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Questions on 50-Year-Old Albizia Mimosa Tree / Silk Tree

westes Zone 9b California SF Bay
3 months ago
last modified: 3 months ago

I have a gigantic Mimosa Tree / Silk Tree in my front yard. As I understand it, this tree is not considered invasive to California. The invasive status is confined to the South and Middle Eastern US seaboard areas. I have some questions on this aging grand old tree:

* I understand that these trees have a 20-year life. My plant is approaching 50 years old (!), so I guess it is living on borrowed time. Realistically, what is the oldest that this tree can ever get?

* Will the end come suddenly, or will it just start to lose main branches one at a time over the course of several seasons?

* The tree definitely has very large dead branches. I guess those should be taken off, both for safety and to lighten the load on the still-living sections of branches?

* I am in California zone 9b. Is it correct that the Mimosa fungal blight disease that is wiping out trees in the south has not gotten here yet? The tree has peeling bark in many sections, but it is not showing the signs of the Mimosa blight: there are no yellowing leaves, no oozing sections, and no rapid deterioration. I assume the dying branch sections and the peeling bark are just part of its multi-year death process?

* Since this tree probably has less than 10 years left on it, and the entire base is now exposed and twisted trunks, I had the idea to grow Climbing Hydrangea on it up from the base. If this tree is going out, then maybe let it go out with a spectacular show. @gardengal48 (PNW Z8/9) @floral_uk z.8/9 SW UK and @NHBabs z4b-5a NH here is your chance to warn me if this is not going to work.

* Specific to how I would plant the Climbing Hydrangea, I would build a small retaining wall against the side of the base of the trunk. This would touch about 20 inches of the base of the trunk to wet soil. While it is not ideal, the area to plant in is very limited where this tree is located. I could put a housewrap paper against the trunk of the tree to waterproof that side of the raised bed, if necessary.. Somehow I think a tree this large can handle such a small insult.

The first photo shows the general span of the tree. The second photo shows the large branch in back of the tree that looks totally dead now.

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