Pawpaw, Asimina triloba (L.) Dunal (Annonaceae), in the Prairie Peninsula of Illinois, USA

Along with a decrease in fire frequency over the last century, fire-sensitive, shade-tolerant, mesic species, such as pawpaw (Asimina triloba [L.] Dunal) and sugar maple (Acer saccharum Marsh.), have increased in importance in the upland forests of Illinois, USA. When invading new areas, pawpaw commonly has a clumped distribution, reproduction being mostly vegetative by root suckers following initial establishment by seed. In these clonal colonies pawpaw distribution is mostly concentric, the largest individual stems toward the middle with increasingly smaller plants occurring at greater distances from the population center. Within the past 30 y pawpaw has increased significantly in Baber Woods Nature Preserve, Illinois. In 1966, only a few pawpaw colonies were observed and there were no tree-sized individuals. During that survey pawpaw seedlings averaged 161 stems ha(-1) and saplings averaged 668 stems ha(-1). In 1998 pawpaw seedlings averaged 1170 stems ha(-1), saplings averaged 897 stems ha(-1), and a few pawpaw trees greater than 9.9 cm (dbh) were present. Survey results varied in other central Illinois woodlots where pawpaw was better established.