Species name: Fallopia japonica
Common name: Japanese knotweed
Location: Ontario
Again, from the common name of this species you should be able to discern that it's a non-native plant (native to Japan, China and Korea), and it is one that is highly invasive in disturbed habitats outside of northeast Asia. In North America, any place that it has been introduced it very quickly dominates, and takes many years of dedicated effort to eradicate it completely. Because of the intense underground network of rhizomes, complete eradication of the plant without use of chemical herbicides is nearly impossible; the next option is to dig up the earth and transport it away from the site (the easiest way to remove Japanese knotweed away from areas to be developed). This involves removing the top two to three feet of soil, a feat that is not possible for most natural or residential areas.
Despite this plant's bad rap, I find it one of the most fascinating plants we have in North America (but I would never plant it myself!). The growth rate of Japanese knotweed is outstanding; it can grow three to four METERS in one growing season from about May until October or November. That kind of growth in a temperate species in a temperate location is unheard of with very few exceptions. Why this plant isn't being investigated as a possible source of biofuel is beyond me (there's no reason why it couldn't be grown in a highly controlled way in a greenhouse or contained outdoor area, and genetically modify it to prevent the formation of seeds). The stems can grow to be so large and so strong that it is often mistaken for bamboo in the cut form (I doubt anyone would mistake it for bamboo when it's still standing in the ground; the leaves are very different! They are completely unrelated species).
In Japan, this plant is a traditional food crop, although not widely served in tourist areas so most foreigners are not exposed to it. The name for the food made from this plant (young shoots and leaves) is called "sansai," but the plant has numerous names based on different regions in Japan. When I was there in 2006, I was convinced to try it (in Hiroshima they call it "itazura") and boy oh boy. "Sour" does not even begin to describe it. I was offered a piece, I tried it, I didn't die, but I certainly wouldn't willingly inflict that kind of cheek-puckering pain on myself again! I didn't notice any reaction to it, but apparently the stems contain high levels of oxalic acid, the same chemical found in rhubarb leaves (and the reason why you should never, ever eat rhubarb leaves).
Today, Japanese knotweed is the most common source of the drug "resveratrol," which has an incredibly large list of reported benefits: life extension (unproven in humans, but works in mice and fruit flies), cancer prevention (no clinical trials in humans, but causes cancer cell death in cancerous red blood cells and smooth muscle like the lining of your intestines), cardioprotective effects (anecdotal evidence; all of the scientific evidence that showed resveratrol had any effect on preventing cardiovascular disease have been retracted because they were published fraudulently), antidiabetic effects (clinical trials have shown it lowers blood sugar), neuroprotective effects (has been shown to reduce plaque formation in the brains of non-human animals; no human studies), anti-inflammatory effects (prevents the progression of rheumatoid arthritis in rabbits; no human studies), antiviral effects (prevents the progression and spread of the herpes simplex virus and synergistically enhances anti-HIV drugs), effects on testosterone levels (increases sperm production in rats and increases testosterone production in mice; no human studies but is currently being sold as a bodybuilding supplement), and finally antimicrobial effects (shown to be ineffective at preventing growth of any microbe, bacteria or fungus, that it has ever been tested against). Should you choose to take resveratrol for any reason, make sure you consult your doctor.
If current medical uses weren't enough, there are also traditional medicinal uses of this plant. Both the Japanese and the Chinese in their traditional medicines used extracts from the leaves of Japanese knotweed as a laxative and to regulate bowel motility.
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