Question
1.  My dad had a question about Moraine Locust leaves-can they be harmful to certain plants?  i.e. asparagus.  He covered his asparagus bed w/ a reasonable amount of moraine locust leaves last fall and some of the plants seemed to have died.        2.  I live in zone5 (s. lower michigan).  When best time to prune trees for shaping, etc?  i.e. hardwood maples, river birches,  crooked willow, moraine locust, and similiar trees.  Would late winter/early spring be best (feb-mar)?  Would pruning in may-sept be very harmful because that is when I seem to think of it and am outdoors.    Thank you very much.  This is a great service

Answer
they contain large amounts of tanin. the leaves may have caused the plants to stay too wet and rot. i doubt if the composition of the leaves damaged the asparagus. is he growing disease resistant asparagus ? newer disease resistant varieties do quite well now. older varieties suffer from a blight.
early spring and early fall are usually the best time to prune. avoid winter and summer weather except to remove damaged or dead branches. always consult a pruning book (sunset, ortho, etc.) before pruning. some trees (maples, birch, etc.) will bleed excessively if pruned at the wrong time of the year (late spring).

we did have a long drought this winter /early spring. that may be what killed some of the asparagus plants.