Hi everyone! I’m cross-posting this in several places because I’m trying to gather as much experience and information as I can to help my client make an informed decision.
I’m an ecological landscaper, and I have a client who lives in an upscale woodland neighborhood in western North Carolina. They recently had a company come in and do extensive invasive plant removal, and they’re hiring me to replace the ground layer with native plants.
It’s a very large project with several different planting zones. Most of them are pretty straightforward, but the largest and most visible area has me thinking through a few different approaches. I would love to hear any firsthand experience, ideas, research, or thought processes that might help me give them the best options and manage their expectations appropriately.
The area in question is approximately 14,000 sq. ft. and is completely covered in Japanese stiltgrass (Microstegium vimineum).
I’m currently unsure what methods the invasive removal company used to deal with the stiltgrass. I have their contact information and plan to find out more, but whether they pulled it or treated it with herbicide, I know there is a substantial seed bank waiting to germinate next year.
These clients seem to have a fairly substantial budget and are willing to invest quite a bit into the project. When I was trying to gauge their budget versus how quickly they’d like to see the area become ecologically functional and visually interesting, I got the impression they would prefer to spend more money upfront to get there faster.
Right now, I’m considering two approaches:
Option 1: Plant directly into the existing soil and commit to intensive maintenance.
We could install the native plantings directly into the ground as it is and plan for several years of consistent stiltgrass removal to gradually exhaust the seed bank.
I would focus on establishing native species that have at least some chance of competing with stiltgrass. I know I have some potential candidates buried in my notes somewhere, but I can’t think of them off the top of my head right now.
The obvious downside is the amount of ongoing maintenance required, especially with thousands of native plants to work around.
Option 2: Bury the seed bank under a substantial layer of wood chips, then plant into it.
I’m considering covering the area with approximately 4–6 inches of wood chips or another suitable mulch to suppress a large portion of the stiltgrass seed bank.
I would only apply that depth in the open areas, keeping it away from the bases and root flares of established trees. Areas immediately surrounding trees would need to be managed through hand weeding over the next several years.
The idea would be to install thousands and thousands of native plugs next spring, after the wood chips have had some time to begin breaking down. When planting, I would likely bring in some soil to incorporate into each planting hole to help support the plugs, since the wood chips would only be partially decomposed by then.
By my estimate, this approach would require well over 100 cubic yards of mulch, so it’s a substantial undertaking. However, I think these clients may be willing to invest in it if it offers a faster or more effective path toward establishing the native ground layer.
My biggest questions are:
- Does anyone have firsthand experience with burying or suppressing a Japanese stiltgrass seed bank under a thick layer of wood chips?
- Is 4–6 inches necessary, or could 2–3 inches be effective at preventing a significant portion of the seed bank from germinating?
- Has anyone tried establishing native plugs into an area prepared this way? What were your successes or challenges?
- Are there other approaches I should be considering that might produce better results?
I realize that any disturbance during planting could bring some buried seeds back to the surface, and I’m not expecting to eliminate stiltgrass entirely with either approach. My hope with the second option is that we could significantly reduce the amount of stiltgrass emerging and give the native plantings a better chance to establish without years of such intensive competition.
I’m very open to ideas, links to studies, firsthand experience, or even reasons why one of these approaches might be a terrible idea!
I take a lot of pride in my work and really try to make the most informed decisions I can, especially on a project of this scale. I want to give these clients realistic expectations and a plan that has the best chance of long-term ecological success.
Thanks in advance for any insight!
Photos are of the area in question.