Landscape Architect Articles

Extreme Makeover08-01-04 | News

Extreme Makeover

Developing and Installing a Sustainable Hardscape

By Alrie Middlebrook

This chaparral planting is Idaho fescue, Siskyou blue and Cleveland sage. California rush is in the pot with Juncus acutus and Juncus patens to the side. Cleveland sage is in the back, left, and the trees are redwoods. The pervious paving is Arizona limestone on decomposed granite.

Life is created by the combination of soil, sun and rainfall. Soil is the product of the decomposition of the earth’s mantel?EUR??,,????'???rich in minerals, and highly varied worldwide. All life on land evolves from this mixture. Some regard dirt as unpleasant and, well… “dirty.” By and large, landscape professionals view dirt as something to be altered, amended, covered up, graded, abraded, weeded, removed, compacted, aerated, drained or otherwise manipulated. In taking action to alter dirt, our assumption is that we are improving it and thereby improving the quality of life on dirt (the earth).

Home and garden improvement programs on television are popular. Instead of a typical garden make-over format, this article demonstrates how we can create sustainable gardens, appropriate to quality living in the 21st century. What kind of choices will be made about dirt, drainage, rainfall, the choice and use of hardscape materials, equipment, landscape materials, plants and managing a sustainable garden? Let’s find out.

The Project

This Spanish style stucco home was built in the 1920s in San Jose, CA. The footprint is original. The house has been maintained but not altered, still retaining its original character. The concrete driveway is original, as well.

The lot is flat and the soil is excellent. Santa Clara Valley is an alluvial flood plain located between two rivers; the Guadalupe and the Coyote. This soil ranks among the top agricultural soils in the world.

My client dreamed of a garden full of outdoor niches–sustainable in principle, and historically linked to her home and neighborhood. She collected garden pieces and hoped the new garden would be an ideal setting for her eclectic collection. She wanted a special place for her child and a retreat for herself, as well.

Before I begin the design process, I remember my specific goals for sustainability. They are as follows:

Alter soil as little as possible, adding no amendments, fertilizers, or herbicides.
Avoid trips to the landfill, reusing existing materials on site.
Avoid use of power equipment that runs on two-cycle engines, as this fuel is among the most polluting in America.
Reduce amount of water required to maintain the garden.
Divert rainfall to designed features in the garden and other landscaped areas. We try to retain all rainfall in site, avoiding flow into the storm drains.
Allow rainfall to percolate all hardscape surfaces, and changing impervious surfaces to pervious.
Design garden elements that feature renewed, reused or recycled materials.
Select plants that are native to California and design with them by plant community, as they have naturally evolved together.

Step by Step Process

Break up the concrete with sledgehammers and digging bars. Old concrete has no rebar and is much easier to recycle. After 1980, code requirements forced the inclusion of rebar. The sustainable solution for concrete with rebar is to resurface it, rather than break it into pieces and re-lay it. There are many reputable concrete resurfacing companies with a variety of surface textures available.

Broken concrete, known as “urbanite” was installed with grey gravel as stepping stones in this Asian themed woodland garden. Some areas have soil or Corsican mint as ground cover between the stones. California wax myrtle is in the right front and back. Mid-ground is Siskyou blue, California rush and Idaho fescue. At the top left is China doll and Western azalea.

Turf areas were removed. The 18-inch to 24-inch broken concrete pieces (urbanite) are re-laid on a prepared bed which is compacted, watered, then compacted again and leveled. A series of patios, stepping paths and foundation stones for the container gardens utilize all the urbanite pieces. More urbanite to complete this project was donated from a landscape architect who planted a vegetable garden on a former concrete patio site.

Our intent with the design and construction of this series of urbanite patios was to alter the flow of rainfall as little as possible.

Before: The concrete hardscape surface had a soft, pebbly texture only 80 years of rainfall could have produced, and the turf areas required irrigation in order to be maintained.

The driveway was replaced with California Gold crushed gravel. It was installed on a bed of compacted base rock and is graded slightly higher at the edge near the house so that water drains away from the house. Only in flood-like conditions will water drain down into the street. When the site is relatively flat (less than five percent grade), it’s easy to retain most rainwater on site. Downspouts are tied into landscaped areas by attaching flexible perforated drain tubing to them. The tubing is at least 12 feet long, and is installed at a two percent grade, flowing to meadow areas away from the house. If the property has a steeper slope incorporate swales, rivulets and catchments into the design.

After: The old water guzzling lawns were removed and replaced with scaled down native grassland meadows, including Idaho fescue, annuals and perennial wildflowers, Pink clarkia is on the lower right and sticky monkey on the lower left.

A dry “creek bed” is placed in the middle of the backyard meadow to capture roof run-off and divert it to the fountain area. Just by luck, a winter storm arrived to help us correct puddling areas and further divert water into the creek area. Rainfall is always the best indicator for determining finished grade solutions. When in doubt about a low spot, with no rain in sight, turn on the hose for a while and see how the water moves through the garden.

We constructed a car park and a backyard ramada from Rocky Mountain Lodge-pole pine posts embedded in concrete and surrounded by gravel. Avoid soil coming in contact with wood. A welded rusted steel trellis by Sierra Mirage was placed on top of the structures. Native California grape vine and morning glories were planted for shade.

It is very important during preparation of the bed for the paved areas to put down a layer of decomposed granite before laying in the urbanite. This allows surface water to percolate directly into the soil.

Plant selections were based on three natural plant communities of California: grassland/meadow, riparian and chaparral. Plants from these distinct communities are grouped together. Chaparral plantings require mounds of fast draining soil be built and compacted. Plants are placed at the tops of these mounds. In planting chaparral plants in heavy clay, life expectancy is around two years. These same plants planted on compacted mounds (and not over watered) may live for up to 25 years. Had we substituted oak woodland plantings for chaparral, construction of the mounds may not have been necessary. However, the client preferred the colorful chaparral plants that grow on hot south and west facing slopes. This required a change in the grade. We recommend the mounds be 12 to 18 inches high.

Unwanted items including plants were recycled and the concrete was broken up with a sledgehammer and digging bars.

The meadow areas were seeded with Idaho fescue and a mixture of poppy, flax and clarkia seed. Individual four and one gallon perennials such as salvia, yarrow, erigeron daisy, and blue-eyed grass were also planted in the meadows. The meadow areas are irrigated with overhead spray.

Grass will not be the familiar green of the typical American lawn: Idaho fescue is a “grey-green,” more the authentic color of dry California. Should one prefer a greener grass, more water can be added?EUR??,,????'???but doing so may shorten the life of some native wildflowers. During the establishment period, weeding is necessary.

All Urban Sites are Disturbed

The micro-relationships in disturbed soils are ideal for invasive plant species to germinate. Eventually, with help from the weed patrol, native species will out-compete invasive plants, and soils will begin to re-establish the critical micro-relationships found in undisturbed sites. This will become evident when oak seedlings and other members of the oak woodland community begin to germinate, becoming visible on the ground.

Care of meadows depends on the tastes and sensibilities of the owner(s). We recommend weed whacking meadow areas two to three times per year. If a spring green color is desired, meadow grass will grow faster with increased water, however, this will also require more maintenance. I personally prefer the look of a natural meadow that uses less water, less work and has abundant pollinators and birds. Young children will have a field day rolling in the long grasses while adults can rest assured knowing there are no pesticides to worry about!

In constructing this garden, we chose solutions employing sustainable techniques and technologies. In many instances, these technologies are low-tech not high-tech. With each project we seek to understand and replicate the natural systems that are presently, or were, inherent at the site before development. Impervious surface areas can alter the water cycle and destroy the aquatic eco-systems. They also change the shape of stream channels, raising water temperatures and washing pollutants into aquatic environments. It’s important to recognize this and reduce or eliminate the use of impervious hardscapes. Use of pervious hardscaping allows rainfall to percolate directly into site soils, producing healthy, vigorous and abundant life while creating naturally beautiful gardens that mimic the exquisite natural landscapes of our planet.

The less we disturb the dirt, the more sustainable the garden will be. A natural garden is the one that thrives with very little help from humans. In planting, we replicate the plant communities that naturally occur in the area.