From the beginning the concept of site-specific, specimen-based records was central to the project. During the 1930s herbarium label data were recorded on manual file cards using Works Progress Administration (WPA) funds. The cards became the basis for the preparation of dot maps. In addition, several collecting trips were undertaken during the summer months, with a bus loaded with graduate students and plant presses, to fill in gaps, particularly in the northern tier of counties. The result was the publication in 1979 of the Atlas of the Flora of Pennsylvania by Wherry, Fogg, and Wahl.

The project entered the computer age in 1980, when the Pennsylvania Flora Database was initiated under the leadership of Morris Arboretum director, Dr. William M. Klein. The database now consists of a set of relational files maintained in Paradox running under Windows 2000.

The basic taxonomic file contains 3432 records derived from nearly 400,000 herbarium specimens. Associated files include a gazetteer of over 10,000 collection sites complete with latitude and longitude coordinates, a distribution file linking species with the sites at which they have been collected, herbarium, synonym, and bibliographic files. Records can be queried taxonomically or geographically. The Vascular Flora of Pennsylvania: Annotated Checklist and Atlas, published in 1993, was the first published product of the database.

The Plants of Pennsylvania: An Illustrated Manual, published in May 2000 by the University of Pennsylvania Press, is a tool for the identification of the native and naturalized plants of the state. This book is designed to be useful to taxonomists, conservationists, ecologists, foresters, land planners, teachers, students, and anyone with an interest in the plants of Pennsylvania. The manual includes keys to families, genera, and species; about 2,500 illustrations by botanical artist Anna Anisko; scientific and common names; and data on distribution ranges, relative frequency, rare and endangered species, blooming and fruiting periods, taxonomic notes, and an illustrated glossary.

Major Publications of the Pennsylvania Flora Project:

Rhoads, A.F. and T.A. Block. 2004. The Trees of Pennsylvania: A Complete Reference Guide. University of Pennsylvania Press, Philadelphia, PA.

Rhoads, A.F. and T.A. Block. 2000. The Plants of Pennsylvania: An Illustrated Manual. University of Pennsylvania Press, Philadelphia, PA.

Rhoads, A.F. and T.A. Block. 2000. Natural Bucks County: Guide to Public Natural Areas. Bucks County Commissioners, Doylestown, PA.

Rhoads, A.F. and T.A. Block. 1999. Natural Areas Inventory of Bucks County, Pennsylvania. Bucks County Commissioners, Doylestown, PA.

Rhoads, A.F. and W.M. Klein. 1993. The Vascular Flora of Pennsylvania: Annotated Checklist and Atlas. American Philosophical Society, Philadelphia, PA.

Wherry, E.T., J.M. Fogg and H.A. Wahl. 1979. Atlas of the Flora of Pennsylvania. Morris Arboretum of the University of Pennsylvania, Philadelphia, PA.