Did you know you might have an orchid growing in your lawn or flower bed? Orchidaceae is one of the largest plant families on earth along with the Asteraceae (aster) and Fabaceae (pea) families. Epipactis helleborine, or broadleaf helleborine, is a member of the orchid family. Before you get too excited about your new orchid garden, you should know this particular one has become a noxious “weed” for many Midwest gardeners, and it is challenging to remove at times.
The history of helleborine in this part of the world has several interesting points I want to highlight; the first is a local one. The Michigan State University article prompting this little bit of prose tells us helleborine was intentionally introduced from Europe and planted in Niles (yup, the one just up the road) in 1891, spreading from there.
The second point relates to the invasive nature of this and other species. Our understanding as to definitions and causes of invasive patterns are undergoing some revisions. However, for the purpose of this rant, I think this species speaks a cautionary tale. What makes a particular species “invasive” and dangerous to existing ecological conditions? An invasive species becomes a threat when it begins to disrupt long established ecological linkages and relationships between established species in a particular location, possibly causing ecosystem collapse. The extreme long-term ecological impacts of invasive patterns are very well understood. We are not sure how adaptable, resilient or flexible ecosystems are to “introduced” species – by introduced, I refer to those introductions caused (intentionally or not-intentionally) by humans because, of course, species have been “introduced” to new environments and new locals from the beginning of time.
Some introduced species have a long recorded history here on North American soil, have naturalized, but have never become invasive. Other species were introduced and remained relatively stable, non-threatening populations for centuries, but then suddenly exploded in numbers and range. What is occurring? What makes a species invasive? Though I am not sure we have the full picture yet, I think we are beginning to get a better understanding. Early invasive and conservation research focused on species characteristics. What was so evil about these darn foreigners? Were they unusually aggressive? Were they not in their native habitats?
“Noxious” weeds like helleborine often have some helpful adaptive strategies. They may vigorously colonize an area through rhizomes or other vegetative structure. They might have seeds with a long shelf-life. They might self-pollinate, thus avoiding the messy process of establishing new relationships with existing pollinators in order to produce seed, lots of seed. These plant characteristics might help explain some invasive patterns, such as a newly introduced species quickly becoming an ecological threat, but it does not explain latent invasiveness. This requires an examination of other possible causes, such as changes in climate or a disturbance in ecological relationships.
It is looking like the more biodiverse an ecosystem, the more difficult it is for a newly introduced species to gain a foothold. Begin to take away existing species and linkages, and openings begin to appear. Unoccupied niches become available for newbies. It turns out disturbance (human or non-human) may be a major driver of invasive patterns, and where do most invasive species gain footholds? In highly dynamic edge zones (road sides, railroad corridors) or places of frequent or high disturbance (industrial zones, agricultural fields, or your typical home garden).
Let us look at two land use examples: abandoned commercial or industrial parks, and the home garden. In either context, the soil has typically been disturbed greatly through grading or cultivation. The biodiversity in either example is usually extremely low and planted with exotics species with very little linkage to the surrounding ecological habitats. It is in these settings one can find the greatest density and diversity of invasive patterns. It is nature trying to figure out a new evolving landscape if given enough time to “figure” what to do with these newcomers.
The above described dynamics are why we have developed the practices at Wellfield of attempting to disturb the soil as little as possible once a garden is first established, all the while ever increasing the biodiversity of both what is living below and above ground. The more we can cover the ground and plant a diversity of plants, the more ecological niches are filled, the more likely plants are healthy and resistant to invasion.
When a new “weed” shows up, the question I need to ask first is not how to get rid of the invader, but what condition is the weed taking advantage of in the first place? Is there a lack or excess of something in the environment the plant is utilizing? Is the new species filling some ecological niche left unoccupied? Most invasive patterns begin, I think, due to either a lack or excess of something in the environment created directly or indirectly by disturbance. Armed with these facts, a gardener can craft a solution that best addresses the concern rather than thoughtlessly reacting with strategies that might exacerbate rather than ameliorate the problem.
Josh Steffen, Horticulture and Facilities Manager