Theoretical Foundations of Horticultural Therapy


Horticultural Therapy (HT) as defined by the American Horticultural Therapy Association (AHTA) is the engagement of a client in horticultural activities facilitated by a trained therapist to achieve specific and documented treatment goals. It contains a sub­category referred to as Therapeutic Horticulture, which is the process that uses plants and plant­related activities in which participants strive to improve their

well­being through active or passive involvement.


While the field of HT is relatively new, its elements in theory can be traced back to ancient times.

Historically, the innate human connection to nature evolved from the basic need for food & shelter to the

cultivation of agriculture and then to the aesthetic, conscious design of gardens and landscaping. Globally, the horticulture of gardens played an integral role in both the public and private spheres of the ancient world.


Gardens were created for their virtue to present an environment that was beautiful, relaxing, meditative and considered healing. Early examples included the Hanging Gardens of Babylon, Japanese zen gardens and Thomas Jefferson’s Monticello garden in the mid to late 18th Century.









Hanging Gardens of Babylon


In 1798 the first clinical observations were made by Dr. Benjamin Rush at the Institute of Medicine and

Clinical Practice in Philadelphia. He noted that field labor in a farm setting had curative effects

on people who were mentally challenged.


Research on Cognitive Restoration:

There have been major research studies on the restorative value of nature, specifically by Dr. Ulrich and

Kaplan & Kaplan. Their detailed theories help to support the effectiveness and assessment of HT. Ulrich’s research and psycho­evolutionary theory (defined as positive emotional and physiological effects of experiences with nature) presents the perspective that our innate connection and response to plants and their environment is evolutionary. He further stated that our first response to nature is “emotional”. In essence, our primal need for survival is closely related to our emotional, psychological and physiological unconscious response to natural settings inclusive of plants, water and rocks. Subconsciously, the natural environment can provide relief from the stresses of life. Findings of psycho­evolutionary theory in Ulrich’s studies included: “viewing nature scenes significantly reduced feelings of fear and increased positive feelings of affectation and delight, compared with scenes of treeless city scenes (1979). Nature scenes reduced stress and resulted in more rapid recovery from stress (1979). And, visual landscapes produce emotional states: negative when viewing urban scenes and positive from nature scenes (1979).”



“Natural scenery employs the mind without fatigue and yet exercises it; tranquilizes it and yet enlivens it;

and thus, through the influence of the mind over the body, gives the effect of

refreshing rest and reinvigoration to the whole system”. ~ Frederick Olmstead, 1865.




Further research done by Kaplan and Kaplan is the Attentional Restoration Theory (ART) – A theory that a natural environment has restorative qualities. The following excerpt is from The Journal of Environmental Psychology (1995): “ THE RESTORATIVE BENEFITS OF NATURE: TOWARD AN INTEGRATIVE FRAMEWORK Directed attention plays an important role in human information processing; its fatigue, in turn, has far reaching consequences. Attention Restoration Theory provides an analysis of the kinds of experiences that lead to recovery from such fatigue. Natural environments turn out to be particularly rich in the characteristics necessary for restorative experiences. An integrative framework is proposed that places both directed attention and stress in the larger context of human­environment relationships.”


They presented 4 key components of what makes a restorative environment.


  • Being away Natural settings are often the preferred destinations for extended restorative opportunities.

  • Fascination Nature is certainly well­endowed with fascinating objects, as well as offering many processes that people find engrossing.

  • Extent In the distant wilderness, extent comes easily.

  • Compatibility The natural environment is experienced as particularly high in compatibility.(Kaplan, 1989)


(ART) concludes that the restorative effects of exposure of nature helps to reduce the fatigue from

prolonged stress of everyday mental activity. The difference between the Kaplan and Ulrich theories can be summarized as: Kaplans’ is based on cognition and Ulrich on affect. Ulrich’s basis is on the “genetic” emotional and physiological response to nature. His belief that nature in of itself, can induce recovery from different forms of stress and that nature can produce positive emotions and decrease negative feelings. Kaplans’ focus is that attention­based deficits create fatigue and that a reduction of stress can be provided by a natural environment or landscape. Studies have shown that whether it is in a garden, a natural view out of a window or even an image such as a poster, all have shown to decrease levels of stress and facilitate relaxation. Each perspective highlights the importance of restorative effects of nature whether innate or evolutionary. Both approaches. along with important research studies have provided support for continued validation of HT.



Both also support the Biophilia Theory – human beings are attracted to other living systems. A term coined by Edward Wilson, "biophilia" literally means "love of life”. He has been quoted as saying in an interview on NOVA, “I'd be willing to place a bet that among people who get out into the outdoors early and really love it, there are fewer depressed people”. He also talked about Biophilic Design, “I recently visited an office building in North Carolina. It was by a professional and very successful architect, and it was designed biophilically. He had selected a little knoll. He had to cut some trees, but he left the rest on his little knoll overlooking a stream. And you sit there with a glassed­in wall endlessly looking out, while chipmunks and warblers and so on are all over the place and the stream is flowing by. And you're at peace” (NOVA 2008). Again, inferring the important on the integration of nature into our lives especially within an urban environment.




Early learning, experiences and culture

Given the research and understanding that human “coding” has imprinted in us a response to nature in regards to visual clues in the landscape for our need of food, water and shelter, it may be important when setting up a program or treatment to have an understanding of early learning, culture, experiences, and memories. Certain foliage, flowers and scents can create a familiar and safe environment.



“To this day I cannot see a bright daffodil, a proud gladiola, or a smooth eggplant without thinking of Papa.

Like his plants and trees, I grew up as part of his garden” ~ Leo Buscaglia



HT environments are an important component to the learning, treatment and goals, whether it be individual or in a group setting, such as:


Garden projects within a shared garden, school, hospital or community.

  • Enabling Garden designed to be accessible.

  • Therapeutic Garden designed within a treatment program.

  • Horticultural Therapy Garden to accommodate horticultural activities.

  • Restorative Gardens for well­being or meditation.



“The glory of gardening: hands in the dirt, head in the sun, heart in nature.

To nurture a garden is to feed not just the body, but the soul.” ~ Alfred Austin



HT can be integrated into in a wide array of settings; mental health facilities, rehabilitation programs, substance abuse programs, hospitals, hospice and palliative care, homeless shelters, correctional facilities, schools, mindfulness programs, community gardens, botanical gardens, senior day care, assisted living and more. It has the capacity to be extended to all age groups, children through senior citizens including the population of those with limited physical and cognitive abilities.


Horticultural Therapy creates a deep context to develop a direct exploration of the people/plant relationship within a therapeutic setting. Combining 3 key elements: environment, activity, and use of self/purpose is a synergetic way to enhance the learning.



These following 4 domains, within the framework of HT, have the capacity to achieve and instill wellness.

  • Emotional: self­esteem, well­being, purposefulness, sensory awareness, management of stress.

  • Physical: range of motion, endurance, fine motor skills, strength.

  • Cognitive: memory, sequencing, problem solving, attention.

  • Social: community involvement, taking turns, modeling, universality, play, eye contact.



“I sit in my garden, gazing upon a beauty that cannot gaze upon itself. And I find sufficient purpose for my day”.

~ Robert Brault


Interaction with nature can help transcend oneself and enable us to be present in the moment, a time for mindfulness and reflection, even if used as brief escape. HT can assist on many levels as it focuses the attention in our mind & consciousness, the healing and restorative qualities of nature, being in a garden, the wilderness or a view out a window.



“Flowers are restful to look at. They have neither emotions nor conflict”. ~ Freud

Different Pillars of HT


Horticultural Therapy – The engagement of a client in horticultural activities facilitated by a trained therapist to achieve specific and documented treatment goals. 


Therapeutic Horticulture – A process through which participants strive to improve their well-being through active or passive involvement with plants and plant-related activities. In a therapeutic horticulture program, goals are not clinically defined and documented, but the leader has training in the use of horticulture as a medium for human well-being.


Social or Community Horticulture – A leisure or recreational activity related to plants and gardening. A typical community garden or garden club is a good example of a social horticulture setting. No treatment goals are defined, no therapist is present, and the focus is on social interaction and horticulture activities.


Vocational Horticulture – A vocational horticulture program, which is often a major component of a horticultural therapy program, focuses on providing training that enables individuals to work in the horticulture industry professionally, either independently or semi-independently. These individuals may or may not have some type of disability. Vocational horticultural programs may be found in schools, residential or rehabilitation facilities, and prisons, among other places.

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