience for me, as I got to learn from and assist international bonsai artists like Jim Smith, Colin Lewis, and others. That weekend convention was very influential and would fuel my desire to continue learning.

Less than a year after that convention, I had an opportunity to move to Baltimore, Maryland, and work at the National Aquarium. I quickly joined the Baltimore Bonsai Society and continued learning. Feeling more and more drawn to a career in horticulture, I made the move from veterinary technician to horticulturist of the Rainforest Exhibit at the National Aquarium. This opportunity made me think that I actually could have a career working with bonsai. Then, during a Baltimore Bonsai Club event at the National Arboretum’s Bonsai and Penjing Museum in Washington, D.C., I had a chance meeting with the curator Jack Sustic. I introduced myself by saying, “Hi, I’m Chris Baker. I have aspirations of being a bonsai curator some day, and I would like to volunteer here at the collection.” That sentence would forever alter my path. My time as a volunteer and then intern at the National Arboretum was inspirational and educational, and ultimately would lead me to Japan.

Jack Sustic would become a mentor and friend; he introduced me to Torhu Suzuki at the Daijuen Bonsai Nursery in Okazaki, Japan, where he had spent some time. Suzuki, or “Oyakata” (an honorific reserved for a person of high authority) as we would call him, was a third-generation bonsai master and prominent figure in Japanese bonsai culture. In 2012, I spent six months as an apprentice at Daijuen. In that time I learned so many lessons and skills that I use every day. It also gave me an entirely different perspective on how the practice of bonsai has evolved in Japan for centuries.

In April 2014, I started as the curator of bonsai at the Chicago Botanic Garden. Having the opportunity to be the first full-time curator here at a collection of this caliber is a dream job, which comes with a lot of expectations and responsibility. During the display season (April to November), horticulturists Joe Olsen and Gabe Hutchinson provided great support in keeping the trees watered and benches looking great for our visitors. The remaining trees are kept on the south end of the Garden, in the production area. Brian Clark, manager of plant production, and his team help care for the trees on my days off. Last but not least, the support of my 12 volunteers is essential. They are a great team of dedicated people who each brings something different to the Collection. 

PHOTO: Volunteer Eileen Michal working on Bonsai with Chris Baker.

Volunteer Eileen Michal working on the Collection with me.

I’m often asked what has drawn me to bonsai, and why would I pursue a career in it, with only ten or so full-time curator jobs in the entire country? For me, bonsai starts with an appreciation of nature over all things. An ancient tree has the power to move people and evoke emotion. It’s what inspired the Chinese centuries ago to take something of beauty they saw in nature and grow it in a container.

Creating bonsai takes the eye of an artist, the horticultural knowledge of a botanist, and the hands of a mechanic. I have been painting and creating art with many mediums for years. I often draw my trees prior to styling them. It allows me to see different style ideas before I even touch a single branch. I love the horticultural aspect of bonsai, from soil science, to fertilizing, to advanced techniques of grafting and air layering. To me, the mechanical aspect is fun as well. I enjoy making large bends in branches using rebar and guy wires on developmental trees, as well as doing the fine detail work for a show-quality tree. A bonsai is never finished, and the skills and knowledge of a true bonsai expert take a lifetime of study to master and fully understand all it has to offer.

Bonsai has taught me many things, introduced me to wonderful people, and taken me to places I never thought I’d see…At this point in my life, it just seems silly for me to do anything else.

PHOTO: Bonsai Book

Know someone else curious about the Garden’s Bonsai Collection? Bonsai: A Patient Art makes a great gift.


©2014 Chicago Botanic Garden and my.chicagobotanic.org