They are relatively non-messy trees. Everyone has a different definition of messy though. In the case of a seedless thornless Honeylocust, it drops debris over a couple of short time frames each year and the debris is easy to clean up.

Trees that drop twigs, nuts, big leaves, sometimes continuously, are messy trees.

Your Honeylocust is a thornless male. It still has flowers (your 'catkins') but no seedpods and (thank goodness) it doesn't drop giant thorns either. Not much else you can do.

This post was edited by smivies on Mon, Jun 2, 14 at 15:15

As a side note, the pollen in my area has been so prolific, that in our last good thunderstorm (last Tuesday), the runoff water going down the street was actually yellow in color.