So far the internet hasn’t provided any definitive answers on this one. We have a 20ish year old JM. It was a seedling at a local botanical garden and very close to the plain green acers, but with better spring and fall color. Trunk diameter is about 8”. A month or two ago I noticed some relatively minor yet early leaf drop at the ends of branches. I’m in South Carolina, so it’s often Thanksgiving before they turn colors and drop leaves. I did an inspection at the time and there were no signs of insects or fungus. The leaf drop has continued and I did another inspection today. It appears that leaves begin to brown at the base, where they connect to the petiole. As that spreads the leaves eventually curl around the dead spot, die completely, then fall. Still no noticeable damage from insects or fungus. Verticillium fungus has come up as a possible culprit but I have not found anything specifically outlining this type of progression in the leaves (browning from base as opposed to tip). I will say that it has been a relatively wet summer that was preceded by a cool spring. But the tree is within the irrigation systems range so I don’t think it’s received any more water than normal. It was just free water. :-) There is a pond about 50’ from the tree.
Hi Jeffrey and welcome to the maples forum A photo would help members to give an answer to your problem. Here is a link on how to do it. https://forums.botanicalgarden.ubc.ca/resources/attach-photos-and-files-from-mobile-device.41/ My initial thoughts is of over watering, as you say the leaves are browning from the petiole. Leaves browning from the tips of the leaf lobe is often a sign of under watering. You might also have a borer problem, but further inspection by you and some photos might help here again.
Thanks for the response Acerholic! I don’t run into problems with these trees often but this group is awesome when I have! I checked the trunk and limbs and didn’t readily see any signs of boring insects. I will look them up and check again though. Too much water could be the issue. I want to say I only ran the irrigation system 6-7 times prior to the second week of August. We have a zoysia lawn and live in South Carolina so that is extremely unusual. I had a copper based fungicide and insecticide mixed up for the tropical plants that will need to come inside soon (always spray once in the fall to keep problems at bay while indoors). I went ahead and sprayed the maple just in case.
Hi Jeffry, I couldn't see the base, but if you have lawn up to the trunk, then this can cause problems,as maples are shallow rooting and get starved of oxygen and nutriens fron turf. I would say that too much water is your problem, possibly trapped in by the turf. Maples like to be in a moist soil, but not waterlogged. They need good drainage and air to the roots. I advise no turf around the tree canopy and especially maples.
20 years old tree was probably planted long ago, but mistakes from planting may appear even now, if for instance root circling was not handled properly or the tree was planted too deep. How was the vigor of this tree recent years? Was it normal or the tree has grown more slowly recently? Another option is that there is some kind of agressive infection (attacking healthy, not weakened tree), but as I never seen this kind of symptom before, so I can't even imagine, what species is the culprit. BTW, how many weeks are remaining before usual leaf dropping?
You must have very hot summers in SC, I also think that opver-watering and/or a soil that retains too much moisture might be the problem. The fourth Thursday in November is about the same for leaves to drop here too. My Acer palmatum which is in the ground (plain species) even retains its leaves up to December most of the time. Here's a picture from last year, December 7th. You can also see another one in a pot, in the background :
No lawn at the base. It has a good 15-20 feet in all directions. That said, it is watered by a zone that also waters the lawn. So that, combined with an abnormally wet spring and summer are very likely the issue. When I first said that the rain was just a replacement for the normal irrigation what I didn’t account for is that the area behind the tree (and where water would flow) is not irrigated. I think it is likely that with all of the soil being wet for so long it kept the typical drain paths from flowing. I inspected the trunk and there’s nothing damage or indications of a boring insect. FWIW, the tree has been in its current location for 8 years. Prior to that I had it in a pot on a drip system, but it broke through the pot well before I moved it here. There was a huge root system but it wasn’t bound since it had gotten out of the pot. Growth this year was great up to a month or two ago. The other acer nearby is perfectly fine, but gets less irrigation when the system is on. And 100% yes to us having hot summers! I’m 100 miles from the coast and 100 miles from the mountains. In that sweet spot where there’s no cooling from the ocean or elevation. We generally start getting into the 90’s in early to mid May and stay there until mid September. Thanks everyone for your help! I am going to do some modifications to the irrigation around there and see if that helps next summer. I don’t think what’s happening now is far enough along to really hurt the tree before then.
