Question
Lily of the valley (Convallaria majalis) is invading my lawn and rock garden. Should I have surrounded this plant with a special grass border to prevent this? How can I get rid of it in an environmentally-friendly way?
Answer
Lily of the valley is indeed a difficult plant to control, due to its long underground rhizomes which spread rapidly. There are several ways of eliminating it:
Thorough Excavation
This technique involves digging up the invaded area to extract all the rhizomes. This method is effective, but demanding, and may require several attempts to completely eliminate the plant, as the remaining rhizome fragments may grow back.
Occultation With Black Plastic Fabric
Cover the infested area with black plastic sheeting and leave it in place for at least a year. This method uses the solar heat accumulated under the cloth to eradicate the plants. It is particularly effective in full sun.
Organic Herbicides
Herbicides based on soap or natural acids, such as vinegar or lemon juice, are also available. Although environmentally-friendly, these products only kill foliage and must be applied several times (2 or 3 times) to be effective. It’s important to note that these substances can alter soil pH and affect other plants in the vicinity. In addition, check that they are legal for use as herbicides in your area before application. By reapplying these treatments each time foliage reappears, you will gradually weaken the plant until its underground reserves are exhausted.
It’s essential to use all products with care and follow the manufacturer’s instructions to minimize environmental impact and avoid harming non-target plants. Thrush management can be a lengthy process, requiring patience and perseverance.
Prévention
To prevent a lily of the valley invasion, plant it in controllable areas, surrounded by deep physical barriers (30 to 40 cm deep) to limit the spread of rhizomes. Monitor the area regularly and act quickly to remove unwanted shoots to prevent their establishment elsewhere. Consider using less invasive varieties. Even if it is not recognized as a harmful exotic invasive plant in your area, lily of the valley can become very invasive and harm local biodiversity and native plants. All parts of the plant are toxic if ingested and should be handled with care, especially in the presence of children or pets.
Larry Hodgson published thousands of articles and 65 books over the course of his career, in both French and English. His son, Mathieu, has made it his mission to make his father’s writings accessible to the public. This text was originally published in Le Soleil newspaper on June 3, 2006.