Beginning this spring my otherwise healthy 15 yr old Magnolia lobneri 'Merrill' began displaying branch dieback. It was through most of the tree, with the heaviest damage on the south east side. An experienced landscaper and the local Extension Agent both took a look at the tree. The Extension agent took a sample and sent it to the lab for testing. There was evidence of brown tissue death when you cut the branch but not streaking under the bark. The preliminary report came back as suspected verticillium wilt but they did not get a positive test result so they are repeating the test. Today the landscaper (and a great plantsman with 35 yrs experience) suggested I dig around the base of the trunk to a depth of about six inches and look for a girdling root. So I did and sure enough I found two. One was 1/2" in diameter and had seriously constricted about 20% of the trunk and was cutting off a major root. The constriction was an inch deep into the trunk and into the major root. The second was a root about 1" in diameter and was constricting another major root, about 1/4" deep. I cut both girdling roots away. I'll be sure to keep it well watered the rest of this year and well fed next year. The landscaper tells me that this may not cure the problem and the tree might not do well. But the cut roots were not huge and I think the tree has a very good chance.
This message was edited Aug 16, 2008 9:18 AM
