The UC Davis Arboretum has opened a new educational resource for Central Valley gardeners—the Arboretum Terrace home demonstration garden. Located in downtown Davis, California, the garden was designed by David Yakish of Gardenmakers and built by arboretum and UC Davis grounds staff, with funding from the campus administration and private donors. The garden is designed in a symmetrical, Mediterranean style using large pottery, lavenders, and cypress as focal points surrounding a central patio accented with more than forty planted containers. Attractive iron fencing protects the garden while providing support for a vine collection to demonstrate the best vines to use in Valley landscapes.
The garden features the “Arboretum All-Stars”—plants that we know to be reliable and easy to grow in the Valley—as well as some newer introductions that we wish to promote and make available for the more advanced gardener. The emphasis is on plants adapted to local conditions, including a good selection of Mediterranean and California native plants, as well as plants that attract birds, butterflies, and beneficial insects. The goal of the garden is to show that gardeners who choose regionally appropriate plants adapted to Central Valley conditions can have a beautiful garden with less work and help promote a distinctive regional style.
Geographics, an exhibit design firm, worked with arboretum education staff to develop interpretive materials for the garden. Attractive educational signage, plant labels, and flip books of plant profiles enrich the visitor’s experience. Take-home brochures help visitors apply what they have learned to their home gardens. A kiosk with changeable signs highlights upcoming arboretum events, and a map of the arboretum and samples of plants in bloom encourage people to move beyond the Terrace to explore the arboretum collections, only a short distance away.
What’s Different About Gardening in California’s Central Valley?
California’s Central Valley shares the mediterranean-type climate with coastal areas of northern the state, but conditions in the Central Valley are more extreme than along the coast. Summer temperatures over 100° F are common here in July and August, with extremely low humidity and an unrelenting sun. Unpredictable and intense north winds, caused by invections of hot air, not only fray the nerves and irritate our allergies but also turn soft, green growth crisp and brown. Winter frost is predictable, and, in some years, arctic air incursions bring temperatures as low as 14° F. Many areas in the Valley have clay soils, making it difficult to manage plants that require fast drainage. In addition, well water may contain minerals that cause soils to become alkaline and make iron and zinc unavailable. High levels of boron in some wells are damaging to ornamental plantings and deadly to particularly sensitive plants. Needless to say, some plants that grow well in milder-climate areas of the state, irrigated with pristine Sierran snowmelt, do not thrive under these harsher conditions.
People who come to the Central Valley and try to reproduce the kinds of gardens they have known from other places may find they are fighting a losing battle. Showy, tender plants with large leaves often require lots of water, soil amendments, fertilizers and pesticides, and frequent attention to do well here. Special protection from wind and sun may be necessary as well.
Mediterranean Garden Style
The Arboretum Terrace incorporates time-honored techniques used in traditional gardens in mediterranean-climate areas to reduce water use and create a cool retreat. A concrete patio and decomposed granite paths encourage outdoor living and reduce the irrigated garden area. Shade structures, such as umbrellas and an arbor, provide comfort in summer heat and reduce heat absorption by the hard surfaces. Container gardens filled with long-flowering selections create an oasis of lush plants while keeping high water use plants to a restricted area.
Some Favorite Plants for Central Valley Gardens
The Arboretum Terrace displays some of the most dependable and colorful plants for creating year-round interest in Valley gardens. The backbone of the garden is provided by evergreens such as green and golden forms of Italian cypress (Cupressus sempervirens and C. sempervirens ‘Swane’s Gold’). Broad-leafed evergreens include large specimens of fruitless olives (Olea europea ‘Swan Hill’), the golden tea olive (Osmanthus fragrans), strawberry tree (Arbutus unedo), and California native shrubs such as toyon (Heteromeles arbutifolia) and San Diego sage (Salvia clevelandii). A screen planting along the back contains the rare but tough Chilean lily-of-the-valley tree (Crinodendron patagua), which is covered with tiny white bells in late spring. Deciduous trees provide shade in summer but offer flowers and color in spring and fall. The intense cerise pink flowers of Taiwan cherry (Prunus campanulata) thickly cover their branches in early spring, and the frilly white flowers of the fringe tree (Chionanthus retusus) are a delight in April. In summer, the tropical-looking pink flowers of X Chitalpa tashkentensis ‘Pink Dawn’ decorate the broad crown of this uncommon tree (a hybrid of Chilopsis and Catalpa); nearby is a pink crape myrtle (Lagerstroemia indica ‘Natchez’). The fall color and winter fruit of Washington thorn (Crataegus phaenopyrum) provide late season interest.
Plants in shady areas beneath the olives include coral berry (Symphoricarpos orbiculatus), with beautiful purple-pink fruit in winter, and early hellebores (Helleborus orientalis), as well as a broad variety of spring-blooming native coral bells, including such cultivars as Heuchera ‘Rosada’, ‘Old La Rochette’, ‘Santa Ana Cardinal’, and ‘Lillian’s Pink’. A geranium that has proved its mettle in shade and difficult soils is Geranium x cantabrigiense ‘Biokovo’. Teucrium fruticans ‘Azureum’ serves as a background plant and displays its deliciously blue flowers on silvery foliage in late winter.
Plants for Hummingbirds and Butterflies
The back half of the Terrace is devoted to a mix of Mediterranean and California natives that provide either nectar or pollen attractive to visiting hummingbirds, butterflies, and beneficial insects. While the heavy clay soil in this area has made it difficult to use some plants, we have found many that tolerate these conditions as long as they get careful and infrequent irrigation. Spanish lavender (Lavandula stoechas ‘Otto Quast’), with large purple “flags” atop each inflorescence, makes a powerful statement next to a rosemary hedge and Verbena lilacina ‘De la Mina’(featured in Pacific Horticulture, Winter 1998). Another area is punctuated by deer grass (Muhlenbergia rigens), whose flower stalks shoot upward like rocket trails, and surrounded with a skirt of Berberis aquifolium var. repens, the nearly everblooming Erigeron ‘Wayne Roderick’, silvery mats of Lessingia ‘Silver Carpet’, and the butterfly-magnet blooms of Origanum ‘Betty Rollins’. To provide food for the locally-native pipevine swallowtail butterfly, we have planted its larval food plant, the California pipevine (Aristolochia californica). This summer we will be checking to see if it is munched by the black and red, road warrior-like caterpillars. Ithuriel’s spear (Triteleia laxa ‘Koningen Fabiola’) has been planted nearby in the hope that we might observe the adult swallowtail sipping its nectar. The plant that attracts the greatest variety of visiting butterflies is ‘Autumn Joy’ sedum (Sedum ‘Herbstfreude’). Glaucous blue foliage and dome-shaped clusters of dark pink flowers are followed by coppery-maroon seed heads providing a long season of interest.
A hummingbird repast is served in all seasons and visitors to the garden who sit quietly near one of their favorite flowers may have a close encounter with them. Vine Hill manzanita (Arctostaphylos densiflora), California fuchsia (Epilobium canum ‘Everett’s Choice’), island snapdragon (Galvezia speciosa), and hummingbird sage (Salvia spathacea) are just a few of the native plants that attract hummingbirds in this area. Non-native plants popular with visiting hummers include coral fountain (Russelia equisetiformis), autumn sage (Salvia greggii ‘Scott’s Red’), Arbutus ‘Marina’ and, planted in a container to keep its spread under control, the long-blooming and heat-tolerant Alstroemeria ‘Regina’, a beautiful and long-lasting cut flower.
Every garden benefits from the graceful movement of ornamental grasses, sedges, and rushes, and ours is no exception. Deer grass (Muhlenbergia rigens) provides an exuberant pattern as a backdrop to foreground plantings as you enter the garden. Slender orange-tinted swirls of Carex testacea glow in the low light of the winter sun. Miscanthus sinensis ‘Gracillimus’ and Calamagrostis x acutiflora ‘Karl Foerster’ create vertical late-season drama that extends into the winter months. Small Festuca idahoensis ‘Siskyou Blue’ softens the path edge with its puffs of powder blue, while Juncus patens ‘Elk Blue’ offers a strong blue accent on a larger scale.
All in all, the Terrace promises to be both a lush retreat and a lively center for gatherings and educational activities. We invite you to visit and discover this gateway to the UC Davis Arboretum and learn how you too can make a more diverse and beautiful Valley garden.
Thanks to the generous donors who made this project possible: Mark and Marjorie Friedman, Lawrence and Nancy Shepard, the Elvenia J Slosson Endowment Fund, the Stanley Smith Horticultural Trust, the Friends of the Davis Arboretum, the UC Davis Grounds Division and Steve Scott of Steve’s Tree Service.