May 8, 2020

Germination, Taproot Removal, and Trunk Training - Oh My!

         As I've said before, there is a widespread, primal appeal in watching a seed sprout firsthand. The bonsai community can and should harness this craze for bonsai seeds by informing beginners rather than shaming them for not starting with more established prebonsai material. I hope that through my comprehensive Bonsai-From-Seed Guide, more of you will readers become disciples of our bonsai hobby and more of you will be successful at creating beautiful trees you can enjoy for decades to come.
          Last month in my serial Bonsai-From-Seed Guide, I already discussed some basic knowledge about the pros and cons of alternative ways to start a bonsai tree and bonsai seed myths which will hinder your seedling's progress if you aren't armed with the correct knowledge. This week, I'm going to start exposing the step by step, year-by-year methods you will need to employ as you watch your seeds sprout and grow. The transformation of your seeds into the bonsai of your dream won't happen just by waiting, it happens with because of your guiding hands (but yes, also with lots of waiting)!

I know glamorous pictures of mature bonsai get more attention, but like the seeds you will plant, today we are starting humbly - with a handful of larch seedlings. 

3. Germination, Taproot Removal, and Trunk Training - Oh My!

3A. Before Germinating

          Some seeds are easy. Apple, lemon, and orange seeds often will sprout without fuss if you stick them straight into soil. Other species need to be seduced into waking up... Try as we might to seduce our seeds, participating in World Naked Gardening Day might scare the seeds more than it would seduce them, so we have to resort to other methods. In botany, stratification and scarification are our main tools to germinate seeds. Cold stratification is a method of imitating the natural effects of seeds accustomed to waiting through cold winter temperatures for months before waking up. The natural freeze-thaw cycle softens the hard protective shell of seeds and allows for water to penetrate the shell, which then signals the seed to start growing. Other seeds that possess harder outer shells may prefer to be coaxed out with a little manual "scarification" or damaging of the outer shell by a small cut. I have yet to attempt a tree seed that requires this treatment, but if you know of one, feel free to tell me in the comments! 
          It's important to note that every seed is different. For long-term storage in a refrigerator, Chinese elms can only be stored for a few months before viability goes off a cliff, however, larch seeds stored dry in a refrigerator can remain viable 20 years later! Also note, many species do better in long-term storage when dry, however, acorns will lose viability if dried too much (acorns are also more difficult to store for long periods). Furthermore, some types of oak seeds will be killed by storing at subzero temperatures but other species are not adversely affected Keeping this diversity in mind, you should look up the specific species you're interested in for the best results. but there are broad guidelines that I have had success with multiple species using and that can be a starting place for you.
          The winter before you want to plant, plan ahead. You'll have to soak your seeds for 24 hours, then place them in the refrigerator for a period of "cold, moist stratification" with wet sphagnum moss or paper towels in a plastic bag for 1-3 months before your seeds will wake up and start growing. Conifers tend to get by with shorter periods (1 month) and maples (3-4 months) tend to have the longest required dormancy. Therefore if you think your last frost is April 1, maple seeds should be moved from their dry long-term storage conditions into moist cold stratification conditions on Dec 1 or January 1. You can also try doing natural stratification by planting seeds outside over winter and this can result in even better germination rates, but you run the risk of critters finding and eating your seed stash.

I encourage you to experiment with many different species and many different methods of germination if you find my suggested method did not work for your species of tree.

3B. Getting Started


          When it is time to plant your seeds (early spring is best, but now isn't too late too!), I like to plant in a sandy mixture composed of the fine particles from my sifted akdama, lava, pumice, and maybe even a little sifted mulch (the large particles of these items are my typical bonsai soil components). This sandy mixture is nutritious and will keep our little baby roots moist without risk of drowning the seedlings. Starting your seeds in simple potting soil can work, but it is less ideal. In the sandy mix, you should water daily especially in the summer unless it rains heavily.
          If potting soil is all you have available, watering becomes a more delicate balancing act. Potting soil stays wet more easily and unfortunately, the dark color makes it harder to tell by eye whether or not the soil is already wet. Daily watering in potting soil can be a recipe for disaster if your seeds never are allowed to dry out. This is because allowing air to enter the roots is an essential part of growing bonsai (in fact bonsai soil is entirely designed on this principle). While many beginners kill their bonsai trees by forgetting to water, others also lose their trees by overwatering, especially if the tree in question is in potting soil. Luckily, I have a quick trick which you can use to avoid this catastrophe. I encourage you to physically touch the soil daily. Connect with the Earth, connect with your tree, and get a little dirty all at once - sounds fun right?? Well, I'm not suggesting it just to be a hippie (though maybe Seattle has turned me into one); if you FEEL the soil is already wet, you should not be giving the tree more water. Only once you feel the soil is drier to the touch should you be watering. That said, don't let it go bone-dry. This is a nuanced difference, but with experience, you'll be able to tell the difference.


          Once you have your soil and seeds both prepared, it's time to sow those seeds and see where they land! I like to poke holes in my soil with a chopstick and drop individual seeds in about an inch apart. When I first started and didn't know how many seeds would germinate, I just threw a bunch down. THAT was a mistake which. A haphazard forest of seedlings makes it more likely that some seedlings will get shaded out and die, and others are more likely to have their roots damaged when you separate the seedlings into individual pots. Avoid this pain and reap what you sow. The extra work in arranging your seeds nicely will pay off next year.

On the left, we have a example which I did not space out enough. Trees are crowded together and roots must be pruned more harshly or they are more likely to get damaged when I separate them into individual pots. On the right, those seedlings are rather nicely spaced. Good job to me :)

Again, this is what NOT to do. Space is good!

3C. Year 1 - Watch Them Go!

          The simplest thing to do in the first year of growth is to water and keep your seedlings clear of weeds. You can also apply some gentle fertilizer while you look forward to separating your seedlings in the following year. Just to be clear, I'm calling this "Year 0" when it is, in fact, the first year of growth because the seedlings are 0 years old right now. This couldn't possibly backfire on me later.

          If you want to try an advanced technique in your first year, the "seedling cutting" method can give you a dense radial root spread on seedlings in a shorter period of time. The seedling cutting method consists of exactly what's in the name. The taproot is cut shortly after the seed sprouts, the new cutting is dipped into in rooting hormone, and each tree can be replanted into an individual pot straight away. This method may risk losing some cuttings if you don't have a nice watering set up to ensure high humidity, but the potential payoff for your future nebari can be significant.  If you're in a hurry, or if you are developing shohin bonsai, this may be an especially appealing technique. In my discussion of "The Root of All Bonsai", I already described Mark Comstock's insane results with this method (pictured below). With the advantage of experience and his own greenhouse, he generates more radial roots than anyone I have ever seen and his pines seem to develop quickly because of it. Another artist who has a wealth of knowledge on this topic is Jonas Duplich of Bonsai Tonight. He has multiple posts on the subject which will be helpful to any daring bonsai artists who want to try this risky technique. I personally don't bother with it as I don't want to risk losing any seedlings because of it, but as my seedlings age and I see what their nebari look like, I may consider coming back to this method.

If you can get this many roots on your pine seedling cuttings, my hat will go off to you. This is one of Mark Comstock's impressive, young Japanese black pines.

3D. Year 2 - Train the Trunks & Trim the Roots!

Trimming the Taproot

          If you did not already plant your seedlings in individual pots via the seedling cutting method, the beginning of Year 1 is when I prefer to do this. Because we will be pruning roots, this is done at the same time as any other repotting operation - late winter/early spring (whatever that means for your area) for temperate trees or at the beginning of summer for tropicals. If freezing temperatures come after you prune the roots of your seedlings, consider protecting them by bringing them inside overnight (an unheated garage would do). You may think we are being an overprotective parent, but this is a good habit because new roots generally grow best at temperatures above 45℉/~7℃. New roots are also liable to be killed by temperatures below 32℉/0℃ as they lack the protective layers that established roots enjoy (think of a new leaf - the same is true of it too). 
          As for the how of the matter, how do we decide how much of the roots to trim? In my experience, once you master watering, not leaving enough roots has been the greatest cause of death to my bonsai, so I tend to be more conservative nowadays, but other artists may tell you you don't need to be - it is a judgment you must develop for yourself based on your local environment and the robustness of the tree you are working with. For example, in the image below, I laid out several Larch seedlings which I recently uprooted. The ones on the right had some damage to their roots already as I was not gentle enough during the uprooting, so I did not prune their roots at all and I would have liked to leave them with more roots than that. The seedlings on the right had no apparent taproot and decent radial root spread already, so I didn't bother pruning their roots much at all either! Only the one in the middle with its long taproot did I prune. Taproots can feed our trees just fine, but in bonsai, they have no aesthetic value compared to radial surface roots which will be apparent on a mature tree. As such, I pruned the taproot about 1/4th of the way down - around the length of the other primary roots. In the near future, I will post a YouTube video about this work if you would like more information.

You might have noticed these larches were uprooted after the needles emerged. Because this root pruning operation happened a little later than the optimal window, that is one more reason to be conservative about root pruning.
As a frugal soon-to-be graduate student, I like to reuse yogurt containers for seedling pots. They do become more brittle with sun exposure around year 3-4 in my experience so far, but that's a pretty good lifespan for something I got for free! I highly recommend drilling holes in the bottom so you don't have to fuss over putting drainage screen in. You can even drill around the sides for extra oxygen, depending on the species (your black pines would love you for doing this).

Trunk Training

          Unless you want a boring, straight trunk, wiring your young trunk is essential. There's nothing wrong with one or two formal uprights, but if I plant 100 seeds, I don't want them to all have the same style! Wiring allows us to quickly set the shape of our trunks into a more natural variety of shapes. The wire will hold the seedling in a new position we impose while it grows and over the next one-two years as the seedling grows, the trunk will expand in the new position, healing any damage from the wire, and allowing us to remove the wire with the trunk permanently set in the new shape. With practice, the seedlings will speak to you and you can make these initial trunk styling decisions quickly. Inspired by the trees I find in the mountains which are often contorted in mysterious ways, I generally make random shapes to see what turns out to be of interest a few years down the road. Below are a few examples of seedlings I wired this year. The larches pictured are the same as the ones I photographed the roots of above. Again, I recorded the process and will be posting my trunk training process on YouTube for your reference... eventually.

Side note, I use the first or second thinnest gauge of aluminum bonsai wire on my seedlings. Annealed copper wire is also an option for styling bonsai. I have no connection to Stone Lantern, but they are one reputable example of where to get bonsai wire (if you have a local bonsai nursery, I encourage you to support them instead!). Your everyday wire at the hardware store does not work as easily for shaping bonsai.

First wiring on one-year-old Japanese Larches.

First wiring of one-year-old Japanese Black Pines. These will also be the focus of an upcoming YouTube video.

4. Next Week...

1. Last Week: The Root of All Bonsai
     1A. Seeds
     1B. Cuttings
     1C. Air layers
     1D. Urban Collection
     1E. Wild Collection
2. "Bonsai Seed" Myths
     2A. "Bonsai seed kits are a great gift!"
     2B. "Bonsai seeds are rare."
     2C. "All bonsai are grown from seed."
     2D. "Growing from seed is the best way to learn about bonsai."
     2E. "The more I prune, the faster my bonsai will grow."
     2F. "Growing from seed is a waste of time!"
3. Initial Growing Plan
      3A. Before Germinating
      3B. Getting Started
      3C. Year 1 - Watch Them Go!
      3D. Year 2 - Train the Trunks & Trim the Roots!
4. Long-term growing plan
    4A. Ground Growing vs Pot Culture
    4B. Sacrifice branches
5. Bonus Gallery

5. Blog Announcements

A.         If you're looking to buy seeds for bonsai - full disclosure - I am writing this series with the intent to sell my own seeds for growing bonsai (see here). At the risk of sounding too sales-pitchy, I am sending an exclusive hard-copy version of this blog series to all my customers. The hard-copy guide will explain in simple terms the complicated 10+year challenge of growing bonsai from seed. If you can't wait for my semiweekly release of future blog articles in this series, you will receive the full guide right away with your purchase of seeds. Thank you in advance for supporting my bonsai work!

B.          Returning readers have already heard, but I am putting together a bonsai talk showJulian TsaiAndy Bello, and I are all experienced bonsai apprentices from different training backgrounds (Julian in Japan at the Fujikawa Kouka-en nursery, Andy in Washington, DC with the National Bonsai Foundation, and myself in Seattle with Dan Robinson at Elandan Gardens). Before the show can proceed, we need 5 more people to submit pictures of trees for us to discuss. This is your chance to get a variety of styling perspectives or technical advice on any trees which may have left you stumped. Please submit your questions here.