Years ago someone thought it would be a great idea to put down plastic mulch and then cover it with river rocks and dirt. Eventually this soil interface was 8" below the ground level. I'm not sure what the goal of this was because if it was for weed blocking, that failed. They all do because weeds have a powerful urge to reach the sunshine. I've seen bindweed roots go straight up 24". They were an easy pull though. This deeper plastic mulch was in a different category of futility and aggravation. First I had to shovel out heavy river rocks in order to get down to the plastic. Then I had to carefully and forcefully pull that up. There was no way to get all the rocks off of it beforehand. Is it any surprise that the plastic was littered with root holes? And that those roots were only from weeds? Never underestimate the power of weed roots. the first photo is the soil/plastic interface from the plastic side. This is the very bottom of the plastic. See how those rots are spreading all over? These are mostly bindweed and crab grass roots. In the second photo, look down and right of the shovel blade. There's a smooth area where the plastic used to be. There are some roots there. They're probably pretty weak but I'll bet you anything that right now, a day after, that they are growing like nuts. Free from plastic at last. Speaking of growing like nuts, dandelions do. I mowed the lawn and 24 hours later I had dandelion flower stalks ranging from 2-5" with most of them in the 4-5" range.