Why is My Japanese Maple Dying? (How to Solve it)

One of my favorite trees for small gardens is the Japanese maple due to its firey red leaves causing a commotion in the corner of any garden!

Japanese maples have a special place in my heart as I used to grow and shape them for sale in a garden center. During my time growing Japanese maples, I encountered most of the common problems, and I’ve become a specialist at diagnosing and reviving them before any problems get out of hand.

I’ve revived lots of Japanese maple trees for many years and in this article, I’ll share with you my first-hand experience, tips, and techniques to help you save your Japanese maple with a step-by-step guide.

Let’s cut to the chase, shall we?

A dying Japanese maple is often caused by fungal disease pathogens that thrive in overly damp soils. Saturated soil promotes root rot, which causes dying Japanese maples. Too much wind, sun, and not enough water also cause maples to have brown, wilted leaves and a dying appearance.

From my research, the most common fungal pathogens that affect Japanese maples are Verticillium wilt and Phytophthora (root rot), which are problems in boggy soil and often kill the tree.

However, I see scorched or brown leaves can also be caused by too much wind, intense sun, or a lack of water, which can be solved with a few adjustments to the Maples’ conditions.

Keep reading about why your Japanese maples are dying and how to solve the problem.

What’s the secret to Reviving Dying Japanese Maples?

I was asked this by a reader not long ago, and if I were to distill it down to one secret, it would be to consider how Japanese maples grow in their native environment and try to replicate these conditions in your garden.

Fortunately, you don’t need a Japanese climate to do this! Instead, we need to plant our trees in well-draining soil, in partial sun, and shelter our trees from excess wind…

Japanese Maple Dying of Verticillium Wilt Or Root Rot

So, how do Japanese maples grow in the wild? Japanese maples are adapted to growing in soils that are rich in organic matter (compost, leaf mold, etc.) with a friable structure that absorbs moisture yet allows excess water to drain away quickly. So this is how we need to grow them.

I discovered that Japanese maples can succumb to the disease Verticillium wilt or Phytophthora root rot in soils that are too damp because of:

• The soil drains too slowly (heavy clay soil)
• Boggy areas of the garden
• Overwatering
• Growing in pots without drainage holes in the base.

All of these factors can cause the soil to be saturated so that the roots are in boggy ground as opposed to well-draining soil.

To be honest, most of the time when I’ve seen this happen it is because the tree is planted in boggy low lying soil, and only sometimes do I see a tree planted in a pot without drainage, but its important to consider.

Verticillium pathogens that affect Japanese maple thrive in damp soils, and unfortunately, I’ve found that Japanese maples are relatively susceptible to fungal pathogens caused by damp soil, with even established maple trees suddenly displaying symptoms and dying.

The symptoms that you need to look out for of Verticillium are leaves that are turning brown, grey, yellowing, and curling inwards or certain branches that drop all their leaves.

I should just clarify that brown Japanese maple leaves can also indicate drought stress, not enough water, and too much fertilizer, but if your maple is in waterlogged soil, then in my experience, Verticillium wilt or root rot is almost certainly the problem.

Unfortunately, it is very difficult to treat a maple with wilt, and I’ve learned from my attempts at revival that prevention is much better than cure.

To effectively prevent Verticillium or any other soil pathogens that can affect maple, I’ve found that the most important step is to ensure the soil is well draining and the planting areas have been amended with lots of compost or leaf mold to provide the optimal well-draining soil structure.

I personally experimented a bit with the Japanese maples I was growing at the garden center and found that adding grit to the potting mix (these were potted Japanese maples, but the same principle applies to those planted in the ground) was a great way to increase drainage and ever since I started using grit I haven’t had any trees suffer with wilt (as the soil is much better drying).

The technical explanation is that adding grit or horticultural sand to the planting area can also help to ensure the soil is porous, which increases oxygen levels in the soil for root respiration and a healthy soil ecology and increases drainage, so in my opinion, it is well worth it if you are planting up your Japanese maple.

Top Tip: I found that using 1/3 grit to 2/3’s compost or leaf mold was the best potting mix to prevent wilt in Japanese maples.

I should also highlight that Japanese maples do not grow very well in heavy clay or boggy areas of your garden, and they are likely to die within a few years due to root rot or other fungal soil pathogens that thrive in damp soils.

In these gardens with heavy clay or just naturally boggy soil due to low-lying areas, I always advise my customers to plant maples in pots or containers as you can easily provide the optimal soil profile as amending unfavorable clay soil to suit Japanese maple can be very difficult as I can tell you from experience!

If the plant has Verticillium I recommend digging it up and burning it or discarding it (to kill the pathogen) and treating the soil with a fungicide (available from garden centers) as the disease can live in the soil and infect new plants if left untreated.

Read this article for a full list of Japanese maple diseases.

Too Much Wind, Sun, and Not Enough Water Causes Dying Japanese Maples

So, we need to remember that Japanese maples are shrubs and small trees that are adapted to grow in the protection of the canopy of forests. If the maple is in an open exposed, particularly windy area then this can increase water loss from the leaves.

We always have to consider how our plants grow in the wild when we are finding a location for them in our gardens…Forest canopies also protect the Japanese maple from intense sunlight, which can further dehydrate leaves, giving them a scorched appearance.

So how do we repiclate this in our gardens? Japanese maples should be grown in a sheltered location, protected from wind, with partial sunlight and consistently moist soil.

If the leaves of your Japanese maple or looking scorched with a perhaps slightly brown appearance at the edge then it is important to…

• Provide a wind break. This can be a fence or additional plants or shrubs that provide a buffer to any drying winds. I personally like to plant my Japanese maples near fences.
• Increase the amount of shade. This is only if your Japanese maples in in full sun. If it has morning sun followed by shade during midday and the afternoon or dappled light throughout the day then this is a good balance. One of my Japanese maples is planted in these conditions and is absolutely thriving. Japanese maples in full sun require shade to stay healthy.
• Water the maple generously and apply mulch. To help conserve moisture, I like to apply a one-inch layer of mulch around the base of my maple of compost or leaf mold.

I would note that Japanese maples do not necessarily require additional watering in temperate climates with high rainfall if they are planted in appropriate soil rich in organic matter. I personally haven’t watered mine at any time other than straight after planting.

However, in dryer climates with hot summers, it is crucial to water the maple at least once per week and to use mulch to help conserve moisture and improve the soil. I noticed this when I lived in California: My Japanese maple was much more susceptible to drought and, therefore, needed a really good soak and a biannual application of mulch.

I love to use compost and leaf mold for mulch as they are the ideal materials for mulch as they add nutrients to the soil and have an exceptional capacity for retaining water yet a friable structure that allows excess water to drain away to prevent the soil from becoming boggy.

Important Tip: My recommendation is to apply mulch at the start of Spring after giving the soil a good soak to lock in moisture in the ground before summer and then I do it again in the fall, just to continually improve the texture of the soil, which year after year I can tell you makes a huge difference to your Japanese maple.

Two other important tips, however, are to make sure that the mulch is 1 to 2 inches thick and doesn’t make direct contact with the wood of your maple tree. The wood is less tolerant of damp soil, which can, of course, cause it to rot.

With diligent watering, the use of mulch, and protection from wind and sun, the Japanese Maple should show signs of recovery in around a week although recovery can take longer depending on the extent of the damage.

If it is not possible to provide a wind break or the soil is very sandy or stony and does not hold any moisture then I would recommend transplanting your Japanese maple if possible to a more favorable location in well-draining soil amended with compost.

Too much Fertilizer Harms Japanese Maples

So, from my research, Japanese maples are not heavy feeders, and they do not require additional fertilizer if they are planted in good soil and amended with compost.

I’ve seen for myself that too much fertilizer is another cause of leaf scorch with brown or yellowing leaves and excess growth with soft stems that can droop.

Too much fertilizer can be too much of a good thing for your maple tree!

Even if you haven’t applied fertilizer to your maple, it is possible that excess lawn fertilizer can dilute in rainwater and run to the soil around your maple, causing the leaves to scorch, which I’ve seen happen more often these days as more people try to create the perfect lawn.

It should be noted that due to cold weather, additional fertilizer can be a significant problem if it is applied too late in the season or too early as it causes the new growth to be more vulnerable to frost damage, but as I said, usually fertilizer is not necessary anyway.

The tender new growth turns black when damaged by frost and can be cut back with a pair of pruners without any significant damage to the tree.

Once there has been too much fertilizer applied, then there is not much you can do other than give it time to recover.

When I had to treat an overfertilized Japanese maple, I trimmed off any excess growth and any badly affected leaves to prevent possible frost damage, aphid infestation, or sun scorch.

By the following year, the Japanese maple recovered! (as long as you avoid the use of fertilizer).

The only time I personally recommend using fertilizer when growing Japanese maples is if they are planted in a pot or sandy soil and you should only use half-strength multipurpose fertilizer.

Personally, I prefer to use miracle-gro fertilizer as it is in granule form, contains all the nutrients at the right concentration for your plants, and releases nutrients slowly to prevent problems associated with too much fertilizer.

In most gardens, however, As we discussed, the use of compost or leaf mold mulch adds nutrients to the soil, improves the soil’s structure, and conserves moisture, providing optimal conditions for your Japanese maple.

Is Your Japanese Maple Dying Because of Alkaline Soil?

So this one isn’t as common a reason for a dying Japanese maple compared to others, but I think it is still worth mentioning. Is your newly planted Japanese maple is dying or showing poor growth? Then this could be because of soil pH.

Most varieties of Japanese maples that are sold in garden centers prefer acidic soil with a pH of between 5.5 and 6.5 (pH 7 is neutral, any number below is acidic, and any number higher than 7 is alkaline).

Does your garden have alkaline? If your garden has alkaline soil, then certain nutrients become insoluble, and the Japanese maple roots cannot uptake the nutrients (chlorosis) that they require, which can cause poor growth or kill the plant.

From research, most gardens have soil that is slightly acidic as this is the pH of most organic matter once it is fully decomposed.

However, some areas do have naturally alkaline soil due to underlying bedrock, building work that is just underneath the soil, or even the use of wood ash around the garden (wood ash is very alkaline). I have made the mistake of amending the soil with too much wood ash in one location before!

But how do you tell if your soil is too alkaline? If acid-loving plants such as roses, blueberry bushes, azaleas, rhododendrons, and camellias are growing in your garden or perhaps gardens in your neighborhood, then soil pH is not a problem, and your Japanese maple is dying of some other cause (assuming you are not using wood ash as a mulch).

However, if it is difficult to determine the soil pH from observation then I recommend buying a soil gauge from your garden center or Amazon. Soil gauges tell you the pH of your soil, they are very easy to use and available for a great price!

If your soil is not acidic then I recommend that you transplant the Japanese Maples to a pot if at all possible with multipurpose or ericaceous compost.

If the soil is neutral or slightly alkaline, or if the soil pH has been influenced by environmental factors, it is possible to lower the pH so that it is more acidic and suitable for Japanese maple. However, I would only recommend this for maples that are too difficult or large to transplant.

In my experience, the key here is to use ericaceous compost in combination with an ericaceous feed to achieve the best results.

Use an ericaceous fertilizer (ericaceous just means that it is made specifically for plants that require acidic soils) and ericaceous compost (available from the garden center or online) and use the compost as a mulch around your maple tree.

Apply a one-inch layer of the compost around the Japanese maple every 6 months or so to maintain a level of soil acidity so that your maple can thrive.

Influencing the pH of the soil is a process that is ongoing so it may take a few months before your Japanese maple shows signs of recovery, which is why I recommend repotting if at all possible, but it can be done!

Have you any more specific questions about Japanese maples? Or do you have any insights or experiences of your own when reviving your tree? If so, please leave a comment below and I’ll reply…I love to hear from you!!

Key Takeaways:

• Your Japanese maple is dying most often because of fungal disease. Damp soil promotes conditions for fungal diseases such as root rot, which causes Japanese maples to die.
• High wind, too much sun, and not enough moisture in the soil can cause brown, wilted foliage.
• Japanese maples require an acidic soil pH between 5.5 and 6.5, and most varieties do not survive very long in alkaline soil.
• I planted Japanese maples in areas with protection from high wind and shade from full sun. I amended the soil with compost before planting so the soil was well-draining yet could retain moisture, which is the optimal balance for Japanese maples.