Based on the additional info, I'm going to guess you have a combination of fertilizer burn and sun burn. I think there's a couple of things going on here. Container culture is very different than planting in the ground, and even If planted in the ground I wouldn't plant a Japanese Maple in a mixture of 50% compost. My guess would be your tree was showing signs of fertilizer burn from the compost, and the high temps aggravated your already stressed tree. I believe I remember reading that when nutrients are too high in the soil, a plant isn't able to absorb water from the soil. With the high temps the tree needed even more water but couldn't get it due to the nutrient imbalance. At this point, if I'm right, I think your only option is to get the tree out of the compost mixture. Did you bare root the tree when you repotted or did you pot up ( ie take the tree out of the pot, loosen the out side roots and pot into the large container placing the compost mix around the existing mostly intact root ball? Reason for asking is, if you only potted up you can likely plant the tree in the ground for this year or pull the plant out of the compost mixture and pot up using a soil with similar soil characteristics as the soil in the root ball. Be careful and try not to disturb the roots any more than necessary. You're getting late in the year to be potting up but leaving the tree in the compost is likely to do more harm. Also keep the roots moist as best as possible during the procedure. If the roots dry out, they'll die and cause even worse problems. The tree should be moved to a shady area protected from wind, after or during the pot up/planting, until it begins to improve. Also a note on full sun, some cultivar of Japanese Maples are listed as capable of being planted in full sun. This is a misnomer because full sun in Japan, western Washington, or even in the north east is different than full sun in California, Texas or Georgia. Although some of the Sango Kaku's are among the more tolerant of sun exposure when planted in the ground, I've read many examples of these trees showing sun exposure stress symptoms when in hotter climates in containers. Hope this helps, and also hopefully one of the others will come along and correct me if I've given information that's too far off the mark. PS The above recommended procedure would only be a temporary fix. Next spring, just as the buds begin to swell, the tree would need a full repot into an appropriate container medium if you wanted to put it back in a pot or keep it in a pot which ever the case may be. Blake

It was suggested "Exact diagnosis can be made by taking a sample to your local extension office but if it is Phytophthora (or another root invading fungus), there is little you can do now." If such a sample is brought to the Extension Service office, please call ahead so that the Master Gardeners have time to locate information as to how to sample the soil & the affected root tips. Also know that a fee is charged, the precise amount depending upon the test to be done -- fees for the OSU Plant Disease Clinic begin at $40.00. Beyond that, I doubt this will be an easy diagnosis. I'd consider multiple factors potentially contributing to the problem: 1. Because OP said s/he "paid quite a bit of money" I suspect it is a sizable specimen. If so, post-plant irrigation is a critical factor in survival. All transplants should go into evenly moist soil, then the rootball should be supplied with more water than the surrounding area during the following months. Failures of recent transplants typically are due to water -- either too much or too little. 2. The sudden very cold weather in December, without snow cover, damaged & even killed many plants hereabouts, including those which survived 10 years or more. 3. The tree is a recent transplant. As such it is more likely to be damaged by cold than an established tree of the same kind. 4. Dormant roots are less susceptible to water damage than are actively growing roots. 5. In general -- and yes, exceptions exist -- root rot results in entire tree failure. 6. It's nigh to impossible to diagnose root rot by looking at dead branches and/or browning leaves. 7. And perhaps most critical, multiple nearby specimen maples are in potential jeopardy if the problem is indeed soil-borne, such as Phytophthora root rot or verticillium wilt. So, I suggest pinkswine consider having a certified arborist or two come for an on-site evaluation. To locate a certified arborist, look in the Yellow Pages under the heading of Trees or something similar. Ads for companies with a certified aroborist will either have a statement or small rectangular logo stating such.

Hi, If your maple was kept in a shaded area at the nursery and then you brought it home and placed it in a place that got more direct sun it could have caused the damage. Plants are like us in that if we stay in the office during the week and then decide to go to the beach we'd sunburn. Same with plants. Whenever you decide to move your plant from a shady area to an area that get more direct sunlight you need to do it gradually. I don't think your problem would be root rot from too much water. It takes a while for something like this to manifest itself. It could be what I mentioned above or it could be from too little water. Remember Japanese maples like a regular watering schedule with moist, but not wet soil. It may have been from fertilizer burn, but you'd really have to over do it with organic ferts., but it doesn't take much with chemical ferts high in nitrogen. Maples aren't heavy feeders so go easy on the fertilizer. I use liquid organic ferts for my potted maples and use only 1/4 to 1/2 the dosage every other watering or so. Layne

There is a good possibility that root rot could be the cause. It is also possible that verticilium wilt is the culprit (hopefully not). If possible take a picture of the damaged limbs to show the coloration of the stem. Also,cut the dead branch off cleanly and look at the wood inside. If it has brown or blackish streaks inside it is possible that verticilium is the cause. If not, it is more likely that a root rot fungus is the cause. This is of course assuming that no damage has been done to the limb or roots.