Thank you for contacting the Growline [Cornell. Cooperative Extension Tompkins County]. I’m sorry to hear you have a goutweed infestation. Goutweed (Aegopodium podagraria), aka Bishop’s weed and Snow-on-the-Mountain, was introduced from Europe and Northern Asia in the mid 1800s. In the middle ages, monks cultivated it for treating gout; hence the name. It thrives in moist, well drained soils in partial sun to full shade. The plant spreads by fast growing underground roots (rhizomes) as well as seeds.
Eradication of this plant takes persistence but can be done. First, remove any flower heads before the plant goes to seed to prevent seed production. Cut and bag the flowers.
There are several additional strategies you could employ:
- Dig up the plants or pull them out of the ground. Pull plants by hand or use a digging fork, as shovels can shear off portions of the root system, allowing for regrowth. Even a small piece of rhizome can re-sprout into a new plant. Dispose of rhizomes and pulled plants in the trash – do not compost them. You will probably need to repeat this process as any underground parts left behind can be rejuvenated and send up new shoots. It’s easiest to undertake this type of control in the spring or early summer when soils are moist and plants come out more easily.
- Cover the area with a landscape fabric or plastic. Place double or triple layers of thick UV-stabilized plastic sheeting, either clear or black, over the infestation and secure the plastic with stakes or weights. Be sure the plastic extends at least 5 feet past the edge of infestation on all sides. Leave the plastic in place for at least 2 years. This technique will kill everything beneath the plastic—invasive and non-invasive plants alike. This option is best done in early spring.
- Mow or cut infested areas 3 or 4 times a year. You will need to keep doing this for up to 5 years. The objective is to interrupt the plant’s ability to photosynthesize by removing as much leafy material as possible. Cut the plants at ground level and remove all resulting debris from the site. With this treatment, the infestation may actually appear to worsen at first–each time you cut the plants back, the root system gets slightly larger. But the plant will also expend its energy reserves to push up new growth. Eventually, you will exhaust these reserves and the plants will die. This may take many years, so you have to remain committed to this process once you start; otherwise, the treatment can backfire, making the problem worse.
Once you have done your best to rid the site of goutweed, plant something else where it was growing to prevent another invasion.
Proper disposal of removed plant material is critical to the control process! Place the plant material in a doubled-up black trash bag and let it cook in the sun for 1 month. At the end of the month, the material should be non-viable and you can dispose of it in the trash. This assumes there is no viable seed mixed in with the removed material!
Whichever method you use, you will need to be vigilant since even one little left-behind piece of root can sprout up into a new plant. But don’t despair. Just keep digging and pulling them out as they come up and eventually you will prevail.
Even a small piece of rhizome can re-sprout into a new plant, so take care to dispose of all plant material carefully and clean your clothing and shoes after going through or working with a patch of bishop’s weed.
Here are some web sites on the subject:
Thank you for contacting the Growline. I hope this information is helpful.