By Gary Jones

It seems all but certain that San Diego will have heavy El Niño rains this winter. Whether the extra precipitation is beneficial or harmful depends on actions you take in your garden, yard or outdoor space. Simple landscaping steps can be the difference between helpful rainfall and water damage.

Winter rains present a wonderful opportunity to establish new plantings, especially water-wise plants. These Mediterranean-climate plants are naturally suited to wet winters followed by a long, hot and dry period. If planted now, they’ll establish strong root systems to sustain them from late spring through fall.

What you don’t want to do is extensive planting on hillsides. Disturbing the soil with a major planting project will create conditions for serious erosion from heavy precipitation. Before El Niño hits, resist the temptation to remove plants, weeds or grasses. The roots that remain in the ground will hold the hill during heavy rains.

It’s OK to plant a few trees or shrubs on a hillside. Just disturb the soil as little as possible around the planting area. Create a “well” with extra soil to hold water at the base of the plant. Check it periodically during the winter as it may wash away.

As you consider what to plant, keep in mind that a mixture of plants is the best choice for several reasons. Various types of root systems are better suited to hold hills and slopes. And a broad selection of plants will attract different types of beneficial insects and provide pollen and nectar for a number of birds, bees and butterflies.

If you have a newly-graded slope or one with little vegetation, consider planting it right away with several types of groundcovers from six-packs, grouped in drifts. Plants in packs have larger root systems and will establish much faster than plants from groundcover flats. You’ll also want to overlay the entire hill or slope with jute netting to help hold the plants and soil in place.

For slight slopes, a 2-inch layer of gravel, mulch or rock can slow down the movement of water, encouraging it to soak in rather than run off. Don’t do this on steep slopes, though.

Scattering seeds of California wildflowers over open areas in yards and on slopes will help hold soil and will provide lots of spring and early summer color. Do this just before a rainstorm and gently rake the surface of the soil. California native plants are especially sought after by native bees and other pollinators.

In addition to planting the proper groundcover on slopes and hillsides, here is a summary of helpful tips to protect your property during El Niño storms:

• Certain plants can help control or cause erosion – Plants that have fibrous roots, such as bearded irises, California wild lilac and manzanitas, are ideal to plant for erosion control. Use this season to sprinkle California wildflower seeds or rye grass over slopes and hillsides, as they’ll quickly establish and can create root structures that aid in soil retention. Include a variety of plants, as their various root systems work together to prevent hills from erosion. However, top-heavy varietals, such as ice plants, can become water-logged and uproot on hillsides during heavy rains, causing more damage and runoff. Save those plants for flat areas.
• New landscaping may need additional care during storms – Avoid replanting entire hillsides or slopes during the rainy season. If you must, hemp nets can help keep seeds and new grasses in place on hillsides during heavy rain. They will naturally decompose with time, leaving behind healthy, established vegetation. Newly created slopes have very unstable soil and will need to be covered with plastic from top to bottom to prevent rain from washing everything away.
• Pay attention to your larger trees – Heavy rains and winds can cause dead branches to fall and possibly cause damage to your property. Make sure trees around your house and other structures are pruned prior to storms.
• Rocks can help prevent runoff – Decorative stones or rocks can help hold soil in place on slight hillsides and slopes by stopping swiftly running pathways of rainwater. However, rocks are not safe for steep hillsides.
• Have your rain barrels ready – With all the rain expected this year, make sure to capture it with rain barrels and utilize the water you collect.

—Gary Jones is Chief Horticulturist at Armstrong Garden Centers, which has locations on Friars Road and Morena Boulevard. Email your drought and gardening questions to [email protected].