Invasive plant of the month: Goutweed (Aegopodium podograria)

Looking in yards in Bayfield and surrounding areas, one will notice the Ivy, Lily of the Valley and Periwinkle in the right way.

Looking on the trails, and you’ll notice Goutweed.

These invasive plants are spreading rapidly and crowding out native plants that serve a critical function in the ecosystem.

As you begin to remove the invasive species in your own yard, you can replace them with native plants and will see an increase in biodiversity, especially with pollinators.

Focus on Goutweed (Aegopodium podograria):

Goutweed is a perennial, herbaceous plant, native to northern Asia and Europe. It was first introduced into America by European settlers during the mid-1800s.

Two varieties exist – variegated and non-variegated.

This plant has been naturalized and locally abundant since the 1960s due to its appeal as an attractive garden ornamental.

Aside from its aesthetic appeal, Goutweed’s popularity in gardening was mainly due to its low maintenance requirements, adaptability to various soil and light conditions, and its ability to grow and spread with little encouragement.

Today, Goutweed is regarded as one of the most problematic perennial garden species.

Despite the harm it causes, it is not currently regulated under Ontario’s Invasive Species Act, and it still commonly sold in garden centres.

Various other common names exist for Goutweed including Ground Elder, Bishop’s Goutweed, Dog Elder and Snow-on-the-Mountain.

Outside of its native range, Goutweed is a highly aggressive species capable of overrunning forests, displacing habitats, and reducing native biodiversity.

Goutweed is a habitat generalist, meaning it can thrive in a wide variety of soil and light conditions, and is highly adaptable to many different environments.

It is highly shade-tolerant and can even invade closed-canopy forests. It can take over fields, trails, tree lines, pastures and disturbed sites where it produces leaves earlier than many native species, giving it an advantage.

Goutweed can also reduce the survival rate of native tree and shrub seedlings by increasing the humidity and reducing sunlight penetration near the herbaceous layer of the forest floor.

In addition, Goutweed’s flowers attract pollinators, altering native plant-pollinator interactions, and possibly decreasing the pollination of the native species.

Goutweed is an extremely resilient plant and once established, can take multiple years to effectively eradicate from an area because it spreads rapidly through a network of rhizomes, allowing it to extend up to 70 cm per year from its parent plant.

The rhizomes easily break, giving rise to new plants from the fragmented pieces. These pieces can survive in the soil for over four years, so avoid planting and sharing Goutweed.

How to Manage Goutweed:

Managing Goutweed is challenging but achievable with persistence and a multi-step approach.

Manual Removal:

Removal is most effective when the soil is moist. Small areas can be dug out by using a shovel, ensuring all parts of the rhizome roots are removed.

Pieces of root left behind can promote reproduction and worsen the spread.

Do not put plants in the compost or municipal green waste. Put them in the garbage instead.

Smothering:

Tarping is another method to effectively prevent Goutweed photosynthesis. Tarping is the most practical during the early spring and can be done with any solid material such as black plastic tarps, sheeting or cardboard.

Cutting Goutweed back to ground level before smothering is most effective and should be done before flowering.

Herbicide Treatment:

Alternatively, larger areas can be eradicated by a herbicide application. Use herbicides only as a last resort, following local regulations to minimize environmental harm.

After removal, replant the area with regionally appropriate native plants. This step is essential to prevent reinfestation and to restore ecosystem health.

Native plants will also attract pollinators and wildlife, improving biodiversity in your garden.

A good choice would be Wild Ginger (Asarum canadense) or Golden Alexander (Zizia aurea).

Education is key to combating invasive plants. Learn to identify invasive species and choose native or non-invasive alternatives for your garden.

For more information visit www.ontarioinvasiveplants.ca or www.ccipr.ca

Renee Sandelowsky and Helen Varekamp are volunteers with the Canadian Coalition for Invasive Plant Regulation