Mountain Gardener: Rainy season opens door for erosion-control plants
by Jan Nelson
Sep 13, 2012 | 1784 views | 0 0 comments | 7 7 recommendations | email to a friend | print
Pretty Practical: Cistus purpureus, aka rockrose, is a beautiful, deer-resistant plant that is just right for erosion control.
Pretty Practical: Cistus purpureus, aka rockrose, is a beautiful, deer-resistant plant that is just right for erosion control.

You know fall is just around the corner when you hear thunder.

It seems as if summer just started, but plants including lilac, rhododendron and dogwood have already set flower buds for next year.

We don't know exactly what winter will bring. Will we receive lots of rain or a meager amount?

The latest from the Climate Prediction Center for the San Francisco Bay Area 2012-13 rainy season is that a mild El Niño event may be setting up. The evidence is that there has been a weakening of the positive sea surface temperature in the Pacific Ocean.

El Niño has been known to carry plenty of rain into our area. We are still in a wait-and-watch mode.

Long-range outlooks for the fall from the Climate Prediction Center run from equal chances for more- or less-than-normal rainfall to a slight tendency toward below-average totals.

For the November-to-January period, the probabilities start to shift, and a slight chance of above-normal rainfall creeps up along the coast from the south.

By the time we get to the December-to-February period, the outlook is for greater than normal precipitation for the whole state, with chances of significantly heavier than usual precipitation for the Bay Area.

Remember, this is not a forecast but an outlook for the probabilities of above- or below-normal precipitation.

If we do get heavy rains in January or February, you should be prepared. Do you have a slope that might have an erosion problem? Now is the time to start planning and planting. The nights are cooler, the days shorter and the soil still warm — everything a new plant needs to get a good start.

When choosing plants to cover a bank for erosion control, assess the conditions of the area you want to plant. Is it in the sun or the shade? Is it a naturally moist area or dry? Do you intend to water it or go with our natural cycle of wet in the winter and dry in the summer?

Matching the plant to the site conditions will ensure success.

When designing a plant layout, I consider whether I want a sweep of the same plant or a tapestry effect with a variety of plants.

Using more than one type of plant allows me to work with contrasting foliage, adding pattern to my composition. To create a stunning combination, choose five or six styles and repeat them in small drifts to carry the eye through the composition. Add grasses for linear texture.

If the area you need to stabilize is large and mostly shaded, consider evergreen currant (Ribes viburnifolium), which grows 3 to 6 feet tall and spreads to 12 feet wide. It needs no irrigation when established.

Another plant that tolerates shade and needs no irrigation after three years is creeping mahonia (Mahonia repens). It grows 1 foot tall by 3 feet wide, spreading by underground stems that stabilize the soil.

Common snowberry or creeping snowberry (Symphoricarpos varieties) can hold the soil on steep banks. These plants tolerate poor soil, lower light and general neglect.

Wild mock orange (Philadelphus lewisii) tolerates some aridity and partial shade. This beautiful, fountain-shaped, fragrant flowering shrub grows about 8 feet tall by 8 feet wide and is not fussy about soil.

A bank in the sun would welcome a different plant palette. Some of my favorite plants to control erosion in this situation include Ceanothus in all its forms. Groundcover types, such as Centennial, Anchor Bay and Maritimus, are not attractive to deer like the larger-leaved varieties.

Rockroses, such as Cistus purpureus, also provide large-scale cover for expansive sunny areas. Their dense, strong root systems help prevent soil erosion. Choose from white, pink or magenta flowers on plants varying from 1 to 5 feet high, depending on the variety. This Mediterranean native grows quickly, tolerates drought and is unappealing to deer.

Smaller plants for color that control erosion are lavender, California buckwheat, purple sage (Salvia leucophylla), California fuchsia, deer grass, needle grass, mimulus, yarrow, Pacific Coast iris, bush poppy, penstemon and artemisia.

These suggestions are just a few of the plants that control erosion. Every area is different and every situation unique. Email me if you would like help with your area.

Jan Nelson, a landscape designer and California certified nursery professional, will answer questions about gardening in the Santa Cruz Mountains. Email her at, or visit to view past columns and pictures.

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