Warton’s Bill Blackledge is one of the county’s most popular and sought after gardeners. If it’s green and needs watering, Bill can tell you about it. He has been answering BBC Radio Lancashire listeners’ queries for over thirty years, which means he’s been there nearly as long as the transmitter!

His knowledge is encyclopedic. After training at the under the then Ministry of Agriculture, Bill spent over twenty years at the Department of Biological and Environmental Services at Lancaster University. Now, he’s a regular course tutor at Alston Hall, Longridge and Lancaster Adult College.

For three decades, Bill has travelled the county with fellow judges as a regional judge for North West in Bloom.

So, whatever the problem, we like to think Bill can sort it out… at least that’s the theory!

Zenab Hira asks…

I have an Acer – Bloodgood. It’s in a large pot, growing very well… the only thing is that it’s growing to one side, kind of leaning more to one side, it hasn’t spread evenly. What do I do to make it look fairly even all round without damaging it too much?

Bill replies…

I am afraid Zenab that this quite often happens with Acers. You will suddenly find that one side of the plant is growing extremely well compared to the other section and I am afraid that if there are no shoots growing from the other section of the stem it is going to be very difficult to achieve an even spread.

Barbara asks…

I have a well-established Acer Atropurpureum but this year buds and new leaves are only appearing on about a third of the tree (near the outside). The branches at the centre and back of the tree are brittle and dead. The same thing has happened to my Ribes. Any thoughts?

Die back of Acers often occurs if the soil is very damp and waterlogged during the winter months and last year Barbara we did have above average rainfalls. You will need to cut out any dead shoots and I would also top dress your tree with a general base fertiliser such as Fish Blood and Bone Meal. I am however slightly worried when you say that the same problem is occurring with your Ribes (Flowering Current) and my immediate reaction is to whether your trees have been infected with the Honey Fungus soil borne disease, symptoms of which are a white fungal growth close to the bark near ground level and also shreds of black boot lace fungi around the roots and at the base of the bark along with amber toad stools appearing early autumn time. More information on this disease is available on the “Hedges” section of this website.

Lily Ghandi asks…

I had bought a foot tall Japanese Acer Sangokaku 2 weeks back and placed the pot in the house during daytime and at night time in the porch in order to protect it from frost. However, a few of its leaves started to wilt. I have fed it with Miracle Grow crystals diluted in water. Today when I moved the plant a clump of leaves fell off. I don’t know where I am going wrong as this is my first Acer plant. Please advise me on watering, feeding and position to place the pot in which I intend to grow.

Your Japanese Acer would be far better placed outdoors in a sheltered position Lily and I am sure that it is the contrasting temperatures which is causing your Acer to lose its leaves. You will need to keep an eye on the watering throughout the summer months and feed occasionally with a balanced liquid fertiliser. Hopefully your plant will start to grow both new shoots and leaves.

Eioleen O’Neill asks…

We have a 14yr old acer which has developed grey blotches on the main branches. Could you advise what they are as the tree has started to bloom and we are afraid to apply any sprays.

The growth Eioleen on your Acer tree is most probably lichen with also some algae growth which will not do any serious harm to your tree. This is a very common problem in the winter months especially in very damp and mild conditions and can also be troublesome if your tree is growing in a very shady spot in the garden. It is not necessary to spray during the growing season but when your tree is dormant during the winter period (December/January) it maybe worthwhile to spray the main trunk and branches with a tar oil winter wash which will kill lichen growth. My only concern with using a tar oil winter wash is that it will also kill off natural predators and if your tree is not completely dormant due to the recent mild winters the winter wash can damage the buds. I am afraid that the only other alternative is to gently brush off the lichen growth during the summer months.

Maria Ash asks…

We have recently moved and have a really lovely acer in our garden which is about 8ft tall we don’t know what kind it is but we have to move it, could you please advise us how wide and how deep approx we will need to dig do get a big enough rootball.

If at all possible Maria you would be far better waiting until the autumn time before transplanting your Acer Tree as the tree will then be dormant. If you cannot wait until autumn time I would suggest that you lift your tree as soon as possible before it is actively growing. As the tree is eight feet tall you will need to try and dig out a very large root ball and the chances of success will depend on the size of the root ball that you can physically remove. However if it is possible to get a small digger into your garden you will find that it will be much easier to lift out your tree and will ensure that you get a large root ball of soil. It is important to keep an eye on the watering of your tree during the summer months and you will need to stake your tree to give support until new roots are established.

Daniel Smith asks…

My mum has an Acer, in a large pot (not sure what kind but it seems to be out-growing it), could you please tell me when we can either re-pot it or move it, should it be at a certain time of year? Thank you.

If you are careful when re-potting you could re-pot your mother’s Acer now Daniel. However personally I find the best time for re-potting Acers is early Springtime before they have come into leaf. Acer prefer a slightly acid soil so you will need to use a ericaceus compost.

Heather Drewry asks…

I have an Acer, which is outside. I have been told it has Mealy Bugs on it. I have used Provado Ultimate Bug Killer twice but it hasn’t made any difference, if anything it seems worse. Is there anything else it could be instead? Or is there something else I could use to clear the problem up, as this plant has been with me for sometime and I don’t want to lose it.

Mealy Bug is problem pest Heather on a wide range of plants and you will find that in time Provado Ultimate Bug Killer will control the pest but what you do need to do is give your Acer a thorough spray with the insecticide and spray to run off. The time to spray is early morning or late evening – do not spray during the day or in the midday sun as this will cause scorching of the leaves. There are other insecticides which you can use such a Liquid Derris Plus – which is a natural insecticide – and also Spray Day Insecticide. The important factor is whichever product you use you need to give your Acer a thorough spray to disturb the aphids which are enclosed in a cocoon.

Sue Eaton asks…

My Acer and Magnolia Susan outdoors have a white glue-like substance on them with disc shaped creatures stuck to it. I looked up mealy bug and I’m not sure if it is this as they are outside. I blasted them off with the hosepipe and the white stuff like marshmallows was all stuck to the fence. These are not on the leaves but on the branches and trunks. What could it be please? My magnolia is 15 years old and never ailed a thing although we moved to this garden two years ago and I brought most of my shrubs with me. Please give me the benefit of your experience.

What you are going to have to do Sue is to spray your plant to run off with a systemic insecticide and the one I would use is Provado Ultimate Bug Killer which will kill scale insects and also mealy bug. I would spray your trees early morning or late evening and if it is a bad infestation you will probably need to spray more than once and as explained above you will need to spray to run off using a powerful jet.

Monica asks…

What tree can I plant in a tiny garden which grows no more that 12/15 ft high? Don’t like those narrow column trees; do love autumn colours though.

If you require a plant for autumn colour Monica and your garden is sheltered I would choose one of the Acer Palmatum Cultivars. There are also the Magnolias and Stellata is reasonable dwarf variety. The deciduous tree Amelanchier Grandi Flora will again give you autumn colour and also Prunus Serrula.

Peter asks…

My japanese acer japonica leaves have shrivelled and withered it is a young tree in a pot… what can the cause be? It came out with a flourish but the leaves never looked right.

You will find Peter that all Japanese Acers do suffer badly from wind scorch damage and also the early morning sun can quite easily cause scorching and shrivelling of the leaves. Acers love to be grown in a slightly acid soil and I find they are far better situated in a sheltered dapple shady spot. With regard to your Acer I would situate it in a slightly shaded spot and I am sure that providing you do not over water it will produce new shoots. The biggest problem this year has been the adverse weather conditions which has caused havoc to a large number of plants.

Rosie asks…

My son has just moved into a rented house and there is a lovely red-leaved acer in a pot in the garden. It seems to be losing its leaves – are they deciduous (?) – and we’re not sure how to look after it! The pot is about 14/16 ins across and the acer is about 3ft tall. Help! As it belongs to the landlord we’re panicking!

There is no need for either yourself or your son to panic Rosie your red leafed Acer is deciduous and produces beautiful colours during the autumn time before shedding its leaves. With regard to ‘looking after’ your Acer. Acers love to be situated in a dappled/shady sheltered position and, in early springtime when it starts to come into leaf do ensure that it is protected from prevailing cold spring winds.

Ann asks…

Hi Bill I planted a young japanese acer (Katsura) in the spring and noticed a few days later that the leaves on the tips of the stems were turning brown and withered. Thinking it was settling into its new home, I left it alone. However all the leaves have now died but they have not dropped off in spite of recent heavy rain hitting the plant. Is it possible for an acer to be affected by Fireblight? If not your opinion would be appreciated. P.S Waterlogging has been ruled out, the land has good drainage and other young acid loving plants in the same area are thriving.

Japanese Acers need to be situated in a shady and sheltered position and I am sure that your Acer has suffered from wind scorch damage and the recent extreme weather conditions. I am however sure that when the weather improves your Acer will produce new leaves. Regarding fire blight your Acer will NOT have been affected by this disease.

Gareth Davies asks…

I’ve been keeping japanese acers for 2 years. Planting them in ericacious soil however this year 3 have died. Where am I going wrong and how can I keep and maintain them?

Japanese Acers lover to be grow in a neutral to slightly acid soil Gareth and for the best results Acers need to be situated in a sheltered and slightly shaded position and, the compost needs to be reasonably well drained, they can suffer from waterlogged conditions. One of the problems with using an ericacious soil is that the majority are one hundred per cent peat based which, makes them prone to waterlogging during wet conditions and what I tend to do Gareth is to use a mixture of an ericacious compost with a soil base compost with ten per cent of a sharp grit which assists in avoid waterlogging during the winter months.

Julie Quinn asks…

I have a small Acer tree Orange Dream and now that we are nearing winter, I have noticed the leaves are showing lighter patches and blotches on the leaves as well as curling and crisping. Can you tell me what is causing this and how I can get it back to good health for next season?

Your Acer Tree Julie is deciduous and what is happening to the leaves is natural senescing before they fall. There is nothing to worry about and next spring your Acer will again come into full leaf. If your tree is growing in a container it is important to protect the young leaves from prevailing winds – the leaves can quite easily suffer from burning and wind scorch, and Acers do prefer to grow in slightly dapple shade.

David Collins asks…

Is it normal for acers to shed leaves at this time of year and start producing new growth or is it due to the mild weather (October)?

Acers are deciduous trees David and will shed their leaves during the winter months. With regard to new growth now appearing this has been caused to this year’s unpredictable weather and the very mild autumn.

Kay McCourt asks…

I have an Acer Atropurpureum in a pot about 18″ dia. I have grown it from a small plant and it is about 1.5m tall and potbound. Can it live on in this pot? Should I transplant it ? Our garden soil is clay which is the reason I kept it in a pot. The leaves are looking dried up and have what looks like wind damage.

Acers love to be kept in a sheltered and dapple shady position Kay as this cuts down the chance of the leaves being damaged by wind scorch. With regard to your Acer you will need to add quite a lot of organic material to your soil, I am afraid Acers to not like being planted in heavy clay soil. An alternative to planting in clay soil would be to transplant your Acer into a larger container and there are on the market large wooden and terracotta containers available.

Andy Robertson asks…

I have a beautiful Acer which has been pot grown for over 12 years now. It is currently in a pot about 2 foot deep and 1.5 feet diameter. Over the last two years, despite careful watering, feeding and mulching, the edge of leaves become brown and dry within two months of the new season’s growth. First question, is there anything I can do to prevent this or is it pot bound? Secondly if I was to put it into the ground, when is best time to do it and what preparation would you suggest? I only have very limited space so the final size of the tree would be a consideration if I was to re-plant it into the garden. It’s currently about 5ft high with a 4 ft spread. I hope you can help.

I am afraid Andy that a lot will depend on which species of Acer you have in your garden as some will grow to a height of thirty to fifty feet or even taller. If your Acer is one of the Japanese varieties such as the Acer Palimatum this will only grow to approximately twelve feet high and with the Japanese varieties you will be able to repot into a larger container. It is important for you can find out which type Acer you have before transplanting into your garden. You mention browning of the leaf edges which, does occur frequently when Acers are just coming into leaf and the Japanese Maples in particular like to be situated in a dapple, shady position.

Rebecca MacFarlane asks…

One of my potted Acers turned black and died. On inspection, the soil in the pot is full of tiny jumping insects. Did these kill my tree? The insects can now be seen under the surface of the soil in my other pots how can I get rid of them before my other trees die?

I passed your question on to an eminent Entomologist at Lancaster University and he has stated:

“If these tiny jumping insects are springtails as I strongly suspect (not being able to think of anything else which would be tiny and jump, at least not without a fuller description) they are most unlikely to have been responsible for the death of the plant as they feed on fungal hyphae in the soil.”

Following the above comments it is difficult to pinpoint what has caused your Acer to die back Rebecca – it could be waterlogging of the soil which quite often happens if you use a peat base compost.

Michelle Aston asks…

I have an acer the stems are covered in what looks like mini legless woodlice! They are different sizes and slightly different colours. Apart from this it seems healthy?

It looks Michelle as though your Acer has been infected with a scale insect and I would spray the stems with an insecticide spray and the one I would recommend is Provado Ultimate Bug Killer. You will need to spray early morning or late evening – try to avoid spraying in direct sunlight which can cause leaf scorch.

Karl Green asks…

How do I stop squirrels eating the new buds on my acer pseudoplatanus?

I am afraid that there is not easy answer to your question Karl. N matter how you try to protect your trees the squirrel will find a way of getting to the new buds and I am afraid the only way to protect your trees is by trapping the squirrels and I would contact the Pest Control Department within your Local Authority regarding traps and how to disperse of the squirrels. I am afraid that you are not allowed to set squirrels free in the countryside.

Sheila Revel asks…

I have a four year old acer which is covered in black fly. I have never had this before and it is affecting the new growth of leaves. Why has problem suddenly occurred?

Black Fly has been a problem this year Sheila and I am afraid that you are going to have to spray with an insecticide to control the problem. If you require an organic insecticide I would use Organic Pest Control or another natural insecticide product is Bio Liquid Derris Plus. Do not spray in direct sunlight – I would advise spraying early morning or late evening.

Robert Blackwood asks…

I have Japanese Acer, it’s about 5 yrs old. Has been doing well but last season developed an orange fungus on one of branches. This I cut out but now is at base of plant and one root is covered. My local garden nursery suggested applying surgical spirit to the affected area. This worked briefly but has come back with a vengeance. Is this fungi scale? From RHS description I read it does not appear to be. No mention of orange. The next problem is the wood then dies. It’s a small beautiful tree and I would hate it to die. Also what is best feed for Acer? Thank you

It is difficult to pinpoint exactly what the fungal disease can be Robert but one of the most common diseases, which attacks a wide range of shrubs, is the Honey Fungus (Armillaria) and the symptoms are a white fungal growth appears near the bark at ground level, and on the roots are strands of fungi which are black and are similar to boot laces, and in the Autumn time amber coloured toad stools appear around the base. The other disease which caused die back of branches is Coral Spot where you will find raised pink spots on the branches. You can also get die back of the branches if your Acer is growing in very badly drained soil. With regard to feeding your plant I would use a general base fertiliser sprinkled around the base of the Acer in early Springtime – Fish Blood and Bone Meal or GrowMore are good established products to use. With your infected Acer you will need to cut out any diseased branches and stems.

Frequently Asked Questions

Do all Japanese maples need to grow in the shade?

How often should I water my Japanese maple?

Should I fertilize my new Japanese maple to get it off to a good start?

When is the best time to plant Japanese maples?

Do all Japanese maples lose their leaves?

What is a dwarf Japanese maple?

What is the most common cause of failure in growing Japanese maples?

Do all Japanese maples need to grow in the shade?

No! Many Acer palmatum cultivars are very happy in a sunny exposure. This includes the red dissectums (or lace leaf maples), as well as trees with wider, palmate lobes. In fact, the red leaved trees need a few hours of sunlight to maintain their red color. In the Sculpture Gardens at Wildwood, one sees many maples growing in full sun. Summer temperatures exceed 100 degrees.

We have found that Japanese maples with green lace leaves prefer partial shade during the afternoon. Cultivars of Acer shirasawanum and Acer japonicum also appreciate filtered sun.

Note: A young tree planted out in full sun will struggle and may not survive. If you wish to start the tree out in full sun, we recommend selecting a specimen that is at least 6 or 7 years old.

How often should I water my Japanese maple?

Roots of these trees need to remain evenly moist; and roots are not deep. Establish a regular watering routine. The frequency of watering depends on the temperature and how well your soil holds moisture. Of course mulching is very helpful. It can keep roots a bit warmer in winter and much cooler in the summer. During the summer it is preferable that leaves be dry by the time the sun reaches them.

Should I fertilize my new Japanese maple to get it off to a good start?

No. Thorough watering is the biggest help you can give your newly planted maple tree. Furthermore, maples are NOT heavy feeds. If the tree is planted in the landscape, it will not need fertilizer every year. Container grown trees benefit from one or two mild applications of fertilizer in the spring when all risk of frost is over.

When is the best time to plant Japanese maples?

Anytime! As long as you can be sure the tree will be properly watered, you may plant a container-grown maple tree (all our trees are container grown) any month of the year.

Do all Japanese maples lose their leaves?

Yes! Japanese maples are deciduous trees. During October and November maples provide a lovely show of fall color. Then in late November, or December, the leaves drop. Buds start to swell in February and March brings fresh new leaves—in colors that some say rival the show in autumn.

What is a dwarf Japanese maple?

In the winter, branches of maples are clearly visible without the distraction (albeit a lovely one) of leaves. Branching structure largely defines the category `dwarf’ maple.

At Wildwood Nursery we grow 60-70 maples (cultivars of Acer palmatum or Acer p.) that remain compact and small. In 12 years, some will only grow to about 4 ft. (e.g. Acer p. Corallinum, Tama hime, or Yuri hime ). Others, like Koto no ito, Olsen’s Frosted Strawberry or Shidava Gold, reach 8-9 ft. in 12 years.

There is some confusion among gardeners and garden enthusiasts when we use the term `dwarf.’ By way of comparison let’s look at maples in the `dissectum’ category. Although they are not actually dwarf trees, their branches arch out and down. See the image of Acer p. Orangeola with its branches beginning to weep. Their structure is often likened to an umbrella; and they grow wider than tall.

What is the most common cause of failure in growing Japanese maples?

Poor drainage. In questioning customers whose maple trees have not leafed out in the spring, we find that the soil around the roots was very wet and soggy. Plant your tree in soil that is well aerated and you will find these trees easy to grow.

Common Potted Acer Tree Problems & How to Prevent Them

  1. Improve soil condition

    Japanese maples thrive in slightly acidic, sandy, water-retentive soil with good drainage. Choose a good-sized pot that has a sufficient number of drainage holes to avoid waterlogging of the soil. Note that loam-based compost for acers is the best growing medium for your beautiful maple tree (ex: John Innes No 2). Furthermore, it’s recommended that you repot your Acer palmatum approximately every 4 years between February and March. As the leaves emerge, you can give your plant a balanced feed, as well. If you’ve never grown a Japanese maple in a container, follow these easy steps on how to plant an acer in a pot.

  2. Cover with mulch

    Mulching around the trunk of your Japanese maple with organic material, such a bark mulch, or with gravel slates will help the soil retain its moisture, especially in hot weather, when you are advised to water the plant a couple of times a day. Make sure that there is some space between the tree and the mulch, however. Again, protecting your acer tree from losing water and drying out is not only a preventative measure against weather-related leaf scorch, but can also reverse leaf damage if the problem is not yet too far gone. In addition, any steps towards enhanced water-retention of the soil will prevent it from case-hardening around the roots, by keeping the growing medium crumbly, but moist.

  3. Move to a sheltered spot

    Finding the right position for your potted Japanese maple is important to avoid the onset of leaf scorch. This means that your plant should not be placed under direct sunlight in hot weather. A semi-shaded spot in your yard, which is sheltered from high dry winds, is the ideal environment for a healthy and flourishing acer tree. You can also resort to using a temporary windbreak around your potted acer plant during unexpected stormy weather conditions.
    In winter, to prevent frost damage, cover your plant in a protective insulating material – a large box, placed carefully over a young plant, overnight, will do. Note that experts do not advise to bring the container indoors, as the difference in temperature when you move the plant in and out, can do more damage than good. Defoliation is a common outcome when contrasting temperatures are at play.

  4. Prune if necessary

    Pruning your Japanese maple is only necessary to achieve an aesthetically balanced shape of your plant, as new shoots usually grow in one direction. The task is best completed in late summer or early autumn. Remember that pruning in the wrong time of the year causes bleeding. Still, if your potted acer tree suffers from mild dieback and browning leaves and branches, pruning those will improve the overall look and state of the plant. Naturally, however, you will need to find out the underlying cause for the poor health of your maple tree.
    A more specific pruning procedure that requires some knowledge and skills is root pruning, that can be done when it’s time to replace the soil or sometimes when you replant the acer tree in a larger container. You should prune the roots only lightly while cleaning them off any dry and hardened-up old soil.


Potted maple tree problems are often preventable by applying vigilance and the right care:

  • Make sure your acer plant is potted in a container that is double the roots’ size to provide them with sufficient space to develop and this way, avoid stunted growth.
  • Infectious diseases and pest infestations are usually manageable when treated at the first signs of the problem.
  • If you’re unsure about how to plant your maple tree and what conditions it will best grow in, you can always seek the professional planting expertise of the Fantastic pros and stay on the safe side.
  • Prevention is always the best course of action, especially when it comes to dealing with acer leaf scorch and other environmental factors that can affect the well-being of your potted maple tree.

We offer all-year-round planting plan. Here’s how to spruce up your garden with Fantastic.

Learn more


Have you had any experience with growing potted acer trees? Let us know in the comments below!

Image source: : By Vahan Abrahamyan

  • Last update: December 5, 2019

Posted in Garden Advice, Plants in the UK

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Problems of Japanese Maple

Tree Grows Poorly
Girdling Roots -Many trees, including sugar and silver maples are weakened and even killed by the tendency of some of their roots to grow closely pressed to the main trunk and around their large lateral roots, choking off water and nutrients. When a lateral root is severely girdled, the branches that depend on it for nutrients are weakened and eventually die. Trees with girdling roots become progressively weaker over 5 to 10 years even with good care. Girdling roots are more of a problem with street trees and in older trees. Carefully cut through any roots that are visibly wrapped around or over large ones with a clean, sharp pruning saw. Do not take the trouble to remove them from the soil, as long as they are severed they are no longer harmful. Do not paint or cover the saw wound.
Surface Roots Or Suckers
Compacted Soil – Tree roots need air, which they normally get from the soil. When the soil where tree roots are growing is compacted, so compressed that most air is squeezed from the soil pores, then roots tend to gravitate to the surface for air. Some trees also generate suckers, extra vertical roots that grow out of the soil as modified stems that access air. Simply pruning off the suckers and covering the surface roots with a layer of soil does not solve the problem. It is a temporary cosmetic measure.
Tree Is Stunted
Too Near Black Walnut Tree – Maple trees can suffer stunting, wilting, or even death when they come in contact with black walnut roots, which give off a substance poisonous to many other plants. This toxic substance affects plants within a radius of 1-1/2 times the distance from the walnut tree’s trunk to its outermost branches (the dripline). Move the maple tree outside that area to restore it to health and solve this problem.
Leaves Wrinkled, Stunted, Defoliation
Aphids – Aphids are soft-bodied and pear-shaped, about the size of a pinhead. They may be green, brown, or pink. They retard or distort tree growth, especially on young trees. Maple leaves may turn yellow or brown, wilt under bright sunlight, or curl and pucker. They may actually drop off the tree. Aphids suck plant sap from the leaves and excrete drops of honeydew. With heavy infestations it can be quite messy, although studies have shown that these abundant sugar secretions, soaking into the root zone, actually benefit the tree.
Branches Girdled, Leaves Fall Early, Trunk Scarred
Borers – Borers are the larvae of various sawflies, beetles or moths that tunnel into maple twigs and cause premature leaf fall. Often their entrance holes are visible, a little deposit of sawdust in the area. Borers girdle branches or even the entire tree as they tunnel. New growth over wounds forms a series of scars and ridges on the trunk. Prevent borer attacks on young or newly transplanted trees by wrapping the trunks in plastic, paper tree wraps or even aluminum foil.
Small Bumps On Leaves and Branches
Scale Insects – Several kinds of scale insects infest maples. Sap-sucking insects that feed beneath whitish, gray or brown blister-like protective shells, scale appear as 1/8 to 1/4 inch bumps on tree twigs and as cottony patches on leaves. Affected leaves may turn yellow. Scale insects often secret a sticky sweet honeydew as they feed which coats leaves and invites sooty mold. Do not attempt to treat this problem in large trees that require you to climb a ladder. A certified arborist can do it more safely. It is more of a problem on young trees, anyway.
Sunken Spots On Leaves
Anthracnose – This fungus disease causes distinct lesions on maple leaves, which appear as moist, sunken spots with fruiting bodies in the center. The leaf spots may run together, causing a blotch or blight. The dead areas follow the veins or are bounded by larger veins. Sometimes the ends of young shoots blight down to several inches. Pustules containing pinkish spores appear. Dieback and loss of foliage may occur in severe cases.
Gather and destroy diseased leaves when they fall to prevent the spread of the fungus. Replace existing mulch with fresh that does not have fungal spores on it. Prune away diseased branches, then disinfect your pruning saw or loppers by dipping them into a solution of hot water and household bleach. Maintain tree vigor by feeding and watering it well, especially during droughts. Mature trees can usually handle this disease and regenerate new leaves.
Swollen, Bleeding Lesions Appear on Stems and Trunk
Canker – A canker disease caused by a fungus attacks maples. Sap oozes from fissures overlying cankers in the bark. Leaves wilt, branches die back. Mildly infected trees may recover without any special care. A similar disease infects the base of the trunk. Once the tree is heavily infected, it cannot be cured. Remove and destroy severely diseased trees. Avoid mechanical injuries to the bark on the trunk, and feed, water and mulch trees as needed to maintain good vigor.
Mushrooms Sprout At Base of Tree
Shoestring Root Rot – A root rot disease caused by a fungus causes gradual or sudden dieback of tree crowns. Affected trees show a decline in vigor of all or part of their top growth. Foliage becomes thinned, withers, turns yellow and drops prematurely. Large white “fans” of fungal mycelium appear between the bark and the hardwood of the larger roots. Often, small, dark brown shoestring-like strands cover the outside of the bark of infected roots. Mushrooms appear at the base of the tree in late fall or early winter.
Once this fungus becomes established, it is difficult or impossible to control. Because the fungus cannot exist under dry conditions, expose roots of infected trees to air. Improve soil drainage in the area by aerating and adding organic matter to the surrounding soil. Avoid overwatering. Dig out and destroy seriously infected trees and discard the surrounding soil. Avoid bark injuries and keep trees in vigorous health by watering, fertilizing and mulching young trees to get them off to a good start.
Foliage Turns Yellow Or Brown & Collapses
Verticillium Wilt – A wilt disease caused by a soil-dwelling fungus sometimes attacks maples. Infected leaves appear pale and wilted, and may fall prematurely. One or more branches wilt suddenly and die, often on only one side of the tree. Infected trees may die slowly (over a period of several years) or suddenly (within a few weeks). Sapwood is discolored. Heavy feeding with a high-nitrogen fertilizer sometimes enables trees to put a new ring of sapwood outside the infected area and the trees may then recover. Prune out dead branches. Remove badly infected trees, together with as many roots as possible. Do not replant with wilt-susceptible shrubs or trees in the same location.

What ails this Japanese maple? | The Sacramento Bee

A reader’s 20-year-old Japanese maple is not showing signs of new growth on its lower limbs. The problem may be linked in part to overwatering, poor drainage or wilt. Albert Terpak

Experts tackle readers’ garden questions.

Q: Something has happened to our Japanese maple. It is planted on the southwest side of the house. None of the lower branches have evidence of new leaves. All the new growth and leaf buds are on the upper branches. We have had this tree for about 20 years and have never had this problem before. We have not sprayed it with any herbicide or insecticide. We have another red Japanese maple about 50 feet away that seems to be doing fine. And we have neighbors that have Japanese maples that had normal spring growth. Should we cut off the lower branches? They seem very dry and brittle. Is it possible to save this tree?

Albert Terpak,


Master gardener Rachel Tooker: To fully diagnose the reason for the lack of new growth on your Japanese maple, it would be helpful to know a little more, such as the variety of Japanese maple, how frequently the tree is irrigated and by what method, how much sun exposure it receives, the soil type, whether there are any other symptoms on the leaves and branches, and whether there are any signs of insect infestation.

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If the tree has been on the south side of your home for 20 years, receiving a significant amount of direct sunlight, it may just be in a slow decline. But here are some thoughts:

Yes, the dead lower branches should be removed. To make sure the branches are indeed dead, scrape off a little of the bark on each branch to see if there is any green tissue underneath. If there is, you can leave the branches in place and see if new shoots or leaves form. If not, you should remove the branches to help keep any potential disease from spreading or insects from entering the dead wood. When pruning, cut back to living tissue, but outside the collar of the branch – this is a small, ridged area where the branch attaches to the trunk. By cutting outside of the branch bark collar, the tree will heal most easily from the cut. In addition, your shears should be sanitized after pruning by dipping them in a 10 percent bleach solution to make sure the disease is not transferred to another plant. Do not dispose of the cuttings in a compost pile.

From your description of the lower branches dying and becoming dry and brittle, it is possible that the tree is receiving too much water and the soil is not draining sufficiently. This may lead to two kinds of conditions: Verticillium wilt and Phytophthora root and crown rot.

Verticillium wilt affects the vascular system of a plant – the network of tissue that transports nutrients, food and water among plant parts. The disease can cause foliage to turn faded green, yellow or brown and wilt in scattered portions of the canopy or on scattered branches. Shoots and branches die, often beginning on one side of the plant, and the entire plant can die if severely infected.

Phytophthora kills the roots and root crown area of infected plants and sometimes spreads upward into the stem. This causes plants to wilt and leaves to discolor, stunt and drop prematurely. Infected mature plants grow slowly and may gradually decline. Twigs and branches die back and the entire plant can be killed. In many, but not all plants, a vertical streak, stain or canker becomes visible on infected trunk wood under the bark. Black or reddish sap may ooze from darkened areas of infected bark.

In both cases, peeling back bark on infected branches may reveal stain streaks in the vascular tissue. The most effective way of preventing these diseases is to provide adequate drainage and practice good water management. Avoid prolonged saturation of the soil or standing water around the base of plants. Irrigate only as much and as often as necessary. Fertilize sparingly with a slow-release fertilizer and continue to prune out any dead wood. The leaves of plants can appear drought stressed, so sometimes home gardeners will respond to these symptoms by adding more water instead of allowing the plant to dry a little between watering.

For more information on Verticillium wilt, go to ipm.ucanr.edu/PMG/GARDEN/PLANTS/DISEASES/vertwilt.html. For more information on Phytophthora, see the UC IPM Pest Note 74133, “Phytophthora Root and Crown Rot in the Garden,” at ipm.ucanr.edu/PMG/PESTNOTES/pn74133.html.

Rachel Tooker is a UC Cooperative Extension master gardener for Sacramento County.

Garden questions?

Questions are answered by master gardeners at the UC Cooperative Extension services in Sacramento and Placer counties. Send questions to Garden Detective, P.O. Box 15779, Sacramento, CA 95852. Send email to h&[email protected] Please put “Garden Detective” in the subject field and include your postal address. To contact UC Extension directly, call:

Japanese Maple Problems – Pests And Diseases For Japanese Maple Trees

A Japanese maple is a glorious specimen tree. Its red, lacy leaves are a welcome addition to any garden, but they aren’t problem free. There are a few Japanese maple diseases and several insect problems with Japanese maples that you should be aware of to give your tree the care it needs.

Japanese Maple Pests

There are several possible insect problems with Japanese maples. The most common Japanese Maple pests are the Japanese beetles. These leaf feeders can destroy the looks of a tree in a matter of weeks.

Other Japanese maple pests are scale, mealybug and mites. While these Japanese maple pests can attack a tree of any age, they are usually found in young trees. All of these pests present as tiny bumps or cottony dots on twigs and on leaves. They often produce a honeydew which attracts another Japanese maple problem, sooty mold.

Wilting leaves, or leaves that are curled and puckered, may be a sign of another common Japanese maple pest: aphids. Aphids suck plant sap from the tree and a large infestation can cause distortions in tree growth.

Tiny clumps of sawdust indicate borers. These pests drill into the bark and tunnel along the trunk and branches. At worst, they can cause the death of branches or even the tree itself by girdling the limb with their tunnels. Milder cases can cause scarring.

A strong spray of water and regular treatment with either chemical or organic pesticides will go a long way to prevent insect problems with Japanese maples.

Japanese Maple Tree Diseases

The most common Japanese maple diseases are caused by fungal infection. Canker can attack through bark damage. Sap oozes from the canker in the bark. A mild case of canker will resolve itself, but heavy infection will kill the tree.

Verticillium wilt is another common Japanese maple disease. It is a soil dwelling fungus with symptoms that include yellowing leaves that fall prematurely. It sometimes affects only one side of the tree, leaving the other looking healthy and normal. Sap wood may also become discolored.

Moist, sunken bruising on leaves is a sign of anthracnose. The leaves eventually rot and fall. Again, mature Japanese maple trees will probably recover but young trees may not.

Proper annual pruning, cleaning up of fallen leaves and twigs, and yearly replacement of mulch will help prevent the infection and spread of these Japanese maple tree diseases.


By far the most common causes of damage to Japanese maple trees are incorrect watering, frost and sun. Especially when Japanese Maples are grown in containers they require even watering.

Planting them in the correct position should avoid much of the damage caused by high winds, extremes of cold and high heat.

Article and pictures by David Marks.



Aphids are tiny insects about 3mm long with the most common types being black fly and green fly. Other types do exist but are rarer. The first appear on juicy, tender young shoots. As the colony increase in number they spread to the underside of young leaves.

They cause damage in two ways. Firstly, they cause leaves to curl up and eventually fall off. Aphids also excrete a gooey liquid often referred to as ‘honey dew’. This attracts lots of diseases which becomes clearer when the ‘honey dew’ changes colour often going black.


Overfeeding, especially in spring, encourages aphids. The plant will quickly produce lots of soft new shoots which are readily colonised by aphids. So, avoid overfeeding your plants especially in the spring.

Early action when greenfly are first noticed or anticipated will enable more successful organic treatment of aphids. Roses are particularly affected by by aphids so the minute you see aphids on roses in your garden or area inspect other shrubs and trees for signs of an aphid attack.

If you aren’t particularly squeamish many of the aphids can be killed by running your forefinger and thumb over leaf and shoot surfaces. This will simply squash them to death! Water over the leaves after doing this will wash many of the dead aphids away. A spray is even more effective.

Preventative treatment that works is a spraying with 2 litres of water containing a teaspoon of washing up liquid. It is thought that the diluted washing up liquid clogs up the aphids and causes them to die. It has no ill effects on the plants themselves. Concentrate spraying on new shoots and the undersides of leaves.

Encouraging other beneficial insects which eat aphids is also another approach which works well. The main ‘consumers’ of aphids include ladybirds, hoverflies and lace wings. Encourage them into your garden by planting marigolds and calendula. Strangely, a patch of nettles is also an excellent way of attracting aphid eating insects. They attracted to the aphid species which colonise nettles but which affects no other garden plants.


Use only as a last resort but often it is the only solution when an aphid attack has become out of hand. There are lots of systemic insect sprays on the market which work well. Check the label to ensure they are good for controlling aphids. Systemic sprays used for roses are excellent.


Verticillium Wilt affects lots of plants, shrubs and trees. Most commonly affected are Japanese Maples, chrysanthemum, carnations, cotinus and catalpa. Strangely, strawberries are also affected.

The main sign of infection is leaves turning brown, especially near the base. Plants begin to wilt in warmer weather although they may temporarily recover if the weather turns colder.

Woody plants such as acers and chrysanthemums will have brown marks on the wood immediately below their bark. Branches may die completely in parts of the plant.


This is a disease which is first spread in the soil. It enters the plant through damaged or weakened roots. Once the Verticillium Wilt fungus infects the roots of the plant it spreads upwards. The plant’s natural defence system attempts to isolate the fungus but in the process it prevents water being passed around the plant internally. This causes parts of the plant to die.


There is no treatment for Verticillium Wilt. Managing an infection is a matter of damage control because the disease can be passed to other plants. One common source of infection is the soles of your boots transferring infected soil from one part of the garden to another.

The plant or tree should be dug up with as many of the roots as possible and burnt completely. Be careful when transferring the plant and roots to the point of burning, do not allow any possibly infected soil to come into contact with any other soil or plant.

Unfortunately, the disease can remain in the soil for up to 15 years so do not plant any susceptible plants on the area for many, many years. Sometimes a new plant will appear to grow successfully for two or three years before it also shows signs of the disease. Don’t waste your time cleansing the soil with Jeyes Fluid or similar preparations, they do not get rid of Verticillium Wilt in soil.

Ideally the area should be grassed over and left. However there some plants which have immunity to Verticillium Wilt and these should grow successfully on an infected site. Apple and pear trees both do well but not plum trees. Conifers are resistant and these come in a variety of forms and sizes. Other plants and trees to consider with excellent immunity include, beech, ginkgo, hawthorn, hornbeam, mountain ash, sycamore and walnuts.


Vine Weevil

Vine weevils have two distinct appearances depending on the stage in their life cycle, When they are grubs / larvae in the soil a vine weevil is about 2cm / 5/8in long when fully grown, white at first but turning brown. Their bodies are “C” shaped and they can be found under the soil near the main stem of the plant.

When they emerge from the larvae the adults are 1cm / ¼in long. They look like small beetles, browny black coloured and pear shaped, the heads are a dark black. The top part is pitted with lots of little indentations. They have what appear to be wings but in fact they are unable to fly.


As adult “beetles”, vine weevils will eat the edges of leaves. This attack disfigures the leaves but healthy plants, trees and shrubs will recover from this damage. However the grubs eat the roots and even sometimes the main stem of plants which, if left untreated, is often fatal.

Note that plants, trees and shrubs grown in open ground are not affected, attacks occur on plants grown in containers. Understanding the life cycle of the vine weevil is essential to minimising the damage they do to plants.


July to August
The adult lays eggs near the surface of the soil. If the soil is mulched the eggs will most likely be laid in the mulch. Each adult will lay about 200 eggs which take about 3 weeks to hatch. Immediately the eggs hatch the emerging larvae begin feeding on the smallest roots of the affected plant. as the larvae grow in size they will ‘upgrade’ to feeding on larger roots and in some cases the main root.

September to November
As the temperature of the soil begins to cool the larvae will gradually stop eating and burrow down lower into the soil where they hibernate over the winter.

March to June
The larvae start feeding on larger roots as the soil temperature increases, In May to June they transform (‘pupate’) into adults.


Vine Weevils prefer container grown plants and small trees. Almost any shrub or small tree can be affected although vine weevils do have a preference for camellias and rhododendrons. Japanese Maples are also a plant of choice.

First attack the adult vine weevils and this can only be done manually. When an adult vine weevil is attacked by a predator it’s natural reaction is to fall to the ground and play dead. Their browny /black colour makes them very difficult to spot on soil. The plan of action should be to lightly shake the shrub which will cause the bugs to fall off – an upturned umbrella will catch many of them. Another method is to lay white paper around the plant so all the Vine weevils to be seen more clearly.

The next treatment is to encourage wildlife which enjoy eating the vine weevil at all stages of their lives. This includes birds, hedgehogs, frogs and toads. One particularly good method is to encourage birds into your garden by providing them with food and water. Position the bird feeder as near to the affected plant(s) as possible.

Biological control of the larvae stage stage of the vine weevil is a good method of interrupting their life cycle. There are a few nematodes readily available from garden centres or online which will attack vine weevils. Our favourite is Steinernema kraussei mainly because it remains active at lower temperatures compared to other nematodes. This allows it to be applied from mid-March through to September.

There are chemicals which can be applied to the soil but they should not be used for edible plants although they are fine for Japanese Maples. Search on the internet for “vine weevil chemical control” if you wish to use the chemical route but the previous suggestions will work as well if not better.

Several different maple tree diseases can cause problems for your cherished trees. If you know what to look for, you can understand which problems are serious and which can be ignored.

Maple Wilt

One of the most common maple tree diseases is known as maple wilt. The causal factors are Verticillium albo-atrum or Verticillium dahliae, which are fungi found in the soil. This is a common and serious problem that can even kill established trees. Maple wilt seems to be most common in Norway maples but is also found in silver, sugar, red, sycamore and Japanese maples.

  • Description: A tree with maple wilt may have browning or scorched-looking leaves, and diseased branches will have small amounts of sick-looking leaves. Sometimes olive-colored streaks will be found in the sapwood of an affected tree. Cut the bark and look for these streaks, then take the bark to your county Extension Office for confirmation.
  • How it spreads: The disease starts in the root system and spreads up through the sapwood into the upper branches of the tree, causing big limbs to start dying back.
  • Prevention: A healthy, vigorous, well-established tree may be able to beat maple wilt, but most trees will die within a season or two of showing symptoms. Unfortunately, the best way to control the disease is to destroy infected trees to keep it from spreading. If that’s not an option, or the tree is not seriously infected, pruning out affected branches may help the tree survive. Keep the tree well-watered during the time it is trying to heal.


Anthracnose (Colletotrichum gloeosporioides) refers to a group of diseases caused by fungi, and it can affect many shade trees. Similar fungi attack other trees such as sycamore, white oak, elm and dogwood trees. They cause a loss of leaves and are usually relatively harmless when the disease only strikes once.

  • Description: This type of fungus is particularly common after unusually cool, wet winters and can affect bud formation, kill small twigs and leaves, or cause premature and repeated early loss of leaves. On maple trees, it causes brown or purplish-brown spots and stripes near the veins on the leaves, and the tree may lose its leaves prematurely. If the disease cycle repeats year after year, the tree may become stunted or deformed because it cannot keep its leaves long enough to grow.
  • How it spreads: Anthracnose spreads by airborne fungus and is especially prevalent during a wet or rainy spring. In maple trees, it is spread in April or May in most gardening zones. Wind blows through the infected trees and spreads spores onto new maple trees. Wet springs provide the ideal conditions for anthracnose spores to take hold.
  • Prevention: It’s important to rake up all the fallen leaves each fall and compost them or burn them (if your area permits burning.) Fallen leaves provide the ideal breeding ground for anthracnose. Another option is to have an arborist spray a special fungicide containing a chemical called mancozeb on the trees. If the damage continues year after year, it could predispose the tree to other problems.

Tar Spot

Another common maple tree leaf disease is tar spot, which can be caused by one of two different fungi: R. punctatum or Rhytisma acerinum.

  • Description: Tar spot is an ugly but mostly harmless disease that strikes several maple species. As its name implies, tar spot disease looks like big black tar spots on the top of the leaves.
  • How it spreads: Infection typically begins in early spring and continues into the early summer. The fungus is able to take hold when there are prolonged periods of wet weather that prevent the leaves from drying off. Leaf spots start out yellow and evolve into a dark, tar color.
  • Prevention: Treatment is generally not recommended for tar spot because it is usually not a serious problem; however, raking up fallen leaves will keep tar spot at bay.


sapstreak (Ceratocystis coerulescens (C. virescens)) is a fungal disease that affects sugar maples. It is a fatal disease that discolors the wood, so salvage is not possible. This disease is mostly seen in parts of North Carolina, Michigan, Wisconsin and Vermont.

  • Description: The disease causes foliage at the crown of the tree to become smaller, and bald spots often appear.
  • How it spreads: Over time this dwarfing spreads and the tree ultimately dies. When the tree is cut down, a radiating pattern will be seen in the wood of the lower part of the tree.
  • Prevention: The only way to get rid of sapstreak is to cut down the tree as soon as possible after noticing the problem. Sapstreak can spread with the help of insects through wounds on the trees, so removal of infected trees is important to keep other trees healthy, if you have multiple maples.


Like anthracnose, phyllosticta leaf spot (phyllosticta minima) is caused by a fungus.

  • Description: phyllosticta causes raised tan or dark brown leaf spots. The spots may turn dry and brittle and crumble away, leaving holes in the maple leaves.
  • How it spreads: As with anthracnose, the fungus that causes phyllosticta spends its winters hiding among the fallen leaves on the ground. It waits until the springtime, when damp conditions give it the opportunity to spread. Breezes carry the spores to new hosts.
  • Prevention: Rake up fallen leaves each autumn and discard them properly to prevent fungal diseases such as phyllosticta.

Preventing Maple Tree Diseases

The best thing you can do for your trees to protect them from maple tree diseases is to take good care of them before they develop a disease. That means water regularly, fertilize annually, keep the area around the trees clean, prune when necessary and seek help immediately if you notice your tree looking ill or having problems.

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