Karin, I guess you are addressing your question to me.

I have also noticed some Crabapples in bloom this fall. I have seen this before in Magnolias but this is the first time I’ve seen Crabapples do it. My theory is that it is a combination of factors; the length of daylight, the temperature and the rainfall. The trees are being fooled into thinking it is springtime. Plus you mention that these trees don’t look too good at this time of year. That’s probably due to apple scab disease causing the trees to defoliate. My theory is that the trees are flowering because of the stresses they are under. The flowers (normally) lead to fruit and the fruit has the seeds, more seeds means more chance of reproducing. You have probably noticed that Crabapples that look terrible in the late summer flower beautifully the next spring. This is because they know (do trees think?) they are in peril and are doing what they can to reproduce themselves by producing as many seeds as possible.

Like I said, this is just my theory as someone who has worked with trees and has observed them in Chicagoland for over 17 years. One of the scientists at the Arboretum could give you a more scientific explanation to either prove or disprove my theory.