Plastics, Permaculture and Weed Control

To use, or reject landscape plastic...that’s the question. I got the idea from Stefan Sobkowiak’s video The Permaculture Orchard Beyond Organic 1:27-2:10


Background Info:
Last year my family began working on a project in rural tennessee (zone 6 to 7) We purchased acreage that had been logged over the previous three years. It is semi mountainous (with some very steep sections) in a heavily wooded area. Our first order of business was to slow erosion. We planted a few hundred pounds of nitrogen fixing ground cover seeds in the areas where logging equipment had created big problems. We also planted three on contour rows of nitrogen fixing trees intermixed with fruit and nuts. That’s when we ran into problems.

We did not till the areas where we planted trees. Instead we cleared them by hand (getting hundreds of ticks in the process) We cleared land in the fall, early spring, and late spring. The focus was primarily on greenbriar, weed trees, and poison ivy. Little did we know that after all of that work the entire area would be covered by fireweed (see image). When I say entire area, I mean by mid summer it looked no different than the rest of the valley that we left alone. At least the fireweed covered the ground and discouraged erosion. But, the trees were completely overtaken by the annual’s immense growth. Also, to make matters worse the fireweed literally covered the entire valley in a layer of seed, so this year will be similarly weedy.

This spring we are at it again, and I could use some help in strategizing the best way to contain unwanted growth and support the growth that we do want. In a couple of weeks the bulldozers will come in to give us a road on the property. We are also cutting swales into the top of the mountain to increase water harvest. We plan to plant this spring only in the areas that we disturb (ie swales and road back cuts) I have ordered a host of nitrogen fixing and edible trees, shrubs, ground cover etc.

Now. I need to know: Should I put plastic on top of my swales to prevent the fireweed takeover? Or, is that a major permaculture sin? Based on the video link, laying down plastic can lead to significantly increased growth. However, I am not particularly knowledgeable about the Sobkowiak school of thought, and I don’t quite understand where nitrogen fixing groundcover enters into the equation.

Has anyone used plastic before? I thought of cutting a ring of small holes around the seedlings and filling them with nitrogen fixing seeds. Could that work? Even our ground covers (Fixation clover, birdsfoot trefoil) have had trouble competing with the native seedbank. Would, planting within holes in the landscape fabric allow ground cover a stronger start before spreading out?

If anyone has tried plastic, or has suggestions on dealing with fireweed I would love to hear any feedback. Thanks in advance for your help.

Here are a couple videos showing Geoff Lawton's food forests and the weed problem: