Japanese maples (also known as acers) ‘Acer palmatum‘ are small trees that thrive in well draining soil rich in organic matter, partial shade and when protected from wind.
A dying Japanese maple is often because of fungal diseases pathogens that thrive in overly damp soils. Saturated soil promotes the conditions for root rot which cause dying Japanese maples. Too much wind, sun and not enough water also causes maples to have brown, wilted leaves and a dying appearance.
The most common fungal pathogens that affect Japanese maples are Verticuillium wilt and Phytophthora (root rot) which are a problem in boggy soil and often kill the tree.
However 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 for why your Japanese maples is dying and how to prevent or or solves the problem…
Japanese Maple Dying of Verticillium Wilt Or Root Rot
Japanese maples are adapted to growing in soils that are rich in organic matter (compost, leaf mould etc.) with a friable structure that absorbs moisture yet allows excess water to drain away quickly.
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
- Over watering
- 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.
Verticillium pathogens that affect Japanese maple thrive in damp soils and unfortunately Japanese maples are relatively susceptible to fungal pathogens caused by damp soil with even established maples trees suddenly displaying symptoms and dying.
The symptoms of Verticillium are leaves that are turning brown, grey, yellowing and curling inwards or certain branches that drop all their leaves.
It is important to note brown Japanese maple leaves can also indicate drought stress, not enough water and too much fertilizer but if your maple is in waterlogged soil Verticillium wilt or root rot is almost certainly the problem.
Unfortunately it is very difficult to treat a maple with wilt and prevention is much better then cure.
To effectively prevent Verticillium or any other soil pathogens that can affect maple the most important step is to ensure the soil is well draining and the planting areas has been amended with lots of compost or leaf mould to provide the optimal well draining soil structure.
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 to increase drainage.
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 thrives in damp soils.
If your have heavy clay or boggy areas in your garden it is best to plant maples in pots or containers as you can easily provide the optimal soil profile as amending unfavourable clay soil to suit Japanese maple can be very difficult.
If the plant has Verticillium I recommend digging it up and burning it or discarding it (to kill the pathogen) and treat 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
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.
Forest canopies also protect the Japanese maple from intense sunlight which can further dehydrate leaves giving them a scorched appearance.
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 is 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.
- 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. Japanese maples in full sun require shade to stay healthy.
- Water the maple generously and apply mulch. To help conserve moisture apply a one inch layer of mulch around the base of your maple of compost or leaf mould.
Japanese maples do not necessarily require additional watering in temperate climate with high rainfall if they are planted in the appropriate soil that is rich in organic matter.
However in dryer climates with hot summers it is crucial to water the maple at least once per week and to use a mulch to help conserve moisture and improve the soil.
Compost and leaf mould are the ideal material 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 becoming boggy.
With diligent watering, the use of mulch, protection from wind and sun, the Japanese Maple should show signs of recovery in around a week although recover 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 you may have to transplant the Japanese maple if possible to a more favourable location in well draining soil amended with compost.
Too much Fertilizer Harms Japanese Maples
Japanese maples are not heavy feeders and they do not require additional fertilizer if they are planted in good soil, amended with compost.
Too much fertilizer is another cause of leaf scorch with brown or yellowing leaves and excess growth with soft stems that can droop.
Even if you haven’t applied fertilizer to your maple it is possible that excess lawn fertilizer can dilute in rain water and run to the soil around your maple causing the leaves to scorch.
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.
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 they has been too much fertilizer applied then there is not much you can do other then give it time to recover.
Trim off back any excess growth and any badly affect leaves to prevent possible frost damage or aphid infestation or sun scorch.
By the following year the Japanese maple should recover as long as you avoid the use of fertilizer.
The only time fertilizer if necessary when growth Japanese maples is if that 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 it releases nutrients slowly to prevent problems associated with too much fertilizer.
In most gardens however the use of a compost or leaf mould mulch adds nutrients to the soil, improves the soils structure and conserves moisture providing the optimal conditions of your Japanese maple.
Dying Japanese Maple Because of Alkaline Soil
If 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 then 7 is 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.
Most gardens have soil that is slighltly acidic as this is the pH of most organic matter once it is full 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).
If acid loving plants such as roses, blueberry bushes, azaleas, rhododendrons and camellias are growing in your garden or perhaps gardens in your neighbourhood 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 soils 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 your transplant the Japanese Maples to a pot if at all possible with multipurpose or ericaceous compost.
If the soil is perhaps just neutral or slightly alkaline or perhaps the soil pH has been influenced because of environmental factors then it is possible to lower the pH so that it is more acidic and suitable for Japanese maple but I would only recommend this for maples that are too difficult or large to transplant.
Use an ericaceous fertilizer (ericaceous just means that it is made specifically for plants that require acidic soils) and ericaceous compost (available from 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.
- The reasons your Japanese maple is dying is most often because of fungal disease. Damp soil promotes the conditions for fungal diseases such as root rot which cause your Japanese maple 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 of between pH 5.5 and 6.5 and most varieties of Japanese maples do not survive very long in alkaline soil.
- Planted Japanese maples in areas with protection from high wind and shade from full sun. Amend the soil with compost before planting so the soil is well draining yet can retain moisture which is the optimal balance for Japanese maples.