The Great Terrain Robbery - erosion prevention in gardening

Flower & Garden Magazine, July, 2000 by Keith Muraoka

The Great Terrain Robbery -- namely erosion -- is a by-product of too much rain falling in too short a time. And now is the perfect time to prevent your garden from slip-sliding away.

The Resource Conservation District notes that the effects of erosion can be both costly and hazardous. Besides causing the loss of extremely valuable top soil, erosion can lead to decreased property values, increased flood hazards and sedimentation of fish habitats to -- in extreme cases -- loss of lives.

Preventative erosion control measures can range from laying down plastic to planting soil-holding groundcovers. Most bare slopes can be planted now without supporting assistance, such as Jute netting. Jute netting acts as a shield to bare soil and is commonly recommended for use in combination with planting on extremely steep slopes. If your slope is in a landscaped area, a permanent, low-growing groundcover is your best choice.

Of course, you shouldn't forget about proper drainage. Drainage ditches to divert water flow from the top of slopes and hillsides will go a long way toward avoiding complete saturation of soil during the rainy part of the year. Ditches should be at least a foot wide on a 1-to-2 percent slope, and be located well away from the edge of a hillside. If rain gutters empty runoff onto an unsafe area, use plastic pipe to divert rainwater to a safe area. Hardware stores sell a variety of corrugated plastic pipe, which come in various size rolls.

Rolls of plastic spread over vulnerable slopes should be considered an emergency measure. This is probably the cheapest and quickest emergency measure to carry water down a slope rather than allowing it to saturate the soil. Other emergency measures may include straw, bark or wood chips and rough rock. Seeding with quick-germinating annual rye grass is another temporary measure of erosion control. There are companies who will "hydroseed" large hillsides, which involves spraying water slurry of seed, fertilizers, stabilizing glues, soil amendments and mulch.

For homeowners wishing long-term preventative measures, the solution lies in a combination of mulching and planting of landscape groundcovers and/or shrubs. Groundcovers may include African daisy (Osteospermum fruitcosum), trailing gazania or even large-leafed Algerian ivy. In extremely dry areas or where slopes are inaccessible to irrigation, varieties of native plants can be used. In California, this includes wild lilac (Ceanothus), California fuchsia or wild strawberry. Drought-tolerant shrubs range from manzanita, cotoneaster and rockrose to toyon, huckleberry and other varieties of ceanothus. Trees which are especially suited for erosion control include varieties of birch, cedar, alder, fir, pine and redwood.

Retaining walls are another preventative measure. If the wall that you are planning is to be no higher than four feet, a number of materials can be used. These range from the new, self-stacking precast concrete blocks to walls made of redwood, concrete or railroad ties. Reinforced rods should be used within concrete or at the end of railroad ties where they can be pinned together.

It should be remembered that erosion and subsequent landslides are among the most unpredictable soil problems. Consequently, there are no guarantees in their controls except to say that the hazard or risk can be reduced if conservation practices are properly applied.

Regular maintenance can be a key to protecting your property against erosion, too. Something as simple as checking rain gutters, downspouts and drainpipes before winter rains hit can be vital in preventing `The Great Terrain Robbery.'

Erosion Controlling Plants

Plant's Name                                               Zone

GROUNDCOVERS AND PERENNIALS

ajuga (Ajuga reptans)                                       2-10
bearberry (Arctostaphylos uva-ursi)                         2-8
wormwood (Artemisia `Powis Castle')                         4-10
dwarf coyote brush (Baccharis pilularis)                    7-9
creeping coprosma (Coprosma x kirkii)                       8-9
bearberry cotoneaster (Cotoneaster dammeri)                 5-8
wintercreeper (Euonymus fortunei)                           4-9
forsythia (Forsythia x intermedia `Arnold Dwarf')           5-8
broom (Genista pilosa `Vancouver Gold')                     6-8
English ivy (Hedera helix)                                  5-9
daylily (Hemerocallis hybrids)                              3-9
creeping St. Johnswort (Hypericum calycinum)                5-8
creeping juniper (Juniperus horizontalis)                   3-9
trailing lantana (Lantana montevidensis)                    8-10
creeping lilyturf (Liriope spicata)                         6-10
mondo grass (Ophiopogon japonicus)                          7-10
Japanese spurge (Pachysandra terminalis)                    3-8
memorial rose (Rosa wichuraiana)                            5-10
star jasmine (Trachelospermum jasminoides)                  8-10
periwinkle (Vinca minor)                                    5-9
yellowroot (Xanthorhiza simplicissima)                      3-9
yucca (Yucca filamentosa, Y  whipplei)                      5-10

ORNAMENTAL GRASSES

American beach grass (Ammophila brevilgulata)               3-9
sedges (Carex spp.)                                         5-9
European dune grass (Elymus arenarius)                      3-9
blue wild rye (Elymus glaucus)                              3-9
eulalia grass (Miscanthus sinensis)                         5-10
fountain grass (Pennisetum setaceum)                        7-10
ribbon grass (Phalaris arundinacea)                         4-9

SHRUBS

Japanese barberry (Berberis thunbergii)                     5-8
Yankee Point ceanothus (Ceanothus griseus horizontalis)     7-10
sageleaf rockrose (Cistus salviifolius)                     7-10
Tartarian dogwood (Cornus alba)                             2-8
pride of Madeira (Echium fastuosum)                         9-10
Cornish heath (Erica vagans)                                5-9
California buckwheat (Eriogonum fasciculatum)               8-10
weeping forsythia (Forsythia suspensa)                      5-8
Oregon grape (Mahonia aquifolium)                           5-8
California bayberry (Myrica californica)                    7-10
Eastern ninebark (Physocarpus opulifolius)                  2-8
fragrant sumac (Rhus aromatica)                             4-8
Matilija poppy (Romneya coulteri)                           6-10
rosemary (Rosmarinus officinalis)                           7-9
Indian currant (Symphoricarpos orbiculatus)                 3-8
lowbush blueberry (Vacinium angustifolium)                  2-7
highbush blueberry (Vaccinium corymbosum)                   3-7
arrowwood (Viburnum dentatum)                               3-9