Making Bonsai Soil and Repotting

by Dave Curbow and Michael Greenstein

February 17, 2017 @ 7pm

One of the questions most frequently asked by people new to bonsai concerns the growing medium we use instead of potting soil. Although commonly called "soil" this medium bears little resemblance to the material you find in your yard or the bag of potting soil you might buy from a nursery. It seems everyone has an opinion about what makes a "good bonsai soil". These opinions are usually based on anecdotal evidence, but some of what we hear is from those selling a product. Michael and Dave have their own anecdotal evidence from their years of making growing mediums they use but they have also been looking into horticultural research that can guide us in making better soil. They’ll be discussing what they’ve learned. They’ll also discuss how to repot trees in different conditions – new, root bound, unhealthy, etc.

For a while we've had a Soil Basics article on our website. According to web tracking reports it's very popular. We'll be using some of that information but we'll also be updating it with more details after this meeting.

Club News

January Potting Party a Success

We had a fabulous sunny day for our January 29 potting party with about 15 members preparing trees for our show sale. A big THANKS to all of you who helped out in some form or fashion

As seen in the photo below, Sandy Planting created a fabulous group planting using Liquid Amber trees. It was amazing to see how she kept everything standing and in the desired location as she single-handedly tied it all together. Hal Jerman did a great job giving Richard Inocencio a one-on-one beginning class on bonsai as they created a number of beginning bonsai. As Richard I. is a new person joining the club, it was great to see him in attendance at our potting party.

Sandy Planting with her newly created Liquid Amber group planting
Figure 1 – Sandy Planting with her newly created Liquid Amber group planting


If you haven’t had a chance to attend one of the previous parties, we hope you can make the next one on March 19. That will be the last potting party before our June show.

GSBF Bonsai Garden at Lake Merritt Update

We sometimes forget how wonderful bonsai are in California. But if you've visited shows in other states or countries you know that some of the best outside Japan are in California. The Golden State Bonsai Federation operates three gardens where some of the best are on display. Many visitors to the Bonsai Garden talk about how they've come to Oakland just to visit the garden - based on it's reputation for fine bonsai.

Of course, a lot of locals out for a walk stumble upon the garden. Often these visitors have no idea about bonsai and are fascinated to see them for the first time. These visitors usually ask a few questions, but sometimes much longer discussions about the creation and care of bonsai ensues.

Visitors are fascinated to see the Daimyo oak - one of the most historically important bonsai in the United States. In 1863 during Lincoln’s presidency, Mr. Burlingame was envoy to China. As he was returning to the United States he passed thru Japan and was given this bonsai.

The garden wouldn't be possible without the volunteer docents who are there to greet these visitors, answer their questions and keep an eye on things. The garden keeps track of club affiliation of the volunteers and we're pleased to report that once again Kusamura was near the top in terms of hours contributed. A lot of those hours are contributed by just a few people. John Mekisich, our club's vice president is the Docent Schedule Coordinator - and always looking for a few more people to serve as docents. If you're interested in learning more about the garden and what it might mean to be a docent talk to John.

Timely Work Schedule

Each month there are a number of tasks you need to do to your bonsai - from repotting, to fertilizing to spraying for pests. We have put together a checklist, customized for the San Francisco Bay Area to help you. This checklist is adapted from earlier work by Mitsuo Umehara.

This month: February Tasks

January Meeting Recap

Ryan Nichols presented a great January program on “Plant Biology and Plant Nutrient Requirements”. Even though most of us have heard lots of information about “What" we should be doing, we haven’t necessarily heard “Why” we should be doing those things. Learning ‘How the “What” and “Why” can transform your understanding of tree development' is Ryan’s primary goal when teaching bonsai techniques. As Ryan pointed out, when we understand "Why", we can evaluate whether something we learn is applicable to our bonsai.

Using slides, Ryan illustrated how trees grow and how we should consider what’s going on “inside” the tree along with what we can see on the outside. Many of us are probably familiar with the terms pith, xylem, sapwood, vascular cambium, phloem, and outer bark that together define the internal layers of a tree. Understanding the purpose of each of these layers enables you to understand why the leaves of a tree are the first to dry out or wilt in a heat wave or why the process of “air layering” can cause a tree to develop roots mid-air where the “ air layering” operation was performed. For me personally, it was very revealing when Ryan said that a cell in the cambium can turn into any type of tree tissue based on what’s needed. In other words, it’s each individual cell that determines if it’s going to be a new leaf bud, a flower bud, a root, etc.

Ryan and his slides
Figure 3 – Ryan Nichols answering a question from the audience

All of us probably know that trees need photosynthesis via the sun, water and nutrients to grow. Ryan discussed photosynthesis, the conversion of light energy into chemical energy, the adhesive and cohesive properties of water enabling it to move about the tree as needed, and the essential nutrients a plant needs to complete a life cycle. When discussing nutrients, Ryan discussed why roots have their own set of nutrients that they need that is separate from the nutrients needed by the portion of the tree above ground. This of course is why a tree may appear to be healthy but if its roots are not healthy, it is only a matter of time before the tree will not be healthy either. Ryan also said that why most of us consider a tree healthy if it has green foliage and is disease free, true health means it is heat tolerant, drought tolerant, disease resistant and of course green.

In the world of bonsai, we must provide the tree and its roots with the proper nutrients via the components in our soil recipe and the fertilizers we apply. Ryan discussed organic vs. chemical fertilizers and pointed out that not all organic fertilizers are equal - i.e., some break down faster than others. FAST is a time frame of two to six weeks. Organic fertilizers are carbon based, natural fertilizers derived from animal matter or plant matter (e.g., leaf litter), require water to activate, soil biota (bacteria, fungi, and other insect/animals), and temps normally above 50 degrees F to work. A chemical fertilizer is an inorganic material often referred to as a salt fertilizer. It needs water to activate, is a rapid release fertilizer and can be risky if applied at the wrong time such as a heat wave causing burning of the tree or plant. In short, while both require water to activate, an organic fertilizer must be broken-down to be converted into nutrients. And, if the pH of the soil water is too high, it will affect the absorption of nutrients. Ryan uses gypsum, a free form of calcium, to leach sodium from soil. Finally, Ryan said he only uses chemical fertilizers on the foliage of plants and pointed out that liquid fertilizers don’t last longer than fourteen days.

In discussing soils, Ryan touched on the benefits of fungi (mycorrhiza) and how it helps plants absorb more water and nutrients. Ryan recommended the product Dr Earth Life as it has mycorrhiza in it and said we should buy products that have this in it vs. trying to reuse mycorrhiza in the existing soil when repotting. At our February meeting, Dave and Michael will elaborate on mycorrhiza in more detail.

A recommended source for beneficial fungi

Figure 3 – A recommended source for beneficial fungi


In addition, Ryan said he likes bone meal because it is a calcium carbonate for the plant that stays in the soil for a long time.
Ryan briefly touched on pests and said that pesticides should be applied on fourteen-day intervals for three times to remove the original pest, its eggs, and any newly born.

It was a great presentation! We’ll have to have Ryan back to discuss pests next time as he clearly has a wealth of knowledge.


Answering aueience questions
Figure 4 – Ryan answering a question from the audience

Club Calendar

March 19: Bonsai potting party
April 21: “Maple Bud Nipping and Pruning” with Peter Tea
June 24-25: Our annual show

Other Events

February 18-19, 2017 Oakland
GSBF Bonsai Garden at Lake Merritt: The annual Mammoth Auction and Sale Fund Raiser will be held at 666 Bellevue Ave. (Garden Center Building). Saturday: Auction preview at noon with Auction starting at 1 PM. Sunday: Vendor Sales start at 9 AM, Plant Sales start at 10 AM, and demonstrations at 1 PM. The date for this year’s event is a week earlier than in the past to let attendees and vendors participate in both the Mammoth and the Bonsai-a-Thon. You are encouraged to submit your bonsai for consideration to be included in the Mammoth Auction as soon as possible. Items will be considered on a first-come-first-considered basis. The Bonsai Garden will be open 10 AM to 4 PM on Saturday and Noon to 4 PM on Sunday, so you can check out the many changes that have been made this year. For more information or to sell trees, email and visit

March 4, 2017, Oakland
GSBF Bonsai Garden at Lake Merritt: Ryan Neil will conduct a re-styling of the BGLM's Rocky Mountain Juniper to be held at the Lake Merritt Sailboat Boathouse from 1 to 4 PM. Demonstration is a fund-raising event in support of the Bonsai Garden Revitalization Opportunity (GRO) project to raise $100,000 to replace benches, upgrade water systems and install new pathways and windows. Tickets are $35 each (tax deductible) and are available on a first-come-first-serve basis. Reserve tickets by emailing with your name, number of tickets requested, phone number, mailing address, and email address. If there is space for you, you will be asked to mail a check or credit card number, expiration date and zip code to GSBF BGLM, PO Box 16176, Oakland, CA 94610. Once purchased, the tickets are non-refundable.


See GSBF Calendar for additional items

We Accept Donations

As a non-profit, we happily take charitable donations to sustain our club. In exchange, we will will get you a receipt to include when filing your taxes.

For more info see Donations

Articles We Recommend

Intro to Bonsai
About Your New Tree
Pine Pests

Other Sites We Recommend

Michael Hagedorn's blog
Bonsai Tonight
Peter Tea's blog

Check us out on Facebook.

Facebook badge