I have clay soil and have been moderately successful adding a surround then filling that in with better draining soil for the new plant. I mulch with leaves and sticks and figure that will all work its way down.

chlene36 said: I have clay soil and have been moderately successful adding a surround then filling that in with better draining soil for the new plant. I mulch with leaves and sticks and figure that will all work its way down.

Layering (horizontally or vertically) different soil types is exactly what you shouldn't do. It creates perched water tables which will drown and rot roots.

Guys I appreciate all the input, my only real question is, will the cardboard effectively suppress the grass so that it never comes back and so I don't have to spend hours of back breaking work digging it out. Its that simple.

I live in an ecological area called a Hardwood Hammock. Its an area of high and low land with old growth hickory, live oak, Sweetgum and palm trees. The soil is known here as Myakka fine sand, it is sand which over many years has been enriched by the deciduous leaf fall of the surrounding hammock trees but its still just sand.

I am not interested in replacing the soil with anything. I know the technique to this is to place the cardboard and cover with compost/topsoil and mulch. Then you can cut through the cardboard layer if need be to plant deeper than whatever layer you place over the grass.

My only real question is, will the cardboard really work as a permanent block for the grass

If done effectively, it will kill the grass that is there now. It can't prevent new grass if seeds get into the area, or infiltration from the edges if surrounded by vine grasses. A barrier of edging, like an outline of bricks, will probably be needed. Regular bricks, IME, are not big enough to prevent vine grasses from creeping in. Bigger bricks made for building a retaining wall are much more effective. They have a flatter surface, are taller and wider. Even better would be 12" patio bricks as an edging. They fit more closely together and the wider width is more effective against something like torpedograss. I still get some infiltration where bricks meet, but it's not usually much work when that happens to pick up a few bricks, pull or dig the invading grass, replace the bricks.

Effective, to me, is using thick corrugated cardboard, overlapping well, and covered with at least 6" of heavy organic matter. One of those times when more is more, especially when you need to kill tough vine grasses. In hot, steamy conditions, decomposition happens quickly, so you don't want to skimp when covering the cardboard with mulch or other OM.

When it's time to use and you dig some holes and install new plants, seeds that were under there can get stirred around and sprout. Monitor closely around newly installed plants to pull any other sprouts while they are small enough to come up easily.

If you start digging in, to add a new plant, and discover cardboard, it needs more time. The cardboard should be gone before the spot is used, and remain unviolated until then.

In your climate, Gina, if you set this up now, it should be ready to be used when it cools off, Oct. or Nov, unless it happens to not rain very much this summer.

You probably already know this part, when mowing, aim the chute away from cultivated areas and back toward the mowed area.

If you lay down a thick enough layer, make sure the seams overlap sufficiently and mulch thickly on top, then yes, after a while the ORIGINAL grass (and annual weeds) will die. More persistent weeds (dandelions, docks...) will most likely not.

Lee-Roy, I don't know why you insist on degrading the idea if you haven't done it. I'm not speaking theoretically, but from the experience of having done this many times in OH and AL. Dandelions don't stand a chance under a decent smother, if you're referring to Taraxacum officinale. They can be smothered with just a few layers of newspaper under mulch. IME, dandelions are not in the same category of "hard to kill" as torpedograss, Bermudagrass, St. Augustine, bahiagrass, and the other weeds that are in our mowed area. Anything that I can pop out of the ground in 2 secs with a dandelion fork is not a formidable enemy.

But if you are having those thoughts, I'm glad to have the opportunity to speak to them. I don't totally disagree - not everything can be killed with the kind of smother we are discussing. For stronger unwanted plants, sheet metal is the king of the smother. Obviously it will need to be removed later, but if you need industrial-strength smothering, that will do it. I've had to do that over spots where there were 2nd and 3rd year baby trees. Cut them @ soil level, cover with sheet metal, secure with a couple concrete blocks, and leave that alone for a year.

Plants with a giant, tuberous root could be strong enough or just be able to wait for long enough to not die under any kind of smother unless you want to wait for more than a year. That's kind of a separate discussion, but in that case, I would compromise the top of the tuber, making a couple chops into the top of it with a shovel, dig a little moat about an inch deep around it, and pour boiling water on it. The moat will help make sure the water goes down while still deadly hot and not just run sideways. I don't have experience with dock, but if that can kill pokeweed, 4'o'clocks, and Smilax, I'm sure it would kill other plants with big/deep tuberous roots.

Tiffany, forgive my attitude, but I don't know WHERE THE HELL you read and keep on insisting that I'm degrading the idea of sheet mulching!!!?? So far I've merely stated scientific FACTS. NOTHING MORE. Take it or or leave it; use the info however you want.

And in case you you haven't noticed, but I live on an entirely different continent. I don't deal with all those grasses here... And while I haven't done sheet mulching with cardboard as much, I HAVE used 6 inches of wood chips. Those have been down for over a year now and I still need to - weekly - cut foliage from those original dandelions and docks.

In any case, I'm done discussing this now.

Lol this is why ignore exists.

I have tried the cardboard method and found you need to regularly irrigate the area or the cardboard will never break down and cause the issues Arico mentions. I had saturated the soil prior to putting the cardboard down and saturated the cardboard before covering it with mulch and a year or so later it was still cardboard. This was in an open area without irriagation where I was just trying to suppress weeds. It did control the weeds but did nothing but harm to the super dry soil beneath it.

Newspapers (remember them?) were another story. I would soak stacks of papers then lay the wet papers out, several sections at a time wherever I wanted to kill sod and cover it all with pine straw. The paper broke down rapidly for me. I got the idea to use newspaper after hearing Pat Lanza, author of the first lasagna gardening book, speak on it. However, her theories have been debunked by science.
https://gardenprofessors.com/t...

Yes Alice I have seen the use of newspapers too. I think my son left a lot of old old large sketchbooks here that he didn't want anymore....some of them I am pretty sure are newspaper type. That may be a good alternative. Since the soil underneath is just sand, I guess it will just stay sand, LOL, even with the mulch and stuff on top....the only enrichment our soil here gets is the leaf fall decay.
I DO have access to a LOT of free pine straw...our private road is lined with it on both sides. I could take my wheelbarrow out and collect it free of charge.

Gina, my sister moved to over near Pensacola and struggled with the garden. After thinking, my theory is the longer warm season and the rain and insect activity means your soil just 'burns' though organic matter faster than for me up here.

Your pines, depends what kind, I get good results from pine straw gathered nearby, my neighbor rakes it up and gives me 5 trash cans full. it's rather soft but still smothers pretty well when thick. I bought pine straw from North Caronlina once, its a totally different, very long and hard needle. not good to walk on.

Ardesia, your post reminded me about something else to be aware of if using the 'no dig' method:

As the mulch slowly degrades over the summer, it "shrinks", so I was finding the edges of the cardboard exposed, and they were drying out, so not degrading as quickly (besides being rather unsightly). I found that I have to go back in 6-8 weeks and replace mulch -- esp. for the 8" or so around the edges. Here in Michigan, this method works for most weeds -- even the dreaded burdock. I wonder if it is also due to our hot summers with plenty of rain -- both factors which speed up decomposition.

I have really appreciated this post -- lots of good suggestions here!

True, you do need lots of mulch. I was fortunate at that house, the local tree guys knew they could dump their wood chips on the lot. It gave me free mulch and they saved the dump fee at the landfill. Hard part was spreading a dump truck load but I was much younger then.

But aside from the mulch, doesn't the added layer of compost/manure/topsoil keep the cardboard from being exposed?

I think it will depend on how much you use.

Just make sure to take off tape, it lasted forever in my garden.

I'm not against the idea, just never tried it. I'm from the dig it up and start over generation. My biggest issue is bamboo from my neighbors yard that keeps popping up on my side. Nothing seems to block it for long.

Good points about wood chips. That would not be my 1st choice for smothering if I didn't have a lot of green stuff to include - and/or enough to make a much thicker layer than 6". Fresh chips would be preferred over aged/dry wood chips. I wouldn't use bark at all, it floats around if it suddenly rains hard enough after it has gotten very dry.

Shredded wood is what I've used as mulch, sometimes with, sometimes w/o added leaves, kitchen scraps, trimmings from shrubs, sawdust, pulled weeds, etc... There is usually a good layer of green under the cardboard from the grass I'm trying to kill.

Outlining the spot with bricks allows the cover to be thick all the way to the edges. Landscape timbers can also be used, but they tend to warp and curve.

I haven't battled bamboo, but from what I've read, I would not expect to be able to smother that. Wouldn't it just creep until it found the sun on the other side?

We had a dog once that loved bamboo shoots, he would snap them off as soon as they came up and that seemed to control the spread. I have no idea which variety of bamboo it was, it was at the house when we moved in but it is worth a try.

I've had great success with it….going on two years now. I hand tilled with a garden weasel to pull up all the grass I could first. I was impatient though and didn't wait. I ordered 12 cubic yards of flower bed mix and mulch and went about it with all my left over Amazon boxes and my wheelbarrow. I have to keep grass from creeping in by cutting and pulling bits with a hand edge tool, nutsedge makes me crazy at times, but I'd certainly do this method again!