Probably an attack by some sort of insect. I have seen some lose a few leaves like that but never very many. Perhaps your tree is under stress of some sort. The trees are starting to bloom now.

No obvious insect damage on the fallen leaves. Just small bunches of green leaves on the ground. Interesting that it's happening at the same time the trees are blooming.

perhaps its some type of mast year seed production .. that opnly happens every decade or two ..

perhaps a call to your county extension office might get you some further info ...

any chance you could provide pix?

ken

Interesting point about mast year seed production. See this picture. It's a few square feed of concrete patio. Pretty much everything on it is from the Cedar Elms. The little green dots are the seeds from the blooms, and there are clusters of fallen green leaves all over the place. This is representative of a much larger area.

Squirrels have been known to chew off twigs.

The same thing is happening to our 17 year old cedar elm. I've never noticed it happening until this year, but there have been several mass leaf drops - little clusters with twigs. The tree doesn't look bad - the leaves seem healthy, but they're dropping as thought there's been a big wind storm.

The same thing happens to our Cedar Elm every year. Watch the canopy - it's most likely squirrels.

My American Liberty elm trees are being attacked by squirrels. I have seen them sit in the trees and chew/bite off the ends of branches that have the little seeds. I live in a wooded area of New Hampshire. I am afraid they are killing my beautiful elms that have grown to over 40 feet tall. My temporary solution is a .22 rifle.