Since it was first planted in 1980, the Ruth Risdon Storer Garden at the western end of the UC Davis Arboretum has been a beautiful place where home gardeners can learn about plants that thrive in California’s Central Valley “without a lot of water or a lot of fuss,” as superintendent Warren Roberts likes to say. The gradual evolution of plantings and themes in the garden over the last twenty-eight years has reflected our expanding ideas of what it means to have a beautiful garden with minimal environmental impact. A major renovation completed last year, with enhanced plantings, irrigation, pathways, benches, and signage, has brought the garden up to a new standard of design, visitor comfort, and educational value that builds on the garden’s well-established strengths.
The garden was started with a gift from Dr Ruth Risdon Storer, a devoted arboretum supporter, pioneering woman doctor in our region, and avid gardener. After enduring the extended drought of the late 1970s, the arboretum staff found it timely and appropriate to choose water conservation as the primary theme of this new demonstration garden. An article in the Spring 1985 issue of Pacific Horticulture described the garden’s first plantings, which featured a diverse mixture of heat- and drought-tolerant perennials, bulbs, and dwarf shrubs selected for year-round color, beauty, and low maintenance requirements.
In 1995, the garden was expanded with a new planting of roses and companion plants in memory of Ruth Storer’s gardening friend and neighbor Mary Miller. You may wonder what business roses would have in a garden featuring drought-tolerant, low maintenance plantings. Roses are actually surprisingly tough landscape plants, especially in California’s Central Valley, where low humidity discourages the growth of fungal diseases. The new roses were chosen for pest and disease resistance and short stature (to reduce maintenance requirements), as well as for the classic qualities of fragrance, color, and re-bloom. Following some of the latest ideas about applying integrated pest management principles to home garden settings, the roses were planted with flowering perennials chosen to attract beneficial insects that would provide natural pest control.
Over time, yearly plantings enriched the garden with a large diversity of new plants, but little thought was given to reviewing the design of the entire garden. By 2005, the garden was ready for a major overhaul. Without a unifying aesthetic vision, the plantings had become a bit of a hodge-podge, and several older plants were either being shaded out, declining with age, or taking over too much territory. The original manual irrigation system used grossly inefficient impact sprinklers to deliver water at high pressure over a large area. The sprinklers were labor-intensive to run, and they blasted some plants while leaving others to wilt in a rain shadow. The garden attracted visitors with its colorful plantings, but little information was available to them beyond plant labels.
With the help of dedicated volunteer gardeners and UC Davis student interns, as well as funding from the Elvenia J Slosson Endowment and the Stanley Smith Horticultural Trust, the arboretum took on a major renovation of the Storer Garden. The first and most essential task was the design and installation of a new automated irrigation system. Rather than choose between drip and overhead sprinklers, our staff decided to use the garden as a demonstration of a variety of efficient irrigation technologies. The irrigation system now includes zones with rotors (large pop-up sprinklers that spray a twenty- to thirty-foot radius), multi-stream rotors (smaller pop-up sprinklers that spray a ten- to twenty-foot radius), and drip tubing with embedded emitters. The rotors and multi-stream rotors are examples of overhead irrigation technologies that apply water at a slow rate so it has time to soak into the soil rather than run off into the gutter.
We used drip irrigation in some of the smaller beds, where we installed the tubing in parallel lines one foot apart on the soil surface to provide full and even coverage. By applying water directly to the soil, drip irrigation reduces water lost to evaporation and eliminates overspray onto pathways and the ensuing runoff. We are also experimenting with a “subsurface” drip system in a new portion of the garden, where the parallel drip lines are buried about a foot deep. These lines water our plants from below, and the extra depth of the tubing keeps it protected from most digging and planting activities.
With an irrigation plan in place, our next major challenge was to improve the planting design. We liked the open views across the garden but felt the garden needed more variation in plant height. We achieved that by adding small trees in the middle of the garden and carefully siting them to preserve and frame important views. In order to cool and unify the eclectic floral color palette, we included plants with blue and lavender flowers, which harmonize with pinks and purples, and complement yellows and oranges. With ornamental grasses and succulents to update the planting design, we provided contrasting textures and forms to the many small-leaved mounding plants that once dominated the garden. Repeating dramatic plants, like giant feather grass (Stipa gigantea), also helped to tie together the garden’s diverse plantings.
Many poorly performing plants, including some from the original 1980 plantings, were identified for removal or transplanting. Some were removed for being too successful: there were huge, old specimens of rosemary, azure bush germander (Teucrium fruticans ‘Azureum’), and mint bush sage (Salvia microphylla var. wislizenii) that had grown to eight or more feet wide and harbored thriving populations of cottontail rabbits and ground squirrels.
New plants selected for the garden included tried-and-true favorites to augment the design’s primary structure, plus several new introductions from nurseries in California and Arizona. All were required to be attractive, drought tolerant, and pest and disease resistant. They needed to thrive in our Central Valley conditions of blazing summers, strong winds, heavy soils, and alkaline irrigation water. Many unusual succulents and desert plants were donated by Mountain States Wholesale Nursery in Arizona for testing in the garden, among them a silver-leaved Texas mountain laurel (Sophora secundiflora ‘Silver Peso’) that rewards us every spring with grape-scented clusters of violet flowers. Some new succulents with ornamental promise include the powder blue pale-leaf yucca (Yucca pallida) and a regal-looking Mexican agave with dramatic pale green foliage (Agave polyacantha). We also emphasized California native plants to demonstrate how natives could be combined to great visual effect with other ornamental plants having similar growing requirements. Deer-grass (Muhlenbergia rigens), California fuchsia (Epilobium canum), and San Diego sage (Salvia clevelandii) now mingle beautifully with other drought-tolerant plants in the garden.
Renovating the Storer Garden gave our staff the opportunity to consider what messages we wanted visitors to take home from their experience in the garden. Water conservation had been the main theme of the garden since 1980; the idea of attracting beneficial insects to provide natural pest control was added in the mid-1990s. By 2005, the concept of sustainability had become important in gardening circles, and an integrated guide to environmentally friendly gardening practices (Bay-Friendly Landscape Guidelines) had been published. Rather than singling out individual resources to conserve, like water, this new holistic approach considered the impact of gardening practices on soil, water, and air quality, energy use, waste generation, wildlife habitat, and more. Many employed for years in the Storer Garden. We coined a new term “Valley-Wise gardening” to encompass the idea of gardening with an understanding of our local conditions and a desire to protect our regional environment.
Valley-Wise gardening practices are guided by three basic principles: conserving natural resources, protecting the environment from pollution and waste, and providing natural habitat and beauty. New interpretive signs in the garden highlight how thoughtful plant choices and a few simple gardening practices can be used to create and maintain a vibrantly beautiful and healthy garden with minimal environmental impact. Experienced gardeners will not be surprised that mulching is one of the key Valley-Wise gardening practices. A two- to three-inch layer of wood chip mulch, applied annually, provides a way to recycle green waste while conserving soil moisture and preventing weed growth. Wood chip and other organic mulches also improve soil structure and fertility by protecting the soil from compaction and erosion, and by adding humus as the mulch slowly decomposes.
With our governor’s declaration of emergency drought conditions this year, and water restrictions being imposed in many communities, Californians have had water conservation on their minds. How often and how much to water is one of our most common visitor questions, so we have devoted one of our new interpretive signs to basic irrigation principles. Installing efficient irrigation systems is an important step toward reducing water use. An equally important step is managing the irrigation system intelligently, so that water is only applied when it is needed. We recommend deep, infrequent irrigation to encourage plant roots to grow down and search a larger volume of soil for moisture. By deep watering (to a depth of about eighteen inches) every two weeks in the Storer Garden, we keep our warm season plants moist enough to flower through the summer, but avoid over-irrigating our more moisture-sensitive California native and desert species that prefer to dry out between waterings. By using an evapotranspiration-based irrigation controller tied to a weather station, irrigation run times are automatically extended during the hot summer months and reduced in the spring and the fall.
Thoughtful plant choices are the foundation of a Valley-Wise garden; with a legacy of over seventy years of documented plant collecting and testing, the UC Davis Arboretum staff brings considerable expertise to this topic. (“If we can’t kill it, neither can you!”) Growing poorly-adapted plants, like cool-season turfgrasses, in California’s Central Valley requires significant inputs of water, fertilizers, and pesticides that deplete our natural resources and can cause pollution downstream. Plants that are well adapted to Central Valley growing conditions, like those growing in the Storer Garden, must thrive on a modest irrigation allowance without the need for fertilizers and pesticides. Many beautiful plants native to California, other mediterranean-climate regions, and desert regions are adapted to hot, dry summers and are naturally pest and disease resistant. Growing California native plants also fosters a sense of place in a garden and helps define a distinctive regional style.
Although the Storer Garden plantings were not designed with habitat gardening in mind, the diversity of the plantings now serves as home and feeding grounds for a variety of creatures ranging from insects and birds to lizards, squirrels, rabbits, and the occasional gopher snake. The diversity of flowers that bloom in waves throughout the season provide a never-ending smorgasbord for pollinating insects and hummingbirds. Ladybird beetles and hoverflies, whose larvae are voracious eaters of aphid pests, feed on pollen and nectar from flowers in the daisy and buckwheat families. Other nectar-producing plants, like autumn sage (Salvia greggii), attract hummingbirds and butter-flies. Tall trees along the borders of the garden provide nesting and perches for a variety of birds; shrubs like mountain mahogany (Cercocarpus) provide them with seeds. A diverse Valley-Wise garden buzzes with life and will tend to have fewer pest problems because beneficial insects and birds will naturally keep pest populations in check.
Arboretum All-Stars in the Valley-Wise Garden
The horticulture staff at the UC Davis Arboretum has selected fifty Arboretum All-Star plants to make it easier for local gardeners to identify and obtain beautiful plants that thrive in Central Valley conditions (see Arboretum All-Stars: Great Plants for Central Valley Gardens in Pacific Horticulture, April 2007). Many of the All-Stars can be found growing in the Storer Garden, and several of them are identified with interpretive signs that show photos of the plant in bloom and describe growing tips. All-Star plants are available at Arboretum plant sales, which are periodically held in our new nursery facility just northeast of the Storer Garden. The following are some of our favorite All-Star plants for a Valley-Wise garden.
Bush germander (Teucrium fruticans) is a reliable and adaptable evergreen shrub from the Mediterranean region with fruity smelling silver foliage. It thrives in full sun or part shade where it can be grown as a loose three- to four-foot-tall hedge or clipped to a more formal shape. Not fussy about water, it does well with deep irrigation once or twice a month during the dry season. Bush germander was part of the original 1980 plantings in the Storer Garden, and many of them continue to add a beautiful silvery accent to the garden. Unlike rosemary, its Mediterranean cousin, it can be cut to the ground every few years in the cool season to stimulate fresh new growth. Pale blue flowers in the winter and early spring provide nectar for bee pollinators and can make a pleasant visual complement to deep blue flowers of ceanothus hybrids. [Sunset zones 4-24]
Giant feather grass (Stipa gigantea) is a dramatic cool-season grass from the Mediterranean region that thrives in full sun with deep irrigation every two weeks. A two-foot-tall tuft of evergreen foliage gives rise in the late spring to several wands of feathery grass flowers that reach six feet or taller. Long-needled awns on the individual grains reveal the giant feather grass’s relationship to our California native needlegrasses (Nassella spp.). Golden bracts persist after the seeds are shed and glow with morning or afternoon backlighting. The wands wave and dance in the breeze and complement the tawny tones of the dry grassy field on the west side of the garden. We deadhead the wands individually in the late summer or fall as they start to shatter and lose their ornamental value. Like other evergreen bunchgrasses, the giant feather grass can provide shelter for overwintering ladybird beetles. [Sunset zones 4-9, 14-24]
The pink ‘Gruss an Aachen’ floribunda rose (Rosa ‘Gruss an Aachen’) has performed beautifully in full sun in the Storer Garden since 1995 with deep watering every two weeks and no fertilizer or pesticide. Clusters of fragrant, soft pink flowers bloom in waves through the spring, summer, and fall. In most years, our dry climate is sufficient to prevent any fungal disease from affecting the clean foliage. Unlike many modern roses, ‘Gruss an Aachen’ has an attractive branching pattern that does not require hard winter pruning. Elegant burgundy stems are nearly thornless, and the foliage takes on lovely purple tints in the late fall and winter. Periodic deadheading and selective pruning in winter keep this rose looking beautiful nearly year-round. [USDA zones 4-9]
If You Should Like to Visit…
To get to the Ruth Risdon Storer Garden from I-80, take the UC Davis exit, and go north into central campus. Turn left at the first opportunity onto California Avenue, cross the creek, and turn left on LaRue Road. Continue on LaRue, then turn left on Garrod Drive. Follow Garrod until you see the garden on your left. For more information about the UC Davis Arboretum, call 530/752-4880 or visit arboretum.ucdavis.edu.