Anne Get an old meat cleaver -- if you lived nearby I have one you could have -- and use it to make your slot. You could certainly hammer it down to break the roots apart. It would take some time if you have a hundred feet to go, but it would do the trick even if it was slow going. I suppose a square shovel would let you do the same thing, probably much quicker! Then, as you note, you could use a cheaper material for the root barrier. I've no idea how long grass roots are; it must depend on the type. But you could water a small area until it's soggy and gently pull up on some of what's there to get an idea of the root length. With a barrier AND a 10-12 inch extension, you aren't likely to get much invasion from the other side!

I've done exactly what you're thinking about doing, if I understand you correctly. I look for rocks with a flat side and bury the rest. I've done this with a couple of long paths. I'm inside taking a short break from installing flagstone for a patio I'm building. I decided to use flatter stones for the patio because I'd don't want my benches or chairs to be tippy. Check out my post here called "Fire Pit and Patio Construction". Also look at my page in the link below for many more pictures of my paths with more rounded stone. Here is a link that might be useful: Stone path and other garden pictures

I've got a little over 1200 sq ft in raised beds right now. I use cardboard covered by wood chips in my pathways. The wood chips hold moisture where the plants can access it - even in hot, dry weather the area under the chips is cool and damp; and I don't have to water near as much. The chips also provide a 4 season path to walk on/work from. I add more chips each year; and if weeds are a problem - ie: if I let lambsquarter go to seed - I lay down a sheet of cardboard over the weedy area before putting down the new layer of chips. The chips break down over a period of about 3 years, at which time I rake back the top, intact chips, then dig out the composted material. I'm a little OCD, so I sift the big chunks out (and use them to mulch around fruit trees), then use the sifted material to mulch the plants in the garden. I don't incorporate it - I let the worms take care of that. Since I rarely turn the soil in my raised beds, preferring to use a bulb auger to dig the holes for my plants; it doesn't get incorporated in a large way, so no nitrogen stealing. [IMG]http://i49.photobucket.com/albums/f262/Polly916/100_0053.jpg[/IMG] [IMG]http://i49.photobucket.com/albums/f262/Polly916/100_0126.jpg[/IMG] [IMG]http://i49.photobucket.com/albums/f262/Polly916/100_0122.jpg[/IMG] The cardboard seems to draw worms to the garden, so that is a mark in it's favor. The paths in the front section of my garden are 3' wide, and that's too narrow to suit me. The paths are about 4 1/2 feet wide in the back section of garden, with 6' wide paths between the sections; and a full 6' wide in the newest section, which allows me to bring a lawn tractor and trailer in to haul manure/compost/mulch/bedding plants/water/etc... The 6' width also allowed room for my Pop's golf cart to pass through. I plan to add another 4, 4x8 raised beds to the garden this year; and if finances allow, I will redo the front section of garden, and widen the paths in that area. I have plenty of ground, so the wide paths work better for me. YMMV.

I don't think it would hurt anything. I use wood chips with cardboard underneath to keep the weed and grass growth down. Wood chips are a good mulch for anything, garden included, if you add lots of composted, old manure to the soil first to replace the nitrogen that the wood chips use up. Sometimes it depends on type of tree the wood shavings are from. Don't use walnut anywhere and use dolomite lime with pine/spruce unless you want the extra acid.