Gardening with Gary

Gardening Advice from an Expert

Japanese Maple

Q. I have a beautiful dwarf Japanese Maple that has very finely cut leaves and until last year they were a very deep red color. I planted it about 10 years ago. The trunk is almost 3" in diameter and it's about 3-4' tall and spreads out about 6-8'. My yard backs up to a white pine & oak woods (which my Rhododendrons and Hydrangeas appear to love). Recently some of these trees have grown on their own in my yard and made it mostly shady, rather than partly shady. Is it possible to relocate the Japanese Maple to a sunnier spot? If so, would I do it after it loses its leaves in the Fall? If not, I could remove the nuisance trees which aren't really desirable types, mostly silver maple, oak and white pine that appeared in the past 5 years or so. If I remove these trees, would it be best to do it now, so that the shade doesn't impair the tree any further?

A. You have an unfortunate occurrence. I hate to see you attempt to move the well-established maple as that is what you like the most. The other trees are not wanted there and are creeping in, taking valuable light, water and food. I would remove or cut back the nuisance trees rather than risk your maple. I have seen maples moved when well along in years, but some have succumbed to the disturbance. It is far better in my mind to rid yourself as soon as you can of the interferences. Drastic trimming is a possibility, but short of that, then cut them off at the base and, in the spring, dig up the root system as best you can. Do not wait until the spring after the leaves have emerged.

Q. I have a Japanese maple (Osakazuki, a somewhat lanky tree form) which has dead spots on the leaves, with a discrete border around them. The spots are small, and the rest of the leaf looks healthy, but there are a lot of spots and they are becoming more abundant. Somebody at the plant store said it was fungus and sold me a traditional fungicide, I recently bought an 'organic' one with I think copper as the active ingredient. Haven't used either of them yet. I am interested in:

1) do you think that is the problem and
2) what can I do to help the plant in addition to treating the fungus itself? I'm thinking maybe soil amendments of some kind?

A. Yes, I thought immediately as I read your post that you are experiencing a fungal attack. It is quite common but must be treated as it will not just go away. Copper has proven to be an effective ingredient to combat fungi. I recommend that you use it as prescribed on the label and do the approved follow-ups as this is not a one shot cure.

As for soil, no there are not amendments to be added to kill the fungi. But, any infected leaves which you trim off and the ones fallen to the ground must be collected, bagged and hauled far away. Pick up any evidence of the spots wherever you see them. The spores spread in this method and fly thought the air in the breeze from tree to shrub to tree!

To me, it sounds like you have the second fungus not the first, but I decided to include both descriptions for you below:

Tar Spots of Maple: Pathogens: Rhytisma acerinum, Rhytisma punctatum

These dramatic, but inconsequential, diseases of numerous maple species cause tar-like spots on leaves which can reach almost 24 mm (1 inch) in diameter.

Symptoms first appear as yellowish spots on the upper leaf surface. Later in the summer, a black, tar-like mesh of fungal and leaf tissue develops within the yellow spot. Some early leaf drop may occur but is not considered serious. Fungicide treatment is usually not necessary.

Phyllosticta leaf spot of maple: Pathogen: Phyllosticta minima

This disease affects a number of maple species, particularly silver, red, Japanese and Amur maple. Leaf spots are roughly circular, tan in color with purple to red borders. Later in the season, black fruiting bodies of the fungus arranged in rings appear within the lesions. Since damage to the plant is minimal, fungicides are rarely recommended.

Control:

Cultural management is generally sufficient to keep these diseases in check. Leaf spot fungi overwinter in and produce spores for new infections on the fallen leaves, which should be gathered in the fall and removed from the site or destroyed. Infection occurs when leaf surfaces are moist; improve air circulation by thinning crowded plants and pruning overly dense growth. Avoid overhead irrigation, or water only in the morning to ensure leaves dry quickly.

Adapted from Stephen Nameth, C. Wayne Ellett and Jim Chatfield, Ohio State University Extension, 1999.

Laura writes~ My neighbor planted a miniature Japanese maple in the back of our townhomes. I don't believe it is very happy at all. Its leaves are turning brown and shriveling. This area receives direct sunlight during the day from about 8AM to 5PM. Is this too much sun? Is there a way to save it or is this a "better luck next time" situation?

A. These trees are fine and beautiful but are temperamental when it comes to light, water and humidity. They love to react with curling dried leaves which drop. Some of this is natural but in your neighbor's case, I feel it is starting to say Goodbye!

This tree needs lots of sun, but shade during the hot summer months, especially between 12-3 PM. It needs plenty of water so that the soil is evenly moist. A dilute concentration of Miracle-Gro should be applied as directed once a week until the leaves drop in the fall.

Soil Type: Sandy or loam pH Range: 3.7 to 6.5 [theirs could be too high, so soil test the pH]

Performs best with rich, moist soil conditions in partially shaded locations. Plant in soil that is well-drained, yet moist.

Keep soil moist during summer. During dry periods, water deeply by placing hose at base of plant and letting water trickle into the soil. Mulch around base of tree in summer.

Summer heat and drought problems:

Mulch trees with 2 1/2 - 3" of shredded bark, preferably hardwood, to insulate the roots and prevent water from evaporating around the tree. Water deeply twice a week; water more often if it is a newly planted tree or a container-grown tree.

Leaf tip burn is unsightly, but not a cause for panic. It is most often a result of too much water, too little water, an underdeveloped root system (as a newly planted tree would have), or too much fertilizer, especially if a salt based fertilizer is being used. Afternoon shade and good watering practices help, but in some conditions you may have to live with it for the rest of the season. Under extremely stressful conditions your maple may drop all its leaves. Do not despair. Maples have a secondary set of leaves waiting for just such a time. The tree is protecting itself and telling you it is not getting enough water.

When your tree is feeling stressed do not try to fertilize it into feeling better. Do not fertilize it at all. Fertilizer is a stimulant and your sick tree does not need a stimulant. Instead, feed it kelp meal or something similarly rich in trace elements. Also, if your tree is stressed, be on the lookout for other problems such as insects or disease to which it will be more susceptible at this time. Catch these problems early so you can deal with them immediately and prevent a spiral of decline.

Pruning for form is best done in late summer or early fall. Good form is largely a question of personal taste. We like to let air and light into the center of the tree so that we can see the tracings of branch structure. Working up from the base and from inside to out, clean out small twigs growing along the trunk and major branches, dead wood, and crossed and rubbing branches. Stand back and look carefully at your tree's shape. If it is not pleasing, look for what you need to remove to improve its form. Before making each cut, study where the branch goes and visualize the tree without it. Cut just above a live bud or just in front of the collar (the small ridge where a branch attaches to another).

Mulching is always a good idea for fall; it will help insulate the roots for winter and protect their early spring growth.

Assistance from: http://www.japanesemaples.com

Moe writes~ I have a 4 year old Japanese Red Maple. This year the leaves sprouted from most of the branches, however, many of the branches on the West side are bare. Should I trim it?

A. Yes, trim some of the branches to round the shape. It sounds like it experienced a partial dieback from the winter cold and/or wind. Protect the tree after the leaves fall, so you do not subject it to harsh conditions, as these maples tend to be quite sensitive. Do not trim or shape after September so that it will harden for the climate change.