Five years ago I had never heard of the Pinellia plant, but I did notice that there was something new afoot in my garden. Appearing between some of my vegetables were three leaved intruders of unknown origin. I didn't think too much of it and just pulled them out.
The next year I noticed they were back...and then some. For every one I had seen the year before, there now seemed to be at least ten. This time I looked them up on the web and found their name, Pinellia Strata, or Green Dragon. I even found some species for sale!
I discovered that in order to get rid of these little Green Dragons (how aptly named they are) I had to dig way down - sometimes as much as 9 inches to get to the bulb from whense they sprung. This bulb was often attached to other bulbs and so I assumed that is how they spread...and it is... but there is more. If you let the Pinellia grow too long it will shoot up a 'charming' small spathe which looks something like a Johnny Jump up and contains lots of seeds.
Even after much digging and covering my whole vegetable garden with an impervious layer of woven polypropylene with holes for the veggies, they still managed to find their way through those holes. I have had that cover on for 3 years now and don't dare take it up. At least I only have the Pinellia coming up in a few places where the mat is not.
Meanwhile it has spread to all my other gardens and is very dificult to remove where it is near valued plants as one has to dig so deep to get out the bulbs. I am a dedicated Pinellia fighter however and can be found at all times of the day and evening with my garden fork and a glint in my eye looking for my arch enemy. I do not put anything from my garden in my mulch pile anymore as I'm sure that is how I spread a lot of this weed.
The point of this long rant is this - If you find any of the plants you see pictured in the Wikipedia article above, do not stop for a minute to think it over. Dig them out imediately. Spray them with Roundup if you won't injure any other plants. Take action, or you will either have to give up your garden to them or spend many hours in following years ruing the day you did not.