Ashes to ashes, dust to dust
1997 will not go into the history books as being a good year for green ash. The mild winter and this past spring with its up and down temperatures has clearly left its mark. All over the Metropolitan Region, green ash, medium to large size, never broke bud and have now died. Trees show external symptoms ranging from lion's tailing (a cluster of leaves at the end of a branch), to death of a section of the crown (right vs. left, top vs. bottom, etc), to total tree mortality (total toast). We have seen trees up to 20" DBH die for no immediately discernable reason.
Is this an indication that green ash is not winter hardy in Minnesota? Not exactly. Effectively all of these trees meet two criteria: (1) they are urban ornamentals suffering a variety of urban environmental stresses ranging from road salt, to lawn care chemicals, to high pH and (2) they are planted, nursery raised stock from unknown seed source (most green ash planted are grown from seed). It seems that the main replacement for the elms in many of our communities, green ash, is not aging very gracefully.
Not winter hardy? Most of the trees showing problems this year came through the record cold of the two previous winters just fine. It's hard to believe that a tree that has taken minus 30 or colder in two successive winters can be seriously affected by minus 15. On the other hand, we almost expect to see this type of problem from green ash following the up and downs of a funky Minnesota spring like 1997. Is it possible to not be spring hardy?