Wow, this space has soooo much potential! Everything from an outdoor kitchen, to a nice seating area, to a hottub. Not too many spaces have character like this. I think you would be absolutely amazed by the site WowMyLandscape.com. If you post this picture on that site, designers from all over the world will compete to provide you the best rendering. From $199 to $399, you will get to see 10-20 different patio/landscape options for this space. To give you an idea of what you will see, I did a quick sample and put it on our Flickr page. This is only a sample, a paid project will have greater detail (and the weeds taken out!)

Check out http://www.flickr.com/photos/wowmylandscape (you may recognize a picture the picture).

If you want to see 10-20 more, go onto WowMyLandscape.com.

We would love your feedback - email me at mike@wowmylandscape.com

Here is a link that might be useful: Your sample landscape design

That response is a flagrant violation of the terms of use here. Please go away, Mr. Wow.

Be patient Grullablue... you will no doubt get some legitimate help.

KarinL

I apologize for the flagrnt violation. By no means did I mean any harm.

Rock walls can be beautiful and yours are a good example of ones made with boulders. Because there are large spaces between the rocks, plants and weeds will grow there. The areas abutting the walls should be planting beds with mulch to control the weeds. I would kill and remove all the grass between the two walls and make another planting bed below the lower wall. Don't skimp on the width of the lower bed. A pleasing curve that ends somewhere logical 3-10' wide would be good. The lower planting bed should be edged so the grass could be mowed along the bed. You should not have grass next to the walls on top or bottom.
Landscape fabric would not help the situation. It collects soil on top and weeds grow anyway.
When you have the beds made, plant creeping perennials at the top of the walls and they will cascade over and look good. You can also plant in the cracks. You will still have to spray/pull the few weeds that grow in the cracks but that will be manageable.
The area can be beautiful and not require a lot of maintenance.

One appearance issue that you have now is that the boulder wall looks man-made as opposed to a part of nature. Scattering a few small rocks in between the large boulders will really help the look a lot. To add even more character, fill the remaining gaps with top soil and plant different types of flowers and vine. This will have to be done over time as some plants will not hold. After two years, you will have a colorful, natural looking wall. Enjoy!

I am offering advice because of the crap that has been posted here so far - sorry about that.

You could dig out the weeds, place landscape fabric down and then cover it with 3-4 inches of stone. It would be a clean low maintenance solution. Another very low maintenance solution which I am sure I will be grilled for on this forum is round up. If you apply round up around the bottoms of walls about a foot out from the walls, it will kill the weeds and grass. It sounds a little harsh, but it actually doesn't look tremendously different from the stone, which also has a somewhat hard effect. You would need to reapply every 2-3 months.

You can strip the sod between the walls and install a ground cover like juniper, bear berry.

In terms of the guy who installed the walls, its my understanding that he should have installed landscape fabric behind the walls to mitigate the runoff issues down a slope. over time its possible that the water can push the stones out of position and effect the integrity of the wall. But there are other people around on this forum who can better comment on this.

I would expend some energy and dig out the weeds - thinking about it is often harder than actually doing it. Some situations call for Round-Up (especially between the boulders) and this might be one of them.

Some chinking would be nice to break up the regularity in the boulder stacking, but barring that... I'm in zone 4 and hens & chicks, phlox subulata, some errant scilla, an even more errant ostrich fern or two, creeping Dragon's Blood sedums, self seeded forget-me-nots, and a mat forming cultivar of dianthus deltoides all thrive in my wall.

I've got a brick patio at the base and going after any weeds that crop up between the bricks with Round-Up doesn't bother me a bit.

I'd begin by spraying a lot of Roundup in the walls and for 6-12" on either side of the walls. Buy concentrate and mix it yourself -- it's much cheaper; buy a good sprayer that will hold a gallon or more and limit its use to weedkiller; consider a backpack sprayer.

Next spread a pre-emergent; the cheapest might be a bag of corn gluten from an agricultural supply place like Tractor Supply Company.

Then add 3-4" of mulch to either side of the walls (you may want to remove the sod/lower the soil first). The Roundup and corn gluten will give you a significant breather, and the mulch should slow down weed growth quite a bit after that. If you don't have a source for inexpensive mulch, talk to tree companies in the area.

Since you have so many walls, you could test various tactics in different areas.

Don't plant anything in or near the walls until you figure out if you'll ever be able to stop using the weedkiller.

I think Drtygrl was responding to Wow, not to Steve, but either way, I agree with Steve and others that grass cannot be adjacent to rocks. And that the rock walls are lovely. I think quite masterfully done.

To fight weeds you have to understand how they spread and grow. Yours appear to be seeded into those cracks, and it's true they will do that with or without landscape fabric. Plus, the landscape fabric looks like crap and if you do want to plant in those openings (I would) then fabric will mess you up. I wouldn't want to use the fabric at all, but that might be influenced by the fact that I hate the feel of the stuff.

Anyway, what you need is to limit (a) sources of weed and grass seed, and (b) light to enable them to germinate if they do land. Mulch right into the openings between the rocks. You will have to be vigilant for a few generations of weeds, probably.

Weeds and grass will fill a vacuum, and if you don't make a decision about what plants, mulch, or hardscape will occupy those spaces (once you evict the weeds), mother nature will!

Count your blessings if you don't have a weed in there that spreads by root suckers!

KarinL

Thanks for all the input! Unfortunately, the source of the seeds probably come by the birds and groundsquirrels which are everywhere, and just behind where I stood to take that picture is the woods we live on the edge of...where I'm sure lots of seeds stray from. I'm not at all opposed to using round up! If I use the stuff, how soon after can I try to plant something within the cracks? I found some creeping phlox on sale and bought some. I love it...cascading down other peoples' walls...may take awhile, but I'd love to have that effect myself. I am not sure if the ground squirrels will mess with any plantings....our yard is overrun with them (rock walls especially), but I'd like to try. Thank you for all the suggestions! I am going to read them all more thoroughly and take some notes.

I saw a rock wall belonging to a neighbor of a friend of mine on Thursday. They have phlox on the top of theirs...it actually grows into my neighbors yard. Perhaps that might even keep the weeds off the top of the rock walls as well?

To the person who suggested inserting smaller rocks in the larger spaces...I've actually started doing that, on another wall, the largest on our property. If interested, I have a photo album that contains pictures of most of our yard...and I believe all but one of the rock walls... you can see them on the link below. yes, I know my whole yard needs a lot of work. Some of you have seen some of these photos before.

Here is a link that might be useful: yard album

You can plant in about a week after using roundup. Leave the sprayed weeds for that week to let the chemical get to the roots and kill the weed.
Creeping phlox will be nice. Dianthus will creep over rocks as well and has nice blue green foliage. You have many varieties of sedum to choose from as you mentioned. Choose plants that do well in that hot, dry environment.

Thanks for the input! I'm trying to get my hands on some more phlox, and I'm going to look up the dianthus you mentioned, Steve. I did plant some sedum in a couple places last year, and where they are planted, they seem to keep the weeds away. In one spot, the sedum has taken over, which is what I want to see....but this rock wall is so big, I've got a long way to go. I've started with round up, but again, a long way to go!