Planting Rooftops for Therapeutic Environments

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A deep-well interior courtyard with 360-degree viewing was designed into the Palomar Medical Center as a therapeutic garden to benefit patients, doctors, nurses, support staff, and visitors. Lush vegetation contrasts the stone and colored glass mulch to achieve biophilic effects day and night. This ground-level planting near the hospital entrance is an introduction to the eleven floors and three rooftops planted for health benefits at Palomar. Photo: Bruce Dvorak

Introduction: A Plant-dependent Species

Humans are a plant-dependent species. After sunlight, air, and water, perhaps no other element of nature is more beneficial to humans than plants! We use plants daily and directly for their consumption as food or drink (fruits, leaves, seeds, nuts, roots, flowers, oils, juices), to make shelter (wood, fiber), as useful artifacts (paper, clothes, etc.), medicine, to feed livestock, modify microclimates and to enjoy in beautiful gardens. Although we are a plant-dependent species, in modern cities, most of our working and living environments are deprived of a meaningful connection with plants and nature. 

The absence of nature in built environments is called “nature-deficit disorder (NDD)” (Louv 2011). Its ill effects are at work all around us. NDD can contribute to anxiety, attention deficient or hyperactivity disorder, the lack or delayed development of the full potential of human emotions, and at least 20 other ailments (“Ming” Kuo 2013). Any resolution to this condition lies in the intentional connecting of people with nature in cities in creative ways (Louv 2011). Although rooftop planting was introduced to modern architecture in the early 1900s (Jarger 2008), for one reason or another, it would take many decades for the idea of planting rooftops to reemerge as several decades of research have demonstrated the positive effects of planting rooftops (Jim 2017). With so much solid evidence in support of the therapeutic benefits of providing views of nature through windows (Ulrich 1984), including green roofs and rooftop gardens (Suppakittpaisarn, Jiang et al. 2017), it brings to question why so many building types lack a connection to nature, especially buildings where people spend many hours or years viewing out across rooftops.

For the greater part of the twentieth century, rooftops of office buildings, resorts, shopping centers, schools, and hospitals have been designed for utilitarian purposes. For more than three decades, this utility clutter roof, like many rooftops in public view, has not been realized for its potential collective benefits to people visiting or working here. Photo Bruce Dvorak

Fortunately, more than a few conscientious developers now consider the evidence and rewards of bringing nature into cities as non-negotiable. Health providers are re-thinking “how” plants and views of nature must become a normal part of their environments and with fabulous results! In this article, I cover a case study of a premier example of how plants have been featured as a focal point in the redevelopment of a medical center in southern California.

Palomar Medical Center

Empathy implies a complex intertwining of human emotions encompassing compassion, consideration, and understanding. Empathy is the lone “word” and theme the interdisciplinary project team conceived as the design concept for the entire property and buildings at the Palomar Medical Center in Escondido, California (Dvorak 2021). Empathy is played out through the planting of a bold and sinuous green spine of plants that leads visitors from the street entrance of the property to the parking lot, through an accessible garden walk from the parking lot to the entrance of the building, inside the building, at eleven elevator lobbies, on three accessible roof decks, from the beds and windows of patient’s recovery rooms, even views for surgeons looking up through skylights (Dvorak and Drennan 2021). At Palomar, plants are not used as a decorative afterthought, plants have been prescribed as an immersive element to perform an essential therapeutic role for patients, visitors, and staff.

Upper left, a garden path accompanies visitors from the parking lot to the building entrance. Upper right, a green screen of bamboo flanks the window façade, bringing views of green inside the building, and out. Lower left, a view of one of eleven interior planted elevator plazas, and the lower right shows a view of the “green wave” roof visible from a patient recovery room. Photos: Spurlock Landscape Architects, photographer Marshall Williams (left column) Bruce Dvorak (right column).

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A skylight connects to a surgery room below. This one is surrounded by Gulf Muhly (Muhlenbergia) plants in bloom with pink seed spikes. Muhlenbergia is a North American native grass. This species is borrowed from out-of-state ecoregions as it brings color to the otherwise dormant native plant pallet during the fall. Natural daylight and waves of grass infuse therapeutic connections from above. Photo: Bruce Dvorak

The 175,000-square-foot (16,258 m2) 360-bed acute-care hospital has three accessible roof gardens and a massive 60,000-square-foot (5,574 m2) green “wave” roof that is visible from patient recovery rooms. The largest of the roof gardens is accessible to the public. Plants used on the roof gardens include common trees and shrubs used in the landscape industry. However, the extensive “wave” green roof, was designed to mimic native coastal meadows with the addition of a few species native to nearby, but not local ecoregions. 

Planting for Biophilic Effect and Color

With empathy in mind, the design team targeted a mix of native and introduced evergreen and seasonal flowering plants throughout the property and rooftops. 

The Green Wave Roof

The concept of the “wave roof” is to create a dynamic environment, where a diversity of plant species, moisture regimes, and slope and aspects can mimic a natural slope. By varying the slope, the plant pallet must adjust to the various profiles of a sloped roof, which allows plants to thrive in their preferred microclimate. Drier environments exist near the crest of the wave, and plants that like moisture occupy the trough. With a 4-inch-deep (10 cm) substrate, the plant pallet favors plants that can tolerate shallow soil profiles. A mixture of five grasses, one annual, seven low-growing shrubs, and seven perennial herbs were planted or seeded onto the green roof. The native voluntary perennial evergreen coyote bush (Baccharis pilularis) self-seeded onto the wave roof and is retained by maintenance crews to co-exist with the planted species as it is not aggressive here and it is beneficial to pollinators including the native Gabb’s checkerspot and Fatal metalmark butterflies (Dvorak and Drennan 2021).

The planting approach utilizes multiple forms of native plants to interpret the green spine through annuals, grasses, herbaceous perennials, shrubs, and succulents. These forms include evergreen plants, tall and low-growing plants, plants with unique leaf forms and textures, and selections based on the colors of their leaves, flowers, or seedheads. The green wave plant list includes plants native to the California coast and some adjacent ecoregions.

A combination of trees and fine-textured ground covers brings shade and color to soothe the emotions of visitors, staff, and surgeons. The day I visited the roof deck, a surgeon walked out onto the deck to get some fresh air. His intense look of stress was eventually calmed after spending some time on the roof garden. Photo: Bruce Dvorak

• Annuals

  • golden yarrow (Eriophyllum confertiflorum)

• Grasses

  • California fescue (Festuca californica), canyon prince wild rye (Leymus condensatus 'canyon prince'), Idaho blue fescue (Festuca idahoensis), purple three awn (Aristida purpurea), and pink muhly grass (Muhlenbergia capillaris) is native to central and eastern U.S. states.

• Herbaceous Perennials

  • California fuchsia (Epilobium canum), common yarrow (Achillea millefolium), foothill penstemon (Penstemon heterophyllus), hummingbird sage (Salvia spathacea), pink yarrow (Achillea millefolium 'rosea'), red California fuchsia (Zauschneria californica), royal beard tongue (Penstemon spectabilis), woodland strawberry (Fragaria vesca)

• Shrubs

  • California buckwheat (Erigonum fasciculatum), Cleveland sage (Salvia clevelandii), coastal sagewood (Artemisia pycnocephala 'David's choice'), Eastwood's Manzanita (Arctostaphylos glandulosa), southern bush monkeyflower (Mimulus longiflorus), white sage (Salvia apiana)

• Succulents

  • Our Lord's candle (Yucca whipplei)

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Here, on the accessible roof garden, drifts of native and non-native plants flank an outdoor seating area to bring color, soothing textures, and beautiful forms of plants for viewing. Up front, a cultivar of the native succulent (Dudleya edulis) adds a playful texture and evergreen color to the garden. Photo: Bruce Dvorak

Summary

Overall, the addition of plants in support of green roofs and roof gardens has helped recover the initial costs of constructing the green roof. A spokesman for the Medical Center Andy Hoang said that over seven years, the green roofs have recovered the additional costs of adding the green roofs through energy savings and water savings (Breier 2010). This case study of the design and construction of green roofs for health and healing at the Palomar Medical Center has yielded a wealth of information for designers and health professionals to learn from.

View of the “green wave” green roof with a horizontal metal grid to form a parapet wall in the distance. The crest-to-trough distance is about 10 feet (3.05 m). Pink seed spikes of gulf muhly grass (Muhlenbergia capillaris) intermix with four grass species native to the California coastal ecoregions. Photo: Bruce Dvorak

• The Palomar Medical Center building was designed through an interdisciplinary and collaborative effort by the project team before any building or site drawings were developed. The entire team, including hospital staff, maintenance staff, and the design team worked collaboratively to envision the project concept.

• The Palomar Medical Center building, landscape, and roofscapes are a model for the future of health care in North America. Patient health and positive environmental experiences are a high priority at this medical center and are played out with a green spine that stretches from the entrance drive to the front door and into and onto the building.

• The level of integrated and systems thinking is outstanding. The collaboration and integration of landscape, building, and interiors make for a healthy and inspiring setting that has a lasting return on the investment.

• Plants were selected for ornamental and environmental conditions. A varied slope roof diversifies the green roof with moist to dry habitats. With the planting of live plants and seedlings, plant self-selection was designed to take place. 

• The maintenance crews understand the planting concept for the green roofs, they know the native plant species on the roof, and understand which volunteers to leave or remove. The integrated efforts of design and maintenance are necessary to make a project of this scope and scale the success that it is.

• The additional costs of adding the green roofs were paid back in about seven years through savings on energy and water costs.

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New Green Roof Biodiversity Courses

To learn about how green roofs can support heat-tolerant plants and biodiversity, see the new Living Architecture Academy Course: Case Studies of Biodiverse Green Roofs, by Bruce Dvorak. 

Bruce Dvorak, FASLA is a Professor at Texas A&M University in the Department of Landscape Architecture and Urban Planning, where he has been conducting green roof and living wall research since 2009. Bruce is a member of the GRHC Research Committee and founded the Southern Plains Living Architecture Center Regional Center of Excellence. Bruce received the GRHC Research Award of Excellence in 2017 and teaches green roofs and living walls in his courses in landscape architecture programs at Texas A&M University. His edited book, Ecoregional Green Roofs: Theory and Application in the Western USA and Canada (2021) provided inspiration and content for this article.

Professor Bruce Dvorak will be giving a masterclass on Designing Green Roofs for Biodiversity at CitiesAlive on Nov. 6. Click here for details, click here.

Acknowledgments

I would like to thank Emily Dowgiallo with Spurlock Landscape Architecture for sharing photographs and project information.

Palomar Medical Center Project Team

Building Owner/Client: Palomar Medical Center

Green Roof Design Team Lead: Spurlock with Rana Creek as consultant 

Architect: CO Architects with Stantec

Landscape Architect: Spurlock Poirier Landscape Architects Installation Contractor: ValleyCrest Landscape Companies Project completion: 2012

Green roof area: 5574 m2 (60,000 ft2)

References

Breier, M. "Green roof at new hospital is more than a cover." The San Diego Union-Tribune, San Diego (2010).

“Ming” Kuo, F. E. (2013). "Nature-deficit disorder: evidence, dosage, and treatment." Journal of Policy Research in Tourism, Leisure and Events 5(2): 172-186.

Dvorak, B. and P. Drennan (2021). Green Roofs in California Coastal Ecoregions. Ecoregional Green Roofs: Theory and Application in the Western USA and Canada. B. Dvorak. Cham, Springer International Publishing: 315-389.

Dvorak, Bruce (2021). Empathetic Design: Integrated & Collaborative Design for Healthy People & Environments, PBS KAMU Television, aired October 26. https://www.pbs.org/video/design-for-healthy-people-and-environments-lyog4z/

Jarger, E. (2008). A Pictorial of Early Roof Top Gardens in the United States. Greening Rooftops for Sustainable Communities, Baltimore, MD, The Cardinal Group, Toronto, ON.

Jim, C. Y. (2017). "Green roof evolution through exemplars: Germinal prototypes to modern variants." Sustainable cities and society 35: 69-82.

Louv, R. (2011). The nature principle: Human restoration and the end of nature-deficit disorder, Algonquin Books.

Suppakittpaisarn, P., X. Jiang and W. C. Sullivan (2017). "Green infrastructure, green stormwater infrastructure, and human health: A review." Current Landscape Ecology Reports 2: 96-110.

Ulrich, R. (1984). "View through a window may influence recovery." Science 224(4647): 224-225.