Bonsai is the Japanese art of growing trees in pots and shaping them to appear like miniature versions of full-size trees. Mastering the art takes patience, practice and commitment, but for novices, getting started isn’t as difficult as it may appear. To explain the basics of bonsai, my guest this week is bonsai artist and educator Bjorn Bjorholm.
Bjorn is the owner of Eisei-en Bonsai Garden in Mount Juliet, Tennessee, on the east side of Nashville. He is originally from Knoxville, Tennessee, but after completing a dual bachelor’s degree in Japanese language and business at the University of Tennessee he moved to Japan for a six-year apprenticeship at Keiichi Fujikawa’s Fujikawa Kouka-en Nursery in Osaka, Japan. Bjorn stayed for a few additional years as a bonsai professional before returning to the United States to open his own nursery. Eisei-en officially opened its doors in September 2018.
Today, Bjorn offers online bonsai courses and in-person intensive trainings, and he’s amassed a YouTube following of more than 200,000 subscribers. Bjorn says practicing bonsai is 70 or 80% horticulture and science and 20 to 30% art.
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How Bjorn Bjorholm Became a Bonsai Artist
Bjorn’s first introduction to bonsai came when he watched the Karate Kid movies from the 1980s. If you’ve seen the films, you probably remember how Daniel-San’s karate mentor, Mr. Miyagi, was also a bonsai artist and used a bonsai tree for his dojo’s logo. Bjorn thought the bonsai trees in the films looked amazing, so he asked his parents for one for his 13th birthday.
His parents got him a Japanese green mound juniper from a big box store, and he’s fairly certain it was already dead when he received it. “It had the rocks glued on the soil surface, and it had the little mudmen sitting underneath it,” he recalls. “And I put it on my nightstand, and within like two weeks it was completely brown. But by that point, I was totally hooked on the art.”
Just a couple of weeks later he bought a new tree and within six months he had a hundred little plants in his parents’ backyard. The internet was still new then, with little online about bonsai, so Bjorn dove into whatever books on the subject he could get a hold of. By the time he was 15 he was teaching beginner classes in the parents’ yard.
Then when he was 16, Bjorn was accepted for a cultural exchange program offered by Panasonic and visited Osaka for two weeks. His host family took him to Fujikawa Kouka-en Nursery, and Fujikawa gave Bjorn his card and said to give him a call if he ever wanted an apprenticeship — though it was a joke at the time.
Bjorn hung on to that business card throughout the rest of high school and then college. When he visited Japan again as a junior in college to complete his language program, he went back to the nursery. Fujikawa did not remember Bjorn and was reticent to have an American apprentice, so after returning to the United States, Bjorn followed up with an email every three or four weeks for months.
Fujikawa didn’t think Americans had the necessary work ethic to be his apprentice and he thought that Bjorn’s Japanese language proficiency wasn’t good enough, but Bjorn persisted and was finally accepted for a three-month trial period. He started within a week of graduating from college at age 22 in 2008.
Bjorn wasn’t the first American to apprentice in Japan to learn the art of bonsai, but he is one of just a few Americans or Europeans who have. Among those who came decades before him are Bill Valavanis, who apprenticed in Omiya Bonsai Village outside Tokyo, and Kathy Shaner, the first non-Japanese and the first woman certified by the professional bonsai grower’s branch of the Nippon Bonsai Association.
In Japan, bonsai exhibition season starts in November, so bonsai artists start prepping in October and take no breaks — not a single day off — for two to four months.
“We’re talking like 7 in the morning until usually 6, 7, 8 o’clock at night, depending on the situation,” Bjorn says. “So if you’re not fully into bonsai, it’s almost an impossible task to finish an apprenticeship.”
Apprentices typically receive room and board but no salary. In Bjorn’s case, he had a small apartment a five-minute bicycle ride away from the nursery. His teacher was called “oyakata,” which translates to “parental figure.”
“Basically, you’re like an adopted member of the family,” he says. “They cover your medical expenses, they cover your food, they cover your apartment.”
He would put aside some of his food budget each month to take his then girlfriend — now wife — out on a date. But once a month is all he could afford.
Most apprentices leave once they are done to open their own nursery, but Bjorn and his wife (who was born in China and moved to Japan when she was 19) had no money and weren’t sure that they wanted to leave Japan. He spoke to Fujikawa, who agreed to let him stay there and work longer but also have time for travel. For the next three years, he was on the road for about 250 days per year, traveling the world to visit clubs and conventions and perform private work. He became part of a handful of traveling bonsai professionals that included Mauro Stemberger, the founder of Italian Bonsai Dream.
When it got to the point that he couldn’t get another visa to stay in Japan, Bjorn and his wife moved to Nashville and started a bonsai nursery. It’s a city he knew well because his grandparents lived there, and there would be less competition with the many well-established West Coast bonsai nurseries.
Bonsai Trees for Beginners
For bonsai beginners who want a conifer, Bjorn recommends as their first bonsai the same species that he first had: Juniperus procumbens “Nana,” the Japanese green mound juniper. These can be found at nearly every garden center, typically in a 1-gallon pot. They can be pruned into some interesting shapes without the need for a lot of wire.
For a beginner-level deciduous bonsai, Japanese maples are really easy to work with. “They’re pretty forgiving for the most part,” Bjorn says. “They’re also relatively slow growing, so it’s not like a Chinese elm, for example, where you’re going to have to prune it 30 times in a growing season. You might prune it once or once or twice in a growing season and be done, essentially, for the year.”
Japanese maples will take a long time to develop into nice trees but from a maintenance perspective and a development perspective they’re one of the easiest to work with, he says.
Bonsai Soil for Beginners
For soil, beginners should stick with a standard potting mix. Advanced bonsai growers use akadama, a granular clay that is porous and has cation exchange capacity, allowing it to both hold nutrients and release them to plants as needed. Akadama mix for bonsai growers may also have humus, lava rock and kiryu, which is river sand with a large particle size.
Large particle sizes may lead to a need to water a bonsai tree three or four times a day to quench its thirst and encourage growth, but for beginners that is asking a lot. Conventional potting mix will hold more moisture between waterings, so watering will only be required once or twice a day in summer, and just once a week or less frequently in winter.
Another thing to know about akadama is it breaks down into smaller particles after one or two seasons, leaving less room in the growing medium for oxygen penetration to the root system. High-quality akadama is high-fired — but not overfired — so it doesn’t break down too quickly.
Pots for bonsai should have drainage holes so roots won’t drown and rot.
Raising Bonsai Trees in Heat and Cold
Many bonsai care practices will depend on climate. For growers in zone 7, like Bjorn in Nashville, there is a wide range of bonsai trees that can be grown successfully. Many trees can tolerate 90° days in summer and temperatures in the teens in winter. Certain species that originated at high elevations will benefit from shade cloth in summer, and frost-susceptible species could use the protection of a cold frame in winter. For more vulnerable trees, such as trident maples and Japanese maples, Bjorn sometimes moves them into his insulated workshop when the weather is going to be really cold. An unheated garage can also be perfect.
Most temperate trees will be just fine if they stay above 20° in the winter and have a little afternoon shade on 90° days in summer, Bjorn says.
The most difficult part of raising bonsai is the watering, according to Bjorn.
“As a matter of fact,” he recalls, “when I started my apprenticeship, Fujikawa-san — probably the second or third day I was there — he handed me the hose and the watering wand and he said, ‘This is going to be the most difficult thing you learn throughout your entire apprenticeship.’”
Bjorn was hard-pressed to believe that, but he soon realized how complicated watering bonsai is.
“Each tree has a different need every day that’s going to change based on the weather,” he says. “And it’s not just that Japanese maples need this and white pines need this and junipers need this. You could have 15 junipers right next to each other that are all cuttings from the same parent plant, so they’re all genetically identical, sitting on the bench growing as bonsai, but each one of them is going to dry out at a different rate during the day.”
It could be due to the health of the plant, like the presence or absence of fungus in the roots from one plant to the next, or various microclimates.
Bjorn’s nursery has between 500 and 600 plants that range from nursery stock material to six-figure bonsai trees, so missing a watering is not an option.
When to Repot Bonsai
Bonsai plants should be repotted every few years to ensure water can penetrate the root system. If water just sits on the surface when applied to the soil, it’s time for the tree to be repotted.
There are a few considerations, including how fast the roots grow, the age of the tree and how fast the akadama breaks down. Bjorn tries to delay repotting as much as he can. He wants at least two growing seasons between repottings.
Trident maples and Japanese maples grow roots quickly and will need to be repotted every two years if not every year. But conifers have slower-growing roots, and Bjorn tries to go four to five years before repotting. He notes that repotting bonsai trees weakens them. Repotting happens in early spring and includes taking some of the old soil out, sometimes cutting the roots, and putting the plant in a pot with new soil. With pines, this stress delays ramification — the building of the branch structure.
Japanese black pines used in bonsai need to be decandled each June when the trees start putting out sap. Decandling is the removal of spring growth, and it results in the plants producing a secondary flush of growth with double the number of buds. But if a black pine was repotted in spring with heavy root work, it may not be strong enough for decandling in June.
When bonsai trees are potted or repotted, they are tied into the pots with wire so they can’t move at all in the wind, which dislodges roots. This also preserves the angle of the plant that the bonsai artist is trying to emphasize. But this means that a tree can’t simply be pulled out of its pot to inspect the roots. Repotting bonsai entails using bamboo shims, chopsticks and steel wire.
When and how to fertilize bonsai trees depends on their stage of development. Trees in early development include seedlings, cuttings and air layers. Trees in the middle stage of development have an established primary structure and work has begun on the secondary branch structure. And last are trees in the stage of refinement, with primary, secondary and tertiary structure established and in maintenance mode.
To encourage early-stage trees to put on mass, Bjorn uses high-nitrogen synthetic fertilizer such as Osmocote Plus. For mid-development trees, he likes Gro-Power fertilizer cakes, which is produced in Chino, California, and has less nitrogen content. And for trees in refinement, he likes Biogold low-nitrogen organic pellet fertilizer that won’t encourage excessive growth but will provide micronutrients.
Keeping bonsai small but healthy requires skilled pruning but perhaps less pruning than you think.
“The misconception about bonsai is that you have to constantly be pruning them back to keep them small,” Bjorn says. “The issue with constant pruning on your trees, whether it’s bonsai or any plant, is that you’re going to weaken the plant over time by doing that.”
Pruning practices vary based on the category of bonsai you are working with. Junipers have different requirements than maples, and even Japanese maples and trident maples are different from one another when it comes to how to prune them. Some deciduous trees fall into the category of trees that can be defoliated during pruning while others should not be defoliated.
“Some deciduous trees and broad-leaf evergreen trees will lend themselves well to defoliation,” Bjorn says.
For certain species, he practices partial outer canopy defoliation. “It’s kind of a term that I coined because we’re not doing 100% defoliation on these trees,” he explains. “We’re literally removing just the outer canopy on the plant.”
Usually, 80 or 90% of the foliage is removed, but the foliage closest to the trunk remains.
“The idea is you get right to those inner areas,” he says. “It strengthens those inner branches, and by defoliating the exterior of the tree, the secondary flush will be twice as much branching and also a smaller foliage so you can maintain a much stronger branch structure across the tree.”
In general, one of the worst things to do is to prune in early spring just as the trees are starting to flush out, Bjorn says. “It’s a terrible idea no matter what the tree is — in the ground or in a pot.”
Pruning terminal shoots (shoot apical meristems) removes growth hormones called native auxins that would normally be transported down through the tree to the root system to interact with cytokinin in the roots and produce a good root system. When the terminal shoots are intact, that cytokinin is transported to the top of the tree where it interacts with the auxin in the shoots and to produce more elongating shoots.
When the tips are removed in early spring, the auxin can no longer reach the roots, which will weaken root production and weaken subsequent growth through the growing season.
“With the exception of just a couple of species, we let pretty much everything here in the spring elongate and grow from early spring until the growth starts hardening off, which for us is usually like mid to late May, somewhere in that neighborhood. At that point, that’s when I start pruning, and each species is going to be slightly different, but most of the deciduous pruning is done in May. Most of the coniferous pruning is done just shortly after that in early June.”
After that first pruning, new shoots will be produced from the side lateral shoots, and in the case of junipers, for example, that second flush of growth with itself be pruned in September, followed by a third flush of growth in late summer and into early fall.
“That means I had a spring flush, a summer flush, and a fall flush,” Bjorn points out. “So I now have tripled the density on my juniper in one growing season.”
Collecting Bonsai Trees from the Wild
Bjorn says the pruning process is how a tree collected from the mountains can be exhibition-ready within three to five years. Trees collected from the wild are called yamadori bonsai, and they could be 200, 300 or even 400 years old when collected. “All of that character’s there,” he says. “We’re just taking the foliage and building like a picture frame around those interesting parts of the plant.”
Collectors take trees from private land or Bureau of Land Management land, with permission.
“I know this ruffles a lot of people’s feathers,” Bjorn says. “It’s like, why would you go out and take this tree that’s 200 years old out of the mountains? Like, isn’t there something immoral about doing that? Which I totally understand the sentiment.”
But what he wants others to understand is that the collected trees are almost entirely conifers, particularly junipers and pines, that are struggling.
“They’re surviving in that environment, but just barely,” he says. “And that’s what’s given them the character, like all the twists and the dead wood and all of these features that we want for bonsai. So when we take those trees out of the mountains, it is our goal to make that tree now thrive. So now we’re giving it the water, we’re giving it the fertilizer, the sun, all of the environment that it needs to thrive.”
This is how a tree with five spindly branches, over the course of five years, develops a canopy it would never have gotten out in nature, he says.
Wire in Bonsai
Copper wire is best for conifers while aluminum is best for deciduous trees. Aluminum wire is much softer, so it is preferred for the softer, easier-to-damage bark of deciduous trees. Using aluminum wire can help avoid “wire bite,” which are the marks left by wire when plants grow around the constraints.
Deciduous bonsai trees are exhibited without leaves, to show off their winter silhouette. So wire scars are a problem. For conifers, which keep their foliage year-round, wire bite is hidden.
Wiring conifers is intended to create pads on the trees that act as picture frames about the interesting features of the plant, Bjorn explains. For example, a juniper with deadwood and a live vein intertwining up the tree may have one section that is the most interesting. A picture frame around that will draw that eye right to that interesting feature.
The art also calls for creating an overall balance of the tree. “When I say balanced, I don’t mean symmetrical, I mean visually balanced,” Bjorn says. “So typically we’re trying to build these trees in a very asymmetrical form. As the older a plant gets, the more asymmetrical it becomes in nature. So we’re trying to mimic that in how we’re building out these plants aesthetically. But in doing so, we’re also trying to create balance in the design.”
This can be achieved through foliar placement but also through pot selection.
Avoid the Biggest Beginner Bonsai Mistake
The biggest mistake that beginners to raising bonsai make is they buy too many plants, according to Bjorn.
Right at the beginning, they dive into it,” he says. “They really want to experiment with this species, experiment with that species, and within like three months they have a hundred plants that they have to take care of. So my recommendation is pick out a couple species that you’re really interested in. Buy one or two plants of each of those species. Learn as much as you can about those because a lot of the information’s going to be applicable across species. “
Learn as much as you can about species and then branch out very slowly into picking up other plants, he advises.
I hope you enjoyed my conversation with Bjorn Bjorholm and learned something new about bonsai. If you haven’t listened yet, you can do so now by scrolling to the top of the page and clicking the Play icon in the green bar under the page title.
Have you raised a bonsai tree? Let us know in the comments below.
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