One of my favorite hobbies is birdwatching, and one of my favorite places for birdwatching in the Philadelphia area is the John Heinz National Wildlife Refuge at Tinicum, a large tract of open water and wetlands, with some surrounding forest, located across I-95 from the Philadelphia Airport. Here is one of the smaller, more secluded necks of water in this refuge, to give you an idea of what sort of habitat can be found there:
While walking on the main loop in the refuge, which goes between two bodies of water, I discovered a patch of naturalized perilla, or shiso. Back in september, I wrote about Red Shiso, or Perilla, a plant I have found growing wild in many locations in Philadelphia. This population of perilla was of a green-colored variety, and the leaves were yellowing slightly as the plant had gone to seed and was preparing to die down for the fall:
I want to write more about this particular patch of perilla, but first, an aside about invasive plants.
Humans, through trade and colonization, have brought numerous plants with them, mostly plants that we cultivate for food, but also weeds that hitched a ride with other cargo. These plants often escape cultivation and establish wild populations in the native ecosystems.
Non-native plants are aliens in the ecosystems which they colonize. In most cases, they are poorly adapted to these ecosystems, and they cannot establish stable populations, and die out. But in other cases, they have unique adaptations that allow them to thrive in a new environment, and the other members of the ecosystems they colonize are not adapted to their presence. In particular, plants like perilla, which produce complex combinations of aromatic chemicals, toxic to insects, are often not eaten by as many native insects. The native insects co-evolve with native plants, and are not adapted to eat these strange new plants. The plant thus gains a competitive advantage, as it has fewer natural herbivores. It then colonizes the ecosystem and grows disproportionately, shutting out other plants.
Note that the perilla leaves show no insect damage. Older leaves of plants usually show some sign of insect damage by fall...for an example, look at the black cherry leaves in my old post on tea monoculture and biodynamic agriculture. While this is good for the perilla, it's not necessarily good for the rest of the ecosystem. Fewer insects eating plants means fewer birds to eat the insects, and total biodiversity is decreased. As biodiversity is lost, the capacity for the ecosystem to adapt to changing conditions is diminished.
I'm picking on perilla unfairly here. Although I've seen it growing quite vigorously and establishing large populations, I haven't seen it establishing a monoculture and totally shutting out other plants, the way some invasive species do. Although perilla is considered to be an invasive species in some areas, it is nowhere near the most problematic one in this area, and in the John Heinz National Wildlife Refuge, it is relatively harmless compared to a number of other plant species. Some more problematic invasive species in this particular refuge are Phragmites, and some of the non-native honeysuckles.
Back to the perilla:
Out of curiosity, I gathered a small handful of leaves, enough for a single cup of herbal tea. The results of drying them can be seen here:
I was steeping this tea as I was writing this post, and then I proceeded to drink a cup of it.
This perilla is noticeably different in aroma and flavor from the red-leafed variety. It has a much more minty aroma. The red variety had a strong licorice/anise quality; these qualities are still present, but weaker, and I would describe them as more fennel-like than anise-like. The flavor is much sweeter. There are still skunky and vegetal undertones that, in my opinion, characterize this herb. I also would say this batch was less basil-like, although still somewhat so. There is a very strong quality of fennel or anise that lingers on the tongue, more so than with the red variety. The lingering finish also suggests dried hay.
Really interesting! And different enough from the red-leafed variety that I can see growing both in my garden! Still, I would prefer to grow native herbs, especially given the considerations I talked about above.
Do you think about whether or not plants are native to your local ecosystems, when considering what to grow in your garden?