Making and planting troughs gardens are fun. It is landscaping on a very small scale although you can make them as large as you want or as small as you want. Remember, you have to move them so keep that in mind. It depends on what you can use as a mold to form them. I am going to describe one that I have made. It was for a bog garden 24″ x 18″. There was no sand in the mix so it was fairly light weight. Styrofoam is great to make forms. Cut out the size you want and put it together with duct tape. Anything that will hold the mix will do but Styrofoam is light and easy to cut. It is strong enough for at least one use. The mix is 3 peat, 3 perlite or vermiculite, 2 Portland cement, and plastic fibers for maximum strength. It must be made very dry.
After you have made the form, line it with a plastic trash bag. This will give it texture but most important, it will not stick to cement. If you want a bog garden only, put in one drainage hole. If you want cactus or other kinds, put in three holes. Remember, these troughs stay out year-round so they must have good drainage. A bog garden needs to drain very slowly. I use Horsetail (Juncus) both dwarf and full-size with Creeping Jenny over the edge and sides.
Okay, now to form the mixture. Whatever mold you decide to use, the mixture must be very dry so you can form it in the mold. Put an inch or two on the bottom then push as hard as you can onto the sides. If it is too moist, it will not stick to the sides. After forming it, cover for twenty-four hours and let it cure. Gently remove the form after twenty-four hours. You can leave it smooth or roughen the sides with a wire brush. Be gentle. It is not strong at this point. Drive a dowel into the bottom to make a drain hole. Remove the dowel. Cover the form again and wait at least a week. The longer it cures the stronger it will be especially if you keep it damp by spritzing it now and then. Don’t hurry it. Let it set for a month before planting it. The plastic fibers act like reinforcing rods. They make it extremely hard. You can buy these fibers at Home Depot. They really are necessary.
