A gardening friend told me that I have a weed called goutweed in my garden. Now that I have looked closer at the beds, it is spreading throughout my shaded garden and even into my lawn and other sunnier beds. What’s the best way to get rid of this weed?
— Betty Layton, Glenview
Goutweed (Aegopodium podagraria) is a vigorous, invasive perennial that spreads quickly by underground stems called rhizomes and can take over a garden and crowd out garden plants, as well as native plants in natural areas. Established goutweed is very competitive in shaded sites in cultivated gardens and native woodlands. Patches of this plant will increase in size through the expansion of the rhizome system. Goutweed will grow into the bases of your perennials and into ground cover beds, making it difficult to weed out. You also may not notice it right away like you might with other types of weeds. There is a cultivated form called Bishop’s weed or snow on the mountain (Aegopodium podagraria ‘Variegatum’) with variegated leaves that is sold in some garden centers that also will be invasive in your garden. It will occasionally revert to solid green or a mixture of solid green and a lighter variegated pattern. Naturalized plants will have green foliage. The flowers are white and last about a month, starting in late spring and lasting until midsummer. It’s best not to plant this in your garden.
Small patches of goutweed can be eliminated by careful and persistent hand pulling or digging up of entire plants along with the rhizomes. The plants will generally break off at ground level if you try to pull them out when the soil is dry. Even a small piece of rhizome can re-sprout into a new plant, so be sure to remove as much of the root system as possible and dispose of it by burning or bagging and putting it in the trash. It is best to avoid putting the plants in your compost pile. Be careful to clean up all rhizomes, which can root again and sprout new plants if left lying on the soil. Continue to monitor the area and be persistent in pulling plants that will continue to grow again over a period of years. Consistent removal from month to month over a period of years is critical to get control of this weed by hand pulling.
Systemic herbicides such as glyphosate (Roundup) that are translocated to the roots and kill the entire plant are effective in controlling goutweed. Be sure to follow the directions on the label and avoid spraying any adjacent desirable plants that would also be killed by the herbicide. In my experience, it will take several treatments of herbicide to eradicate a patch of goutweed. I started spraying the goutweed in my garden three years ago and most of it is now gone, but it still sprouts in the same area after more than six applications of herbicide. I use a broadleaf herbicide to spray the goutweed growing in the lawn because I do not want to kill the grass. You can also try covering the goutweed with black plastic in early spring to prevent it from photosynthesizing. The plastic will need to remain in place for most of the summer to achieve decent control. This technique will not be practical in most situations.
For more plant advice, contact the Plant Information Service at the Chicago Botanic Garden at plantinfo@chicagobotanic.org. Tim Johnson is senior director of horticulture at the Chicago Botanic Garden.
