Pretty Pests of PA: Attractive Invasives

On one of my many summer runs I came across a patch of these wonderful purple flowers. The only time I ever allow myself to stop during runs is when I see a pretty flower that I want a picture of.

Dame’s Rocket, Hesperis matronalis


Dame’s Rocket

After going home and trying to look up pictures of what I thought it was, a phlox, I noticed that it was a four petaled flower instead of five. I then realized that this pretty little flower actually was not as great as I thought it was. This purple flower that is common on Pennsylvania hillsides is the Hesperis matronalis, or the Dame’s Rocket. Introduced as a garden flower in the colonial period, Dame’s Rocket is commonly found in the wildflower seed mixes found in home and garden stores. The flower disperses its seeds which it produces between May and July and takes over the habitat of native wildflowers and plants on roadsides and woodland edges competing for water, light, and nutrients.

This made me think of what other attractive plants in my area had a dark side. Here are some common beauties that may be causing more harm than good:

Orange Daylily, Hemerocallis fulva 


Orange Daylily

This little guy I actually found was purposely planted in my front lawn. Much like with many other invasive plants, the orange daylily was introduced as an ornamental and is extremely popular in American landscapes. They are a bulbous perennial with long grass-like leaves. They expand through their tuberous roots and can form a dense cluster very quickly. They are especially problematic in sensitive habitats that would normally have high diversity such as in river floodplains. Often times when gardeners discard of a whole plant they will unknowingly be spreading the flower to these areas recking havoc on the local ecosystem. Pretty yes, but look into some other less harmful look-a-likes instead such as the yellow lily or wood lily!

Purple loosestrife, Lythrum salicaria

Purple Loosestrife

Purple Loosestrife

Purple loosestrife is so destructive that it has actually been banned in most states throughout the U.S. Again, this plant was introduced as an ornamental in the early 1800s and has since spread throughout most of the country. This purple flowered plant has a woody like stem and can grow pretty tall- getting up to 4 to 10 feet! Its flower spikes are in bloom through the entire summer. And because of its plentiful flowers, it also has plentiful seeds which it is happy to spread around. You will see these guys in wet areas as it prefers wetlands, marshes, river, and stream banks. They compete highly with wetland organisms and are even putting some native orchids in danger. They form a large and dense cluster that have the capability of displacing an entire wetland! Not so pretty anymore.

Wild Chervil, Anthriscus sylvestris L. Hoffmann

Wild Chervil

Wild Chervil

Here is another one that I mistook as a common native, Queen Anne’s Lace. Boy was I wrong, Wild Chervil is not only highly invasive, it is also a host to yellow fleck disease which attacks some of our favorite vegetables such as carrots, parsnips, and celery. This plant has fern-like leaves and can grow pretty tall with a general average of 4 feet but the ability to get to 6. Its flowers have five petals and grow in an umbrella form. They are in bloom from May through early July. You can see these guys on roadsides, woodlands, and in open pastures and fields. It’s deep tuberous tap root makes it extremely hard to pull out and allows it to spread rapidly. Wild Chervil’s seeds can be transported by birds, mammals, and humans. The introduction of this plant is said to be from wildflower seed packets distributed in the early 1900s. You really need to be careful with those things.

Yellow Flag Iris, Iris pseudacorus L.

Yellow Flag Iris

Yellow Flag Iris

Many iris plants are native, but not this little yellow guy. Originating from Europe, the Yellow Flag Iris was imported to the United States as an ornamental wetland plant and was actually thought to do some good by preventing erosion and removing metals from sewage plants. Although it does have some good traits, this iris also can form dense colonies in wetlands displacing native species and altering the habitat. It is also poisonous if you were ever thinking about tasting it and have a thing for flowers. It has now been spotted all the way from California to the East Coast, only leaving some states in the midwest to spare (and Hawaii/Alaska). This plant is a herbaceous perennial that can grow from 3 to 4 feet high. Although the flowers are usually yellow, they can also appear as a cream color.

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