Invasive Plants

My Experiences with an An Alien Invasion: Japanese Hedge Parsley (JHP) or Just a Hellish Plant

Those of us fighting invasive plants on our property often feel we are standing in a stream of rushing water plodding slowly upstream. Occasionally we reach a shallow point and feel a sense of progress or temporary control, but we never truly expect the flow to stop. We seek, but never expect, total eradication of the invasive plants that have our property in their grip. Nevertheless, we continue to hope we will reach a point where the flow is greatly reduced or even becomes a trickle, and that with proper management protocols firmly in place, perhaps including funding after our deaths, we might possibly feel, if not fully secure, at least resigned and stable.

But what happens if upstream, and out of sight, a dam is leaking and about to break? This danger is how I would describe the coming invasion of Japanese Hedge Parsley. This plant represents an overwhelming flooding, a massive onslaught of invasion, because it is rapidly suggesting behavior as bad, and probably worse, than Garlic Mustard. It is however manageable, and my helper of many years remembers the first time he saw it around six or seven years ago, and what has happened on that 100 square feet since:

"I saw the first plant under the ancient apple tree west of the silo, where you've since planted wild ginger. I thought it might be poison hemlock. Sometime later (I can't remember how much later) I described it to Mike [Anderson], and he thought it might be JHP. By the next season or two there were several more plants, [and a year later an explosion throughout the property]. Today [in this first location one sees] very little of it compared to what there once was."

But JHP is extremely aggressive, can appear practically anywhere, and one plant today will be 3,000 tomorrow. Avoid allowing any seed to form and disperse - they are stick-seeds and disperse widely and easily, so without application of bull dog like tenacity Japanese Hedge Parsley rapidly becomes practically impossible to control.

Part of the reason is it easily missed and difficult to see unless it is a flat emerald-green first year plant rosette on bare earth immediately following snow melt, or blooming robustly in wispy sprays of miniature Queen's Ann's lace-like florets of a cool gray-white color. Between these stages it can look very much like Sweet Cicely (Osmorhiza), a native, and aside from a darker green color, and slightly different leaf character, the two plants are very easily confused, or overlooked, and both enjoy similar woodland conditions.

As mentioned above, several years ago we noticed an unknown plant on our property in rural NW Green County. Unfortunately we ignored it for a year or two and now from those half dozen Japanese Hedge Parsley plants has come a severe and gripping infestation now active in practically every possible condition - from beneath 30 year old pines, where it successfully booms, to the bright sunny rocky shoulders of the road. The only place I have not seen it is in an upland (mesic and dry) planted prairie, but anywhere it receives even the slightest amount shade (and up to zero sun and/or eternal gloom) it will thrive.

We can tell where the first migrating plants were unknowingly allowed to go to seed for these are the most stubborn "hot spots" on the property, and clearly year after year, though we allow no flowering, the seed bank remains plentiful; and will remain so for an unknown number of years, one sadly assumes, based upon a multi-year history that only now shows a modest reduction in hot spot activity. The only place we see anything close to eradication is the original minuscule spot mentioned above, and I would assume even the slightest disturbance there would produce another flush of germination.

Yes, we have successfully contained the invasion, and it is only this containment that makes control and progress possible. Without control any number of acres would easily and quickly become infested making future control next to impossible.

The plant blooms at any height from about four inches (after cutting too early, or too high) to a massive size. This report from one of our crew, "We found a record size hedge parsley plant. It was approximately 7' tall by 6' wide. It was near the big bur oak in the center of the walnut plantation," suggests the tens of thousand of seeds that will flow from a single plant.

So here is what one must do from first thaw to late summer:

Each spring seek and spray (with Roundup) the vivid dark green flat rosettes (the first year plants appear very bright dark green as the snow melts, and stand out boldly). The earlier the better reduces collateral damage from spraying at this stage of control.

In warmer weather pull or cut and bag (bag after August 1, or whenever flowers are aging and especially if seeds are beginning to form), or spray at first sight. In summer, if I am not bagging it, I take pains to pull it, if possible (a wet year really helps), or cut it at ground level being careful to cut all the many tentacles of the octopus like growth habit of this wily, but physically weak and easily broken, plant. After pulling or cutting It only takes me a moment to cut the plant into pieces to decrease the likelihood of rogue seed development, and especially when pulling I would suggest, if not bagging, to, at a minimum, cut the root from the plant.

Based upon what I have seen over many years, I would suggest that our self-inflicted "global weirding" is an accelerating macro disturbance favoring all weeds, including, and especially, poison ivy, which I notice is now rapidly spreading from areas it has occupied modestly for 30 years, and which is a frequent nurse plant to JHP making control onerous, and providing an additional argument for early attack and relentless control..

My neighbor adds the following, "I would not call JHP an annual because I see it germinate in the spring, over winter as a rosette, and bloom the next year. More like a biennial. I think it can germinate in the fall as well, so that may be why some call it a winter annual. I have seen JHP grow in all environments - shade, sunny, savanna, prairie, woods etc. The one place is seems to struggle is wetlands. However, I have found it growing with very wet feet. JHP can compete with all plants. I have seen it grow tall and skinny when competing with giant ragweed, and then with wide, low-sweeping, multiple stems when growing elsewhere with short competition. It can form very dense monocultures with little else growing underneath it. If the seed hits the soil, the plant will grow regardless of where, or what else is growing there. It successfully competes with everything. My fear is that this plant will be worse than GM. The seed can travel great distances due to its "velcro" coat.

The only solution seems to be get to know this plant NOW and hit it hard the moment you see it. Waiting even one year may increase the work required 100 fold in the years to come.

More detail, good images, and all dry, technical information is easily available at these sites:

DNR Fact Sheet:

DNR Invasive Plant List

Chuck Bauer
August 10, 2009