Rock and Cactus Garden
This is going to be a rather long thread so you may want to book mark it to find it easy to return to or it will be listed in the DIY projects. I'll include everything as I do it, from making the boulders and stone border to mixing your own cactus soil. If you run into a problem or have a question, just email me. This project will take the better part of a week to complete but most of that time is dry time for the concrete and you'll only be spending a couple hours on it each day. This is a great project for a raised garden, everyone will like it and it will continue to evolve as the cactus grow over the coming years. The cost to have someone else do it would be to costly to consider.
My though is to start with small inexpensive slow growing cactus and to let nature take its coarse. I actually know very little about cactus, thanks to the people that brought cuttings to me and the information they supplied. Even before the cactus get to any size it should be interesting with the stone border and faux boulders. I don't have a lot of room for this project which may be a good thing when I start carting in the sand, rock and concrete.
Make a list of what you'll need as you read through this, unless you have a heavy duty truck you will not be able to haul all this stuff home in one trip. I wouldn't be able to unload it in one trip, it's that getting old thing again, for the most part everything in this project is heavy. The only thing you'll need to store inside is the concrete, so just pile everything else at the project site as you get it.
In these first pictures you can see that I have a clean slate to work with. This is the first thing you see when you walk through the gate to my back yard, not very impressive, but that will change. I have ginger plants here now but they don't like all the sun they get and the kittens like to stomp all over them, I have no idea where I'll be putting them.
I'll start by laying a landscape timber border, mostly to conserve on concrete and I already have them from a pond border I replaced. You can also just mound up some dirt to save concrete. Wood works great since it will break down in time and if you ever have to remove this it will be a lot easier to break up. I'll be using stucco or sand mix for the concrete, it's very smooth to work with and will have plenty of strength for what I want and it's also inexpensive. 5 or 6 - 80 lb bags should be plenty for what I want to do.
If you have sand left over from another project or pond dig, just get portland cement and mix your own, very cheap, the instructions are on the bag. I'll also pick up some river rock to cover the concrete border as I make it. I'll be using a tray to mix the concrete and just a garden hoe. I find that the pointed trowel works best for me for most projects. Pick up some plastic gloves also to keep the lime in the concrete from destroying your hands, get the large pack, you'll be playing with concrete often after you see how easy it is to work with.
I'll also be using dry concrete dye (Home Depot) on the faux boulders. I'll probably settle for concrete sand for a planting media although I would like a coarser sand if I can find it. Weed block is worthless as far as weeds go but it will keep your sand and smaller rocks from settling into the soil and is well worth the cost to use it before adding the sand, soil and stones.
At this point I'll put a thin layer of concrete over the timbers to tie everything together, this will probably crack but don't worry about it. I'll also be adding some styrofoam boxes to be made into boulders. The boulders will be finished first to keep from slopping up the border as I add the second coat of concrete and set the river rock into it.
Styrofoam boxes are everywhere, look behind stores or in dumpsters, they make a great core for your boulders. You are not limited by the box size, you can stack them or turn a number of boxes into 1 large boulder. If you build them tall and narrow you may want to dig a hole on a couple sides and put some rebar along the sides and set the rebar in concrete. The boulders are hollow and will become top heavy if very tall, be especially careful if you have kids playing in the yard. I didn't have much room on this project so I left them fairly small.
I did the the first coat on the boulders different this time, instead of a wire wrap of chicken wire I just scored up the boxes with a knife and spread the first coat on. It is a little harder to get it to stick so if you have a problem here just wrap the boxes in chicken wire, hardware cloth or whatever you have, it's just to make the first coat of concrete go on a little easier. If you are going to tip these at an angle the wire wrap is probably a must. You'll want to leave the concrete rather thick to do the boxes so it hold its shape while you put it on. The second coat will go on much easier and you'll be using your hands to start shaping them. It will also stay on better since it has the foundation coat to grab onto.
When you start covering the border you'll want the concrete a little thinner so just add some water and work your way around. It's not important to get this first coat smooth since you'll be covering it with two more coats for the boulders and 1 more coat to set the river rock on the border. If you have any left over mixed concrete just add it to the boulders. Have the boulders where you want them, they may be hollow but they will still be very heavy.
The next day after this is dry it's time to break out the rubber gloves. Wet down the whole project, you'll need to do this every day for about a week to keep the concrete drying even or it will crack and get crumbly. I'll be putting on the boulder shaping at this point. Mix the concrete very thick. I find it is a lot easier if you mix it thin and then just add more dry to thicken it up. Just use your hands to add clumps of concrete to the boulders shaping them as you like, try to have this filled in rather smooth, you will be adding a third coat for the color, but it will make that final coat easy if you don't have to fill in large gaps. At this point you want the boulders to loose the box look, so toss plenty of concrete at the corners. Just put it on with a trowel, your hands or what ever you have, you'll be coming back in an hour to add more and smooth this all in. You'll see in the next pictures that the boulders are starting taking some shape of their own.
For the color coat mix the concrete thin, about like pancake batter. I just rub a coating over the complete project, let it dry for about 15 minutes, sprinkle on the coloring and pat it out to a smooth finish. I want a rather drab desert boulder color so I just used black and the natural concrete color. I like some natural appearing flaws when I finish up boulders so I score them with a trowel or knife and even just poke my fingers at them. For a very smooth flawless finish brush the finish coat with a damp fiber brush to get it the way you want it. There are all the base colors available so you can color any way you want. When you are patting out the color coat keep a bucket of water near and wash your hands which should be in rubber gloves between the colors or you'll have them all mixed. There will be plenty to make a blend from one color to the next as you go along. If you don't rinse often the entire project will mix and turn into a brown color. I let this dry for about an hour and go back with wet gloves and do a check over on the colors to see if I need to blend or smooth something out. Even later if you don't like your original color you can add more dye, keep in mind that it will continue to fade with time.
If you want a crack just use a knife, if you want any other flaws this is the time to do them. You can pat in wood mulch which will fall out in time in a few spots to look like flaws in the boulders or I have even heard of vermiculite being patted in to get a low luster sparkle but have never tried it, with black it would probably look like granite. In the past I have put in metal shavings and you get a cool bleeding effect as it rust but it only last till the shavings rust away. Concrete dye is very vivid when you first put it on but will mellow in a short time in the sun, if you want to keep it bright you'll have to use a concrete sealer on it. I never have, so you'll have to follow the instructions.
Now just mist these down every morning and move on with the project, which will start moving very fast from here on out. Since about 8" of these will be covered with planting soil, you won't have to finish down to the bottom like I did, I just wanted you to see the boulder effect and the other side has a plant blocking the view for a picture.
Boulders come in all shapes and sizes so don't worry about the shape as you do these, they will turn out great. Building up to a border with a number of boulders as here is a little harder than just a single free standing boulder, but you'll have no problem, it's like working with kids clay. After you get them the way you like, let them sit for about an hour them come back and smooth out the surface with a damp sponge or rag. If they are not to your liking come back the next day and add more concrete.
I wasn't real pleased with just the black so I got some yellow dye and used a throw away brush to add some more color. I just dip the wet brush in the dry dye and start at the top, it's very bright when you first put it on but just dip the brush in more water and start blending it to the bottom, continue to go over it with just water until you get the look you want, a third color can be added the next day if you choose. I always start with the dark colors and work lighter. Next we finish up the border, very easy and fast. Click Here to continue.