River rocks provide an attractive mulch under bushes and are a useful solution for busy moms who want a beautiful garden that requires minimal maintenance. A thick layer of river rocks suppresses weeds and provides a visual link between shrubs and reflects light, retains heat and offers complementary or contrasting color. Large river rocks make bold structural statements in landscape designs with bushes and are tough enough to withstand the most adventurous children.
Clearing and leveling the ground around bushes, and covering it in landscape fabric or a layer of fine gravel, give a long-lasting professional finish to river rock mulches. Remove weeds from around your bushes, taking care not to damage plant roots on bushes. If the ground is uneven, loosen the soil and level it with a garden rake. A layer of pinned-down weed-suppressing fabric prevents weeds growing through river rocks; alternatively, a 1-inch layer of fine gravel holds large rocks firmly.
Thickness and proximity to bushes are the main considerations when laying river rocks. Over time, rocks settle and gaps appear if river rocks are laid too thinly, exposing the rock bedding material or bare soil and allowing weeds to flourish. Spread a 2- to 3-inch layer of river rock for optimum coverage, which is about one 50-pound bag for 3 square feet. For a seamless effect, spread rocks beneath bushes so that their foliage overhangs the mulch, but don't allow rocks to touch the bases of bushes, because this can trap water and cause rotting.
Removing plant debris, cleaning and weeding river rocks maintain their attractive appearance. Dead plant material and soil provide a growing medium for weed seeds, so remove fallen leaves, twigs and other detritus from river rocks, and clean them weekly with a strong jet of water from a garden hose. If weeds do appear, pull them out by hand.
Large river rocks are an effective element in landscape designs. For a natural effect, choose rocks similar in color and shape to existing rocks in your garden, and nest them in the soil by digging out a shallow trench or hole for the rocks to lie in. Scrap soil up around their edges and grow bushes next to them to make the rocks look at home in the garden. The face, or widest part of the rock, should be on top and turned toward the garden viewing area. If large river rocks are prohibitively expensive, use a collection of smaller ones for a similar impact.