PA Native Plants with High Wildlife Value - Notes
The lists of Pennsylvania native plants with high wildlife value are drawn from two primary sources.
First, Douglas Tallamy, entomologist at the University of Delaware and author of "Bringing Nature Home", identified plants for the mid-Atlantic that had both a high wildlife value, as well as value as landscape plants. In this list, "high wildlife value" means that the plant is used by native insects as a food or breeding source. Insects are food, in turn, for native birds and other desirable wildlife - and in fact, are a critical link in sustaining those wildlife populations. Thus, native plants that are used by insects are important pieces of the ecology of an area - including our gardens.
I then cross-referenced this list with the book "The Vascular Flora of Pennsylvania", by Rhoads and Klein. This book lists every plant that is found in Pennsylvania, and indicates whether the plant is native to PA, or introduced. Further, it lists every known occurence in the state, thus providing an idea at the county level of how widespread or limited the distribution of the plant is in the state.
Using this information as a guide, I cross-referenced each entry on the Tallamy list, and indicated whether or not the plant is found natively in PA, in Berks County, and then an indication of the statewide distribution of the plant. This last step was a subjective assessment. Here is how I defined each of the categories I used:
Wide: the plant is found in every county of PA, and is extremely common in every county. This is a plant that is easily found everywhere in PA.
Moderate: the most common listing for a plant. A moderate distribution indicates that the plant is found in all counties, or all but a few counties, of PA, and is relatively widespread throughout those counties.
Limited: the plant is found in less than 2/3 of the counties in PA, or has a restricted range in the state. In the counties where the plant occurs, the distribution may be widespread or not.
Very limited: the plant is found in fewer than 3 counties in the state, usually in a very restricted range.
Whenever there is a clear restriction in statewide distribution, this is indicated in the table, such as "SE PA only", as are notations when a plant has protected status.
Why would you need to know the distribution of a plant in a state?
This information will help you plant the varieties that have co-evolved with the local flora and fauna in an area; these varieties will tend to be hardier, better adapted, and more usable by the native insects in the area. Thus, while Baptisia australis (False Indigo) is indeed native to PA, it's only found natively in a small part of western PA. This doesn't mean it's not hardy in southeast PA, or that it won't grow well here; what it does mean is that there is probably a reason why its native range didn't extend farther east, and it is unclear whether or not the insects adapted to southeast PA could utilize the Baptisia as a food source, since they have not been exposed to it over thousands of years of co-evolution.