I planted a young Mimosa tree this spring, and although it seems happy and...

Asked September 10, 2016, 2:52 PM EDT

I planted a young Mimosa tree this spring, and although it seems happy and is sending out lots of new growth, I noticed that the leaves on one of the branches shows yellow on the far edges of the tips of each of the fronds. The fronds closest to the stems are a nice healthy green, but the edges are yellow. I am worried that this could be wilt. I love these mimosa trees and hope that it is not infected.

How does the wilt manifest itself at the beginning, Does the entire leaf turn yellow all at once, or does it start at the edges of the leaves?

Washington County Oregon

9 Responses

Thanks for your question about your mimosa's leaves. Is it possible for you to send a picture of the leaves, as well as the tree? It could be as simple as a lack of nitrogen in the plant, which can cause chlorosis, or a yellowing of the leaves. Fusarium wilt can appear in mimosas, but let's take a look at the damage.

I'll keep checking for your photo!

Thank you for your kind response. I tried to take a picture with my cell phone, but in the bright sunlight was unable to do so. I will try again with my regular camera and hopefully get clear enough detail of the leaves that have the yellow margin, as well as the little tree.

Oh dear, my worst fears have been confirmed. My lovely mimosa trees (I have two of them newly planted in June,}seem to be definately infected with the dreaded wilt. I went out this morning and the leaves which had yellow on the edges, have turned all yellow, and some have fallen off. I was under the impression that this wilt was not a problem in Portland but evidently it is.. There used to be a large number of these trees in my area, but lately I have noticed that there is only one, and some of the branches are bare.

I understand there is no cure for this wilt, but will continue to water them and will feed them with a balanced fertilizer in hopes that they might survive. If not, I will replace them with flowering cherry trees. Best wishes. Alma

sometimes the leaves of trees this late in the year start to turn color. You will know if your Mimosa tree has fusarium wilt if a cut branch has black areas where the tree tried to cut off the fungi (usually too late) and yes, yellow leaves. But sometimes yellow leaves are just late fall. Usually the fusarium wilt causes the leaves to be stunted and turn yellow in the summer. I would check to see if your University has a pathology lab and send a branch that has very yellow leaves to them to see if they can detect the fungus. Watering the tree and giving it a balanced fertilizer is a good thing too!

Thank you so very much for giving me hope that my wonderful trees may not have the dreaded wilt, and that the yellowing is just something that happens in the fall.. I will continue to water them and feed them a balanced fertilizer.

The good news and hopefull sign is that the other branches are all growing beautifully and putting out new growth. My goodness those trees do grow fast.

please also find a plant pathologist if in the spring the new leaves turn yellow!

As Ginny mentioned, Oregon State University has a plant pathology clinic: plant-clinic.bpp.oregonstate.edu. You'll find directions there on submitting a sample. They'll need a branch that is yellow so they can examine it longitudinally.

Here is an excellent fact sheet on Fusarium Wilt fungus in Mimosa trees that gives a story line of what happens first, next and last. At this time there are no cures for this disease in the plants which is a shame as the trees are so lovely.
https://pubs.ext.vt.edu/2811/2811-1020/2811-1020_pdf.pdf