New Rock Garden with established large rocks - How to?

Calgary, Canada

So I have these 3 large flat top rocks embedded in the ground sticking up 6 inches or so. They are spaced about 6 inches apart and are located in front of a raised bed in full sun. They are too large and heavy to lift. They are currently surrounded by grass/lawn. What I want to do is to plant some plants around them but don't want to have the grass from the surrounding lawn invade the rock garden (I don't want to have to pull out grass all the time). It has also got to be able to be mowed around (no trimming, or else my hubby will go crazy) and cost little. What I was thinking of doing was:

1) Using round up to kill all the grass in between and around rocks
2) Digging up about 6 inches of soil
3) Placing weed barrier fabric along the edges (to prevent grass from coming in) 6 inches deep. Also embedding 4x4 slabs of wood we have hanging around level with the surface on the edges of the bed so the hubby can mow the grass around it easily. This is treated wood, but will this be a problem with rotting? I don't really care how they look, so it doesn't matter much to me.
4) amend the removed soil with peat moss / sand and fill into bed again. I have clay soil, so this is why.
5) planting my plants that will be non-toxic to my puppy (I have some plants in the front flower bed I want to move: sedum, speedwell, contained ribbon grass and maybe thyme), and surrounding the plants with small rocks I have lying around.

Does anyone see any problems with this? I really want it to be no maintenance, and I haven't done a rock garden before so I don't really know what I'm doing.


This message was edited Aug 2, 2010 11:45 PM

Calgary, AB(Zone 3b)

It will make for a lot easier maintenance to avoid both the weed fabric barrier and the 4x4s, as well as being less costly. Avoiding the wood "cage" idea will look much better, too.

If you are going to kill the grass with Round-Up, you'll have to apply it more than once, with a period in between applications. The grass must be green and actively growing for it to work, as well. Use a spray shield (piece of cardboard), and don't do it on a windy day.

The best lawn edging is none at all. All those other things just get in the way of the regular edging-out that you will need to do, probably at least once a year... more often if your lawn is invaded with weedy, running grasses. Just get yourself a nice sharp lawn-edging tool, i.e. like a spade, with shoulders at the top to step on but, instead, with a flat semi-circular cutting blade.

Also, I'd recommend cutting out the grass at least a foot out from the bed you are creating - that is, cutting down through the entire root mass and removing it - the wider the edge, the better. Then fill the void between the lawn edge and the "rock garden" edge with bark mulch, rather than with soil. As grass roots invade into the loose mulch, they are much easier to strip out than if that area was filled with hard soil.

Also, I guess I might as well disabuse you of the notion of a "no maintenance" garden - such a thing does not exist. Sorry.

Saint Bonifacius, MN(Zone 4a)

I also think the weed barrier will be for naught. Grasses, especially, if they are still alive under it will find a way through.

I believe I have done the exact same thing as you describe, but with 4inx5inx8ft treated timbers. I sunk them into the ground at the edge of some landscaped areas. I can mow right over the 4x5s. I think it works fairly well. Once or twice a year, I do clean it up a bit to look nicer: even though the grass hasn't jumped over and only minimal tunneling under to the other side, the grass does lean over the top side., making it a bit unsightly for garden visitors. Probably not a concern for you.

I had laid them with the 5 inch side horizontal, and 4 inches vertical. The only problem is that the bottom side absorbs moisture, while the top side stays dry. This caused some of the timbers to warp upward, so the ends stick out of the ground more. Subsequently, I have solved the problem by using 6x6 timbers.

Down here in Minnesota, blue grass is very susceptible to Round up. I have never needed to spray more than once, but if there are other things, like quack grass, in amongst, you may have too. Keep in mind that Round up works like other lawn weed killers in that it is taken in by vigorously growing plants. If your grass/weeds are stagnant or semi-dormant, they may not be killed outright. Be very cognizant of drift.


Caldwell, NJ(Zone 6a)

I have had good success in planting a rock garden in my front lawn where it gets full sun.I first got rid of all the grass by putting down1' blocks of newspaper until I had raised the level of the bed 2' higher than the surrounding soil. Next I made a mixture of very small stone (1/4")sand and peat moss mixed with some vegetable matter and covered with gravel on top, altogether about 1' of soil above the newspaper and the gravel. I did roll some large Moss rocks to the top of the bed and placed them down slightly under the top gravel. I used larger boulders of a type of Pumice stone to key 4 Quadrants of the garden and buried them slightly. These stones are very light in weight and can be easily moved even for a 2x 2.5' stone. The newspaper gradually decays but acts as a water sump for the roots of the plants above. I planted mostly very dwarf evergreens with their roots under the rocks and the upper growth out in the open. The garden has been in place for 20 years and now is a lovely mound of evergreens and scree. The labor was very intense but I was much younger then.

Caldwell, NJ(Zone 6a)

Without actually moving the rocks out of its place you can elevate the imbedded rocks up a few inches to as much as 6". by putting down a small rock a few inches from the one you want to lift and using a large 6' pry bar as a lever under one side of the rock and prying up the side of the rock and filling under it. If you put the roots under the rock they will be healthier when you remove the lever and let the roots grow into the soil beneath.

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