Do they have a hole in center of them? If they do that is where the rebar goes & then fill center with cement or at least the couple of ft. closest to the ground. Same way a block wall is built that doesn't require a retaining wall.A retaining wall,would be better if this is on steep slope, then you would dig out area couple of inches wider than the blocks & about12-20 in deep, put in a base of poured cement ending with 1st block secured in the fresh cement with rebar in center. If no hole in center of blocks you could run a piece of rebar up the outside. I would undercoat it with rust preventive paint & then paint it same color as block & it would hardly be noticeable. I didn't try bringing up your block as that never works for me. Jan

I reread your post. You should go 20-24 in. deep as I think in Ca. that is retaining wall foundation & cement inside all the way up as Wisteria vines are are lot of weight If no hole in center I think I would rebar on 3 sides with it in the foundation cement the vine should be planted on 4th side so decide where it will be planted & vine will act as 4th rebar. Don't know how you would bolt rebar on, could use aluminum straps going from 1 rebar over to other side & around 3rd & set in cement of each row. The vine side gives you a place to fit the blocks in & connect it all together as you go. With the 3 rebar in the foundation a good ft. it should be a strong pillar for your project. Check codes for retaining walls in L.A. or whatever county you are in. So you get foundation deep enough so less likely to have problems & survive any quakes also.

I really appreciate you trying sunnyca, but these are different kind of square blocks. Maybe this link will help? I want to stack them 10 high, on level hard compacted ground or I can dig down and put something of a foundation if needed.... These ornamental squares though you really have to see to know what I am talking about. They stack on their sides

Here is a link that might be useful: {{gwi:2704}}

OK I know what they are, have couple in back. You probably should put a little cement base with rebar inside the 1st block in 2 places where biggest holes are & then just mortar each row as you go up. 4 in. x 10 blocks=40 in. plus mortar about 1 in a row so you are talking about 50 in. high 4ft or so. Rebar in cement would keep them safe & secure in most cases. Kid running bike into them, grandma almost falling & grabbing for support etc. Also would just rock in quake. My dad has a real problem with the new requirements for block walls, he says it defeats purpose, Used to put a little cement base, about 4 in. put rebar pushed into bottom of fresh cement & build your wall. Rock & rolls with the quakes, reason it falls in most cases is because owners plant trees & shrubs with big roots too close to it. 1st quake no problem except where it went between houses & my house higher than neighbor's, my sidewalk caused it to break loose, then my Meyer lemon was other problem, took it out. 2nd quake, broke in 3 places where trees had grown up, rest stood up fine. With new walls lot of them will fall as they are so rigid that they can't roll with quake, the cement will break causing wall above it to break apart. I trust my dad's judgement as he has built several houses & always had solutions for almost any situation, nothing shabby or junky either, he wouldn't hear of that. He taught me well by making me do it as he watched. I was 6 when he put a hammer in my hand & can of nails. 1st you hold the hammer out at the end, otherwise you don't get the nail in 1 or 2 hits, next don't bend them over, can't afford to waste any, 3 let't get this done, winter is coming fast & watch me once & do it just like I do I learned real fast & it was masonite too & hard to get nail going into it. He's 93 now & losing his eyesight but he still is putting in new lawn in back with mom who is 87. They are not your average old folks!! Good luck!! Waiting to see pics of finished project!!Jan

I have a friend who made walls for a compost pile out of these. He calls it the Taj Mahal of compost bins!