One way to minimize runoff from driveways is to cluster native plants with fibrous roots along the edge of paving. Native plants are well adapted to local conditions. Plants native to Mediterranean areas are adapted to dry summers and wet winters. They also do well at absorbing unexpected excesses of moisture. If the soil next to your driveway is compacted and difficult to turn, pocket planting and soil improvement can make what is often known as the "hellstrip" easier to cultivate.
Xeriscapic Oases Along the Driveway
Next to the heat-absorbing concrete or tarmac of a driveway, grass often develops bare spots and soil becomes compacted. Sometimes long-term neglect or lack of knowledge about low-water gardening can lead to totally bare ground next to the driveway. Yet what appears to be a wasteland can be transformed into a colorful low-water landscape, or xeriscape -- an oasis of tenacious, drought-resistant native plants that welcome driveway runoff as long as they are planted in soil that doesn't stay wet. By absorbing sudden gushers, these plants become what the California Water and Land Use Partnership calls a "low impact development" tool to manage stormwater. The plants' roots decrease soil erosion and minimize the amount of pollutants, such as fertilizers, that go into sewer systems.
Good Choices for Driveway Edging
To minimize irrigation of the landscape sending water coursing down driveways, select edging plants that are drought resistant. Plants native to an area are drought-resistant once their roots establish. The edging plants should be compact so they don't obscure sight lines for automobiles entering and exiting a property. Some good plant choices include, yarrow (Achillea millefolium californica), hardy in U.S. Department of Agriculture plant hardiness zones 3 through 9, scarlet larkspur (Delphinium cardinale), hardy in USDA zones 5 through 9 and sticky monkey flower (Diplacus aurantiacus), previously known as Mimulus aurantiacus and is hardy in USDA zones 9 through 11. All work well in Mediterranean climates, which are characterized by dry summers and wet winters.
Soil Amendment and Pocket Planting
Many xeriscapic plants do best in low-fertility soil. However, amendments such as compost and crushed rock may be necessary to aerate the soil and make it drain better so that plant roots don't drown during a downpour. Sometimes it is difficult to till the entire edge of a driveway due to compaction. In that case, it works well to use the pocket planting method in which you dig roomy holes and add loamy soil for individual plant sites.
Mulching to Reduce Runoff
Applying mulch to edging plants also reduces runoff and encourages root growth of native species by helping to retain moisture. For soils that are compacted and exposed to high heat, such as along driveways, it is best to use organic mulches -- including wood chips, compost, straw and pine needles -- that improve soil aeration, water absorption and fertility. Native plants don't need much fertilizer because they can thrive on the nutrients from the mulch. Earthworms aid amendment of the soil by decomposing the mulch and dragging it down into the ground.