These are growing up all over my property. They can make a great companion plant, nitrogen fixer and compost accelerator. 

They grow up extremely fast and the leaves can be harvested a few times each year. 

While they don't spread and multiply on there own like other invasive plants, they are pretty much impossible to get rid of once established, so I want to offer a disclaimer.

Any small fragment of the root that is not eliminated will continue to grow and in fact it will regrow as many new plants. There was a small patch in my back yard, but when we dug up the old septic system and did some foundation work, we accidentally distributed parts of the roots all over the yard and back filled around the foundation of the house.  And now it's everywhere and just keeps coming back! 3 years of lawn mowing some patches hasn't stopped it from coming back. Any attempt to dig it up results in more sprouting from the same spot from the retained roots (that go down like a million feet or something crazy). I also built a huge flower bed over top of a few patches and covered them with landscape fabric, but a few managed to reappear in my bed through 2 feet of back fill, and others are poking out in front of the retaining wall for the bed. 

So please heed my advise, don't plant it anywhere you are going to be digging ever again!

As for growing conditions, pretty much anywhere. I even tried to haul some of the dirt that likely contained root material to fill a hole with standing water and sure enough it pokes right up out of the puddle, so you can't drown in either.

Lastly if your not using it and harvesting the leaves it's going to leave you with a kinda gross slimy black patch when it dies itself in the fall, and smothers everything and nothing else grows up around it.