GRAVEL IS A QUICK and efficient material for laying eco-friendly garden flooring, and it won’t break your back or the bank! Permeable or porous surfaces, like a gravel path or patio, allow rainfall and irrigation to percolate into the soil, reducing potentially toxic runoff that taxes the municipal waste system and threatens fish and wildlife. But that’s not all, gravel is also an effective strategy for managing dryland plants.
In her book, “Fearless Gardening” (Timber Press), Portland-based plantswoman Loree Bohl confesses her “obsession” with plants of the desert Southwest. Her remarkable garden is a stylish space populated with dramatic agave, hardy Opuntia and several mature Yucca rostrata, plants that tolerate our region’s low temperatures but often succumb to winter wet. The gardener credits the success of her eclectic collection of arid-loving plants displaced to our rainy climate to adequate soil preparation, selecting the hardiest forms, and mulching beds with gravel.
Think of a jar of marbles; even if the container is filled, airspace remains between the individual marbles. In the case of the garden, water passes through gravel mulch without pooling, keeping sensitive plant crowns dry during the rainy season. On the flip side of the calendar, mulching with gravel helps to slow down moisture loss and moderates soil temperatures on hot summer days.
Years ago, we removed an old deck covering an even older carport. Rotten wood and a thick concrete slab were removed so I could play with the idea of a gravel garden with plants set directly into a 4- to 6-inch layer of crushed basalt.
To minimize waste that would otherwise end up in a landfill, we hired a contractor to cut the parking pad into large angular pieces that we repurposed around the garden as stairs and short retaining walls. Imagine our surprise when vibrations from the heavy equipment collapsed our ancient sewer line, considerably adding to the cost of the project.
Today an informal landscape with clumps of woody artemisia, and a stand of Angel’s Fishing Rod anchor the new garden. Self-seeding Peruvian verbena, ornamental oregano and fine grasses wander at will around the space. Bluestone pavers add structure and provide a pathway through the space. Even during heavy winter storms, the gravel keeps the crowns of the plants above the waterline while the surface blends seamlessly into adjacent gravel pathways.
Available by the bag or by the cubic yard at stone yards, gravel is graded by the size of its rock particles and whether it contains “fines,” or stone dust that helps create a solid base when tamped down. Washed gravel and pea gravel are both fines free and better choices for areas, like planting beds, where compaction would be a problem.
But just because gravel is practical and reasonably priced doesn’t mean you can’t have fun adding other durable materials to permeable surfaces. Stone yards and landscape material suppliers stock crushed, recycled concrete or brick as gravel alternatives, as well as crushed rock sorted by color. Local recycler Bedrock Industries ) is a source for tumbled recycled glass, and an online search will turn up locally sourced crushed oyster shells, river rock — even coffee beans or hazelnut shells for a very Pacific Northwest vibe.
Strategically using gravel throughout the landscape to lay permeable pathways, mulch sensitive plants and create visual continuity makes sense environmentally and economically, which helps offset the cost of replacing a sewer line.