To say that humans have had an immense impact on the ecology of urban areas in North America is nothing less than an understatement. The vegetation of an urban area like Philadelphia is largely comprised of non-native species. This is due to a number of factors. Urban weeds are often cosmopolitan, at least as far as their temperature-based hardiness zones allow. This is due both to similar weed-friendly permanent "disturbed-area" nature of cities as well as the spread of species by humans either on purpose or by accident. One category of species spread by humans is the set of common container-garden ornamentals. These are the plants commonly found in planters and window-boxes. They are generally smaller species with showy flowers or ornamental foliage. Of those, the most likely to spread are those that are easily able to grow in cracks with little dirt to speak of. Typical of this category are Petunias, Pansies, Moss Rose Purslane, dwarfed Snapdragons, Madagascar Periwinkle and Coleus. These species may not be able to consistently regenerate to create longer-term infestations like more aggressive weed species such as Small Crumbweed, Common Purslane, Low Mallow, Dandelions or Pennsylvania Pellitory. They are, however, consistently resupplied by those planted intentionally year after year.

Petunias are difficult to categorize taxonomically, as there are a number of different species, a multitude of cultivars and very little available taxonomic information available.

This gallery is intended to express the prevalence and variety of this common volunteer. While possibly excessive, this collection is far from an exhaustive exposition of my collection of photographs of the species. I omitted many of the earlier examples that were taken on more primitive photographic equipment and did not come out very well. I will be adding to and likely subtracting from the collection as time goes on. This is the first version of the collection, published on July 27th, 2019.