Ever heard of Japanese knotweed?
The Ohio Department of Natural Resources lists it as one of the state’s top invasive species, among the ranks of Japanese honeysuckle, garlic mustard and purple loosestrife. The shrub-like herb can grow up to 10 feet tall, its underground root system can grow up to 60 feet in length and it’s not exactly easy to control.
Japanese knotweed originated in parts of Asia — Japan, China, Korea and Taiwan — and was introduced in the United Kingdom in the early 19th century as an ornamental plant, according to the Indiana Plant Species Assessment Working Group (IPSAWG).
What does Japanese knotweed look like?
Japanese knotweed has reddish-brown hollow, smooth stems and swollen nodes, the Ohio Invasive Plants Council explains. The plant’s leaves are pointy and can be oval-shaped or triangular, and they are about 4 to 6 inches long and 2 to 3 inches wide. Japanese knotweed flowers in late summer. The plant’s flowers are small and green-white in color.
Where does Japanese knotweed grow?
Japanese knotweed grows in open areas, according to ODNR. You can find it along roadsides, riverbanks and woodlands. The plant grows in moist environments.
Japanese knotweed typically emerges and begins to grow in early spring. It’s underground rhizomes grow quickly, allowing the plant to expand into dense thickets, according to The Wisconsin Department of Natural Resources.
Does Japanese knotweed grow in Ohio?
Japanese knotweed is pretty common in the Buckeye state, especially in eastern Ohio.
The Ohio Invasive Plants Council offers a map that shows the counties in which Japanese knotweed was reported, as of 2010.
Can you eat Japanese knotweed?
Surprisingly, you can.
In Pittsburgh, knotweed grows in abundance in empty lots and along the city’s rivers. The Wall Street Journal takes a look at how the invasive weed is being used in culinary creations at local restaurants and urban farms. So far, knotweed has been used in sauteed dishes, honey, beer, ice pops and even desserts.
How do I control Japanese knotweed?
If Japanese knotweed has made a home on your property, you can control it mechanically or chemically.
The Wisconsin Department of Natural Resources explains that cutting off the aboveground portion of the plant doesn’t really solve any problems, as it will continue to grow from its underground roots. The plant’s energy comes from its rhizome. However, weekly mowing of the plant can wear down on its energy reserves, helping to eradicate the plant.
If Japanese knotweed has become widespread and thick, digging up each plant will be time and energy-intensive. The Ohio Invasive Plants Council says that if there are only a few plants, consider digging them up, making sure to remove underground rhizomes. Dispose of the plant in plastic bags. Physical removal of the plant may have to be repeated in a single season.
As for chemical control, the Ohio Invasive Plants Council says that spot application of products like Roundup or Habitat, along with repeated cuttings, can help to get rid of Japanese knotweed. Read more about chemical applications here.
ODNR recommends spraying leaves, cutting the stems and spraying the plant with herbicide. A full how-to that combines mechanical and chemical control can be read on this Wisconsin Department of Natural Resources guide.
Have any other tips for Japanese knotweed control and removal? Let us know in the comments section.
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