i don't ever recommend that black plastic stuff that is about 8inches tall, it's just not deep enough for a lot of the problem grasses/weeds like quackgrass or horsetail. 18 inches minimum. even a few layers of overlapping cardboard (use the plainest kinds you can find (no shiny stuff and remove all tape and staples)) if that is all you can find to use, it may not last longer than a few years but at least it is better than nothing. in our soil/subsoil it can be pretty tough to dig down that deep but once it's done at least i know i won't have as much troubles for a few years.