Hello, I'm wondering if anyone can identify the plant in the attached photo. It grows to at least 7 feet tall and looks like something out of a tropical rainforest. The plant in the photo is a transplant and is just under 4 feet high, it had only tiny buds 6 weeks ago. We found them growing wild in the bush in an old abandoned coal or logging industrial site that has probably been disused for at least 40 years. There is a patch about 60 feet by 60 feet of them in a clearing off a trail. They completely disappear in the winter and then grow at a furious pace in the spring and summer. They grow in clumps connected by very fat roots a couple of inches in diameter that grow almost on the surface of the ground. We've been jokingly calling them "triffids", I've searched the internet several times in vain, I'd really like to know what they are. I suspect someone who lived at the old industrial site got them from somewhere many years ago and planted them and they've gone wild. I have never seen anything like them natively growing on the island. Any help would be appreciated.
Wow, thank you, if that's knotweed it's a very nasty invasive plant! I did a search on Knotweed and everything seems very similar except the leaves look different, some sort of hybrid maybe. It's a shame because it's such a nice looking and unusual plant. I wonder if it was grown in a concrete planter it would be safe. Perhaps I should report it to someone, we spotted it in a place that it could easily spread out to the wild.