Can I revive a young Japanese Maple tree if the leaves were drying out and curling in the fall?

Question:

I planted a Japanese Maple / Acer in the summer. In early October, I noticed that the leaves were drying out on the end and curling in. It lost most of its leaves without ever turning red or orange by late October. How can I revive it or is this normal for a younger tree?

Answer:

Jonathan Foster, Home Horticulture Outreach Professional

There are a few things that night be going on here. When we see brown tips like this, it suggests that the plant may not be processing water efficiently, which makes the least important parts die first. This can be drought related, although that seems less likely as we had rainfall and it looks like you do supplemental watering (at least through the bottle) and it’s in a protected spot. Ironically, this can also be caused by overly wet soil, which would be my larger concern here because the mulch looks quite moist and fill near the house is often compacted and poorly draining for plants. I’d ask you to do a little careful excavation under the mulch and see if you can get a peek at the roots. As long as you don’t see sliminess or smell rankness, it’s probably fine (healthy roots are firm, and often white). If you did proper preparation of the hole before planting, this is less likely, too. If you do find rot, you’ll want to immediately cut supplemental watering and start putting an inch of good high quality compost on the area each year–this will improve the drainage over time, but it might not be fast enough if the rot is advanced (FYI, I don’t think the tree looks like it has serious root rot).

It’s also possible that it might be sun scorch, but the localization at the tips doesn’t make me lean this way–if you do any overhead watering and it gets particularly hot here (if this is, for instance, south facing), I would discontinue and focus on the soil for irrigation. Also, I can’t be sure what’s on the other side of that fence, but it looks patio-ish. If that area typically gets salted during the winter to melt snow and ice, it’s possible you may have a salt buildup in the soil here (common with houseplants) from melt and runoff that can cause this kind of damage.

The last thing to consider is something like verticilium wilt, but I would really expect to see more dramatic collapse of the trees with that. If that concerns you, you could cut a cross section of a healthy stem and see if there is dark coloration or streaking inside (a symptom). You can always submit your photos and a physical sample to the UMaine Plant Disease Diagnostic Lab for testing (there is small fee for their service), but I don’t think you’re quite at that point yet.

My advice would be to make sure it’s nicely hydrated, but otherwise stop watering for the season. The maple has a strong stem and a lot of nice green to it, so I don’t think it looks terribly worrisome other than the leaf tips. Cover the area with a nice 3″ thick, flat layer of organic mulch (don’t quite let it touch the stem, leave a little circle there) to help insulate the crown for winter. In the spring, as soon as the soil is thawed and no longer sodden, have it tested through the UMaine Analytical Soil Lab for nutrition and pH levels (which will also indicate a salt buildup, if there is one). And we’re reevaluate how it looks then.

Happy gardening.