Mulching With Oyster Shells: How Crushed Oyster Shells Help Plants

Oyster Shells On The Beach
oyster mulch
(Image credit: Dale Fornoff)

Are you looking for something different to use as mulch in your flowerbeds? Perhaps, a bed of dark blooms will benefit from a design of lighter-colored mulch. Maybe you think green foliage will look more defined with pale ground covering underneath. There are several light-colored mulches from which to choose, one being crushed oyster shells.

Using Oyster Shells in the Garden

Mulching with oyster shells adds calcium to the soil and makes it more alkaline. Oyster shells in the garden eventually break down, but if you want to use them as a groundcover under plants that need acidic soil, apply them on plastic. Plastic works as an extra layer of protection to stop weeds from sprouting and to conserve moisture.

Mulching with oyster shells also improves soil health while adding a professional, well-manicured appearance. The addition of oyster shell mulch improves chemical balance in the soil, adds many nutrients, and improves water penetration. Calcium in the soil promotes a bigger root system, often leading to larger top growth on foliage and flowers.

Plants That Benefit from Oyster Shell Mulch

The cool season garden and many of the plants we grow tend to get bigger and more vigorous with a mulch derived from oyster shells that are pounded into a powder or allowed to decompose above their growing spot.

Leaf lettuce, spinach, kale, and cabbage enjoy this amendment in their growing space and penetrating their soil. Broccoli and the cool season lavender herb enjoy the nutrition as well. Studies have shown shell as a fertilizer increases crop productivity.

The sharp edges of oyster shells act as pest control with moles and voles. Locate them at the edges of tunnels to deter them. Slugs often refuse to crawl across those that are crushed and surrounding your plants.

Where to Find Crushed Oyster Shells

Obtaining oyster shells to use as mulch can be done in a variety of ways and at various prices. Work a deal with a seafood shop to pick up their shells at a nominal price, then rinse them and crush yourself. If you eat seafood regularly, try bringing the shells home. If you live near a beach, collect them and add to others you might get in different ways. Consider using other shells from the beach to increase the decorative value.

You can sometimes purchase them mulch-ready at a landscaping supply company. If you get them in other ways, always rinse well to remove the salt. Some suggest boiling the shells first to make sure to remove all traces of salt that can damage plants.

Consider the use of oyster shells for plants in your garden. You’ll likely see healthier and more vigorous plants that grow bigger than you’re accustomed to having.

Becca Badgett

Becca Badgett was a regular contributor to Gardening Know How for ten years. Co-author of the book How to Grow an EMERGENCY Garden, Becca specializes in succulent and cactus gardening.