My usually healthy and very large four-trunk Katsura tree (15+ yrs) – has been dropping shriveled dry black leaves. I sweep them from deck every day – not many (20 or so) – BUT it is very concerning. Please advise & thanks!
Thanks for contacting Toronto Master Gardeners. Your concern about the tree is understandable. Katsura trees are known for their beauty and four season interest. As a rule they are not vulnerable to pests and diseases. Katsuras are known to need evenly moist soil and cannot tolerate compaction. Soil compaction limits the amount of oxygen reaching the roots and can result in damage to that part of the tree. Heavy rain and frequent foot traffic particularly on clay or loam soils lead to soil compaction. It is possible that during this wet spring the soil around your tree has become compacted. This would affect the roots of the tree and cause leaves to drop. At this point it would be helpful to check for soil compaction around the tree. If you have mulch around the tree make sure it’s spread to only two to four inches thick and not touching the trunk. During hot dry times during the summer provide regular moisture but don’t saturate the soil. Adding leaf mold or finely shredded leaves around the base of the tree will improve drainage over time. For more information, see the following sites:
https://ask.extension.org/questions/463743
https://www.canr.msu.edu/news/what_to_do_about_compacted_soil