The Contrary Countryman
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Ferrocement Garden Bed
The challenges to gardening here at Heartwood in southern Missouri include juglone from walnut roots, moles, armadillos, groundhogs, raccoons, deer, and aging bodies that become more unhappy each year with bending to the ground to plant, pull weeds and harvest.
After years of making our raised garden beds of oak planks and having to replace them as they rotted, I resolved to make permanent structures. I have made two ferrocement beds previously by making a framework of rebar and then tying poultry mesh to that framework. Tying the wire and then applying the mortar are both tedious and time-consuming. So this time I decided to experiment by making wall sections on the ground and raising them into position.
Our main garden is laid out on the contour, to make irrigation more effective. After checking position and dimensions I poured a mowing edge around the bed outline, leaving the inside form two-by-fours in place. Then I dug up the soil inside the form boards so I could use it for making the sides in the shape I wanted. I removed all rocks and roots. I drew the shape I wanted onto a cedar board and cut it with a sabre saw. In the following photo the board is used to make the shape of the floor that will also be the shape of the future wall sections.
Note that the right edge of the bed is lower than the left side. This is due to the slope of the ground downward to the southeast. Finished, the upper wall is 30 inches high and the lower wall is 41 inches high. This works well for Chris, and I, who are seven inches different in height. That’s right--she takes the high road and I take the low road. Such is much of our married life.
I next poured the bed bottom, to make it impenetrable to walnut roots, which produce juglone, a substance that kills tomatoes and many other garden plants, and to thwart our common burrowing animals, groundhogs, armadillos and moles. I used the side design board to screed the concrete floor, making a form, so the ferrocement wall sections could be made to a consistent shape. The other important thing at this point was that by leaving the inside two-by-four form board of the mowing strip, a groove was created that would later accept the wall sections.
After the concrete floor set for a couple days covered with a tarp, I removed the tarp and laid heavy black plastic sheet on top of it and proceeded to make the wall sections.
For reinforcement wire I used five-foot poultry mesh with one-inch openings. I calculated the wall height, measured that times four on the mesh, cut and folded it to create the matrix ready for mortar. I tried various materials to hold the mesh to the curved shape. In the next photo I was using stones, small pieces of wood held down with my heavy digging bar (an old wagon axle found along the stream road), and concrete blocks. I laid two-by-fours at the bottom to create a straight edge that would be mortared into the recess I had formed between the mowing edge and the floor.
The lower edge is at the top of the photo.
I use a simple 1:3 mix of Portland cement and sand for mortar.
Mortar was pushed into the mesh and left to dry overnight. The next morning I removed the weights and applied mortar to the entire section.
Note in the photo above that before mortaring I laid in a heavy wire lengthwise. Also note the little non-mortared area in the center of the section. This was later used to connect cross-ties.
After each mortaring, the section was covered by the blue tarp to retard fast drying.
Below, note how strong the wall section is the next morning.
The next step was to move the section into position. After this first section was in position I brought in the garden tractor to make sure it would run along the mowing strip and not touch the wall. Perfect. I love it when a plan comes together.
The concrete mixer in the background was used to make the mowing strips and the floor. The paint mixer in the orange bucket was used to mix mortar, using a half-inch cordless drill for power. Various trowels were used to apply and smooth the mortar.
I continued making wall sections, setting them into position and mortaring their bottom edge where they fit into the groove between the mowing edge and the bed bottom.
The lower edge required taller sections so that the finished bed would be level across the top.
To strengthen the corners I placed a heavy wire at the top and joined it with the sections and corner mesh by bending pieces of the wall section mesh around it and using soft wire to thread around it. The two-by-four and clamps kept the top edge of the wall tight together until the mortar dried.
Here below, the completed corner. Those visible rough sections later got a final coat of mortar. For final mortar coats, I sift the concrete sand down to a smaller particle size.
End sections required a sloping bottom to fit the contour. The north end is shown above. A friend who served in the Navy says it looks like the bow of a ship he served on. In the south end section shown below I left lots of mesh at the sides to facilitate making the corners.
By the time I got to the last side section, shown below, I had smartened up and graduated to laying down mortar on the plastic, then the mesh, then sufficient weights to push the mesh into the mortar. I let that dry overnight, then the next morning removed the weights and applied the inside mortar face. This produces a stronger, although thicker and heavier unit with a smoother outside surface.
Below, the final section raised into place. Note the drainage holes left open at the bottom edge. This was done with all lower wall sections.
Making curved sides sure made corner construction more challenging.
The final ferrocement work was to finish the corners, join the sections, make the top edge straight and level and do final smoothing. Below, the upper side of the permanent raised bed after all the joining and smoothing had been done.
Below is the lower side. Note the drain holes at the very bottom. The dark spots are where interior wire cross supports are connected. I don’t know if they are necessary but it seemed prudent to install them.
Wife, Chris, painted the ferrocement with stucco paint, partly to cover any wires that were not fully embedded in mortar, to resist rust.
The bed was filled with—from the bottom—big rocks, small rocks, large rotten oak branches, small rotten oak branches, soil from the edge of the stream that contains humus, silt and sand, then forest soil, a layer of chicken manure/macerated oak leaves/rotten sawdust, and finally a top layer of garden soil.
We finished the project late in the year, too late for summer crops, so we leveled the soil and planted the new bed to garlic. Below is the crude screed I nailed together to make the soil level.
Here, Chris is putting garlic cloves into the holes created by the garlic planting stick seen at the far end.
I planted some seeds of lettuce, spinach and kale around the edges. Some came up but the cold weather kept them from developing. In the eternal words of the inveterate gardener, just wait until next year!
If I do this style of bed again I will make longer sections so that there are fewer connections to be made. Making ferrocement walls on the ground and then tipping them up into position saves a lot of work. The only constraint is having the muscle power to lift them into position. Two or three people could tilt up a substantial wall.
Gardening at waist level is very comfortable. Knowing that the walnut roots, moles, groundhogs, armadillos and other critters are excluded gives much comfort and consolation after years of dealing with them.
I have another design in mind. The next experiment will strive to produce much the same results with less work. Stay tuned.
Copyright Gene GeRue 2009
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