Posted in Technique

Air Layering

Air layering is a propagation method dating back over 2,000 years! Layering is often done when a portion of a branch or a trunk is desirable for bonsai but the rest of the plant may not be.

Layering shares some things in common with rooting cuttings but had a more complicated process. One advantage it has over a cutting, though, is that it continues to be supported by the parent plant while new roots are being created. This not only allows for a larger stem to be used but also gives the opportunity to “try again” if the first attempt doesn’t work (unless the layer is below the first branch).

There are primarily two types of layering: simple layering (also known as ground layering) and air layering.

With simple layering, a stem or branch is bent down and staked or partially buried. It can naturally occur when a branch touches the ground for a long period of time and can also be the result of excessive mulching. Once sufficient roots have formed, the stem or branch is separated from the parent plant.

For air layering, the stem (trunk) or branch is wounded and then protected from dying out so that new roots can form. Like a simple layer, once there are sufficient roots to support the new plant then it is separated. Layers generally take around 90 days but can take several years with some slow-to-root species.

One method of performing an air layer is known as the slit method.A long slit is made in the branch or stem and wedged open. It is then usually wrapped in sphagnum moss and plastic to keep it moist so new roots can grow. Without this moisture, as the plant sends out new roots they would quickly desiccate and die. This method is not generally used for bonsai because it tends to result in a one-sided root system that requires additional work to create pleasing nebari (above ground roots).

Another method is the tourniquet method where a wire is twisted into the branch or stem until it bites deeply.

The third method of air layering is the most commonly used and is known as the girdle or ring method.

With this method a ring of bank is removed from completely around the stem or branch. This is usually done by using a sharp knife to make a circular cut all the way around the branch. A second circular cut is made approximately 1″ below the first one. These two cuts are then joined by a vertical slit and then the bark is peeled away.

Sometimes a wire is added to the top of the wound in order to help prevent “bridging”. Some people will also cut upwards under the remaining bark at the top to flare it out a bit with the thought that it might help improve the taper.

To understand how this all works it helps to review a little bit of plant biology.

All woody plants have stems and branches composed of various type of cells arranged in layers. The outermost part is the bark that everyone is familiar with. The bark helps protect the tree from insects, disease, and desiccation.

Under the bark is the phloem, which carries the sugars and starches the foliage has produced via photosynthesis down the branch to the stem to the roots which feeds the plant.

The next layer below the phloem is the vascular cambium. This layer produces the phloem and the xylem cells.

The innermost portion of the tree is the xylem which is separated into the sapwood and the heartwood. The sapwood is the portion of the xylem that transports the sap containing water and nutrients up from the roots to feed and hydrate the plant. The inner layers of xylem are dead cells that support the tree like bones.

It is this upward and downward flow that we are most concerned with when it comes to air layering. We want to stop the downward flow but not the upward flow. This keeps the section above the air layer alive while it forms new roots.

So, we want to sever these layers as shown in the cross-section on the right. The tourniquet method crushes and cuts into the bark, phloem, and cambium to sever this downward path. However, the cambium is very good at repairing damage and can often heal around the wire without sending out roots. With the ring method, all three layers (bark, phloem, and cambium) are removed. Without cambium the other layers cannot regenerate. However, it can be difficult to remove all the cambium which, again, can cause enough healing to bridge the gap. Because of this it is advisable to really scrape the cut and be sure all of the cambium is removed. Some people advocate using rubbing alcohol to kill all the cambium, others will leave the would open for a couple of days to be sure all the cambium cells are dead before covering the wound.

It can be tricky to tell exactly where the cambium stops so you know where to stop cutting but in general it is difficult to cut too deeply (provided a reasonably large branch or stem is used). As you go deeper into the tree the layers will change color until becoming a very light brown that is almost white. The cambium is usually a greenish color (and is what you see when you do a “scratch test” to see if a tree or branch is still alive).

Air layers are best started in the spring or early summer and since plenty of sap is flowing the bark tends to be pretty easy to remove. Often you’ll be able to just peel it off and that makes it fairly easy to see where to stop. Later in the season it can require more work to get the bark removed but again, as long as the branch or trunk isn’t very small (usually 1/4″ is the smallest diameter you’d want to attempt an air layer but 1/2″ is more reasonable as a minimum) it is hard to mistakenly remove too much xylem (wood) to kill the tree. Beginners usually remove too little rather than too much!

The way all of this works is that once you sever the downward flow of nutrients those will start to build up at the top of the cut site. Auxins, a plant hormone responsible for growth, will also begin to accumulate in higher concentrations and trigger growth.

The tree will first create a callus (the bumpy growth you see in the picture on the right) and then roots will emerge from or above the callus.

Since the upward flow of water and nutrients is still intact the upper portion of the tree is usually not harmed at all. This is why some layers can survive for years while they slowly form new roots. An exception to this, though, is if you do the layer below the first branch (often incorrectly referred to as a ground layer when that term is more correctly applied to a simple layer).

If your layer is below the first branch then there is no foliage to feed the roots. It is now a race against time to create the new roots before the old roots die. If the old roots die before there are enough new roots to sustain the tree then the entire tree will die. Such drastic layering should only be attempted with deciduous as evergreen can rarely win this race.

As mentioned earlier, the new roots must be kept moist to keep them from drying out and dying.

This is usually done by wrapping the wound in sphagnum moss (not peat moss) and wrapping that with plastic. Some people prefer to wrap the plastic with aluminum foil to keep it dark and simulate below-ground conditions. Foil is used as opposed to dark plastic because dark plastic risks absorbing too much heat and cooking the new tender roots. Care must also be taken that the bottom is not wrapped too tightly as this would not drain properly and any new roots would drown. The plastic is left on until sufficient roots can be seen.

Another method sometimes used is the “pot method” where a container is fit around the branch or trunk and filled with bonsai soil. It is thought that this results in stronger roots that are less tangled than the “bag method” described above. This method doesn’t work quite as well on branches that are more horizontal but there are special containers specifically made for air layering that do not have an open top so can secure soil when horizontal.

Regardless of which method is used you will need to check on the progress of the layer periodically. Some plants can have sufficient roots in as little as two weeks but most take about a month an a half. You should plan on having the layer complete at least 8 weeks prior to the first frost so the roots have time to get established before winter. Interestingly, layered roots that are still attached to the mother plant tend to be more winter hardy while attached so most layers can easily survive harsh winters. So, if you don’t have sufficient roots by the 8 week mark it is best to leave the layer attached until spring.

With all layers the final step is separation! After verifying you have sufficient roots you’ll want to separate the layer as close to the new roots as possible. If grown in sphagnum moss some people like to plant the tree into pure sphagnum to give the new roots a chance to toughen up before being planted into a training pot or bonsai pot. Whichever you plant into you should be cautious handling the roots as they may be a little fragile until they mature.

You can now enjoy your new tree!

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Posted in Care & Feeding Winter

Dangers of Early Season Cold

In the next few days most of the northern United States and Canada are expected to experience unseasonably cold weather. Here in the Cleveland, Ohio area, for example, it is predicted to drop to 27° tonight and 19° tomorrow night when the averages for those days are 38° and 37°.

Why should that matter for bonsai trees that are hardy to lower temperatures and do we need to provide extra protection to our trees?

I would advise that extra protection be given to trees, even if hardy to those temperatures, because there is a chance the trees have not yet acquired their full winter hardiness this early in the season.

Part of cold hardiness comes from the concentration of sugars in plant cells. This concentration increases starting in early September and reaches maximum in late November to early December. Then it holds steady until early April and begins decreasing as the plants wake up and begin to utilize that sugar for spring growth. Since plants reach their maximum concentration in late November that is when they have their maximum tolerance to cold temperatures.

The fact that it is early November means that it would be prudent to provide additional protection against the cold temperatures but care should be taken to avoid keeping the plants too warm which could delay cold hardiness.

Some good options for protection for the next couple of days include an unheated garage or shed, a cold house or cold frame, or setting on the ground and covering with mulch.

Your trees might not be ready yet for winter storage but would benefit from a little protection until temperatures return to normal in a few days.

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Posted in Bonsai Show

2019 Summer Show People’s Choice Winners!

The results of the People’s Choice voting from our 2019 Summer Show are in!

Congratulations to Alex H for his Hawaiian Schefflera which took First Place!

Second Place went to Steve Z and his Juniper Sea Green and Anne H’s Japanese Larch forest took third.

The nicest, most heartening aspect of the whole thing is that, except for a couple of trees out of the whole 60+ trees in the show, every tree appealed to at least one person enough to list it on a ballot. Tells us that each person’s efforts, even when the result isn’t a spectacular runaway winner, added a little memorable beauty that touched someone that day. What more reward could we ask for the work we put in?!

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Posted in Bonsai

Spring awakening

Spring is a time of renewal and our bonsai trees are waking up!

Not everyone realizes that most bonsai trees are outdoor plants. While there are a few tropical species that can live indoors, even most of them prefer to be outside when it is warm. For the majority of trees, if they aren’t allowed to go through their natural cycle of dormancy they will eventually weaken and die.

Here in Cleveland, spring is upon us and our trees are coming out of their winter dormancy. Buds are cracking open to reveal new leaves, new needles, and in some cases even blooms!

Take a look at these photos submitted by a few of our members and their trees enter spring glory.

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Posted in Show

Cleveland Bonsai Club member wins MidAtlantic Bonsai Society President’s Award

The Cleveland Bonsai Club is very proud of club member Mel G who took home the President’s Award for his Shohin display, as well as Best Accent Plant, at the MidAtlantic Bonsai Society Spring Festival last month. Mel’s display consisted of: Top–Japanese Back Pine, Upper left–Star Jasmine, Upper Right–Japanese Chojubai Quince, Lower left:–Zelkova elm, Lower Right–Kumquat–Outside tree–Shimpaku Juniper. Note that each pot is a different color and shape which is one of the important criteria for a good shohin display.

Well done, Mel!

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Posted in Meetings

Eastern Hemlock

At our April 2019 meeting member David Bennett gave a presentation on utilizing Eastern Hemlock (Tsuga canadensis) for bonsai.

David talked about some of the benefits of this tree, such as the fact that it is locally available and hardy to the area. It is shade tolerant (though prefers sun), fast healing, has good needle reduction, and tends to have compact growth when cultivated properly.

Because it is fast growing David prefers using guy wires instead of wiring branches and pointed out that hemlocks tend to have a lot of “memory” in them and bends don’t always hold. He also warned that they don’t usually backbud on old wood so that needs to be taken into consideration when styling the tree. They are also strongly apically dominant so need frequent pinching to maintain shape.

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Posted in Collecting

2019 Collecting Trip

Last weekend, Cleveland Bonsai Club members Dan White and Adam Shank went on a collecting trip just south of Conesville / Coshocton Ohio. It was state-owned property with public access and we had obtained permission to collect trees for bonsai.

Browse through the images below to see our story!

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Posted in Bonsai

Story of a Tree

Bonsai trees come in many different sizes, styles and types but one thing that is common to a refined bonsai is the appearance of age. A bonsai should appear to be much older than it actually is (in general, some bonsai truly are hundreds of years old!).

A very old pine tree that finally succumbed to the elements. It would have made an excellent yamadori bonsai!

It is often said that a bonsai is the artist’s interpretation or impression of a tree. While some bonsai are replicas of full grown trees in their glory that have been rendered in miniature, there are also many that are made to look like an ancient tree that was kept small by nature and the elements. Those natural trees are the true inspiration behind the bonsai art, originally found in harsh mountainous environments. Trees that are naturally stunted in this way can be worth tens of thousands of dollars and are known as yamadori.

To me, some of the best bonsai are recreations of these unique trees found in nature and should be able to tell a story of how they ended up in such a form (rather than simply be bent into a S shape like so many mass-produced “bonsai” you might find at a box store). I like to look at these twisted form and imagine how they might have ended up that way. When designing my own bonsai, I try to continue this element of realism into the composition. Let’s look at a few trees and guess their stories.

Take this tree, for example. It is easy to imagine that while it was still young another tree fell onto it, knocking it to the ground but not killing it. As the tree recovered, it grew around the fallen trunk and branches and back up towards the sky, ending up with the twisted base and trunk that you see pictured. Eventually, the dead tree that caused all of this rotted away leaving its tale of woe in the victim’s twisted form. The tree also had to fight soil erosion that exposed the roots and threatened desiccation in the harsh environment.

In this next example, perhaps this tree was nearly blown over. But I think it is more likely that it was growing on the side of a cliff, clutching the rock face for its very life and the elements and gravity pulled down against the upward growth. A rock outcropping above could have forced the strong lean as it reached out for light. In my own backyard I have a similar tree growing beside a creek. Early spring storms flood the creek and erode the bank as the tree slowly falls over the side, held in place only by strong support roots on the other side.

This poor, tortured soul looks as if it hasn’t had a pleasant day in its life. Try as it may to thrive, harsh desert winds beat upon it, blowing sand stripped the bark, falling rocks crushed and deformed, and animals grazed on its branches. You can see where the main trunk snapped, leaving a side branch to take over as the new trunk line. Another branch was not so lucky and remains as a lifeless, bleached appendage. Yet through it all a vein of live growth persevered and managed to survive. Eventually, enough growth was able to make it above animal grazing level to thrive, a head of healthy green to contrast with the gaunt skeleton below. A constant reminder of all that was endured.

Even this strong grower was no stranger to the elements. Fate deposited multiple seeds near to each other that took root and the brothers fought each other for decades while harsh storms bent and snapped branches. Eventually, a gale broke the larger of the two nearly in half but it wasn’t enough to kill it. Weakened, it still continued to grow and struggle against the world.

When you look at bonsai trees, whether your own trees or someone else’s, what stories do they tell?

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Posted in Bonsai

Seasonal Color

We’re now into meteorological winter and a time of dormancy for most bonsai trees. However, the end of the season offers once last chance for enjoyment before the winter doldrums hit.

Browse through the gallery below to get a look at some seasonal color from a few of our members’ trees!

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Posted in Care & Feeding Winter

Best Practices for Bonsai Winter Care

One topic that comes up frequently, particularly as winter approaches, is how to safely overwinter bonsai trees. There is no one answer but there are several important guidelines to keep in mind.

First is the hardiness of the tree. The hardiness zone refers to the annual extreme minimum temperature of a region. It is used as an indicator of what plants can survive winters in that region. For example, northeast Ohio is zone 6a and generally doesn’t exceed -10°F. It is important to remember that this is for a plant growing in the ground. A plant in a pot does not have any insulation for its deeper growing roots so a good rule of thumb is that you lose a zone when the plant is in a pot unless additional measures are taken. Therefore a plant that is hardy to zone 6 is really only hardy to zone 7 when it is in a pot and unprotected.

When we talk about winter protection for a plant there are really two things we’re looking at: temperature and wind damage.

For plants that are hardy beyond your zone, (for example a zone 3 plant living in zone 6) you likely will not need any temperature protection. Even in those cases, though, it is advisable to give some protection to the roots to ensure the best chance of survival. So how do you do that?

One method is to simply put the plant into the ground. Dig a hole and either remote the plant from the pot or put it into the hole pot and all (assuming your pot is capable of withstanding the cold temperature). Some bonsai practitioners will remove their tree from its ceramic pot and put it into a plastic pot for overwintering in the ground. Then, cover the rootball as you would when planting a tree in your yard. Be careful to not plant it lower in the ground than the current surface level of the tree to reduce the chance of water damage. For easier removal in the spring, some choose to backfill the hole with woodchips, mulch, or sand.

Another similar method is to place the plant on the ground and “heel-in” with mulch piled up to the level of the first branch. Again, sand or woodchips works here. Some people use straw or hay but there is a danger of weed seeds getting into the bonsai soil if you do that. Hay and straw can also be attractive to mice which can then chew on the roots or trunks and kill the tree.

Speaking of mice, it is generally advisable to wait until everything is well frozen before putting away your trees for the winter. Some people in the USA use Thanksgiving as the target weekend. Doing so increases the chance that vermin will have already located their winter quarters rather than making a home in your trees. To further decrease the odds of rodent damage you can also spread around some mouse bait (taking care that your dog doesn’t get into it if you have one!).

Some people choose to use a structure such as a greenhouse, shed or unheated garage. That can work but there is a danger of temperature fluctuations. Generally, you want to buffer the plant against rapid changes in temperature. If you get a warm winter day or a stretch of warmish days in the early spring you don’t want your trees to warm up too much as they could come out of dormancy, lose their ability to handle extreme cold, and then die when it cools back down. If you have no other option you may end up doing the “two-step” in the spring and taking your plants outside during the day and bringing them back inside every night.

Wintering inside a heated structure can be deadly for plants that require dormancy. If a plant needs dormancy and doesn’t get it then it will usually weaken and die within three years. So, bringing them into your house, a heated garage, or a warm greenhouse will usually kill it. This does not apply if it is a tropical plant (which doesn’t require dormancy and will die if it gets too cold) or if you’re merely applying minimal heat to keep the temperature consistently around freezing.

The other factor to consider is wind. This is usually the most dangerous aspect of a bonsai tree’s winter survival.

As wind moves across a plant it causes moisture in the plant to evaporate. This is the primary reason why deciduous trees lose their leaves in winter. However, there can also be moisture loss through the bark and buds. Even trees with thick, waxy leaves or needles (which are designed to minimize moisture loss) will often benefit from wind protection.

As we noted earlier, trees growing in the ground year round have roots below the frost level in the soil so never freeze. If the tree loses moisture, the unfrozen roots are able to replace it. Bonsai trees, even if put into a hole in the ground, are not below the frost level so once the soil freezes the roots are not able to replace the lost moisture so the tree can desiccate and die.

There are many ways of offering wind protection. Most people place their trees up against a building. This is often on the north side of the building to lessen the chance of the sun warming the plant too much in the winter or early spring even though many prevalent winds come from the north. Keeping in mind that you need to balance temperature protection with wind protection it is often advisable to supplement being up against the building with leaning or erecting a cold-frame (clear plastic or glass), snow fence, or some other structure to further block or slow the wind.

Wind protection is one of the reasons people often want to use an unheated garage or shed but we already discussed those dangers. Underground structures, such as root cellars, can lessen the chance of temperature swings. However, if using such a structure be advised that evergreens continue to photosynthesize in the winter so will not do best in a completely dark location.

While temperature and wind are the two greatest dangers their are other things to keep in mind when overwintering bonsai trees. Take care to ensure they don’t dry out (you might need to water them on warm days). Beware of varmint damage from mice, voles, rabbits, and deer. If stored in a location with little air movement then mold could be an issue. You also need to keep in mind your particular microclimate as influenced by factors particular to your yard such as buildings, landscaping, etc.

While winter can be a dangerous time for bonsai trees, with a little preparation there is a good chance your trees will be fine!

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