Invasive Plants
For information on many other noxious and invasive weeds, check out the Pennsylvania Department of Agriculture's Controlled Plant and Noxious Weeds list.
Japanese Knotweed (Fallopia japonica)
Japanese Knotweed is an herbaceous perennial member of the buckwheat family that was introduced from East Asia in the late 1800s as an ornamental and as a plant to stabilize streambanks. Now there are concerted efforts to remove or control its spread. You can find out more and learn how to identify Japanese Knotweed at Penn State Extension.
The hillsides in the Pittsburgh area are covered with Japanese Knotweed which is crowding out all native plants. The Garden Club of Oakmont is participating in an eradication project in Dark Hollow Woods. Season One of the Japanese Knotweed project has concluded. We completed four two hour sessions of knotweed herbicide injection. We targeted four different areas in the park that are along Dark Hollow Creek. The areas that we injected were marked with high viz tape so that we can identify the area in the spring. Evidence of the injections was clearly visible with each visit to the park. The knotweed was clearly dying off in the areas we had treated. We now wait until spring to assess the effectiveness of the treatments and plan the next season treatment area.
Japanese Knotweed is an herbaceous perennial member of the buckwheat family that was introduced from East Asia in the late 1800s as an ornamental and as a plant to stabilize streambanks. Now there are concerted efforts to remove or control its spread. You can find out more and learn how to identify Japanese Knotweed at Penn State Extension.
The hillsides in the Pittsburgh area are covered with Japanese Knotweed which is crowding out all native plants. The Garden Club of Oakmont is participating in an eradication project in Dark Hollow Woods. Season One of the Japanese Knotweed project has concluded. We completed four two hour sessions of knotweed herbicide injection. We targeted four different areas in the park that are along Dark Hollow Creek. The areas that we injected were marked with high viz tape so that we can identify the area in the spring. Evidence of the injections was clearly visible with each visit to the park. The knotweed was clearly dying off in the areas we had treated. We now wait until spring to assess the effectiveness of the treatments and plan the next season treatment area.
Burning Bush (Euonymus alatus)
> Another popular landscape shrub is headed for Pennsylvania’s banned list
"Burning bush – a widely planted landscape shrub popular for its fire-engine-red fall foliage – has been deemed invasive by the state Department of Agriculture and will be phased out of sale in Pennsylvania. The Ag Department’s Controlled Plant and Noxious Weed Committee voted to add burning bush as well as four species of privets to the state’s Controlled Plant and Noxious Weeds list as of Jan. 10, meaning those plants will be banned for sale in Pennsylvania garden centers and nurseries."
Many volunteer burning bushes reseed themselves throughout our woods.
> Another popular landscape shrub is headed for Pennsylvania’s banned list
"Burning bush – a widely planted landscape shrub popular for its fire-engine-red fall foliage – has been deemed invasive by the state Department of Agriculture and will be phased out of sale in Pennsylvania. The Ag Department’s Controlled Plant and Noxious Weed Committee voted to add burning bush as well as four species of privets to the state’s Controlled Plant and Noxious Weeds list as of Jan. 10, meaning those plants will be banned for sale in Pennsylvania garden centers and nurseries."
Many volunteer burning bushes reseed themselves throughout our woods.
Bradford Pear
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Bradford Pear trees (aka Callery pear or Pyrus calleryan) were brought to the United States in the early 1900s. Their lovely white flowers in early spring brought beauty to many landscapes and made them a very popular tree. Unfortunately, as with many imported plants, it has spread into many areas and disrupted ecosystems by displacing the growth of native plants. Ohio and South Carolina are in the process of banning these trees. In November 2021 the Pennsylvania Department of Agriculture added the Bradford Pear to its noxious weed list.
The ban begins February 9, 2022 and will be phased in over the next three years. A timeline for compliance to the ban can be found in their article, link below:
https://www.agriculture.pa.gov/Plants_Land_Water/PlantIndustry/NIPPP/Pages/ Callery-Pear.aspx This article is from Penn State Extension and provides photos to assist with identifying Bradford Pear trees and information on management and various treatments and timing of treatments: https://extension.psu.edu/callery-pear This article from the Western Pennsylvania Conservancy contains photos and videos to help with proper identification, the ecological threat, control and removal as well as Native alternatives. Link below: https://waterlandlife.org/invasives/callery-pear/ |
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Weed Guide
The weed guide is meant to help learn about common local weeds: which are native and which are not, which you might want to leave for pollinators and which you’ll want to root out.
Click Here for Weed Guide
Click Here for Weed Guide
Garlic Mustard
Garlic Mustard is an invasive biennial plant. It can grow in full sun or full shade, but prefers shade. It out-competes other vegetation and can crowd out other more desirable plants. Plants can produce 500 to 600 seeds in the second year of growth. These seeds can live in the soil for 5 years.
One way to get rid of garlic mustard:
1 Remove during the flowering period before the flowers go to seed.
2 Pull at the base of the plant and get as much root as possible.
3 Flowers will still produce seeds that can live in the soil for 5 years. Any plants that have flowers should be disposed of in plastic bags placed in trash, NOT yard waste.
One way to get rid of garlic mustard:
1 Remove during the flowering period before the flowers go to seed.
2 Pull at the base of the plant and get as much root as possible.
3 Flowers will still produce seeds that can live in the soil for 5 years. Any plants that have flowers should be disposed of in plastic bags placed in trash, NOT yard waste.
Poison Hemlock
How to safely get rid of Poison Hemlock
Every part of the Hemlock plant is poisonous. If you find it growing in your yard you must be very careful when you remove it. Wear heavy gloves, long sleeves and long pants. Make sure you are very well covered. After, be sure to wash all your clothes and clean all your tools.
Method 1: Cut it up and dig up the roots. Put everything in large garbage bags. Let it dry out in the bag. Dispose of it in your garbage, not your yard waste.
Method 2: One farmer found success by letting the plants flower, BUT NOT GO TO SEED. Then cut them back, using the same precautions as above. Because it has used all its energy to grow flowers it will not have enough energy left to grow back. This works because it is a biennial; it has a 2 year life span. It flowers in its second year. If it is allowed to go to seed it will definitely spread.
There are also chemical methods available to get rid of Hemlock plants.
How to tell the difference between poison Hemlock and Queen Ann’s Lace:
Both are in the Apiaceae family and have hollow stems, but poison hemlock's stem is hairless and has purple blotches. Even a very young poison hemlock will display the purple blotching. On the other hand, the stem of Queen Anne's lace doesn't have purple blotches and is hairy. For more information and photos see the link below.
http://ravensroots.org/blog/2015/6/26/poison-hemlock-id
Every part of the Hemlock plant is poisonous. If you find it growing in your yard you must be very careful when you remove it. Wear heavy gloves, long sleeves and long pants. Make sure you are very well covered. After, be sure to wash all your clothes and clean all your tools.
Method 1: Cut it up and dig up the roots. Put everything in large garbage bags. Let it dry out in the bag. Dispose of it in your garbage, not your yard waste.
Method 2: One farmer found success by letting the plants flower, BUT NOT GO TO SEED. Then cut them back, using the same precautions as above. Because it has used all its energy to grow flowers it will not have enough energy left to grow back. This works because it is a biennial; it has a 2 year life span. It flowers in its second year. If it is allowed to go to seed it will definitely spread.
There are also chemical methods available to get rid of Hemlock plants.
How to tell the difference between poison Hemlock and Queen Ann’s Lace:
Both are in the Apiaceae family and have hollow stems, but poison hemlock's stem is hairless and has purple blotches. Even a very young poison hemlock will display the purple blotching. On the other hand, the stem of Queen Anne's lace doesn't have purple blotches and is hairy. For more information and photos see the link below.
http://ravensroots.org/blog/2015/6/26/poison-hemlock-id
Tansy Ragwort (Stinking Willie)
Tansy Ragwort, also called Stinking Willie, is also harmful to humans and livestock. Below is a link to how to tell the difference between Stinking Willie and St Johnswort.
https://www.swcd.net/news/tansy-ragwort-st-johnswort/
Stinking Willie/Tansy Ragwort, perennial behind Oakmont Commons also poisonous to humans and livestock
Tansy Ragwort, also called Stinking Willie, is also harmful to humans and livestock. Below is a link to how to tell the difference between Stinking Willie and St Johnswort.
https://www.swcd.net/news/tansy-ragwort-st-johnswort/
Stinking Willie/Tansy Ragwort, perennial behind Oakmont Commons also poisonous to humans and livestock
Hairy Bittercress
Hairy Bittercress is a winter weed that comes up as lovely little rosettes of green when everything else is dying. Nobody seems to eat the leaves but that is probably it is too cold for invertebrates like insects and slugs to be out and about. Eventually it will produce pretty little white flowers but then, WATCH OUT! Those flowers turn into seedpods that eventually will pop their seeds all over your garden. So you want to get the weed before it goes to seed, unless you don't mind the pretty rosettes in your garden...
More info: https://www.bbg.org/news/weed_of_the_month_hairy_bittercress
Hairy Bittercress is a winter weed that comes up as lovely little rosettes of green when everything else is dying. Nobody seems to eat the leaves but that is probably it is too cold for invertebrates like insects and slugs to be out and about. Eventually it will produce pretty little white flowers but then, WATCH OUT! Those flowers turn into seedpods that eventually will pop their seeds all over your garden. So you want to get the weed before it goes to seed, unless you don't mind the pretty rosettes in your garden...
More info: https://www.bbg.org/news/weed_of_the_month_hairy_bittercress
