Japanese Maple - Aesthetic Pruning 

Q: There are several Japanese maples in our landscape that have never been pruned.  We are interested in hiring a professional for the work, but are confused with what the difference is between "pruning" and "aesthetic pruning"  and which is best for our trees.  

A: You are wise in wanting your trees professionally trimmed.  Within the pruning profession, there are many different approaches to pruning a Japanese maple.  Unfortunately, not all result in a healthier appealing tree after the work has been completed.  In some cases, the tree becomes too stressed and sadly goes into decline.  

Here briefly is the difference between "pruning" and "aesthetic pruning".  The term "pruning" generally applies to the process that is based solely on horticultural science and practices.  The results are healthy for the tree, but usually lacking in aesthetic appeal.  However, "aesthetic pruning" takes the horticultural science and combines it with the creative interpretation of the essence of a Japanese maple.  This will bring out the beauty of the tree, while maintaining a harmonious relationship in the garden.  

Either of these approaches when properly executed, will achieve the desired goal and encourage a healthy response by the tree.  The decision therefore should be based on what affect you are seeking for your tree and garden space.  When selecting a possible professional for the pruning work, be sure to insist on someone that is ISA Certified (International Society of Arboriculture) or APA Certified (Aethetic Pruners Association) or both.  

 

Japanese Maple - Pruning Older Trees 

Q: We just recently purchased a home with a very old Japanese Maple tree.  It is supposedly over fifty years old and in need of some pruning.  What recommendations do you have for approaching this task?  

A: This is an excellent question and one that should be asked by more homeowners.  Unfortunately, to many beautiful mature Japanese maples have been ruined from very aggresive pruning practices by individuals claiming to be experts.  

There are many things to consider before you actually begin pruning your tree, however, only a few will be discussed here.  First, the scope and magnitude of the pruning is always based on the trees health and age.  If the tree is stressed or unhealthy, little or no pruning should be done.  The trees age is extremely important when determining how much can be safely removed and the size of the cuts that can be made.  Younger trees are normally quite vigorous and can tolerate more extensive pruning with larger cuts.  Conversely, an older tree is no longer as vigorous and any pruning should be carefully evaluated before cautiously undertaken. 

Second, the history of the tree should be known.  This information is vitally important, especially when determining extent of pruning that can be safely performed on older trees. Environmental factors, such as weather patterns over several years and if there were any aberrations that may have had a negative impact on the tree.  

If the intent of the desired pruning is to correct major structual issues, that window of opportunity has passed.  These imperfections are now part of the trees character and cannot be corrected at this time.  They should have been addressed earlier, when the tree was much younger and able to respond favorably to larger cuts.  Any pruning cuts made now should be limited to the size of your thumb and focused mainly on the removal of all dead and diseased wood.  The bottom line - be very careful with your pruning objectives on older Japanese maples, as they may have unintended consequences that greatly impact the trees longevity.  

An excellent source for additional information on this subject is Brooklyn Botanic Garden's Gude; The Tree Care Primer.  The chapters "Early Mature and Mature Trees" and "Ancient Trees" are very informative and useful. 

 

Japanese Maple - Early Training 

Q: A few weeks ago I purchased a young Japanese maple. The tree was purchased because it appeared very healthy and was very full. How soon should I begin training it and how frequently should pruning be done?  

A: This is an excellent question and I'm pleased that you are interested in getting your new tree off to a great start. Since your Japanese maple was purchased at a nursery, the tree is old enough to be safely pruned to begin development of a structually sound and balanced tree. To start the process, a thorough evaluation of your tree must be completed. Important items to take note of are: trees health and vigor, dead or diseased wood, rubbing or crossing branches, number and spacing of vertical branching, balance of energy and growth, density of foliage and canopy, severity of any tip pruning or topping, and basal root system. Upon completion, a comprehensive and realistic pruning plan can be initiated. It is always best to proceed slowly and judiciously, realizing that some imperfections cannot and should not be corrected in one pruning session, but rather over an extended period of time. There also may be some that will never be able to be corrected and will simply be appreciated for the unique charcter they impart on the tree. 

Moving forward, your Japanese maple should be evaluated at least once or twice each year, with any identified pruning being performed. By adhering to this proven approach, you will be able to watch your new tree over time, become an amazing specimen that will reward you with many years of viewing pleasure. The important point to remember, is that significant corrective or styling cuts should begin when your tree is young. The removed material will be much smaller in diameter at this point than if attempted later, when it will be larger. This translates to small pruning wounds that heal quicker, which is the primary objective, versus big ones that will take considerably longer. 

 

Japanese Maple - Winter Pruning 

Q: I have a Japanese maple that needs some pruning and have tried researching as to when the pruning should be performed. Many different sources say that winter is the best time to prune a Japanese maple because there are no leaves and it is easy to see the trees structure and branching. Is this in fact true and if not, when is the best time to prune my tree? 

A: This is a great question that has many different answers depending on whom you ask. Though it is true that a trees structure and branching are very evident during the winter months, this alone should not dictate the timing of your pruning. Despite the tree being dormant, the sap is usually flowing in winter, which means that any pruning cut made at this time will result in the tree bleeding. Unlike a human, the tree will not die if the bleeding is not stopped. It does, however, stress the tree and therefore any winter pruning of live wood should be avoided. One pruning task that can safely be performed in winter is the removal of all dead wood, which is unattractive and very obvious.  

For general maintenance pruning of your Japanese maple, the months of May and June are best. There are two good reasons for this. One, with the trees recources at their highest level during these months, the physiology supports the scientific part of the equation. Two, the aesthetic part is supported in the fact that the tree is completely leafed out and it is much easier to determine the full effect of your pruning cuts as they are made. If a regular pruning regimen is followed, there should never be the need for winter pruning. 

 

Japanese Maple - Transplanting

Q: We have a sparse, six-foot tall Japanese maple tree that is only a foot or so from the side of our house.  Can we move it?  When would be the best time?

A: You are wise to consider moving your tree from its current location as it would not have a happy life.  The tree can be moved, with January and February being the ideal months to perform this task.  Prior to digging up the tree, its new location should be determined and prepped.  Using a shovel, dig around the tree about a foot and a half from the trunk.  Remove and transport your Japanese maple to the desired location.  Plant the tree with slightly amended soil, ensuring the base is a few inches above grade.  A good two inches of mulch should be spread over the planting area.  This helps retain moisture, prevent soil erosion and regulate soil temperature.  Water in with a gallon or two of water.  Regularly monitor the tree to detect any complications that may arise as a result of the move.  If you listen closely, you will hear your Japanese maple say - Thank You. 

 

Japanese Maple – Late Winter Damage

Q: Several of my Japanese maples have appeared to have survived the cold snap, but then suddenly, the leaves wilt, then fall off. Do you know of any reasons for this sickness? Can I expect them to survive?

A: Unexpected overnight freezes in early spring (especially after long periods of warm weather), can have significant negative effects on Japanese maples. For some, the damage is very minimal, while for others, the damage can be more extreme. In a worst case scenario, the damage is too much and the tree dies. Usually there is only leaf dieback and occasionally some stem or branch dieback.

Healthy trees will push out a second set of leaves to replace those that were damaged. In so doing, the trees draw from their energy reserves. This in turn adds additional stress to the trees. To help lessen the stress, a light fertilization is recommended (preferably a fertilizer having an NPK of 2-3-4). A soil drench with “SUPERthrive” appropriately mixed in would also be highly beneficial. Depending on the severity of the freeze damage, pruning should be limited or put off entirely until the following year.

Gardeners should also look at protecting the crown of their trees, especially the dissectum (laceleaf) Japanese maple varieties. Without a good leaf canopy to protect the upper trunk from the harsh summer sun, the trunk will be susceptible to sunburn damage, which in severe cases results in dieback of the crown, leading to more exposure and more damage. Exposed crowns should be protected with shade cloth placed over them to help the trees through the hot summer months. 

 

Japanese Maple - Variegation 

Q: We have a Japanese maple with variegated leaves. Over several years we have noticed that some of the foliage has lost the wonderful variegation the tree is known for. What is causing this and is there anything we can do to reverse the loss or at least keep it from continuing?  

A: There are a number of possible explanations for the lost variegation in your Japanese maple. First, look closely at the leaves and verify they are not reverting (usually a distinct solid green palmate leaf occuring sporadically throughout the canopy rather than the entire tree). If so, the undesirable leaves should be removed. The end result if left uncorrected, will be a tree with very little or no variegation. Another cause of loss of variegated leaf charcteristics is purely genetic, in that with some variegated varieties, the older the tree becomes, the less likely it will retain the desired variegation in the leaves. The tree is said to be "growing out of" its variegation. A good example of this is Acer palmatum 'Oridono nishiki'. This cause unfortunately is not correctable. 

Other probable causes can be grouped under cultural influences. These include such things as over feeding and watering, resulting in vigorous radical growth in which the desired leaf character may be absent. Also included, is extreme soil pH or lack of one of the minor elements necessary for total nutrition. Another, is a disparity in the essential macro elements, in particular, excessive nitrogen with the absence of adequate phosphate and potash that can result in leaf variegation being masked or subdued. A simple soil test and analysis will provide the necessary information to confirm or eliminate any of these possibilities. Lastly, it is also feasible that climatic conditions, such as the south's high heat and humidity can adversely affect some variegated forms of Japanese maples.  

 

Japanese Maple - Leaf Reversion 

Q: One of our Japanese maple trees has beautiful thread-like leaves. The other day we noticed that some of the foliage has changed to the typical palmatum leaf. Should we be concerned and is there something we need to do?  

A: Fortunately, you have found your problem early. Reversion sadly is quite common with certain cultivars of Japanese maples and may be due in part to weak scion wood selection when grafting. This uncharacteristic growth, if left unchecked, will eventually dominate the tree and the desired leaf may only be a memory. It is always best to remove this growth immediately upon seeing it, if suspect. Reversion in Japanese maples is typically limited to the strap-leaf linearilobum cultivars (A.p.'Beni otake' in particular) and some of the variegated cultivars (as discussed in the previous question). If the observed reversion is occurring on a relatively young tree, it may be that it hasn't developed the anticipated leaf trait yet as suggested by J.D. Vertrees. In this case, a wait and see approach (one or two growing seasons) is best. 

 

Japanese Maple –Leaf Characteristics in Mature Trees  

Q: Several years ago, I purchased a Japanese maple that was known for its intense spring color. For some time, I've been able to enjoy the fire-engine red foliage when the tree has flushed out in spring. Last year and again this year the leaf color has become less spectacular. What's happening? Is there something I can do to revitalize the desired trait before it is completely gone?  

A: Age is an interesting variable when it comes to changes manifested in some Japanese maples that had been cultivated with specific characteristics unique to a certain variety. The influence of age is readily seen in the maturation of the bark and to a lesser extent in the leaves. I have sadly watched the spring color of my A.p.'Shin deshojo' gradually shift away from those prized scarlet red leaves, to a muted orange or pink. This natural process is considered to demonstrate the trees ability to "grow out of" a particular trait and is usually not correctable. As mentioned in an earlier response, this tendency can also be observed in some Japanese maples with variegation in their leaves. 

There is a possible solution, but it comes at a steep price. If the aesthetics of the tree are of little concern, then severely pruning the tree as recommended by Peter Gregory in the 4th edition of Japanese Maples, can be attempted. This rejuvenates and encourages fresher growth, that in some cases once again show the desired trait in the leaf.  

 

Japanese Maple –Vigorous Green Dissimilar Growth

Q: My Japanese maple started growing a totally different tree. In looking closer, I can see that below the graft, a uniquely different tree is developing. Should I cut off this undesirable growth?

A: Yes – remove the green growth. Undoubtedly you have a red-leafed Japanese maple grafted onto a green-leafed rootstock. This rootstock produced a sucker shoot, which if not removed, will eventually take over the tree. You will then have a totally different Japanese maple; one not worth the price of the original tree. Keep an eye out for a possible recurrence in the future. There usually is no way to prevent it from happening again, but is very simple to correct. Lastly, sometimes tree stress can result in sucker shoots forming. To remove this cause from the equation, simply provide the basic needs of your tree and the outcome will be a healthy and happy Japanese maple.

 

Japanese Maple – Coloration

Q: My Japanese maple gets morning sun and afternoon shade, yet the red foliage is turning more green now. Is there something I can do for redder foliage?

A: There is not much you can do. Two key factors play an important role in the coloring of a Japanese maples leaves; sun and genetics. Some red leafed trees naturally change from red to a greenish hue in summer. Though most Japanese maples greatly appreciate afternoon shade, typical red cultivars without the benefit of full sunlight for part of the day will not retain the red color into late summer. In general, the color of most red varieties is strongly enhanced in full sun, and in some forms, leaf color readily reverts to green in too much shade.