Thanks very much sumec and floral_uk. No wonder I was stumped by this plant. I don't think we even have this family in NZ. The images I unearthed for P. viulgaris from Mr. Google look like the plant I saw. The Devil's Kitchen was a real treat. So many interesting plants in an afternoon's walk. Cheers, daccup.

Well, I am in Michigan, and the Michigan Plant Invasiveness Assessment System (June 2008) lists it as not problematic here, but does acknowledge the problems it has caused elsewhere: There are no reports of it being identified in the wild (this does not include cultivated gardens) in my county, either -- http://michiganflora.net/species.aspx?id=808 I have a small amount of it in two flower beds, with no trees for it to climb (though it is growing up into a purple-leaved barberry in the bed... that'll be fun and painful to sort out). It seems pretty content clinging to the house in this spot, and I like it there. Shouldn't be difficult to keep it trimmed and contained where it is. This is nothing compared to the invasiveness of the japanese knotweed in the back corner of the lot.

Plumbago sort of pulls you in with it's tropical icy blue flowers that bloom almost all year, and if you forget to water it, it rewards you with more pretty flowers. When did plumbago become a noxious weed? About a year after we planted it on our slope. It's climbed over fences, completely grown over other large plants, and grown up and tangled itself through italian cypress trees more than 30 feet tall. It's popped up in neighbor's yards across the street and several houses away, just guessing by seeds, oh, those stinkin' little seeds!!! We've picked off millions of them from our skin, socks, clothes, cats, etc. If it hasn't reached your house yet, give it just a little more time. It's on it's way and will surely get there. Anyone want it for free? I'm in Walnut, near Pomona. Email me and you can come and take all you can fit in your car, and come back as often as you like, lol. Linda

Happily, I haven't had to deal with knotweed personally... but it doesn't sound good - this is one tough and invasive plant. Hopefully someone else (or your county extension agent) will have some suggestions for efficient long term removal, but it looks to me like you will be at this for a while and will need to use more than one method of control. Wish I had better news... Mechanical Large colonies of this species are extremely difficult to dig up due to their high rhizome densities. Digging of large colonies is not recommended as it is very labor intensive and unlikely that all below ground material can be removed. Small patches may be dug, however care should be used in removing plant material as improper disposal can spread the species further. Repetitive cutting or mowing within a single growing season to deplete stored reserves and remove photosynthetic tissue has been effective. Eradication of the rhizome system is necessary for control of this aggressive invasive species. Chemical Herbicide has been generally effective at controlling this species. Repetitive cutting of stems with spot application of Roundup®, Accord® or Glypro® to the stumps, and foliar spraying in large populations has been reported to be successful. Biological There are currently no biological controls available for Japanese knotweed.