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!