If you put black plastic down inside the greenhouse, you may solarize the soil. That greenhouse may hit triple digits on sunny days without good ventilation.Mine was at 100 degrees yesterday with an exhaust fan running.

Wheather that is what you want to accomplish, may be a good thing or bad thing.

Also depending on the contour of the ground, it may hold the water(if it ever rains again) in that leaches through the ground. Might have some sour dirt under it if in a low area.

I dont have a reccomendation as to what you might use other then the fabric type weed control. That would allow the ground to breath and not smother the benifical organisms.

I assume this is just a temporary thing to control any grass that may grow through the winter, and be removed when said beds are configured.

I wonder if cardboard would work. It might not be that fun to walk on when it's wet and you'll have to put rocks or something on it to weigh it down so it won't blow or float away. It's probably cheaper than weed cloth, though. Just make sure to layer or overlap it enough so that the grass won't grow in between the pieces.

Thanks for the thoughts. I should mention that it's 20'x36'. I see where cardboard might be a start for paths, but my initial intent is to kill off the grass. I don't plan on long term coverage, so now I am thinking I should not buy the plastic and just get the beds marked off and put a heavy layer of mulch down.

I use a heavy grade ground cloth in my greenhouse, covered with pea gravel. We use the same ground cover in our vegetable garden. It works well to prevent weeds. I buy it at American Plants on NW 10th in OKC. It's much better than any weed cloth you can buy at the big box stores, and seems to last forever.

Thanks for that idea. I would love to find ground cloth that would last more than a season. I'll have to run by there when we go get the last of our pipe.

I used gravel on the floor of my small lean-to style greenhouse when we lived in town. We have since moved to 20 acres & I don't plan on putting the small greenhouse back up. We are going to build a hoop house this fall as well. I think plastic on the ground would be a safety issue. Wet plastic would cause me or one of the kids to slip & fall. I had not yet thought about the ground inside the new hoop house! I honestly had a horrible problem with stuff growing on the ground in the middle of the summer in my greenhouse. I didn't battle weeds & grass in the winter months. So hopefully you will be ok at first while you come up with a plan of attack.

Yes, you definitely need a barrier to prevent weeds. When we built our greenhouse, we did it perfectly, overlapping the groundcloth very well before putting down the pea gravel and concrete pavers pathway. I NEVER had any weeds. When we moved several years later we located the greenhouse in an area that already had a gravel pad with no weeds or Bermuda grass. Because of that we didn't prepare the ground well enough, thinking that was adequate. We didn't completely cover the floor with ground cover nor use nearly as much pea gravel. OMG, the weeds were rampant during the summer when the greenhouse wasn't being used ~ and it was horribly hot inside to try and get rid of them. So I recommend you use a good weed barrier from the beginning. My greenhouse is 12 X 35' and I used three 35' long strips of 6' wide ground cover, overlapping it well. That, covered with pea gravel works great to prevent weeds.