Tom's Blog

Wednesday, June 18, 2008

Japanese hedge parsley starting to show

Japanese hedge parsley (Torilis japonica) is one of the so-called emerging weeds for southern Wisconsin. Unfortunately, it has been at Pleasant Valley Conservancy ever since we started restoration work. I'm not sure whether it has been spreading or whether we have just learned to recognize it better, but it seems to be more widespread. The photo to the left, taken yesterday in a fairly shady savanna, shows how difficult it can be to spot when just in the vegetative state.

Hedge parsley is what is called a "winter annual", which means that its seeds start to grow the same year they are formed, overwinter in a vegetative stage, and then flower the following summer. It is found mainly in shadier areas.

It is a member of the carrot family, and when small its leaves can be mistaken for those of Queen Anne's lace, another exotic invasive plant.

The first collections at the U.W. Madison Herbarium were made in Walworth County (on the Illinois border) in 1976. My dear friend Olive Thomson made the first collection in Dane County in 1982. It is now found in several counties bordering Illinois and as far north as Waupaca and Manitowoc Counties. Unless a concerted effort to control it is carried out, it will undoubtedly spread widely across southern and central Wisconsin.

Unless one has a large infestation, hand pulling is about the only control method, although I did find that spraying the "winter" plants with Roundup in late November or early December worked. However, in the wooded areas where it is mostly found, it is covered with leaves that time of year and hence hard to spray effectively. Fortunately, it pulls very easily, lots easier than wild parsnip or sweet clover, for instance.

Because of its delicate flowers, it is fairly hard to detect even in mid summer when it is in full flower. We have been keeping notes on where we have found it, and use those notes to keep on top of our main infestation sites.

I haven't found any data on seed bank conditions, or on how long the seeds can be expected to persist. So far, we still find it in areas where we first found it ten years ago, suggesting that the seeds may have considerable longevity.

Hedge parsley is undoubtedly lots more common in southern Wisconsin than suspected. I have seen it all over, including one very serious infestation that was a long distance from any nearby roads.


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