Wild Parsnip

Wisconsin DNR's Parsnip page: Wild Parsnip (Pastinaca sativa)

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Tips for controlling Wild Parnsip

A few comments on parsnip control as a result of 30+ years working on its control in the [Dane] County Parks:

Mow after the 4th of July as earlier mowing allows the parsnip to resprout and produce a few seeds. Pull or slice off the top of the root before the 4th of July because mowing before the 4th means it will surely resprout and produce seeds.

If parnips are mown with a rotary mower, it is very unlikely that there is enough juice in remnants of stem to produce seeds, so mow with a rotary from week after 4th of July to the end of July and you should be successful in reducing the population after 5 or so years.

The population of parsnip increases after the first mowing because you are releasing the vegetative parsnips.  Remember, parsnip is not biennial, it is monocarpic...it blooms and dies.  However it may take a decade before it will bloom.

As for seed production after cutting down the stems with a scythe, it is very unlikely, in my experience, that the parsnip produces real seeds.  Whenever I check what looks like seeds, they are empty.  If you choose to check them ... take a few of the "seeds" and bend them in half ... if they bend like a piece of paper they are empty.

On rare occasions a parsnip pulled from the ground with soil attached to the root and placed in the shade has an ability to keep growing.  But even then it has difficulty producing seed.

As for herbicide use, Escort seems to be the best parsnip killer available.

  -- Wayne Pauly, Dane County Parks Naturalist

 From:  The Blue Mounds Area Project List

Also …
 The "parsnip predator" shovel, sold through The Prairie Enthusiats is a great tool, not only for parsnip, but for other tap-rooted plants as well.  The shovel is designed to plunge into the ground, cutting the parsnip taproot deep, effectively killing the root.  A tug with your free hand pulls out the parsnip.  Much easier on the back than the two handed struggle.  You can find the shovel on the TPE website under merchandise.