kanders,

I think with clay, you're going to have to get down & dirty. Just mulching, aka laying on top, will not penetrate. You'll probably have better success if you dig and turn. Every time I plant a flower, be it annual or perennial, I dig a hole probably 3 times what is required. I take the nasty clay dirt out and replace with a combination of peat, compost, and ammended potting soil. The more I plant, the better off my soil becomes.

I really don't know, but I would think grass clippings would be excellant. It just might take a few more amendments along with the grass to really do the trick.

Ann

Grass clippings can be part of the organic content you work into your clay soil to improve it, but not the only thing. The reason is that clippings are composted mostly of water, and you need something with some staying power. That is also why clippings don't make a good mulch, per se. Mulch is the organic matter that is applied to the top of the soil surface in a 2 to 4 inch layer. Wood chips or pine straw are typically used for this purpose. Grass clippings could be added, too, but do not serve as a mulch.

I agree that you will need to gently work the organic matter in to the soil if your beds are already established. Avoid tilling if the landscape is already in! Use your clippings and bagged compost and work it into the top inches of soil with a garden claw. You want to combine the soil with the organic matter. Then, apply a layer of mulch on top!

Annual garden areas, or new beds can be rototilled with plenty of organic matter. Clippings should comprise a minor portion of your amendments. Truthfully, the grass clippings provide more benefit to your lawn if left where they fall, rather than collecting them.

Okay, first let me say I am talking from experience, not something I read in books. I've been using grass clippings, as mulch without Ever digging them in for 34 years now.
Some things I read I have to diasgree with. One was that grass clippings are mostly water, and therefore don't make a good mulch. While fresh grass clippings do have a high moisture content, grass itself contains every nutrient plants need. A little reflection would lead to that conclusion, since they are after all plants. They contain about 4% nitrogen- even more if you have clover in your lawn- and more than enough potassium, phosphorous, sulfur, calcium, and every other nutrient plants need. Again, I know from experience since I have'n spent one cent on "fertilizer" since 1972.
The other thing I have to disagree with is the need to dig in the clippings, or any organic matter. To some people, I'm sure, this sounds like a Radical New Proposal. But if you stop and think, it is Tilling or Digging In organic matter that's "the new kid on the block." Nature grew plants for millions of years before we came along, without ever digging or tilling, and they did just fine.
(There are actually two things that will put organic matter into soil, much deeper than you possibly could, and without you lifting a finger. The first is earthworms. The right species, the bigger ones like nightcrawlers, put organic matter as deep as six feet underground. Worms don't like cold soil touching their bodies, so they line their burrows with bits of organic matter- leaves, grass clippings, or whatever's handy. The other thing that puts organic mater into your soil, again much deeper than you could, is something that most gardeners just don't think about- the roots of the plants you grow! Things like tomatoes and corn, for instance, can grow roots up to six feet deep. No one digs up the roots after they harvest their crops! Rototilling or hand digging can't put organic matter anywhere near that deep.)
Now I know that people have tried mulching, without digging, and not gotten very good results the first year or two, especially in clay soil. I've tried to figure out why, since I got fantastic results the very first year I began mulching. And I think I've finally figured out the reason: I think how you water is crucial. Clay soil absorbs water, I once read, only a little faster than Concrete? So you have to water a looong time go get water deep into the soil, to soften it up so your plants' roots can penetrate. You can either leave the water running at a very low volume, or use an osciallating sprinkler. I've read that they let each "wave" soak in before the next one comes along, reducing runoff.
I know there will be people who read this and doubt it.The simplest way to find out if it works is to experiment.
Do whatever you think is best on part of your garden, and on another part just cover with a good 3 inches of grass clippings. Oh, always water well Before you apply the clippings. That way they can "lock in" the moisture. Mulched soil will be damper and softer a week after you water than unmulched-un protected- soil will be a day after you do.
Like the old cereal commercial with Mikey used to say, "Try it. You'll like it."

You're correct, Kanders. Grass clippings are an excellent material to mulch with and to incorporate into your soil. The do break down quickly as was noted which goes a long way to releasing their nitrogen when incorprated into the top few inches of your soil as described by Rhizo.

Clay holds moisture very well as you are aware and adding peat as suggested may be not advisable. But adding as much other, preferably free, organic matter in addition to your clippings to your soil definitely is advisable.

Mulching alone will eventually loosen and improve any soil, no doubt. As you have found out, incorporating the organic matter into your clay by using Ma Nature's no-till mulching approach can take many years. For more immediate results, tilling or digging lots of organic matter into the top few inches where it will help keep the soil loose, hold moisture and make nutrients available is an excellent way of jump-starting your garden. Then, keeping a layer of mulch on your garden will provide a continuous feast for your worms and micro-organisms and reduce the amount of tilling or digging required in the future.

I can only smile at watering heavy clay for a long time. We used to do that every year. It was called mud season.

Wayne in the Adks, where clay is a thing of the past.

In interesting comment by Tyrell, in my opinion, was how roots and watering methods can loosen clay up.

I live in a house built in 2004, as such, much of the soil nearby the house is heavy clay...the stuff at the bottom of the hole they dug for the foundation. It's not particularly nice dirt to work with.

My first experience with gardening my own property was putting down some roses with huge sentimental value near my house. I just dug a hole and put em in, didn't even eliminate the grass from the area right away. I figured that grass had to go though, so to eliminate the grass, I started layering grass clippings from my lawnmower around the base of the rose bushes. A few months later, I topped the clippings with a layer topsoil and manure (2 or 3 inches deep), then hardwood mulch. The bed was ugly, not even edged, but I was satisfied that it was at least functional (this was last June about that I made the bed, June 2005).

Fastforward to a week ago (oct 2005). I was ready to make a real bed in the area, which basically meant I had to clean up the edge real good. The only difference between this area and any other part of my yard were 3 things: Roses, grass clippings and other soil amendments, and the fact that I deep water my roses 2 or 3 or even 4 times a week. That means I lay the hose there for 10 minutes at a time, with the hose flowing at a fairly slow rate...totally soaking the soil.

So, to finally get to the point I'm trying to make, there was a MARKED difference in the soil structure where the roses are compared to the soil structure elsewhere on my property. The soil I dug up to create an edge adjacent to the roses was soft, crumbly, to the point where if you grabbed a handful, it would try to fall out of your hands and even out from between your fingers.

Only a few feet away, where I had not watered all summer and no plants where there, the clay soil was like concrete. It was rock hard, and would not crumble...you could pick up 20 pounds chunks and bigger. And to seperate the chunks, you needed either a shovel or a hammer. It was a nightmare to work with this soil, and I couldn't imagine plants would take to it very well.

So, to summerize (I ramble so summerization is required!), thanks to some organic additions, deep watering, and plants with deep/active roots, I was able to see a signifigant change in the soil structure of clay soil at my house in a 6 month period. It'll only get better from here!

I have used grass clippings as mulch for over 30 years in heavy acid clay here on Vashon Island. Tilling this sort of soil does more harm than good. The worms will do it for you. Just let the mulch rot on top and add more year by year. Leaves mixed in with the clippings keeps them from matting and getting soggy in wet weather. In rock hard areas of clay/glacial till I sometimes put a single layer of scrap plaster board (contractors love to give it to you. On top of grass, weeds, etc. Cover with a heavy mulch of leaves, grass clippings, straw - whatever and let it sit for a year. Dig holes and plant through it. You'll add lime, organic matter and kill off the weeds all in one step. Don't do this in the vegetable garden.

I'm another vote for no-till. Put organics on top, layer it, deep water it, and for some reason newspaper between layers of clippings/mulch/compost/shredded paper works even better for me. I don't know if no-till works because the worms come up and till down for you, or if the runoff from the upper organic materials improves the clay as it sinks down - but it works. Definitely. The only caution I would add is that very green clippings used immediately can burn plantings (high nitrogen I think) if touching your plants. I leave a couple of inches around plants.

I know this is an old thread, but I am currently in the process of bringing a spot in my in-laws' yard "back to life". I wanted a garden, but don't have a yard of my own and the only "good" spot was right next to their shed... where the dirt was so poor that *nothing* grew there. Not grass, not weeds, not even those little tree seedlings. Nada. My sharpest, pointiest shovel wouldn't go more than 4 or 5 inches deep, even with me hopping on it like a pogo stick. About that time my father-in-law had just dug some holes to plant some shrubs. I took the leftover dirt and cover grass and placed it green side down over the garden, breaking it up as much as possible. To keep the dirt from getting hard again, I left a couple buckets out to collect rain water to regularly wet it down, smothered it with grass clippings, and when I wasn't messing with it, I covered it with a large sheet of old plywood that was laying around. I had some zuchini seeds, a few bush bean seeds, and a couple tomato plants I'd been given. I went ahead and planted all of them just to fill the garden with something. The zuchini did *great*. If I didn't check them regularly, it was nothing to go out and find a few the length of my forearm and up to twice as round. The tomatoes grew, but I couldn't keep the bugs off of them. Other than a few leaves, the beans didn't do squat. That was summer. Yesterday I decided to dig it up a bit and try to prep it a bit for next year. The first thing I noticed was that not only were weeds growingm, but the ground was MUCH easier to work. I dug almost twice as deep as I did just this spring. I dug in, filled it with leaves, topped it with composted manure, and covered it back up with the dirt. When I finished the entire garden, I topped it off with another layer of compost. I'm working on a compost bin for the winter so I can have some extra dirt for containers next year. Basically, it's a large trash barrel with a latching lid that I can roll around on the ground to mix everything up instead of "turning" it the normal way. In short: there are many free materials you can use to improve your garden and while you may not get immediate results (like you would with bagged stuff from the store), it's still better than where you started.