Mystery Plant Indentified!

For the last two weeks, the best butterfly action in the area has been on an unidentified bush down at the beach.  I've seen as many as six different species of butterflies at one time, and many other moths, beetles, bees and wasps on it profuse feathery white blossoms. I've tried a number of ways to identify it and come up short. This morning we passed a desiccated twig of it with flowers off to a friend to have SERC's master gardener identify it.  The ID came back by e-mail a little while ago: Japanese Knotweed, a relative of common Pinkweed and Buckwheat. And wouldn't you know it, it turns out to be a dangerous invasive:

It is listed by the World Conservation Union as one of the world's worst invasive species. The invasive root system and strong growth can damage concrete foundations, buildings, flood defenses, roads, paving, retaining walls and architectural sites. It can also reduce the capacity of channels in flood defenses to carry water.

It is a frequent colonizer of temperate riparian ecosystems, roadsides and waste places. It forms thick, dense colonies that completely crowd out any other herbaceous species and is now considered one of the worst invasive exotics in parts of the eastern United States. The success of the species has been partially attributed to its tolerance of a very wide range of soil types, pH and salinity. Its rhizomes can survive temperatures of −35 °C (−31 °F) and can extend 7 metres (23 ft) horizontally and 3 metres (9.8 ft) deep, making removal by excavation extremely difficult.

The plant is also resilient to cutting, vigorously resprouting from the roots. The most effective method of control is by herbicide application close to the flowering stage in late summer or autumn. In some cases it is possible to eradicate Japanese knotweed in one growing season using only herbicides. Trials in the Queen Charlotte Islands (Haida Gwaii) of British Columbia using sea water sprayed on the foliage have demonstrated promising results, which may prove to be a viable option for eradication where concerns over herbicide application are too great.

So, I guess we won't be planting any in our butterfly garden, and I'll just have to monitor the ones I know about in the field (I know of at least two on the beach, and a few on the roadside. On our beach, it clearly lives within the reach of Kudzu, so I suppose the question now it who will win, the Japanese Knotweed, or the (Japanese) Kudzu. My money is on the Kudzu.

But the good news, as Euell Gibbons used to say is that "some parts are edible":

It grows widely throughout Japan and is foraged as a wild edible vegetable (sansai), though not in sufficient quantities to be included in statistics.They are called by such regional names as: tonkiba (Yamagata), itazuiko (Nagano, Mie), itazura (Gifu, Toyama, Nara, Wakayama, Kagawa),gonpachi (Shizuoka, Nara, Mie, Wakayama),sashi (Akita, Yamagata), jajappo (Shimane, Tottori, Okayama), sukanpo (many areas).

Young leaves and shoots, which look like asparagus, are used. They are extremely sour; the fibrous outer skin must be peeled, soaked in water for half a day raw or after parboiling, before being cooked.

Places in Shikoku such as central parts of Kagawa Prefecture pickle the peeled young shoots by weighting them down in salt mixed with 10% nigari (magnesium chloride). Kochi also rub these cleaned shoots with coarse salt-nigari blend. It is said (though no authority is cited) that the magnesium of the nigari binds with the oxalic acid thus mitigating its hazard.

Sounds like a lot of trouble to go through when you can buy bad tasting vegetables at the store.