Rocks On Top Of Soil In Houseplants . The first reason home gardeners choose to put rocks on top of their potted plants is the aesthetic looks. Hoovb zone 9 sunset 23. Can You Put Rocks On Top Of Soil (Of Potted Plants)? Gardening Mentor from gardeningmentor.com Using cinnamon to kill white mold. One common solution is to add landscape rocks beneath the potting soil so that water has a place to pool. In general, it’s not necessary to put rocks in the bottom of plant pots.