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A Bonsai from the Backyard: Collecting a Small Sweetgum

June 01, 2023Beginners, General, Plants

Sweetgum bonsai-in-training after it leafed out in spring.

Field collecting for bonsai doesn’t have to involve wandering through fields and woodlands. Landscape plants slated for removal or those that have sprung up wild in the backyard can make excellent potential bonsai. In this article, the second of a two-part series on the subject, we collect a small sweetgum tree and begin its bonsai training.

My interest in bonsai seems to have conditioned my eyes and mind to automatically evaluate the bonsai potential of almost any tree or plant I see. Whether I’m on a hike in the woods, browsing through garden center stock, or working in my backyard, I’m subconsciously on alert for prospective future bonsai.

A few years ago, when I noticed what I assumed was a little maple sprout in the landscaping of my backyard, I decided to leave it there to grow rather than pulling and discarding it. Its leaves were not those of a common silver maple or sugar maple. It was a different variety, and I was interested to see how it would develop.

Last summer, I took a closer look at the little tree. It had grown to be more than two feet tall and almost an inch thick at the base. The trunk exhibited some damage, most likely from nibbling rodents and/or the weed trimmer. The damage added visual interest, making the little sapling look older. It had pretty, star-shaped leaves and good bonsai potential.

Up to this point, I hadn’t given much thought to the species of the tree, but now it was time to identify this prospective member of my bonsai collection. I was delighted when I realized that the tree was not a maple, but a sweetgum. 

The tree had reached a good point to begin training as a bonsai, so I made plans to field collect the little sweetgum early the following spring.

A Bit About Sweetgum

My little tree is a Liquidambar styraciflua, the sweetgum species native to North America. The genus name, Liquidambar, refers to the fragrant, fluid golden sap characteristic of sweetgum trees. Over the centuries, people have found numerous practical and medicinal uses for the tree’s sap. The resin has been an important ingredient in soaps, perfumes, medicines, and flavorings, just to name a few of its uses.

Sweetgums are frequently mistaken for maples since the leaves and the growth habits of the two look quite similar. Despite their resemblance, the species are not related. The easiest way to tell the difference is to check the growth pattern of their leaves. Maples have pairs of leaves that form directly opposite of each other on the stem, while sweetgum leaves form alternately.  

Liquidambar is an ancient genus of deciduous trees in the witch hazel family. It contains 15 species native to temperate climates in various parts of the world. The styraciflua species has palmate, star-shaped leaves with five to seven long, pointed lobes. The bark of young twigs and branches often sport interesting, corky ridges. 

Sweetgum trees have lovely star-shaped leaves.
Sweetgum trees have lovely star-shaped leaves.

Sweetgum’s sap provides food for hummingbirds, butterflies and moths, and its prolifically produced seeds are enjoyed by squirrels, chipmunks, and birds. It is an important hardwood tree for the lumber industry, second only to oak in lumber production. 

Sweetgum for Landscaping

The sweetgum has enjoyed high regard as a street and landscape tree. Prized for its beautiful fall foliage, sweetgum typically displays a mix of colors. It’s not uncommon to see a mix of yellow, orange, red, pink and maroon displayed on the same tree or even the same leaf. In the photo of my sweetgum last fall, note the variety of colors, including the single dark maroon leaf.

This sweetgum tree in the landscape where it sprouted a few years ago. It displays a variety of fall colors.
My sweetgum tree in the landscape where it sprouted a few years ago. Note the variety of colors in its leaves.

A downside of Liquidambar as a landscape tree is its seedpod. Sweetgums produce fruit in the form of a hard, woody, spiked ball-shaped capsule. Often called “gumballs”, the profusely numbered seedpods drop to the ground in the fall, where they can pose a nuisance for lawn cleanup and a potential safety concern for walkways. 

Collecting the Sweetgum

I chose a sunny day in late February to collect my sweetgum tree. The best time to field collect and repot bonsai is in late winter when the buds are starting to swell. Our mild winter and especially mild February had encouraged the Sweetgum to begin its springtime wake-up, and I wanted to get it out of the ground before that progressed much further.

Digging the Sweetgum proved somewhat difficult due to the tree’s proximity to the fence, deck and a landscape plant. I was forced to do the majority of deep digging from only one side instead of a full circle. This made me nervous that I might be sacrificing too much of the root ball, particularly since the roots that remained with the tree seemed long and rather sparse.

During the digging, I made an interesting discovery. The little sweetgum had sprouted directly on top of a flat rock buried under the dirt. As a result, it had developed a couple of quite thick lateral roots on the rock’s surface.

What wonderful luck! That made the tree a perfect candidate for a root-over-rock planting. I didn’t want to use the large rock from the landscaping, but I found a smaller, interesting flat-topped rock that would work better in a bonsai pot and look more attractive to boot.

The rock the sweetgum was growing on (left) and the smaller, taller, more interesting rock (right) that is now its new base.
The rock the sweetgum was growing on (left) and the smaller, taller, more interesting rock (right) that is now its new base.

Potting the Sweetgum Bonsai

I decided to plant the newly collected sweetgum in a generously sized plastic nursery pot, with the intention of leaving it there for a couple of years. That sparse root system needs some time to develop fine feeder roots and conform to its new rock base. 

I wired the tree to the rock, then wired the combination into the pot. Eventually, most of the rock and the roots growing over it will be exposed, but I covered all but the large base roots in soil for the time being. I was concerned that the sweetgum needed every bit of the scant root system working to support the tree. 

A view of the large surface roots and trunk damage on the sweetgum tree.
The large surface roots and trunk damage add visual interest to the sweetgum bonsai.

I trimmed away a good portion of the top growth. After trimming, the sweetgum was 14 inches tall with only three branches. My goal is to develop side branches and a pleasing canopy of foliage while keeping the tree close to its present height.

The sweetgum after trimming and potting.
The sweetgum after trimming and potting.

The Sweetgum Bonsai Three Months Later

Despite my concerns about the sparse root system, the sweetgum budded, leafed out, and appears to be growing vigorously. It has added a full four inches of top growth since unfurling its first leaves about a month ago!

Vigorous new growth on the sweetgum bonsai.
Vigorous new growth on the sweetgum bonsai.

I’ll let it grow to its heart’s content this summer, then start to do some shaping next year. If all goes well, I’ll probably move it and its base rock to a bonsai pot the following year.

Excellent examples of sweetgum bonsai exist, but Liquidambar offers more challenges for the hobbyist than many other tree species. They tend to have long internodes and leaves that are somewhat resistant to size reduction. They require diligent pinching and pruning to avoid gawkiness and achieve an attractive, compact tree. It will be an interesting exercise to develop this little sweetgum bonsai over time.

To learn more about successfully gathering and transitioning ground-based stock into training, check out the first article from this two-part series about field collecting bonsai.

This article walked through the process of field collecting a young sweetgum tree that grew wild in landscaping near a house. It covered digging the sweetgum, potting the tree and monitoring early progress in its training as a bonsai.

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