With California facing a historic water shortage, the Nichi Bei Weekly asked award-winning landscape architect Takeo Uesugi and his son, California State Polytechnic University, Pomona landscape architect professor Keiji Uesugi, how one can make their Japanese garden drought-resistant. Here is their reply via e-mail.

Nichi Bei Weekly: Given the drought facing California, what type of Japanese plants are considered drought-resistant?

Uesugi: Japanese garden design includes principles to draw upon regional climatic considerations for inspiration and plant selection. In Japan, it is common to see plants in gardens that are adapted to the temperate climate of East Asia where annual rainfall is much higher than California. Even in California, we have a variety of environmental conditions that influence plant selection. There are several aspects of Japanese garden planting that should be considered for drought situations: pH level, sun orientation, water quality, etc. For instance, azalea, camellia, maple, etc. prefer soils with pH levels under 7 (acidity), many plants in the Japanese garden prefer half-sun and half-shade conditions, and California water is higher in alkaline level that affects the growth pattern of Japanese garden plants. In addition, camphor trees or crape myrtles that work well inland may not be appropriate along the coast where sea spray can affect them. Japanese black pine is stronger than Japanese red pine due to the dryness of California climates.

Nichi Bei Weekly: For those who currently have Japanese gardens, in what ways can they conserve water, without sacrificing their gardens?

Uesugi: The previous points of pH, sun, and water quality should be considered for drought conditions as these three elements are related in terms of drought control. Composting, mulching, overhead tree planting, use of natural rain water, etc. could help the plants grow under drought conditions. 

If their garden is about 20 to 30 years old, it is a good time to consider replacing shrubs or small trees that have become too woody or are close to their maximum life expectancy. In this case, looking to replace them with low to medium water-use plants is recommended. 

If there are certain plants that are high water-use they want to continue having in the garden, consider planting them on the north side of buildings where shade is dominant, or consider companion planting with a shade tree that can protect the understory. This can help reduce plant stress and the need to excessively water.

Also, it may be a good idea to re-evaluate the layout of the garden and consider decreasing the size of planting areas. This way you can keep plant types you like in your garden while cutting down the square footage of space that needs to be irrigated. Replace the removed planting areas with other garden elements such as rock features and gravel in the character of a dry stream (karesansui).

Nichi Bei Weekly: When is the  best time of the day to water Japanese gardens, in terms of water conservation?

Uesugi: The best time to water is in the early morning. The watering will help the plants throughout the day, especially if it is hot, and less water is lost to evaporation. Evening water is fine, but try to avoid watering the leaves as mold and mildew could become a problem.

Nichi Bei Weekly: Are there typically any drought-resistant plants used in a Japanese garden?

Uesugi: As mentioned in the first response, the types of plants used in a Japanese garden can change based on environmental and climatic factors influencing the garden. Historically, Japanese gardens built outside of Japan tried to imitate the physical look and character of those found in Japan by using plants native to East Asia despite differing climates. Recently, Japanese garden design trends have matured and have resulted in increased use of native and drought-tolerant plants in regions where rainfall is scarce. 

Nichi Bei Weekly: What kind of drought-resistant plants can serve as good substitutes in a Japanese garden?

Uesugi: There are a variety of trees, shrubs, and ground cover that are low to medium water-use that can work in a Japanese garden in the California climate. The following is a small list of plants compatible in a Japanese garden that can work with low to medium watering:

Japanese black pine (Pinus thunbergii)

Juniper (Juniperus procumbnes ‘nana’)

Camphor tree (Cinnamomum camphora)

Strawberry tree (Arbutus unedo)

Evergreen pear (Pyrus kawakamii)

Crape myrtle (Lagerstroemia indica)

Olive tree non-fruiting (Olea europaea)

Chinese elm (Ulmus parvifolia)

Giant timber bamboo (Bambusa oldhamii)

Heavenly bamboo (Nandina domestica)

Coyote brush (Baccharis pilularis)

Ceanothus (Ceanothus ‘concha’)

Pomegranate (Punica granatum)

Indian hathorn (Rhaphiolepis indica)

Sage

Shiny xylosma (Xylosma senticosa)

Pittosporum tobira (Mock Orange)

Pyracantha

Cotoneaster

Creeping thyme

Nichi Bei Weekly: If one has a koi pond, or pond of any kind, in what ways can the owner conserve water?

Uesugi: Evaporation resulting from daytime heat and light exposure increases the need for water to be refilled in water features. If possible, provide shade for the pond with shade trees or a shade structure such as an arbor or temporary covers such as tents and canopies.

Takeo Uesugi, Ph.D., FASLA (Fellow of the American Society of Landscape Architects), is a principal of TUA Inc. and professor emeritus of Cal Poly Pomona University. With more than 40 years of professional and academic experience, his work includes the award-winning James Irvine Garden at the Japanese American Cultural and Community Center in Los Angeles, Japanese Friendship Garden San Diego, and Huntington Library Japanese Garden in San Marino. He received the Order of the Sacred Treasure from the Japanese government in 2010 for his lifetime of work of nurturing ties between the U.S. and Japan through landscape architecture.

Keiji Uesugi, ASLA (American Society of Landscape Architects), is a senior associate and landscape architect at TUA Inc. He has more than 13 years experience in cultural landscapes with an emphasis on Japanese gardens, urban design and revitalization, park and open space planning, community master planning, campus and residential design. His work with Japanese gardens spans the U.S., including the Huntington Library in Pasadena, Calif., and the Johnson County Community College in Kansas. Additionally, he is faculty at Cal Poly Pomona University where he instructs courses in landscape architecture and design, construction, graphics and Asian gardens.