Late Spring Tips

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Well, here we are, rather stranded by COVID. For many of you, including myself, it has led to more time with the bonsai. I am really looking forward to seeing the results in your trees with all of this time at home. I know that my bonsai have really taken off this spring at an unprecedented pace and I have been barely been able to juggle repotting, pinching, pruning, styling, etc… The spring weather certainly has been cooperating with a mild winter and a dryer and warmer than usual spring. This has accelerated the development calendar by a few weeks so that buds on different species have emerged and elongated nearly simultaneously, it seems. I barely get my maples in refinement pinched then the spruce start running and it’s time to pinch them too.  Then there are the firs and hemlocks. 

I actually started experimenting with extending my pinching regimen to species I usually just pruned after hardening. Many of those are now transitioning from a developmental mode into a refinement mode. Which really means that I am moving from developing the trunks into developing quality branching, especially on deciduous trees that I have grown from scratch. 

A refined Sargent’s crabapple with its first crop developing

Let’s start with fruiting trees. My regular habit is to prune off any fruit that starts to form so that it does not take any energy away from my primary goal of developing trunks or branches. However, I was very pleased to see tiny apples forming on one my shohin Crabapples in refinement for the first time. The fruit only develops on second year spurs, so as I pruned for refinement year after year, I was pruning away all the flower buds. This was a known tradeoff, but the results are worth it. This year I pruned the branches just past the fruit to check their growth, and am praying that the tree does not respond by aborting the tiny, quarter inch apples. So far, so good. 

But I regularly prune off all the flowers of my plum trees, knowing that a few escape and develop fruit anyway. These trees are now getting close to where I would allow them to develop fruit. However, the fruit tends to ripen mid-summer when there is no one around to share it with, but the birds, so off it comes. I did get to enjoy the sweet flesh myself, one year. Full size apples and pears pull a lot of energy from the tree. Be wary about what you let grow. 

Placing tall plants inside of a second container to prevent blowing over.

You must also consider how great a target they make for critters, who seeking sustenance, wreak havoc trying to get at your fruit. A huge black crow landed on a newly repotted juniper yesterday and I was so glad that it was both tied into the pot, and tied down to the bench. I would have hated to lose the new pot after just a few weeks. 

At the time of this writing, most of my deciduous trees have hardened off their initial growth and are continuing to push. I have some of the aforementioned shohin crabapples in development that have rather tall spikes of growth (3 feet) to thicken up the trunks. Because I am developing them as shohin, the pots are still small, so the wind likes to blow them over. In the past, I took this as a cue to repot the tree into a larger pot. 

The same shohin tree in development under all those long branches.

The problem is that the tree does not have enough foliage mass to take up all of the water that a larger pot will hold and they stay too wet. Since I am growing these trees in terra cotta pots, one of the simplest ways to handle this is to simple place it inside a pot of the next size up, them just a quick wire around to keep everything together. This has proved very effective and set me up perfectly when I prune off the sacrificial spur, being left with a small tree again.

My fertilizing has been a little off this year. I haven’t really started until now, because I wanted to keep my trees more in refinement. However, there are some trees that I really want to make some hard prunes on to redirect growth and initiate a dynamic and profuse response. Those I should have been fertilizing since they first started growing. My mistake in the past has been to make a big prune without fertilizing appropriately. The response I would get from the tree is meager and not consistent. So, while I want to prune really badly, I am going to wait a few weeks and build up their strength. 

What I do have going well for me is that I did fertilize strongly in the fall, which is why everything has pushed so well this spring. I will start by pruning my Japanese maples, the ones that I want to keep in refinement. With those, I have already pinched, and pinched, and pinched  again, as new growth continues to respond to previous pinches, from strong to medium to weak. 

Now that it is hardening off, I am going to take off one leaf of the any pair of leaves, and leave only one internode, unless it is impossibly short (less than a quarter to half inch, depending on tree size). Generally speaking, the tree does nothing in response. We are getting more light to each leaf that is left, so it is doing just fine and it is happy to stay right there for the rest of the year. 

A cherry, pruned, then leaves further defoliated by cutting in half.

However, if we want to elicit a growth response, for a new set of growth, we can go back and cut each remaining leaf in half. Remember, anything that is left is still photosynthesizing. So instead of complete defoliation, you end up with about 75%, which should stimulate the tree to put out new growth. You can apply this principle to most deciduous, and even some broadleaved evergreen trees. However, we usually only do this on larger leaved varieties. See the example of the cherry in the photo.  

We also need to address watering at some point here. This is the most critical time of year for watering. We have a lot of factors that are in continual flux until things sort of settle down to a regular routine in early summer. As the trees push their buds out, they begin to use more water. Sometimes an immense quantity in just one day. All of the new foliage the tree is adding does not have a cuticle formed, so it can lose moisture rapidly. We have to be spot on with water until the foliage hardens off and is able to retain moisture consistently. 

The next challenge we have with water is the darned weather. It rains, then it’s hot, then it rains some more. Trees with a heavy canopy may not receive that much water. I have a large Norway Spruce that sits under the neighbor’s Norway Maple and both the maple and spruce’s own canopies prevent it from receiving much rain water. The neighbors must think that I am crazy, out there watering just one tree when the rain has been going on for hours. 

I find that even after raining all morning, that some trees need water in the afternoon, just because they are growing and transpiring rapidly. And the more developed a tree, the more water it will need. And now, here is where caution needs to step in. Once we start pruning, defoliating, etc…, the amount of water the tree needs with temporarily decrease. Also, as the tree hardens off, its need for water will decrease, so we really need to pay attention every day to its changing requirements. 

Since the leaves on most of our trees are beginning to harden off, this is also a great time to make air-layers and make large, hard cuts to the trunk or branches. Now that trees are back into an energy positive, where the brand-new leaves that they have just invested in can pay back, the tree is in a position to make a positive response to drastic action. In the case of air layers, the tree can use these new leaves to power the generation of new roots. In the case of drastic trunk chops and defoliating, and drastic pruning, the tree has recharged its batteries so that it can channel energy into generating new buds, redirecting growth, or compartmentalizing and healing wounds. 

What do we mean by hardened off? You will see the color of the leaves change and the leaves become firmer. This will start at the base of the branch then continue out to the newest leaves. If we have allowed a shoot to elongate and it has, say, ten leaves on it, we can start to prune back anytime we have four or five leaves at the base that have already hardened off. That’s all we need. 

Be aware when you prune that many species will not generate a bud from the first leaf or two. These basal leaves are usually small and it can be better to just remove them, rather than rely on them. They are often a totally different shape than the regular leaves. But sure then, to end up with at least two good leaves when pruning, whether at the same node with species of opposite leaves, like maples, or two separate nodes in alternating leaved species (Almost everything else but maples).

And finally, I know this is getting long, be ready for the water shift in the summer. As we mentioned, plants will begin to harden off and reduce their water usage. Some plants also shift into semi-dormancy, further reducing their water usage. Another shift will occur any time we perform decandling or defoliation techniques. Each tree is different and will shift at different times. 

Have a great, growing spring. I look forward to seeing all of you and your bonsai results soon.

Scott Elser

Mid-season Pruning

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There will always, always, be a place for a Japanese Maple on my bench. If I could have but one tree, that might be it. It would be a tough battle though, with pines. The varieties and types of maples abound, and there are lots of techniques out there for handling them. The goal for refining any Japanese Maple is to create a light and airy feeling full of grace and suppleness, even when growing a rather masculine or stumpy shohin, the branches are still delicate. These trees naturally grow in the mountains of Japan. We have our own vine maples which grow from the sea to the cascade crest and they will help inform the graceful shape of a maple. I was recently in downtown Lake Oswego and saw perhaps the largest specimen of Japanese Maple that I have ever seen with a trunk diameter probably over 24 inches. It was like unto a towering oak. The reason I mention it is to say that we can find substantial examples of mature trees to observe and learn from. 

I have several varieties of Japanese maples. Without a doubt, my favorite is just the plain, standard species with its delicate and lovely green leaves. I have about a dozen from shohin to medium and large size trees that I am growing from scratch. Other varieties include a Shishigashira (Lion’s Mane) that was begun by Edris Stryker, and a red Deshojo developed by Anne Spencer. Lastly, I have a pair of Okushimos that were started from cuttings. All of these trees have their pluses and minuses, and their own unique growth habits. So that is the subject of this month’s Branch Tips. 

The standard operating procedure for Japanese Maple care when I first started, that was touted in all of the books, was to entirely defoliate the tree in late spring or early summer. The goal was to create a second flush of growth with shorter inter-nodes and smaller leaves. There are several problems with this technique. First of all, if your tree is not strong enough, you might kill it, or at the least lose some branches. Enough said there. Secondly, if you have pencil size trunks and you perform this technique, they will remain pencil size indefinitely. No one ever told me to do it AFTER you get it to the size you want. This is a maintenance technique, not a development one. And thirdly, you risk burning the trunk or branches and doing permanent damage to the tree. So, entire defoliation is a bad idea. I can’t think of a situation where I would recommend it. 

Then along came Boon and offered a big upgrade to this technique. Instead of removing all of the leaves, remove one leaf from every pair across the tree, cutting across the petiole. You can leave both leaves on weak interior shoots. If you have particularly strong leaves, you can cut the outer portions off to reduce the solar surface area. The effect is twofold; first, since you have only removed half of the foliage, the tree is not forced into making new shoots and is happy to live the remainder of the season with what it has, and secondly, it reduces the amount of sugars and starches being produced. This keeps the branches from thickening too much and becoming coarse, preserving the light and airy feeling that we cherish so much in maples. Be  sure to be aware that although all maples have an opposite branching habit, they alternate in orientation. This is to say that one set of buds aligns vertically, the next set horizontally. Ideally, they would all align laterally, so keep this in mind when pruning. If the inter-nodes are really short, then you have some options to choose the orientation that you need. This has become my de facto standard technique for maintaining already developed maples, and many other deciduous trees as well. 

So this technique is all well and good for regular, species maples, but the varieties that I mentioned above present some unique growth habits that require us to alter our technique. The general idea is to create a short inter-node (recalling Dennis Vojtilla’s rule of thumb – about ¾ to 1 inch) and we do this by pruning back to the first set of leaves on a maple. Since they produce opposite pairs of leaves, there is always a fork or bifurcation at any node we prune to. When we come to a species like Shishigashira, which grows very slowly, the nodes may only be 1/8 inch apart, or virtually absent. If we continually cut back to the first node, we get nowhere, and the nodes are too close. Here we do the opposite of all of your bonsai training. We cut the leaves on the inner shoots closest to the trunk and leave the pair of leaves at the point where we want the next set of branching, which is most often the very last pair. This can be tedious work but leads to a ramification that develops more quickly and is more maintainable in the long run. 

Our next guest on the turntable is the Deshojo variety. This is an older cultivar and has beautiful deep coral foliage in the spring as shoots emerge that contrasts beautifully with the mature white bark. There is nothing quite like it. Alas, the foliage the rest of the year causes one to wonder why you are growing it in the first place. It’s sort of a mottled, drab, greenish affair. It also happens to be a fairly weak grower, like many of the special varieties. It often has droopy foliage and only a few elongating shoots. For this specimen, I still remove every other leaf, but I leave more leaves in the weaker areas, like the lower branches and interior shoots. I wire up the weak shoots so that they can get more light and gain enough strength to hold themselves up and I make sure to not remove any leaves, except to shorten the overall length. This process has really improved the overall health and strength of the tree. 

I can detect no graft union in either the Deshojo, or Shishi but they are often propagated by this method. Most special varieties do not propagate true from seed, and they often have a weaker growth habit necessitating the need for the graft onto the stronger, species stock. An exceptions to the rule are the two Okushimo trees that I have been growing, like forever. Both were from a set of about ten, two-year old rooted cuttings by Wright’s Nursery, which is no longer in existence. Two each of five species. I won them in a raffle at my very first convention, in 1990, before I was even a member of BSOP. Maples are difficult to root from cuttings, so these are very much an anomaly. That is borne out by the fact that the other eight trees died within two years. That may also reflect in my lack of skill, but I did keep everything else alive. These two grow really slowly. I had them in the ground for several years and they barely grew. I gave one to my grandfather and it passed back to me when he died. They have the strangest leaves, which are not to everyone’s taste. But I like ‘em. Since they were grown from cuttings, the roots emerged on just one side, so I have in-arch grafted species roots to fill in the bases. In all that time, these trees are still only an inch and half in diameter. They are growing stronger than ever though. They really want to send all the energy to just a few shoots, so I use pruning to redirect that strength more evenly. 

Lastly, I would like to mention our own native Vine Maple. I love these guys too. These are the closest relatives to Japanese Maples outside of Japan. Try the same techniques, but a few words of caution. They prefer dappled sunlight in the summer. They naturally grow in the margins of the forest to deeper shade. I keep mine in full sun in the spring until sometime in June, then it’s under cover. These trees are coarser than their Japanese cousins, so they tend to get very thick and long inter-nodes if allowed to rage on. 

When I prune in late spring to early summer, I sometimes cut off entire nodes because they have gotten too long or heavy. I take off every other leaf on the rest. During this pruning I make sure to space out the remaining leaves such that there is equal distribution to light. This requires a little thinking ahead and watching the area as much as an individual shoot. There is also a large discrepancy in leaf size, so I often resort to cutting off the exterior leaf mass to make them more equal. 

I even showed this tree in the fall after cutting the leaves down to size but matching the overall leaf shape with five points. No one noticed! In situations where the whole shoot has been pruned, the tree responds with new shoots. In the long distant past when I entirely defoliated the vine maples, they just sat there the rest of the season and waited until the next spring to grow again. Be aware of that thought but temper it with the fact that I did not fertilize much and they were very small trees growing on a rock – not many resources. Now that the tree is in refinement, that drastic technique is not needed. 

So jump in and prune your maples to direct development and protect them a bit after you do so. Stay cool.  

Elongating species Japanese Maple in development. Let it grow!

Okushimo. These leaves are certainly unique

Deshojo Maple. Note the red leaves, just like spring growth, that emerged after flush pruning.

Shishigashira before pruning. Note the extremely short internodes – really isn’t one.

Shishi after pruning. We cut the leaves nearest the trunk. Since we have another branch nearby, we eliminate the weak shoot. For scale, see my fingers!

Vine Maple. The overall size of the larger leaf has been reduced to match the smaller leaf.

Learning from the Landscape

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Last month I took advantage of the fact that there is a small window to prune Japanese Maples, just as their leaves are dropping, so that they won’t bleed. I pruned a few of the bonsai on my benches, but my main targets were the trees in my landscape. When moved to a new house, we inherited a ginormous weeping Japanese maple, front and center in the most prominent area of our yard. It’s probably 15-20 feet across. I was able to cut it back a bit last year, mostly to keep it off the driveway. 

But this was the year that I wanted to get in and do some real structural work. Along the way, I pruned another large maple in the yard, as well as my mother in law’s maple, and another friend’s large specimen. For some reason, after twenty years of pruning this type of tree, things really started to sink in, so I thought I would share some new and confirmed insights. I can now prune with confidence at a fairly feverish pace and the decisions fall easily right into place.

First of all, the most important aspect here is the non-bleeding time of year. I find that a good time is when there are just a few fresh leaves on the tree, but it’s lost all the others. Take a snip and wait just a few seconds. If it bleeds, wait another week. 

As the leaves start to abscise from the tree, the sap is also slowing down to a halt. Otherwise it would be pushing sap out of the points that just lost leaves. The tree then begins to heal over and seal up these areas and the sap re-pressurizes a few weeks later. So, if you prune in December, you get bleeding all over again. It can extremely weaken the tree if you let it bleed profusely. In the spring, it provides entrance for fungi. You can prune safely after the leaves have hardened in the spring, around April or May, but it is very hard to see the overall structure.

Next, and just as important, is the fact that although maples have an opposing leaf structure, those opposing pairs rotate 90 degrees every other pair, making horizontal or vertical oriented buds. I have not really paid all that much attention to this feature in the past, but things really started to click when I did. I now understood why some branches seemed to just reach for the sky and others spread out. It was just they way they started on the main branch.  

Look at the photos. You can see in the first one the orientation of the buds, how they alternate along the branch. In photo two you see an unpruned branch and how the structure is developing into vertical branches and horizontal branches. I no longer prune back to the first node on a branch, but to the one that is oriented in the direction I want. In bonsai, I always prune to the horizontal branches, unless I have a need to create depth. On these weeping landscape trees, I am going for something a little different.  

Here is the interesting part. Remember those vertically aligned shoots? As I went to prune this year, I noticed that 95% of the dead branches were those that were the bottom half of a pair, the ones facing down. It didn’t matter if the branch was one year or five years old, those were the ones that were getting weak and dying on their own. The tree was educating me and telling me how it likes to grow. It was doing it’s own pruning.

Look at photo two and you will see that the downward facing buds have disappeared on their own. So taking that cue, I began cleaning out those downward branches anywhere I could. It’s a quick way to shorten branches or thin things out. After several seasons and/or several cuts you begin to develop an undulating structure that creates great movement and allows you make foliage pads on a weeping tree.  

Look at photo three and you can see the effect of this style of pruning. I have been pruning like this for awhile, but now I finally understand that alternating nature, how to use it effectively, and what to expect next year.  

So my suggestion is to grab your saw and pruners and dive into one of these trees and see what you can learn. There are so many more branches to work with than on bonsai, so much more practice. And if you make a mistake, it’s easy to grow more branches. It’s not so critical as your prized bonsai and you can relax a bit. Take that snip and see if you are still in the window for pruning.