Pinellia ternata
I have learned many new plants in my three months at the Scott Arboretum. In fact, it would not be an exaggeration to say I learn a new plant every day. One of the very first plants I learned upon starting work here, though, was not a cutting-edge cultivar or a unique specimen tree. It was a plant with quite a reputation around these parts, not for its aesthetic appeal, but instead for its stubbornness and invasiveness. This month’s Plant of the Month is the weedy Pinellia ternata.
The volunteer who first introduced me to Pinellia described this invasive plant with a tone of loathing and detestation. If memory serves me correctly, I believe she described Pinellia as the “bane of [her] gardening existence.” At the time, I thought that was a pretty strong statement for such a small weed. But, after three months of first-hand experience with this seemingly ineradicable plant that always reappears with gusto, I now understand what the volunteer meant.
Pinellia ternata is native to Japan and is sometimes referred to as cow-dipper. The plant possesses trifoliate leaves and a flower typical to plants in the Araceae family (think of a jack-in-the-pulpit with its spathe and spadix flower). Similar to other Araceae plants, the flowers of Pinellia are hermaphroditic. One of the secrets of Pinellia ternata’s success is that its stem regenerates from a corm that resides inches below the soil’s surface. As a result, hand-pulling is nearly always ineffectual in ridding a garden area of Pinellia. The best method I have found for dealing with Pinellia is to push a hori-hori (Japanese digging knife) or other digging tool deep enough in the soil (a few inches) to excavate the entire plant. Success is achieved if the removed plant still has a spherical corm attached to its long white stem.
P. ternata thrives in the mid-Atlantic region and, left on its own, is capable of nearly doubling in population every year. However, with consistent and accurate weeding, it is possible to control the spread and reduce the pervasiveness of Pinellia in your home garden. Just be sure not to dump Pinellia in your compost pile; instead, tie it up in a plastic trash bag to prevent it from spreading its weedy ways.
Until next time, good luck in your weeding adventures and happy gardening!
Philip Schumacher October 16, 2008 at 8:31 am
Pinellia ternata was widely sold 10 or 12 years ago in Southeastern PA as the only Pinellia that wasn’t invasive. In it’s EARLY years in our garden it was a delightful plant but in 6 or 7 years it gets entrenched and the plants begin to appear further and further from the parent clump. I agree it should only be grown by those who understand it’s true nature. It could easily become problematic. Last year I saw a new variegated form that was very tempting and I’m sure many have a tiger by the tail.
Sarah Hutchin July 1, 2009 at 8:32 pm
When we first saw Pinellia ternata, it was growing in a newly built raised bed that had been filled with fresh soil . I am glad that I saw a picture of it in an id of invasive plants book that I had purchased recently. I wrongly thought that it was some kind of Jack- in- the -Pulpit and was going to plant them in my garden at home. I would seriously look out for these “cute ” little pulpit look-alikes in soil brought in when preparing a new garden site or raised beds! This is what seems to have happened to us , as I certainly hadn’t seen hide nor hair of them prior to the raised beds being built and filled with soil.
Nancy S. Czarnecki September 28, 2009 at 6:51 pm
I have been fighting this monster weed for over 15 yrs. Don’t know from whence it came, but i may be responding to Trichlopyr (Ortho). We have not been able to correctly identify it until today from the wonderful Atlantic Co. Extension agent. Digging it out – corm and all, is not enough. It keeps spreading by the corm and gazillion rhizomes. extending from the corms (or nuts).
Andrew Bunting October 1, 2009 at 8:32 am
Pinellia is one of the most pernicious weeds in the gardens at Swarthmore. We have eliminated it from some garden areas, but only by digging out the soil, sifting it through a screen and picking out all the parts of the Pinellia.
Andrew Bunting, Curator