Broad-leaved helleborine: A weedy orchid invading lawns and flowerbeds
Broad-leaved helleborine is once again causing trouble for those finding it in their lawns and flowerbeds.
Broad-leaved helleborine (Epipactis helleborine) is quickly becoming a problem for gardeners and landscapers this spring. We have had multiple samples submitted to Michigan State University Plant & Pest Diagnostics. This plant is in the orchid family, Orchidaceae, and is sometimes referred to as a “weedy” orchid. It was intentionally introduced from Europe and is spreading throughout Michigan in lawns, flower beds and along driveways. According to Voss’s "Michigan Flora," roots and seeds of helleborine obtained from New York were intentionally planted in Niles, Michigan (Berrien County) in 1891. It was noted to be widely established in the Niles area by 1919. It is not known whether any other plants discovered throughout Michigan were derived from this population.
Helleborine is a monocot that arises from fleshy roots or rhizomes. This allows for several stems to develop from the same rootstock. The leaves are alternate, parallel veined, sessile and clasp at the stem. The flowers are bilaterally symmetrical and are greenish-white with a violet tint. This plant can grow up to 36 inches tall.
Controlling this plant is proving to be quite difficult. The best time to dig them up is when they are starting to flower in hopes that their root and rhizomes are at their weakest. The problem is that you must get all of the root/rhizome system, which is not an easy task. Herbicides can help. You can spot-treat with glyphosate (the active ingredient in Roundup Weed and Grass Killer and other brands), but it will likely take multiple applications. Glyphosate will kill or injure the plants of any green tissue, green bark, exposed roots that it contacts, so use with caution around desirable plants. There is a product called Roundup Precision Gel, which resembles a large stick of deodorant, that may help reduce off-target movement.
As always, remember to read and follow all labeled instructions. If you do choose to use glyphosate, make sure there are not any other active ingredients in the product except pelargonic acid, as they may have unintended consequences. There are other herbicides that may also be effective, but they are more likely to move and cause problems with desirable plants.