Designing a Garden of Native Plants

Ceanothus in bloom and low-growing baccharis harmonize with the cool green hillsides of spring. Photographs by the author.

Ceanothus in bloom and low-growing baccharis harmonize with the cool green hillsides of spring. Photographs by the author.

Well designed native plant gardens are beautiful as well as responsive to the need to conserve water in areas with a growing population and low or fluctuating water supply.

Being all too susceptible to the beauty of plants, I must, as a designer of gardens, continuously guard against my own inclination to include far too many kinds of plants. Yet when Bill and Peggy Grier first approached me to design their garden, one of their goals was to include as great a diversity of native plants as possible. With some trepidation I prepared a preliminary design for the garden and managed, without bursting the compositional seams of the one-acre site, to include forty or fifty kinds of plants. They received the plan enthusiastically, but commented that they had hoped for twice that quantity. I promptly, and willingly, complied.

The Grier garden is set in a fairly steep, sloping bowl roughly 200 feet above the floor of Happy Valley in Lafayette, California. The house, patio, and pool are on a shelf midway up the northeast-facing slope, so there are slopes both above and below the house. This has both positive and negative implications for garden layout. Much of the garden is not comfortably accessible, and erosion, particularly in the beginning, was a serious consideration. But there are fine views of the ridge across the valley to the north and of Mt Diablo to the east, and neighboring houses are either below eye level on the downhill side or up and over the slope and thus out of view. The property is surrounded by natural scenery that forms a superb backdrop for the garden.

One corner of the property supports a small stand of mature valley oaks (Quercus lobata), and one widely spreading specimen rises from an indented deck on the east side of the house. Temperatures vary from 80° to 100° F. on a typical summer day to 25° to 30° F. on winter nights. With the exception of one vein of sandstone running down the steepest slope to the west and above the house, the garden is built upon dense clay. The bulk of the garden received no soil preparation other than a bit of mulch incorporated into each hole at planting. Exceptions to this are the rock gardens and the shade gardens. The rock gardens have had liberal amounts of coarse sand, gravel, and composted fir bark mulch thoroughly mixed into the native clay and are topped with several inches of gravel. In the shade gardens large quantities of composted fir bark and some coarse sand and peat moss were blended into the clay.

Warm tones of pink-flowered erigeron and pink- and yellow-flowered buckwheats blend with the brown hills of summer

Warm tones of pink-flowered erigeron and pink- and yellow-flowered buckwheats blend with the brown hills of summer

Having lived in various parts of the United States and Europe, the Griers had come to appreciate the special qualities of the California landscape. We were brought together in 1979 as a result of our shared passion for these special qualities and our interest in alternatives to the exotic and unimaginative plantings often seen in newer gardens here. We agreed on a naturalistic design that would harmonize with the surroundings and, with the drought of 1977–78 still fresh in everyone’s minds, the use of plants that would conserve water. The Griers’ desire to use only plants native to California — and lots of them — was a challenge I embraced with enthusiasm.

To accommodate the diversity the Griers wanted it was necessary to capitalize on or create a wide range of microclimates and exposures. Considerations included sun, wind, pockets of extreme temperatures, soil types, and natural or created soil moisture levels. At the same time, we sought to enhance, frame, and create views, provide warm and cool spots for outdoor living, relate the garden to the architecture and floor plan of the house, and deal successfully with the many other problems and needs commonly met in residential landscape design. To resolve all these, while incorporating a wide array of plants in a design that was more than a plant collection, was the heart of the challenge.

In retrospect I see myself as creator of only the framework and major features of the garden, for the Griers judiciously add to it each fall. Aside from using the garden as an outdoor laboratory for students of landscape design, my only involvement now is to offer occasional gentle advice on maintenance and new plantings. My goal is simply to keep the framework intact and to forestall overplanting, which could obscure significant features of the design. My input is almost a formality at this point, for the Griers themselves have become knowledgeable about native plants and their use in garden design. Peggy Grier co-chairs the propagation and plant sale for the San Francisco Bay Area Chapter of the California Native Plant Society.

The Garden

Repetition of three genera of plants — Ceanothus, Arctostaphylos, and Baccharis — serves as a common thread that brings order to the diversity of plants and helps to reconcile the complexity of the garden with the geometric simplicity of the paving, patio, pool, and house. Fortunately, two of these genera, Ceanothus and Arctostaphylos, offer both a wide choice of species and, if properly chosen and placed, a continuum of visual characteristics. The third theme plant, dwarf baccharis, helps to control erosion, one of the main problems of the site. Although it is somewhat overused these days, its lime-green color blends with the grassy hillsides in early spring, and its rapid, dense growth and tolerance of many soils make it invaluable for this site.

The house, its rough-sawn cedar siding aged to a silvery gray, is approached by a drive flanked on both sides with ceanothus, mahonia, and flowering currant. From the drive a long, straight path running parallel to the house leads toward the entry. This path runs through the level, east-facing rock garden in front, which is surrounded by a collection of manzanitas. A big-leaf maple (Acer macrophyllum) anchors the corner furthest from the house at the edge of the slope. With the house it frames a view of the ridge across the valley, and with the oak across the street it frames a view of Mt Diablo. A small gravel path lined with Pacific Coast irises leads to a bench at the base of the maple where one can rest in the shade and view the front garden with the house as a backdrop.

Colorful rock garden along path to the house is surrounded by manzanitas

Colorful rock garden along path to the house is surrounded by manzanitas

Manzanitas in the front rock garden include Arctostaphylos manzanita ‘Dr Hurd’, A. densiflora ‘Howard McMinn’, A. hookeri ‘Wayside’, A. hookeri ‘Monterey Carpet’, A. uva-ursi ‘Pt Reyes’, A. ‘Emerald Carpet’, and an unidentified A. edmundsii hybrid. The rock garden is forever changing and at various times has included such plants as Armeria maritima var. californica, Phlox douglasii, Lewisia cotyledon, Oenothera deltoides var. howellii, the tiny Arctostaphylos uva-ursi from Convict Lake, Erigeron glaucus, Sedum spathulifolium ‘Cape Blanco’, Ceanothus hearstiorum, Kalmia polifolia var. microphylla, Hypericum anagalloides, and Eriogonum umbellatum var. polyanthum. Across the walk and against the house are red-flowering currant (Ribes sanguineum), coast silktassel (Garrya elliptica), and evergreen huckleberry (Vaccinium ovatum). In the entry court is a cool, shaded garden beneath a trellis covered with our native clematis (Clematis ligusticifolia). Here in the humus-rich soil grow Western azalea (Rhododendron occidentale) and vine maple (Acer circinatum), while beneath them Trillium chloropetalum, Erythronium tuolumnense, and leopard lily (Lilium pardalinum) come up through a mixed ground cover of redwood sorrel (Oxalis oregano) and Vancouveria hexandra. Though most colorful in spring, the front garden retains splashes of color well into summer with orange lilies and yellow eriogonums. Finally, as fall approaches, the fluffy, silky seed clusters of the clematis reflect the morning sun as it rises further to the south. Proceeding around the northern side of the house one passes vine maple, Fort Bragg manzanita (Arctostaphylos nummularia), salal (Gaultheria shallon), and tree anemone (Carpenteria californica). All of these thrive in the cool north exposure, and the tree anemone graces the walk with its clusters of white, anemone-like flowers in early to mid-summer.

On the other side of the house is a deck that is almost a mirror image of the entry court but larger and faded to the same silvery gray as the house. A large and wide-spreading valley oak grows through the deck, and pots placed around the deck are filled with native wildflowers. Across the deck a view of the west-facing rear garden opens up. It is a level garden, backed by a steep slope, almost one hundred feet deep at its north end and narrowing to ten feet on the south. The northern half is dominated by pool and patio, while the southern half is a rock garden, similar to but larger than the one in front. The rear garden is surrounded by extensive slopes carpeted in Baccharis pilularis ‘Twin Peaks’. Flowing down these slopes are billowing masses of ceanothus, manzanita, buckwheat, sage, and toyon. The feature plants here are the dark green ceanothus, which are transformed into solid masses of purple or lavender-blue in late March and April. Though short-lived in this climate, Ceanothus ‘Julia Phelps’ is well worth occasional replacement as in spring it covers itself in a dense cloud of dusky purple-blue flower clusters. Similar and perhaps longer-lived here is C. ‘Dark Star’. The steadfast C. ‘Concha’ is my favorite, with deep, almost cobalt blue flowers. Here too is the waist-high and widespreading C. ‘Joyce Coulter’ with flowers the color of faded blue jeans, and milky-white-flowered C. thyrsiflorus ‘Snow Flurry’. Others are C. griseus ‘Santa Ana’, C. ‘Frosty Blue’, and the flat-growing C. hearstiorum in the rock garden. These are all set off in contrast with baccharis and the occasional gray-leaved buckwheat (Eriogonum arborescens) or Cleveland sage (Salvia clevelandii). A particularly striking effect is provided by the huge white flowers of matilija poppy (Romneya coulteri) as they raise their tall stems behind the ceanothus in June and July.

A color combination for which California in spring is famous, with lavender provided by ceanothus, sage, and woolly blue curls and orange by California poppy

A color combination for which California in spring is famous, with lavender provided by ceanothus, sage, and woolly blue curls and orange by California poppy

Plantings in the rear rock garden repeat those in the front rock garden for the most part. Due to the exposure, however, there are differences, and in the rear garden one finds blue-flowered Penstemon heterophyllus, silver-leaved Artemisia pycnocephala, the spreading mounds of Eriogonum latifolium var. rubescens, and red-flowered California fuchsia (Zauschneria californica). After the ceanothus have finished highlighting the cool tones of the spring hillsides, the pink and yellow of the buckwheats and the California fuchsia bring out the warm tones of summer. On the house side the rock garden is bordered by a long, straight walk that runs parallel to the house. The narrow beds between walk and house receive the full blast of the afternoon sun. Colored cinnamon and purple, the sinewy and twisted branches of Arctostaphylos densiflora ‘Sentinel’ have been trained flat here, creating fascinating patterns against the silvery wall of the house.

On the south side of the property the slope comes right down to the house, and the walk is sandwiched between the house wall and the retaining wall supporting the slope. A meandering gravel path with railroad tie steps leads up the slope and into the south garden. Beyond a tree-like specimen of Ceanothus ‘Ray Hartman’ an oak-lined ravine opens up to view. This grove, consisting entirely of Quercus lobata, sits between the house and the road bordering the far side of the property. An amusing but ultimately tragic event occurred in this ravine during construction of the garden. Before leaving for lunch one day I asked a worker to hand dig to the roots at the base of one of the mature oaks until he found the natural swelling of the burl. I suspected that soil had built up around the base of a few of these oaks during grading for the house and wanted to restore the original soil level. I returned to find the industrious worker waist deep in the hole he had dug. After three days of tractor work and reappraisal of the design for the area, it was necessary to construct a bridge over the spot which had not been a ravine in my original plan. The developer of the lots, it seems, had simply filled in the ravine around the oaks with as much as five feet of soil. We attempted to reconstruct the original grade, but since filling had occurred four or five years earlier little remained to guide us in the work. A significant portion of the root systems undoubtedly had already suffocated, and the tops of the trees were heavily pruned to compensate for the root loss. Despite our best efforts, the largest oak, the roots of which had been buried by the road, and a magnificent old bay tree were both lost. Some of the remaining oaks are slowly declining as well. Each fall seedlings are selected and allowed to remain, and acorns are planted in crucial positions to allow for the ultimate replacement of the grove.

Back on the gravel path, a short walk leads to the bridge over the ravine and into the midst of the oak grove. All of this southeast corner receives little if any irrigation. The steep-sided and shaded ravine, which is exceptionally wet during winter, affords a situation that can accommodate special plants. The larger shrubs here are Ribes sanguineum var. glutinosum with rose red, pink, or white flowers, scarlet-flowered R. speciosum, and yellow-flowered R. aureum. The smaller shrubs here include a beautiful purple-flowered native solanum of unknown species and the rare Arctostaphylos franciscana. Perennials include the California gold fern (Pityrogramma triangularis) and California maidenhair fern (Adiantum jordanii), both tolerant of summer drought (indeed, the maidenhair requires it ), columbine (Aquilegia formosa), and blue-eyed grass (Sisyrinchium bellum). Of particular interest is the California Dutchman’s pipevine (Aristolochia californica) climbing up the rails of the bridge. The Griers enjoy the unusual and beautiful pipevine swallowtail butterfly, the caterpillar of which feeds on the Dutchman’s pipevine. The price of lost leaves is insignificant when weighed against the pleasure of watching the butterflies hover around the bridge and ravine.

On the other side of the ravine the path leads out onto the dry and sun-drenched upper corner of the property. On a warm summer evening the smell of sage and the sweet, pineapple-like fragrance of woolly blue curls are strong here. This area has been dubbed the sage corner. It is also the area where annual wildflowers such as linanthus, poppies, clarkias, lupines, and baby blue eyes are naturalized. This dry corner contains some of California’s most beautiful plants. The magenta pea-like flowers of Cercis occidentalis, the yellow cups of Fremontodendron ‘California Glory’ and Dendromecon harfordii, the purple spikes of Trichostema lanatum, the rose-colored, snapdragon-like flowers of Galvezia speciosa, and the lavender blues of several sages occupy this warm spot. Even the intensely deep rose-pink flower clusters of Lathyrus splendens once shared the wire fence with wild grapes.

Mounding ground cover of baccharis on bank suggests the rounded forms of hills beyond

Mounding ground cover of baccharis on bank suggests the rounded forms of hills beyond

The sages that grow here include the white-leaved Salvia apiana, silvery-leaved S. leucophylla, showy lavender-blue-flowered S. clevelandii and its hybrid S. ‘Allen Chickering’, flat-growing S. sonomensis and its bushy hybrid S. sonomensis ‘Dara’s Choice’ with electric, almost true blue flowers. Though quite dormant by August and September, the pleasures of this area early in the year are priceless.

Leaving the garden, one looks across the ravine and up the sweeping slope of baccharis into a half-circular grove of mountain mahogany. To the west the silky seed tails of the mountain mahogany catch the light of the setting sun and reflect it so intensely that the dwarf trees appear to be laden with silvery white blossoms.

This is a garden rich in compositional diversity, and I believe the diversity itself is a source of much pleasure. And, after all, is not one of the best indicators of a garden’s success the pleasure it provides those who use it?