Wow ... this posting is strewn with inaccuracies and untruths. Confusing grubs gastronomical preference for grass clippings with grass roots is but one. Setting all of that aside: The strength of this posting is an encouragement to utilize whatever is handy, available and cheap (free) as a mulch product in your locale. LetÂs think about our choices and not fall prey to blind consumerism. Many, many products make excellent mulch. Grass clippings can certainly be one consideration. One neednÂt spend 8 to 10 dollars for a 2 cubic foot bag down at the local big box store -- which doesn't go very far. I shake my head at Midwestern folks who have fallen prey to an old TV episode of Victory Garden where Roger Swain (The same Roger who "taught" all of us how to sharpen the wrong side of a garden spade.) advises everyone to use salt marsh hay for mulch. They then fret that they canÂt find it or it is only available on special order by the truck load. I have seen a bunch of unusual but wonderful mulches used in site-specific locations. One city park extensively uses oat hulls from their local Quaker Oats plant that makes Quaker Oatmeal and other related cereal products. A lot of local Hosta-holics mulch with a rich, black compost that is available for about ten dollars per heaping pickup load from a state-of-the-art, municipal compost facility. Others covet shredded leaves as their chosen favorite. Ground corn cobs also make great mulch  if available. (Find those, Roger!) My father used finely shredded cornstalks for his commercial strawberry beds because they seemed to impart the same weed suppression qualities as the much more expensive herbicide, corn meal gluten. Rock gardeners may choose a scree and/or pea gravel. The point is to generally use whatever you have cheaply available, locally. Of course, there are numerous, viable reasons for choosing exceptions. Many times these exceptions are considerably more expensive. However, the cost can be minimized by using the "cheap, ugly stuff" underneath and scattering a thin layer of something like cocoa shells (or whatever) over the top for that desired aesthetic look and/or smell. In fact, back when my wife and I got married in our garden (and we were broke), the beds were mulched with a couple of inches of grass clippings with a thin layer of cocoa shells on top. The look was great and the aroma had wedding guests swooning. However, if you have windy conditions, make sure you wet down the cocoa shells before they all blow away. I currently use a mulching mower so I have no grass clippings. However, I have a free and ready supply of hardwood chips about 10 blocks away at our city refuse drop off site. I run these through my chipper/shredder and quickly have a pickup full of small chips; large enough not to blow away but yet, soft to kneel on and free of sticks. IronBelly

MG potting mix is good stuff, I grow a couple tomatoes in it each year. I tend to use cheaper brands though unless it's on sale, or buy a bag of each and mix. Plants can certainly grow in half-composted material - look up lasagne gardening. Your idea could work, although you might not need the tubs. Why not just dig a hole, fill it with a good topsoil/compost mix and plant in that? Is your goal to eventually level this area? If so you'll need soil, not just organic matter or potting mix. What's going to happen to the tubs of potting mix at the end of the season? If you leave the stuff there it will continue to decompose and shrink and your slope will still be there. That's why I'd suggest some topsoil and not just 100% organic matter. But if you're not trying to eventually have a level, raised bed there, it doesn't matter as much.

Thanks for the responses... This isn't a vegetable plot. It is an ornamental garden. The plants are well-established for the most part. Although (my personal opinion) the plants are being moved around a bit too often for this dry hot weather. I could make an onsite compost pile (or 20)nobody would try and stop me but I was looking for a quick fix. LOL People around here seem more interested in plants than soil. I like dirt so am sticking to that part of the process. I guess I have silty sand because this stuff is HARD. It is almost as hard as clay but when you do get the clods to bust they break up into fine pieces instead of chunks like clay does. The fine bits just reform into a hard layer once it is watered and left to dry. The area is mulched but the water just goes through the mulch and runs off the beds and into the paths. We do water but I do not think it is a very effective system. I've been digging holes and trying to break up the top soil and watering into the holes instead of watering the top of the mulch or soil. I guess I'll just make some "community garden" compost and keep picking out what I can from around the dump area to use to amend the soil. I can "liberate" the grass clippings and hide them until fall and start a regular compost pile and maybe some leaf mold. I can find a place that is a little out of sight near the garden and get some wire fence from the junk yard and see what happens. Thanks again.

For the original question - I think it depends on whether your weedy grass has gone to seed before it gets cut. If allowed to go to seed and then blown in, yes it could cause weeds. I used to use grass in my vegetable beds. First I put down a layer of partly composted straw to keep the grass from matting too badly. Then the grass clippings would go on top of that - part of the trick I think was to have it thick enough to block all light for germination to anything below it, but not so thick that water wouldn't penetrate. It worked pretty well. For regular flower beds I've always just used bark mulch but grass would work too as long as you have enough clippings coming to keep it a certain thickness. Mary