Pea gravel is a growing medium used in extremely dry landscapes and extremely wet landscapes. In dry landscapes, pea gravel helps suppress weeds and dust while protecting the root systems of drought-tolerant plants. In wet environments, like bogs and backyard ponds, pea gravel withstands erosion and acts as an anchor for bog plants and floating aquatic plants.
Pea gravel is used in Mediterranean gardens as a mulch to protect the roots of herbs and other drought-tolerant plants. Pea gravel reflects heat and provides good drainage for rosemary, thyme and sage -- herbs that flourish under dry, hot conditions. Other plants that do well in coarse soils include blanket flower (Gaillardia), yucca, yarrow (Achillea) and lantana. Prepare flowerbeds and growing areas by digging down approximately 2 inches. Incorporate organic matter such as compost into the remaining plant bed's soil. Do not use a weed barrier. Place small pea gravel of 3/8-inch diameter on the top 2 inches of soil. The pea gravel suppresses weeds and provides drainage.
Lily pads and lotus may appear to be floating freely on a pond's surface, but in reality their roots are anchored in the pond's bottom while their stems extend up, to the surface. Backyard garden ponds are usually lined with plastic or covered over with concrete. These barriers do not permit emergent water plants to anchor their roots directly in pond bottoms. Instead, water gardeners plant lotus, hardy water lilies and tropical water lilies in baskets filled with heavy, clay garden loam. The tops of the baskets are lined with pea gravel. Pea gravel provides erosion control and water permeability.
Dense, heavy soils are difficult to cultivate and unsuited for many types of plants. The heavy soil repels water and chokes root systems. This type of soil must be amended by incorporating organic materials uniformly throughout the planting bed. In extreme cases, holes are drilled into dense soil layers. Stove pipes are placed in the holes. The pipes are then filled with pea gravel, which is used to provide aeration and water movement. Commercial growers use this technique to improve planting conditions for citrus and avocado crops. These crops require well-draining soils.
Pea gravel does not always need to be used in outdoor growing situations. Benefits of in-home pea gravel use include the material's ability to withstand fungal infections and other waterborne plant diseases. Orchids and ferns are grown using pea-gravel mediums. Other indoor growing systems, such as hydroponic systems, use pea gravel to stabilise plants like tomatoes and lettuce. Pea gravel lines the bottom of a planting bed and nutrient solution drains through the gravel, effectively feeding plants.