San Francisco is not the only city that repurposed dunes, but it happens to be the one I know best. The western third of the city near the Pacific Ocean sits on an area once filled with dunes and called the Outer Lands. My place is some 10 blocks from the tideline and when I plunge a shovel into backyard soil, it is as sandy as Copacabana Beach. Every gardener in my neighborhood has become an expert at dealing with sandy soil in gardens. Here are some hard-won tips.
The Good and the Bad – Sandy Soil Benefits vs. Disadvantages
Now sandy soil in gardens has advantages as well as disadvantages. Epically well-draining, water slips right through, so you don’t ever have to worry about rotting roots. It is also very easy to pull weeds out of this kind of soil, since the roots are only lodged in sand.
The bad part is pretty obvious: sandy soil doesn’t hold moisture or offer many nutrients to plants. Unless you plan to plant beach-grass or scrub that grows on dunes, your plants won’t last long unless you amend the soil.
The Fast Fix for Sandy Soil Issues
When I first moved to this area and surveyed the bleak expanse of backyard, it took only a moment to opt for the quick fix: raised beds. Building raised beds gets you through any soil problem – I’d done that successfully in France where the mountain slope is particularly rocky.
I installed a few garden beds by building simple rectangles from wooden fencing boards. Each one was about 6 feet (2 m.) long and 3 feet (1 m.) wide. The boards were 24 inches (61 cm.) wide themselves, so when I laid out the rectangles on the ground, they made great raised beds.
I dug out the sand a bit to sink a foot or so into the ground, then filled the rectangles with a mix of topsoil and compost. Hello vegetable garden!
The Longer Fix for Sandy Soil Disadvantages
Amending the current soil is a longer term fix when your backyard is sand. Over time, I worked with this approach as well, making a compost heap near the garden. Since I am a vegetarian, I added to the compost every night with fruit cores, veggie peelings and other kitchen compostables. Fall brought fallen leaves too.
While rotted manure is an excellent and nutrient rich soil amendment, I didn’t use it because of the high salt content. My sandy soil came from the Pacific beaches, so the salt level was already somewhat high. That made using a plant-based compost the perfect choice.
As my compost developed, I used it in the garden, layering it thickly atop the sandy beds, then working it in well. Over time, my sandy soil turned into an excellent mix that allows many flowers, veggies and shrubs to grow.
Sandy soil and gardening is definitely achievable if you know how to do it. While you could choose plants for sandy soil, disadvantages include a not-so-huge selection. Raised beds, on the other hand, along with compost amendment, means more plant diversity and a beautiful garden.