I want start a garden in an area that is wild with lily of the valley. I have heard they are poisonous. I wonder how I can remove them so I can plant an edible garden. What process do I need to follow? - Krys, Racine.
Lily-of-the-valley (Convallaria majalis) is a beautiful plant often used in naturalized areas because of its amazing ability to survive, thrive, and yes, invade. I often get the question "How do I get rid of this plant?" because of its extreme tenacity. It will move readily through the garden by roots and seeds. Although attractive when flowering and very fragrant, people tend to tire of the standard species because of disease problems on the foliage which makes it unsightly later in the season, and its aggressive nature.
Interestingly enough, very few people ask me about the toxicity of lily-of-the-valley. It is poisonous, and all plant parts from roots to seeds could make you very ill if you were to ingest them. However, that toxicity is not in the soil, so growing other things in that location with or without the lily-of-the-plant still there is not a problem. Just don't eat the lily-of-the-valley.
Lily-of-the-valley typically thrives in shady, moist locations. So if you are planning on planting vegetables and herbs in that location you may need to assess the light availability and condition of the soil prior to investing time, energy and plants in that area. Vegetables and herbs require full sun (greater than six hours of direct sun each day) and very well-drained soil.
To remove lily-of-the-valley try a total vegetation killer that contains glyphosate when the daytime temperatures warm up to 45 to 50 degrees. Spray the green, growing plants following label directions, then wait for a week or two and reapply as needed. Glyphosate is translocated to the root systems of green plants (actively growing, green plants). Once there it disrupts essential chemical reactions within the plant causing death. Lily-of-the-valley is quite tough though, it may take two applications to really kill all of it.
If you prefer not to use chemicals, a shovel is in your future. Dig out the plants making sure to get all of the roots.
You will not get them all the first time around, but if you are turning the soil and incorporating compost for a vegetable garden you will break up the remaining plants. Diligent hand weeding should take care of the rest, but it will be an ongoing process.
Don't be surprised if you have more plants sprouting up each year due to bits and pieces of roots in the soil, and from the seeds that may have been deposited there over the years.
For new garden sites I have found that covering the site with 12 to 15 layers of newspaper and topped with four inches or more of compost works well to smother grass and other weeds. In addition, having the soil covered keeps weed seeds from germinating.
This is best done the year before you want to plant your garden so the weeds have time to die and decompose under the newspaper. However, it can be done in the same year with some success. The more compost you can put on top of the newspaper, the better.
UW-Extension Master Gardener volunteers serving as plant health advisers can help answer your questions at email@example.com or (262) 886-8451 at the Racine Horticulture Helpline.
They are on winter hours now, but please leave a message and they will return your call. If you have e-mailed or called recently, and have not received a return call or e-mail, please send your question again or give us a call.
Dr. Patti Nagai is the horticulture educator for Racine County UW-Extension. Submit your questions for the Journal Times Q&A column to Dr. Nagai at Patti.Nagai@goRacine.org and put "Question for RJT" in the subject line.