![]() Historical records from the late 1800s through the mid-1900s show a distribution in southeast Pennsylvania along much of the Piedmont-Coastal Plain boundaries, including southwest Philadelphia. Seeking additional Pennsylvanian locations of Quercus falcata, we pored through herbarium collections shared through the Mid-Atlantic Herbaria Consortium. For two of these collections, the southern red oaks were mixed among other native trees species in a dense forest the third location was a grove of separate mature trees growing in a heavily grazed cow pasture, all within sight of the Herr’s Snack Factory, a local landmark. Quercus falcata stand out among other oaks, having coarsely lobed leaves with sickle-shaped (falcate) terminal lobes, and dense grey down (pubescence) beneath. These three populations, within two miles of each other, were made up of large mature trees that were at least 50 feet tall. Collecting was easy along the county roads, however, where we made three separate collections from trees whose acorns were within reach of our pole pruners. (Serpentine barrens, with thin, nutrient-poor soils, support high levels of unusual, rare, or endangered species, in contrast to adjacent areas.) We had targeted Goat Hill based on recent herbarium records from this location, but we did not find any southern red oaks there. In September 2020, we focused our collecting on nearby populations of Quercus falcata, which occur on serpentine soils and their associated barrens. Conversely, for the northern species, the southernmost populations could possess greater heat tolerance, allowing us to continue to grow these as their native populations retreat northwards in the face of warming climates. For those southern species that reach into the mid-Atlantic, the extreme populations might possess traits, including cold tolerance, that provide opportunities to grow these beyond their traditional horticultural ranges. This included targeting the southern ranges of northern species (such as Larix laricina) and, vice-versa, the northern limits of southern species (for example Quercus virginiana), with the goal of growing plants suitable for changing climatic conditions in the Delaware Valley. ![]() In fact, due to its rarity in Pennsylvania (fewer than fifteen populations are known in the state), the Pennsylvania Natural Heritage Program lists it as a species of special concern (an S1, for those familiar with the coding).įaced with travel restrictions due to the COVID-19 pandemic, starting in the late summer and fall of 2020, we decided to look for local opportunities for collecting seed, pursuing a range of regional collecting objectives that we had previously not achieved. Southern red oak barely extends its range into southeastern Pennsylvania, southern New Jersey, and possibly Staten Island and Long Island. Each of these three species, which are widespread further south, reach the northern limits of their native ranges in southeastern Pennsylvania, southern New Jersey, and Long Island. Maturing at approximately the same size as red oak, all three are potential substitutes as high-canopy, overstory shade trees. As possible substitutes for this and other susceptible oaks, we targeted populations of Quercus phellos, Quercus michauxii, and Quercus falcata native to southeastern Pennsylvania. ![]() For example, red oak ( Quercus rubra), one of the more prominent shade trees at Longwood Gardens, in recent years has been among the most susceptible to bacterial leaf scorch ( Xylella fastidiosa), which can weaken and eventually kill mature trees. Why Quercus falcata? Based on biological and climatic threats to tree species traditionally grown at Longwood Gardens, we have focused recent efforts on native species that combine ornamental traits with disease resistance and greater heat tolerance. After a fruitless morning at the Goat Hill Serpentine Barrens Preserve, we found much better success along local county roads. This certainly was the case in September 2020, as we searched for Quercus falcata (Spanish oak, or southern red oak) in southern Chester County (PA). This is especially true when searching for tree species, where roadsides or power line rights-of-way provide light (for tree growth) and ease of access to fruiting branches (for collecting convenience). While plant collecting is often romanticized as occurring in pristine natural habitats, much of the most successful seed collecting is done in more prosaic locations. Zale seek native trees that can adapt to the shifting climate.
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