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.
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.
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: condition of basal root system, trees health and vigor, dead or diseased wood, rubbing or crossing branches, number and spacing of vertical branches, balance of energy and growth, density of foliage and canopy, severity of any tip pruning or topping. 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.
Q: I have a few Japanese maples in my garden that I would like to prune. What books would you recommend that I read to help me better understand what should and shouldn't be done when taking on this daunting task?
A: Fortunately, there are several good books that will help you make the correct choices when you are ready to prune your Japanese maples. It would be great if the information you seek could be found in just one book. Sadly, that is not the case. I learned many years ago though, that even if after reading an entire book, you are only able to use one idea, principle or technique, that would be one thing you would not have discovered had the book not been read.
Starting off, it is very important to understand how your Japanese maples grow and function. This will provide you with the essential science behind your pruning and the responses the trees make. A must read is Brooklyn Botanic Garden's Guide; The Tree Care Primer. Follow that with The Art of Natural Bonsai; Replicating Nature's Beauty written by David Joyce. Another good book is Cass Turnbull's Guide to Pruning. An entertaining, as well as, educational book is Cutting Back; My Apprenticeship in the Gardens of Kyoto penned by a good friend and accomplished aesthetic pruner, Leslie Buck. Additional books of interest can be found in the Resources section of this website.
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, under normal circumstances, never be the need for winter pruning.
Learning How to Prune
Q: I have several wonderful Japanese maples that have never been pruned. I'm an avid gardener interested in learning how to properly trim these trees and would like to know if there are any classes that are offered. Also, what other resources can you recommend?
A: It is admirable of you to want to learn how to properly, emphasis on properly, prune your Japanese maples. The journey you wish to take, can be very challenging at times, but the rewards, so worth it for both you and your trees. Depending on where you live will determine your access to pruning classes. The aesthetic pruning program taught at Merritt College in Oakland, CA is highly recommended. There are pruning classes offered periodically at many of the botanical gardens and a few local nurseries. Should you look to YouTube for help in your quest, just be careful with what is presented as gospel. Unfortunately, in many cases the information is actually false and misleading.
Books will be another great source, though there is not just one that will provide everything that is needed to fully grasp the craft of pruning. To begin, it is extremely important to be knowledgeable on how your Japanese maples grow and function. This allows you to fully understand the science behind your pruning and the responses the trees make. A must read is Brooklyn Botanic Garden's Guide; The Tree Care Primer. Next, you need to immerse yourself into the aesthetic philosophy and techniques. An excellent book to start with would be The Art of Natural Bonsai; Replicating Nature's Beauty by David Joyce. When you are ready to work on your trees, it is important to be patient and observant, remembering that your pruning skill and confidence will come with practice.
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 relocating your tree from its current location, as it will not have a happy life. The tree can be moved, with January and February being the ideal months to perform this task. When preparing your tree for moving, ignore the common misconception that reducing the trees mass by removing or shortening some of its branches helps aid in the recovery process. The exact opposite is true. By removing this woody material, you are actually taking away some of the trees stored energy that will be vitally important in its recovery. More importantly, should the transplanting occur after the tree has leafed out, the reduced leaf area will significantly limit the trees ability to adequately hydrate when misting the foliage. Remember, the trees primary means of absorbing moisture from the soil has been considerably minimized because many of the main roots have been severed. Having an alternative means will prove very beneficial.
Prior to digging up the tree, its new location should be determined and prepped. Then, using a shovel, dig around the tree about 18-24 inches from the trunk. Some larger roots unfortunately will be cut. Remove and transport your Japanese maple to the desired location. Plant the tree with slightly amended soil (river sand, soil conditioner and PermaTill mixed with existing soil), ensuring the trunk/ root flare is a few inches above grade. A good two inches of mulch should be spread over the planting area. This will help retain moisture, prevent soil erosion and regulate soil temperature. Finally, water in with a gallon or two mixed with SUPERthrive. Be extremely careful not to overwater the root zone, as the risk of suffocating the roots is high and will not end well for the tree. If the tree is moved after it has leafed out, as mentioned above, the trees foilage will need to be initially misted daily or every other day. 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.
Pruning After Transplanting
Q: We just recently moved one of our Japanese maples to a better spot in our garden. How long should we wait before doing any pruning on the tree?
A: Time, patience and restraint are key components to the healthy recovery of a Japanese maple after being transplanted. Some pruning could have been done prior to moving the tree, but not now. In the first year the focus should be all about recovery, so it is very important to provide the tree with the essentials for a healthy recovery, which are sun and water. No pruning should be attempted during this period. In the second year the tree has re-established itself enough to safely perform minimal pruning. If after the third year the tree has fully recovered, then a regular pruning regimen can be safely resumed. It is important to note that at any point in this process dead or diseased wood can and should be removed. Any major pruning attempted before your Japanese maple has fully recovered will add unnecessary stress to the tree and most likely will have undesirable consequences. Patience is key.
Q: I have a wonderful Japanese maple that is the focal point of our front yard. The other day I noticed a root that appears to be encircling the main trunk. Will this likely kill my tree? I'm afraid to remove it, as I might cause more harm than good. What should I do?
A: Fortunately, this is a correctable problem, but if left alone, there is a high probability that partial dieback will occur. In very extreme situations a girdling root can result in the ultimate decline and death of a tree. If the offending root is not of significant size, it may be successfully removed at any time. However, if the root is substantial, the preferred time to correct this problem is in winter while the tree is still dormant. Do not attempt to remove the girdling root once the leaf buds begin to open.
The size and position of the root to be rremoved will determine the type of tools required for the operation. Ideally, if the root is small and accessible, then simply remove it with a pair of pruning shears or small hand saw. If the root is larger and imbedded in the trunk, then it is best to use a good quality wood chisel. Once the problem root has been extracted, it is not necessary to apply a wound dressing to the affected area. Should you not feel confortable performing this task, please consult ONLY with a certified arborist or a certified aesthetic pruner.
Q: We have a beautiful Japanese maple that has been doing well since being planted four years ago. Now there are a few branches and stems that have died suddenly for no apparent reason. The tree appears healthy with no visible discoloration in the wood or leaves. What do you think is causing this and is there anything we can do to help the tree?
A: What you describe is something that unfortunately still occurs yet is easily preventable. It is caused by an untrained work force and poor installation practices. All indications are that something is wrong in the roots or near the base of the tree. My suggestion is to remove any pinestraw, mulch or soil until the root trunk flare is exposed. I suspect that upon doing this you will most likely find a piece of nylon strapping material used to secure the burlap around the trees rootball. Both of these materials should have been removed during planting. If I’m correct, yours was not and after a few years the trees trunk became larger and the strapping material did not expand to allow for this increase in caliper. The result is that the strap is now girdling the tree, blocking the flow of vital resources necessary to the trees health and growth. Hopefully you have caught it early enough that the strap is accessible and can be easily cut and removed. (In extreme situations where the strap has become encapsulated in the trees wood, it would be wise to consider cutting the tree down and starting with a new tree. In this scenario the girdled area will be a constant weak point leaving the tree vulnerable when put under heavy load forces from either major wind, rain or snow events). Upon finishing, it is strongly recommended that the root trunk flare remain exposed with no mulch or soil put back to replace what was removed earlier. Your Japanese maple can now breathe a sigh of relief and grow to be the healthy beautiful tree you envisioned.
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.
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.
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.
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.
Dissimilar Vigorous Green 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.
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.
Early Fall Color
Q: We just recently planted a new Japanese maple. It has been doing great for several weeks, but has now started changing to its fall color. It is only July. Should we be concerned?
A: You should not be overly concerned as the condition most likely was caused by an improper watering regimen. It is very important to remember that Japanese maples require a consistent amount of daily moisture, especially during the hot dry months of summer. When this requirement is not properly achieved from a lack of water, the tree becomes stressed and shows this by exhibiting pre-mature fall color. (In extreme cases the leaves dry up and fall off). Once the fall coloration occurs it won’t matter how much water you put on your tree, the color will remain the same until the leaves drop later in the year.
What is meant by consistent amounts of daily moisture you ask? The amount of moisture required by a Japanese maple is dependent upon its landscape environment. If in an arid location the tree will adapt to survive with traces of rain over a period of several weeks. If the tree has successfully adapted to this minimal watering regimen, do not on a whim decide to intervene and provide it with too much water as this will stress the tree. The ideal conditions for a Japanese maple to flourish are good soil and an inch or less of rain per week (hopefully delivered over a couple of days rather than all at once). Your tree however is newly planted and requires more than a weekly dowsing of rain. Until the roots are able to expand out of the original planting rootball, it should be watered every three to four days with about a half-gallon or gallon of water depending on tree size.
Discolored Splotches on Leaves
Q: We just recently had our home pressure washed to remove all the spring pollen. Shortly thereafter a Japanese maple near the house had discolored splotches on many of its leaves. Could this have been caused by the pressure washing? Is there anything we can do to prevent this from happening the next time we have the exterior of our home cleaned?
A: Yes, you are correct in identifying the pressure washing as the cause of the leaf splotches on your Japanese maple. Most contractors add some bleach (the exact amount varies between contractors) to the water used to pressure wash your house. As you have learned, any concentration of bleach on the leaves will burn them. If proper steps are not taken throughout the process, there will be damaged leaves.
The next time your home is to be pressure washed, talk with the contractor beforehand about the preventative measures you want done prior to and during the cleaning process. First, wet the foliage of the Japanese maple with plain water before commencing pressure washing. Placing protective plastic over the tree is optional though not necessary and usually not that effective. Second, during the pressure washing process the tree’s foliage should be washed down once the area on the house around it is cleaned. Third, after the pressure washing is totally completed, a thorough fresh water washdown must be done to remove any residual bleach from the leaves. Adhering to these simple steps in the future will ensure there are no repeat incidents of damaged leaves.
Q: A severe weather system came through recently that produced a brief hail storm. Despite it not lasting long, the evidence after it passed was very apparent. What can I do to help my tree heal?
A: The wrath of Mother Nature at times can be quite devastating. Though there may have been significant damage, there fortunately is very little that needs to be done to help your Japanese maple to recover. The broken stems and branches should be removed by cutting back to an advantageous growth point that will produce the desired response. The damaged bark tissue along the branches will callus over on its own without intervening. In time the tree will recover, and the once evident signs of the storm will no longer be visible.
Premature Dead Fall Leaves
Q: This fall was turning out to be amazing with spectacular fall color. Then one morning last week all the leaves on my Japanese maple appeared to have died and are all dried up. What happened and is there anyway this can be prevented in the future?
A: Sadly, there are times when mother nature does not work in your favor. Most likely what happened was a blast of freezing weather came through overnight and decimated the leaves. This severe temperature dip froze the leaves and shut down the leaf’s normal fall mechanisms resulting in the premature dead brown leaves.
If this tree is a fairly sizable landscape tree, there is not much you can do except hope that there is not another weather anomaly next year. You could go to an Army surplus store to see if they might have a used parachute to cover the tree though not sure if that would be cost effective or how much protection it would actually provide. For a smaller Japanese maple an old sheet can be used to cover and protect it. Be sure to remove the covering in the morning so the leaves can be fully exposed to the sun, which will allow them to continue with their fall progression. If your tree happens to be in a container, simply move it into the garage or basement overnight.
Q: I have always admired the wonderful fall color of our Japanese maples. Is it possible to capture and preserve the amazing colors by drying the leaves? How would one go about doing this? Is it also possible to dry some of the new spring foliage?
A: This is an excellent question and not sure why more people do not try it. The process is quite easy and fun. My first attempts at drying leaves started many years ago when I wanted to add something to my client’s Christmas cards that was unique and special. It is a tradition that continues to this day and I have been told that it is the one thing that is always anticipated come November.
There are a few simple things to remember when pressing leaves. First, is to always start with fresh quality leaves, void of any defects. Second, is pat off the leaves to remove any moisture should it have rained before harvesting them. Third, is to frequently change out the paper initially to prevent mold or any discolorations caused by direct contact with damp paper. Fourth, is not to stop the drying process prematurely thinking the leaves are completely dried only to discover they were not and are now curled up deformed facsimiles of leaves. The complete process should take about two days.
The materials needed for this process are good leaves, several pieces of paper (I have a nice stack of recycled printer paper that is reused each year), and something with a nice flat surface that has weight such as books. There are commercially available leaf presses that do a fine job should you decide to use them. To begin, I simply lay out two pieces of paper on a good-sized book (I’ve found that it is best to use two pieces of paper between each layer of leaves for the first 24 hours due to the initial moisture content of the leaves). Then the harvested leaves are carefully placed on the paper ensuring there is sufficient space between each leaf. (Depending on the size of the leaves to be pressed, it is recommended to only place five or six leaves on each layer, fewer for larger leaves). Next, place two more pieces of paper over the leaves making sure that they remain flat and not bent. Continue adding leaves and paper until all the leaves have been used. Now carefully place several large heavy books on top to press the leaves. After four or five hours the books can be removed, and the pieces of paper are replaced with fresh new paper. When exchanging the paper, be sure to examine the leaves to verify they are drying properly. The books are again placed on the leaves for another four or five hours. This process is continued for the first 24 hours after which the procedure is modified. At this point most of the moisture in the leaves has been drawn out, so for the next 24 hours the length of time between paper replacement can be extended to six or eight hours and only one sheet of paper can be used. The steps in the process, however, stay the same. During this phase of the process, you will notice unfortunately that the vibrant colors in some of the leaves are now more muted but still very nice. Once this phase is complete, the leaves are ready for use. Place inside a greeting, thank you or sympathy card. They can also be effectively used to make unique amazing personalized cards.
With regard to pressing Japanese maples new spring leaves which can display colors that in some of the cultivars are more impressive than their fall color, pressing is a possibility. I unfortunately have found that these leaves are rather difficult to dry because the leaf tissue is thinner and more easily damaged. They lack the density and rigidity of fall leaves because they have not had a complete growing season to develop. You should also try to dry some summer leaves as the variegated types are quite pronounced at this time.