In a different post, Hugelkultur for Urban Conditions, I asked Wiggy if we could use Japanese Knotweed stalks to create a raised bed. I thought his response deserved it's own post. Here goes:
****Wiggy's Response on 07/31/09 ******
Yes, Jap. Knotweed (Fallopia japonica, Polygonum cuspidatum, Reynoutria japonica) seems an ideal species for building up soil. It's listed in the worst 100 invasives list, but is really an underappreciated and under utilized plant.
After studying invasives in school, and observing them daily with a permaculture mindset, I want to let everyone know invasives are not going to go back to where they came from, they've naturalized so well they can outcompete most native plants. Humans did this, Knotweed seed pods and branches were great packaging material for Asian markets. As soon as we put the first crate full of goods from Asia on a train we started planting knotweed in it's prefered riprarian habitat ( railroad cooridors).
This plant is tough, growing in a wide range of soil PH's, and very salted soils, knotweed's roots can spread 32ft horizontally and 9ft deep from a single seed (goodluck digging it out), not to mention being capable of resprouting from a little bit of root cutting. I'd imagine the seed germinates amazing well with the smallest amount of soil and moisture.
The problem is the solution however, and our opinion of invasives is all about perspective. The plant is a commercial source for resveratrol supplements, Hu Zhang root extract is a traditional Chinese medicinal treatment, along with being a source of emodin (a bowel movement regulator). The young spring stems pealed of leaves are a choice edible with a flavor like rhubarb, and I'm sure livestock would have no problem consuming the entire plant. Interesting also is it's potential as a good honeybee plant, being in the same family as buckwheat, it's flowers produce a nectar that bee's convert into a high quality monofloral honey.
The fast seasonal growth, hollow stem structure, and light woody texture make it ideal for composting, growing mushrooms, or launching diverse soil biology. Caution should be used to eliminate mature seeds before using it in composting or mulching applications, roots should also stay out of the beds and compost piles as they quickly resprout.
The method of control or elimination used by our lovely government agencies is the widespread spraying of heavy duty herbicide poisons (great for our drinking water and native plants). We can either utilize knotweed positively, or waste lots of energy and money poisoning ourselves and what seems to be a very useful food, medicine, and mulch plant.
The future potential for utilizing this "Nasty Invasive" is unlimited and well suited to urban environments. I see future farmers using it as a keystone species in mushroom and composting operations, livestock forages, bee forages, and edible greens, along with it's current commercial use as a source of medicinal compounds.
Be creative and remember the problem is the solution.....and may feed many hungry mouths in Pittsburgh's future.