How to Use Crushed Shells as Mulch
Gardeners have many reasons for using mulch. In landscaping, it provides decorative ground cover that lends a tidy appearance and color contrast to the green shades of lawn, trees or plants. Mulching around plants keeps moisture levels higher, reduces weed growth, insulates soil to provide more even temperatures and aids in the growth of root systems. Mulch can be made from many materials, including bark, wood shavings and gravel. Mulching with sea shells will make a contrasting white ground cover for plants of brighter shades. Sea shells also contain calcium that enters the soil as the shells decay.
Weed the area you are mulching. Remove any previous mulches, as well as rocks or sticks that may be mixed in with the mulch.
Determine the amount of mulch you need. At 2 inches thick, it will take about 3 pounds of shells for each cubic foot of ground you wish to cover. Purchase the shells, or pick them up along the beach if you live in an area where this is feasible.
Boil the shells to remove sea salt and organic matter if you have picked them up yourself. Once the shells appear clean, drain the water and rinse the shells.
Crush the shells. Once again, this step won't be necessary with store-bought mulch. Place the shells in a cloth bag; a plastic or paper bag may rip. Tie the bag shut and pound it with a hammer until the shell pieces are the size you desire.
Spread the shells in the prepared areas around the plants or landscape. Layer the shells 1 to 2 inches thick. The shells will send calcium into the soil as they decay, so if you are spreading them around plants that will be harmed by calcium you must first lay down plastic. Calcium makes soil more alkaline, so plants that like acidic soil won't tolerate too much. Rhododendrons, juneberry, columbine, manzanita, azalea, heather and foxglove are a few plants that like acidic soil and won't like excess calcium.
Cut a sheet of plastic -- a garbage bag will be suitable -- to the dimensions of the mulch area for those plants that don’t require additional calcium leached by the crushed shells. Leave an extra inch of plastic next to the plant to form a lip. Lay the plastic down where you plan to add the shells. Layer the shells on top of the plastic, folding the extra inch of plastic around the base of the plant up over the side of the shells. Pick up any shells that fall off the plastic. If you wish, you can create a barrier around the shells with a small line of gravel or another type of mulch to ensure they don't run off the plastic.
Jill Kokemuller has been writing since 2010, with work published in the "Daily Gate City." She spent six years working in a private boarding school, where her focus was English, algebra and geometry. Kokemuller is an authorized substitute teacher and holds a Bachelor of Arts in English from the University of Iowa.