So pretty, so nasty: A guide to invasive plants in our area

By Marilyn Rosenthal
MILFORD — Invasive plants? They're everywhere — sometimes in little clusters along the Delaware River, sometimes on the berm between the three-lane and I-84 across from Wal-Mart, and sometimes even in my backyard.
"Some of these invasives can actually blind you or even kill you!" says Susan Breyer.
Breyer is a retired science teacher at Delaware Valley Middle School, where she motivated her students and problem-solved with them.
Her enthusiasm for science is contagious. This is especially evident in "Hooked on Science," a book she wrote that was published by Prentice Hall.
"It's basically for teachers — to show them how to engage kids, to get them really excited about science, and to help them problem solve and use their critical thinking skills," she said.
Get her talking about invasive plants, and her whole face lights up.
Giant Hogweed Heracleum mantegazzianum
Breyer dubs this huge, deadly plant "The nastiest for all the invasives." Its sap is activated by UV light and causes sever burns on exposed skin. If the sap gets into a person's eye, it can cause permanent blindness.
Each plant can produce about 100,000 seeds, which are spread by wind and animals, and can grow to 20 feet high. It has bunches of pretty white flowers high above its very tall stalk.
Pigs, goats, and cattle are immune to the ravages of this plant. The Giant Hogweed is found along roadsides, railroads, streams, and fallow fields.
If you believe you touched or even just seen the Giant Hogweed, the Pennsylvania Department of Agriculture asks that you inform them through its Invasive Species Hotline: 877-464-9333.
Poison HemlockConium maculatum
Pretty poison hemlock came to the United States as an ornamental plant. It is important to note that this is not the hemlock tree but rather a dangerous, invasive weed often called the "water hemlock." It is ascribed to be the plant used to make a final beverage for Socrates.
It resembles the Giant Hogweed but only grows to about 10 feet tall. It looks quite similar to Queen Anne's Lace, but all parts of this deadly plant are poisonous, especially its seeds. Poison hemlock can be found along roadsides, ditches, and stream banks. Ingesting any part of it can cause seizures, nausea, abdominal pain, vomiting, and even death.
Purple LoosestrifeLythrum salicaria
With its rich, beautiful purple flowers, purple loosestrife was brought to the United States in the 1830s as an ornamental plant. In the 1990s it lined the banks of the Delaware River. Biological control measures, with leaf feeding beetles and root feeding weevils, were taken to kill these plants.
This was a great victory — but Breyer has recently seen clumps of purple loosestrife on that berm in front of Wal-Mart. Each plant can send out nearly 50 roots a year that can grow at a rate of one foot per year. This creates a dense mat of roots that blocks out native plants like cattails and other wetland species.
Japanese KnotweedFallopia japonica
Another ornamental invasive, Japanese Knotweed, grows along construction sites, roadsides, riverbanks, fields, and even backyards and lawns. Its enormous root system damages anything in its path including dams, foundation, roads, and retaining walls.
Breyer has seen this plant in Port Jervis along Canal Street and also in nearby Deerpark, N.Y.
Oriental BittersweetCelastrus orbiculatus
This climbing, woody, perennial vine produces a beautiful red berry with orange leaves.
The seeds are eaten and dispersed by birds. People use it in decorative floral arrangements and wreaths. Its dense foliage and thick bittersweet vines can choke a tree and smother any existing vegetation.
Breyer said she's spent endless hours manually cutting the vines and digging up the roots of this plant, which has made its habitat in her backyard.
Garlic MustardAlliaria petiolata
This is a cool season biennial that smells like garlic when it's crushed. Plants develop rapidly and produce thousands of seeds. The seeds self-germinate or are spread by people and insects.
Garlic mustard exudes certain compounds that inhibit seed germination of other species. Garlic mustard also happily invaded Breyer's garden, but she saved the situation by pulling out the emergent plants in the early spring and removing any remaining seeds.
Dave Taft, in The New York Times in May, referred to garlic mustard as "evil, invasive, delicious." He actually enjoys the raw leaves in salads, especially those grown in shade, which are less bitter.
On the whole, however, it's better to just look at, but not touch, these gorgeous invasives if you don't know what they are — yummy salad possibilities notwithstanding.
Editor's note: This article has been updated to correct typos.