Ginkgo tree leaves suddenly wilting and falling off

Question: Hello! This is my third growing season with this Ginkgo biloba 'Jade Butterfly' tree in my backyard. It thrived the first two growing seasons, putting on height and width. This past winter, we had a vole infestation and I saw holes around the tree. We got rid of the voles, and I did some spot checks on the roots, which looked healthy. When the tree leafed out this year, the leaves were green and healthy, although there were fewer of them. I thought the tree may be recovering a bit from vole damage I didn't see, but since what was there looked great, I wasn't too worried. In the past two days (since I last checked the tree) the leaves have gone from that healthy green to yellow and wilted, even completely shriveled and brown toward the base. I am torn between whether this is over-watering or under-watering and unsure what to do next to give the tree the best chance of survival. Any advice would be greatly appreciated. Here are a couple of other notes which may be helpful: In the past, I have not watered the tree during the summer; this summer I have watered twice, hoping I might help it bounce back from anything the voles may have done that I didn't see - now I'm worried those two extra waterings have harmed the tree I fertilized the tree the first year, but not the second, and not this year One of our dogs started peeing in that area this April; we put a stop to that with the chicken wire you see in the photo, and the tree leafed out like normal in May  Thank you so very much for your time and assistance!

responder: Alison O'Connor, PhD  Replied July 04, 2024, 11:19 AM EDT
response: Hi Sarah,  First, resume regular watering - it's been so hot and this is still a very young tree. Second, remove all the grass below the tree and add a layer of wood mulch. Keep it a few inches away from the base of the tree. The grass is competing with the tree for water and resources. I also have concerns the tree may be planted too deep. This is a grafted tree, so there will be a crook that should be above the ground - and then the roots would be a couple inches below the graft union. If it's planted too deep, then the roots are not at the soil surface and may not be getting adequate water.  If it is planted too deeply, you can dig it up and plant it properly.  But start by removing the grass and then checking the soil moisture. It's been so hot and all of our trees will need some supplemental water, even if they are mature. Younger trees will show signs of stress more quickly.  Let me know what you find!

responder: The Question Asker Replied July 04, 2024, 11:45 AM EDT
response: Hi Alison, Thank you so much. I will get started on those steps right away. I should have mentioned that the tree does get watered by the sprinklers every other day. How often should I water in addition to that?  Sent from my iPhone On Jul 4, 2024, at 9:19 AM, Ask Extension <<personal data hidden>> wrote:   ﻿

responder: Alison O'Connor, PhD  Replied July 04, 2024, 11:53 AM EDT
response: Hi Sarah,  That depends on if the tree is actually getting the water or if the grass is mostly using the water. But aiming to water the tree directly once per week with a few gallons would be ideal.  If you replant the tree, then follow the steps for newly planted trees - essentially you'll water often for several weeks: https://extension.umn.edu/planting-and-growing-guides/watering-newly-planted-trees-and-shrubs

responder: The Question Asker Replied July 04, 2024, 12:54 PM EDT
response: Okay, I’ve just started doing some digging. I’ve removed about 4” of mulch/soil and am just hitting the roots. A couple of inches were mulch, so the soil was hitting about 2” above the roots and the mulch another 2” above that. What do you think about depth? I’m not sure I’m much good at identifying the grafting crook you referred to.   Sent from my iPhone On Jul 4, 2024, at 9:53 AM, Ask Extension <<personal data hidden>> wrote:   ﻿

responder: Alison O'Connor, PhD  Replied July 06, 2024, 5:17 PM EDT
response: Hi again,  Sorry - long weekends are hard to respond to questions.  While you found small roots, have you located a buttress root? A large root that will be located near the top of the root ball. This would be what forms the flare as the tree matures - the sloped base.  The buttress roots need to be located just below grade.   The graft union may look something like this: https://images.app.goo.gl/H3WGNARxu4byqP3w9  Great job exposing as much as you have already! When you replace the mulch, be sure to keep it away from the trunk and expand it as far as you wish.

responder: The Question Asker Replied July 09, 2024, 12:08 PM EDT
response: Hello!  No problem at all. I dug deeper and did locate the buttress root you described, and it was about 4" below grade. Since we last spoke, I've done the following:  Watered 3 gallons July 4 and covered the small exposed roots with mulch (not soil, since it was sounding like I'd need to re-plant)Yesterday: Exposed as many roots as possible and raised tree about 4" higher  Re-mulched, with a few inches clear around the trunk Watered 3 gallons  I will plan to follow the newly planted watering guide you sent from here on out. The tree is continuing to look worse and drop leaves – am I too late, or does it still stand a chance?   Photos of re-planting and current state of leaves attached. One of my kiddos put a flower by the tree for good luck ;)   On Sat, Jul 6, 2024 at 3:17 PM Ask Extension <<personal data hidden>> wrote:

responder: Alison O'Connor, PhD  Replied July 09, 2024, 4:15 PM EDT
response: Hi Sarah,  You did such a good job! I'm really excited and proud of you - most people are pretty hesitant to do major excavation.   I hope the tree will set buds - that's the most important thing. As long as the leaves are on the tree and somewhat green, they will photosynthesize. If they can stay on for another few weeks, I *hope* they will set buds for next year.  Keep up with the watering schedule you've established - if we cool off and the root ball stays moist, skip a day or two.  There is a root that I'm going to recommend you remove - it's photo 1434 and the root on top that curves left and behind the tree. I've attached a photo of the root. Clip it back to where it originates from the root ball....or clip it back to where it grows out straight. Either way.  I've also made an arrow about a root that probably should be removed, because it could compress the trunk as the tree grows. But it's also very large and would be a significant cut. It might be ok, because the crook is AWAY from the trunk. See what you think in person, since I'm looking at a 2-D view.  Let me know if you have other questions - and feel free to email me directly: <personal data hidden>