ISSUE 86  |  To the Beach

A Gift From the Sea: Oyster Shells in the Garden

August 22, 2013 3:00 PM

BY Janet Hall

A landscaping material, a nutrient-rich soil amendment, and a natural pest deterrent. Who knew the lowly oyster shell was such a boon to the gardener? 

Above: The oyster shell works hard in the garden.  It is composed mostly of calcium carbonate (95 percent), which means that when mixed into soil (especially when crushed) it provides a slow release of calcium that de-acidifies and helps balance soil pH. It can loosen clays and improve drainage. And, that’s just what it does when in the ground. 

Above: On top of the ground, oyster shells act as a hardworking hardscape material. Oyster shell paths originated in Colonial times as a result of early-American recycling efforts. Oysters and other shellfish were a primary source of food, and the thrifty settlers put the discarded shells to use as a paving material. Paired with brick, the oyster shell paths in Colonial Williamsburg make a handsome path. Photograph by Stephen Katz via the Virginia-Pilot.  

Above: An oyster shell garden courtyard at the Zero George Street Hotel in Charleston. 

A great alternative to gravel, crushed oyster shells can be used as a cover material for paths, patios, courtyards, driveways, and even bocce ball courts (the crushed shells don’t hold water or imprints from shoes and balls). As shells get walked on or driven over, they break into smaller pieces to create a stable walking or driving surface. Like gravel, oyster shells require periodic replenishment. For large areas, it is wise to purchase bulk crushed oyster shell which can be found at some landscape suppliers (or, surprisingly, mushroom farming suppliers like Myco) and is comparable in cost to crushed stone. 

Above: At Sleepy Hollow Farm in Michigan, the proprietors created a garden path using crushed oyster shells sold as a chicken food calcium supplement in the local feed store. Photograph via Sleepy Hollow Farm Life.

Above: An oyster shell path in a kitchen garden does double duty as a pest repellent. According to the gardeners at White Flower Farm, crushed oyster shell placed in the planting holes under bulbs and other tasty plants will keep small underground pests like moles and voles who don’t like the gritty substance from burrowing up and feasting from underneath. The texture of the shells also naturally deters leaf-eating slugs (they won’t slither across the rough surface). This was the only chemical-free method that worked in my fight with Pacific Northwest slugs: I tried the beer trick. I ran around with a salt shaker (and closed my eyes). But, it was when we lined our garden beds with crushed shells, that the slug fest came to an end. Image via Garden Cuizine

Above: Oyster shells help neutralize soil acidity for tomato and vegetable gardens. Mix crushed oyster shells into the soil for container gardening. The coarse texture promotes drainage. Photograph via White Flower Farms.

Above: To use oyster shells as a soil amendment, sprinkle crushed oyster shells in the bottom of planting holes for vegetable and bulbs. Using coarse crushed shells, as opposed to oyster shell flour, provides an even release of calcium throughout the growing season.


Above: The White Flower Farm Potting & Garden Oyster Shell Amendment is $10.99 for the 10-pound bag. 

For more Gardenista-recommended ideas, see our complete list of Garden Supplies.