Hi Mike,
You state the soil is clay, is the ground waterlogged also acers like an acid soil. you can see my Tamukeyama at the link below.
George

Here is a link that might be useful: George's Japanese Garden

When you say trunk rot, could you mean sun scald. The trunk will look rotten because it gets a localized scald and then dies. Sounds like sun exposure to me. I have the same problem.

If your in full sun, zone 7 and clay soil then the variety you lost is inappropriate for that specific micro setting w/o some parameter ajustments, but sun exposure is the most important. If it's afternoon sun then you need to look at another local with afternoon shade. There is point at which the late afternoon sun's incedent angle has an intensity similar to killing bugs with a magnifing glass and it will fry the bark in a specific location where the surface is near normal to the sun. If the tree is not completely dead it can be moved to a shady spot and nursed back health.

If you had poor drainage, the trunk would not rot, but roots would die and the tree would go into decline.

I would plant on a mound, up out of the clay with good drainable and amended soil, mulch and protect from afternoon sun and winter wind.

I agree with jeepster's suggestions about planting on a mound. Be careful not to plant on a steep mound which will create run off so fast that will make it hard to keep the root zone moist. Make the mound wide enough so you can create a flat top so the water can slowly seep in to ensure you can keep the soil moist but not wet. The second thing is the protection from afternoon sun in your area is a must. If you can provide them a place with filtered sun or morning sun with afternoon shade you stand a much better chance seeing these trees not only survive but thrive.

Kent

JAPANESE MAPLES (2001, Estate of J.D. Vertrees) says

"One of the most talked about and least understood problems of Japanese maples is twig dieback. Any one of a number of fungal diseases, insects, climate conditions, cultural practices, and soil chemistry can cause this symptom. Disease, however, should not be confused with a certain amount of "natural pruning," which takes place as the plant matures."

Key words:

Verticillium Wilt
Fusarium
Botrytis
Pythium
Pseudomonas
Anthracnose
Cankers

Thanks for all the suggestions. In my case, it wasn't twig die-back, but the entire plant just suddenly died (without dropping it's leaves). It is at the bottom of a berm (east side)and may very well get wet feet from its location, and there is a fair amount of afternoon sun in the summer. I like the suggestion of planting it up on a mound, so I'll give that a try next, and hope for the best.

Mike,

In addition to looking into the other factors listed above, you might want to get your soil tested. If your previous trees died from Verticillium Wilt, then that bacterium (virus? I forget) is still in the soil and is the very DEVIL to get rid of. It will continue to infect (and possibly kill) any maples (japanese or otherwise) that you put in or near those spots.

Sorry to be a doomsayer, but J. maples can get pretty expensive, and I'd hate for you to keep pouring your money into firewood like that. :)

Cheers,
Susan

I think Susan is probably right on the Verticillium Wilt. It'll kill a tree outright without much warning. I read a post here a long time ago about it and the person writing had cautioned about working in the soil near the roots. JM's have a very shallow root system and when you start digging near them, that introduces the wilt into the plant.

I also second the opinion on the drainage and heat. I live on Long Island where the climate is very similar to that of Japan and is moderated by the water. If you're more inland the summer heat and humidity will work against you. I'm fortunate enough to have 100% fast draining sandy soil which is perfect for just about everything! Finally, google up " Mountain Maples " in California. They have a tremendous selection of JM's, although a little pricy. However, they are very helpful and probably can steer you towards some varietys that would do better in your area.

Mike,
Verticillium wilt is a strong possibility. Every once in awhile I do a post cautioning people not to garden or disturb soil under maples and dogwoods. VW enters a plant through broken/cut roots. If you still have the dead maple, remove a good sized limb and split the limb down the center vertically. If you note a dark green to black line running down the center of the branch this is a sign of VW. Check more than one branch and it wouldn't hurt to also split the trunk apart to see how that looks. The discolored 'line' does not always appear on every branch even though the tree is infected with Verticillium wilt.

There's not enough information here to pin down a pathogen, if that's even the problem. My point in posting the Vertrees excerpt was to show that more is going on out there than verticillium. And looking at the plant may not be enough to make a diagnosis. Declining Acer macrophyllum in the Seattle arboretum turned out to be hosting several kinds of water molds, after root samples were placed on agar in a lab.

I would doubt verticillium wilt. If that was in the soil, your other plants-juniper right next to the maples--would be having similar problems.

J. maples in the D.C. area have trouble for a number of reasons, sun scald is a big one, especially with thinner skinned and lace leafed varieties. Summers are very hard on these types. Also just because a maple's leaves shrivel up and drop in summer, doesn't necessarily mean the tree is dead. Could just mean too much sun. This happens regularly at nurseries here. J. Maples in containers usually come on sale for 60-70 percent off after they're scun scalded and lose their leaves. They are still very much alive, and come back well the next spring, if properly cared for...

Additionally, trees here tend to get planted too low in the ground. The underlying clay soil acts like a bowl for newly planted trees forcing them to sit in soggy soil. Planting the main portion of the rootball above grade and using mulch can help tremendously with getting J. maples started.

We have a japanese maple approx 15feet tall by 10 feet wide.It's not a bloodgood. I'm not sure of the name.We purchased it two years ago from a nursery.It had a4ft diameter root ball.It has been a beautiful tree up until now.It is now in full leaf and I noticed a main arm approx 3" in diameter that had no leaves at all on it.This was in the center of the tree and the tallest branch. I cut off an extending branch from it and went to a nursery to see what they thought. They thought it was the verticillium wilt disease. I was recommended to prune back the large arm to where the last leaves are still alive. To fertilize it monthly with 6-8-6 fertilizer and hope for the best.The nurseryman looked at the end cut of the branch I took him and noticed a brown ring inside the diameter of the cut.
Is there any true way of knowing for sure or any other information you would have? I would hate to lose this tree.
Also is this spreadable? I do have a smaller bloodgood in another bed.What should I disinfect my pruners etc I have used around this tree?Any information would be greatly appreciated. Sincerely, Cindy in Canada

Ask your equivalent of Cooperative Extension, down here this works with state universities. If you have a local ministry office maybe they can put in you touch with a lab that can see what grows from tissue samples of your tree on agar (for a fee).

Wow, how much did that tree cost? (15' tall, 4' rootball).

I bought a healthy Crimson Queen Lace-leaf Japanese Maple 4 weeks ago. After about 2 weeks I noticed that the leaves started wilting/drying and curling. When I touched the leaves they just fall down. This tree gets a lot of direct strong sun for 4-5 hrs per day. The soil in my area is very clayish. I dug a little soil around the tree to see if tree is drowning or suffocating and I saw that there was pool of water around it. Looks like the soil in my area is not draining but retains all water. Would this property of soil drown the tree? Do I need to move it somewhere else. Is it enough if I remove the tree add a little soil under it to increase the height and replant it in same place ? I also tried to break some small branches and it looks like some are brittle and they easily snap. The bark looks green. Please advise on options. I don't want this beautiful tree to die. Is there a test to tell if it is alive.

I bought a healthy Crimson Queen Lace-leaf Japanese Maple 4 weeks ago. After about 2 weeks I noticed that the leaves started wilting/drying and curling. When I touched the leaves they just fall down. This tree gets a lot of direct strong sun for 4-5 hrs per day. The soil in my area is very clayish. I dug a little soil around the tree to see if tree is drowning or suffocating and I saw that there was pool of water around it. Looks like the soil in my area is not draining but retains all water. Would this property of soil drown the tree? Do I need to move it somewhere else. Is it enough if I remove the tree add a little soil under it to increase the height and replant it in same place ? I also tried to break some small branches and it looks like some are brittle and they easily snap. The bark looks green. Please advise on options. I don't want this beautiful tree to die. Is there a test to tell if it is alive.