What type of tree is planted in honor of Ofc. Dunn?
Sandusky Greenhouse manager Tom Speir provided the following answer:
The tree planted for Officer Dunn is an Ohio Buckeye (Aesculus glabra) donated by Barnes Nursery in Andy's memory.
The large tree near this Buckeye is a Common Horsechestnut (Aesculus hippocastanum).
As for the Tuliptree (Liriodendron tulipifera) that was planted several years ago, it is located east of the floral clock in Washington Park near the Popcorn Wagon. I'm not sure what trees the reader is referring that are planted on a mound, but I would guess she is referring to non-hardy Hibiscus that are returned to the greenhouse in the winter.