How we built our terraces

When we bought our property six years ago, we had a few non-negotiables when it came to the house and the site, and this little suburban plot addressed them all. Quiet, but close to town. Rural sensibilities and no restrictions on use. Southern exposure. Water on-site. Three bedrooms. The house is a nondescript rancher on a one-lane dead-end road that, frankly, alarms visitors. We have fewer than ten neighbors, all sitting on between two and eighty acres, with most of the properties connecting to a large creek that winds along the base of a ridge, or to the smaller stream that feeds it. The lane sits in a hollow between two large ridges, one very close (maybe two hundred yards away) and the other about half a mile away.

Our property is shaped like a triangle, with one side bounded by the lane, one side bounded by the stream, and one by a barbed-wire fence that adjoins a neighbor’s pasture. The house is oriented to the cardinal directions, with the backyard facing directly south. To the east is a small but steep hill, atop which runs the lane, and at the bottom of which sits the eastern wall of our house. When we moved in, the hill was overgrown with scrub pine trees (loblolly, to be specific) and a particularly nasty Asian privet that spreads by dropped berries (which are poisonous) and runner roots, like bamboo.

There were signs of an attempted terrace — a fairly orderly stack of creosoted railroad ties. Because the hill slopes to the south and west, and because our soil is an extremely dense clay, we knew the hill would be the best site for a vegetable garden. It would receive the sun for most of the day but be shaded in the hottest afternoon hours of summer. It would drain better than our flat ground. So we set about clearing the privet and pine. Although we’re averse to soil compaction, a little work by hand made it clear we’d need to call in the big guns. The best we could do was remove the invasive growth, then reverse the soil damage that removal caused.

Once the heavy equipment had done its work, the damage was clear to see. That first summer, on a tight budget and a tighter timeline to get plants planted before summer had come and gone, we installed four 4x8 raised beds and ordered gabion baskets and a truckload of stone. Over the next year, we slowly built the second terrace by hand — installing the gabion baskets, filling each basket with stone, installing a drainage system behind the gabion walls, and then backfilling the terrace by hand. Just two people, two shovels, and one wheelbarrow.

We covered the bare soil with weed block, then covered that with several inches of wood mulch. Once the gabion wall was finished and the second terrace had been backfilled, we built five additional 4x8 raised beds — each filled with mushroom compost.

To orient yourself in those images above, photo 1 and photo 4 are taken from almost the same position. The plants in the bed on the far right are asparagus. In photo 4, the stump from photo 1 has been removed. In the photo grid above this one, that same raised bed is visible in photos 3 and 4 (before it was planted with asparagus).

By the third year of gardening on this property, we had decided we wanted one last terrace — largely to help control runoff and to make the final top slope of the hill more manageable. Although we liked the look of the gabion walls, we finished the third terrace in 2020, when supply chain issues (and being essentially stuck at home) limited our design options. We installed a wooden beam wall and backfilled it with the soil remaining on-site: almost wholly subsoil, the type of clay someone could make bowls out of, and lots of rock. Interspersed with the subsoil, we backfilled the wooden wall with sticks, leaves, pinecones, and other plant material, which would slowly rot down and create bands of humus among the subsoil. Hopefully, this would help prevent compaction and help restore life to the poor soil.

In the photos above, you can see the impoverished nature of the third terrace soil. Despite laying as it was for nearly two full years, it was still completely bare — not even weeds would grow on it (best seen on the left slope of the middle photo). The amount of stone we have leftover from gabion-building is also apparent. Anyone want any rocks?

The third terrace was planted in it first year, although all the plants fared very poorly (the corn as you see it in the middle photo, above, never got any taller than that; in a raised bed, it commonly grows to eight feet high). That fall, we heavily mulched the third terrace soil with six inches of fallen leaves, autumn-cut plant materials (cannas, elephant ears, corn, okra, kale, sweet potato vines, and anything else we could find), and topped that with six inches of wood mulch. Over the winter, the layers rotted down to about four inches deep. The next year, plants fared a little better — okra, roselle and sunflower performed best. In its second winter, we repeated the thick lasagna mulching technique with plant materials, fallen leaves, and shredded paper. Because wood mulch takes so long to rot, and because it locks up nitrogen in the soil while it does, we didn’t add any more except to the areas we intended to be paths.

This year is the third terrace’s third summer, and the soil (while still not excellent) is measurably better. The top three inches of soil are dark brown and crumbly, filled with earthworms and laced with mycorrhiza. This year, the third terrace is supporting 36 tomato plants, about 40 beans, 1 cucumber, 1 gourd, 4 squash, 4 melons, and 7 dahlias. When we planted each seedling, we supplemented the soil with compost.

All the plants look beautifully healthy and happy, but we’ll continue our heavy mulching with plant matter and fallen leaves each fall for several more years.

This year, we also made changes to the first and second terraces: namely, we painstakingly pulled up the weed block. Call it a lesson learned. As the wood mulch composted down on top of the weed block, it created gorgeous, black, crumbly soil. But this new soil was kept separate from our clay, which desperately needed improving (not only for soil nutrition, but for soil composition and drainage) and remained desperately unimproved. Further, the newly formed soil on top of the weed block became a haven for opportunistic weeds.

So, carefully, we pulled up all the weed block. We removed the weeds from the rich, crumbly, black soil and spread it over our wet, heavy clay. Over the healthy soil, we spread more wood mulch. Now, over time, the soil between our raised beds will improve — allowing us to plant this space with flowers for perennial fruiting plants and pollinators, currently including cherry bushes, sunchokes, poppies, sedums, roses, rosemary, hyssop and borage.