Neurologists, sociologists, environmental psychologists, architects, filmmakers and many others have been researching the various ways people and plants relate. Here are a few resources that should open the door to further inquiry and not simply answer questions.
Horticultural therapy belongs to a growing family of Ecotherapy approches. You can read a good summing up article here on various Nature guided therapies written by a Uk academic.
The Masters degree dissertation thesis by this Danish academic also offers a good synthesis and review of nature related therapy research.
A good general overview here in a collaborative team effort addresses nature benefits for wellbeing. And here is a review of the scientific literature on biophilia/ contact with nature and the various positive health benefits.
This recent article does à fabulous job summing up the possible pathways or causal links between nature and health. And here also is another literature review by researcher Berto who has a number of articles worth citing.
The incredibly enriching Therapeutic Landscape Network TLN, has a bibliography page well worth visiting regularly .
The AHTA has a current research page that is updated by its curator.
And less ambitious but more personal and for example the horticultural therapy page of a UK based peer in the profession, the Horticultural Therapist has a blog with good ressources. As does this US based peer blogger and contributing Horticultural Therapy Institute editor.
Individual Scolarship, Contemporary and Classic
There are the now classic studies by the Kaplans and Ulrich. But also the work of others like Peter Kahn and Stephen Kellert who continue to interrogate E.O. Wilson’s biophilia thesis. Kahn’s The human relationship with Nature, development and culture raises the question of socio-cultural factors when discussing the biophilia thesis, taking a scrutinising look at the evolutional and environmental psychology work and suggesting some historically contextualising factors at play. A literature review of classic Attention restoration theory is also a good place to start.
My explorations often take me closer to the humanities (art, literature, anthropology…) And so the work of Ronan Berger, who uses psycho-drama and narrative approaches for his nature based therapy is very inspiring.
The Journal for Environmental Psychology is a good bet.
The International Society for Horticultural Science, the ISHS has several good publications, in particular their people plant symposium
There is of course the Journal for Therapeutic Horticulture, edited by the AHTA
Nursing journals often have excellent papers on horticultural therapy and health.
Google scholar is a good place to check for academic journal articles.
Academia is a forum that is open to the public, and far more easily accessed than Researchgate. Its a surprising place to come across good research. There are others of course like Mendeley or citeulike. But here is a cheatsheet on getting access to documents when you are on a students shoestring budget.
Some Specific areas of study
ART and SRT
The key theoretical lines of inquiry are complementary but have different points of departure. The affect/aesthetic based theory, often refered to as Stress Recovery Theory (SRT) is aligned with a cognitions based approach known as attention restoration theory (ART).
In the case of Stress recovery, psychologist Ulrich notes that humans respond to nature on an emotional level (a limbic system level response) and has little to do with information processing. Viewing nature produces positive emotions and lessens negative feelings, providing an oportunity to restore from stress.
On the other hand, the Kaplans theory of attention concerns itself with attention based deficits and depletion of the attentional reources which result in fatigue. This cognitive work of moving in and out of direct attention occurs in the neocortex, the most recent part of the brain in evolutinary terms.
Connectedness to Nature Research: The Skeptics
It would be unfair to not include a few references to those who question the foundations of Nature approaches and Biophilia. A few articles are worth pointing out. These authors dont mean to suggest that there are no therapeutic benefits to spending time in Nature, they are simply concerned with unraveling what exactly we are talking about and with whom.
The funniest one I have come across was published in the European Journal of Ecopsychology. The author of the article Is Horticultural Therapy a Myth? , points out that horticulture is hardly therapeutic. The “rates of suicide, as in agriculture, are high, the pressure intense, the life isolated and the wages are low”. The volunteers coming from a mental health institution and involved at the nursery are not interested in plants, may find them frightening, dangerous, poisonous, dread or avoid them, may not even like being outside or getting their hands dirty. But what they do get is community, a place where they feel unthreatened, unjudged and safe. The author quotes one volunteer who says “it wouldn’t matter if we made pies, it’s the working together that counts”.
Connectedness to Nature Research and more Biophilia
There have been several teams working on developing measurement of involve,went with nature such as the NCS nature connectedness scale. Here
Stewardship and the link with positive nature experiences, here
There is growing literature on work place stress and nature related breaks. However, as this article suggests, “rather than the specific nature of activities, it may be more important that the activities match individual preferences and needs”, underscoring the inherent problem of confounding variables in this sort of study.
Here is work on the INE or indoor nature environement. Some horticultural therapists refuse to acknowledge the importance of indoor nature. While man made gardens are not somehow more natural than botanical gardens or tropical indoor container gardening,effects of exposure are different. The cognitive and affective effects tend to be well worth researching. Here is an article that suggest just that.
Matt Wichrowski paired up with cardiologists to better study mood and cardiac rates after horticultural therapy interventions.
One of the pervasive issues in designing good research are the confounding factors which dog methodology.
Ecopsychology & Ecotherapy
The European Journal of Ecopsychology is a peer reviewed journal published annually.
New publications 2015/2016 include Ecotherapy with chapters by the likes of doyen linda Buzell or Green Studio with contributions by academics and practitioners in the arts and nature such as Ronan Berger
Designs for Healing
Here is an article with design recommendations
Contiguous areas of study
The family ressemblence betwwen certain Art therapy approaches and Horticulture and Ecotherapy approaches is based on the the fact that there is a third term. The mediator complexifies the relationship between client and therapist. There is a “something else” to get ones hands on and wrap ones mind around. Soil or oils, plants or plaster, willlow twigs or textile fibers, there is a material that is fluid, resistive, evocative symbolic and maybe dirtying. We transform something and come away transformed by materials over which we think we have a certain measure of control. As holistic therapies concerned with human wellbeing and not simply functional biomechanical concerns, Art therapy the profession has much to teach Horticultural Therapy the profession in terms of the organisation of career growth, social implications, academic excellence and continued demonstation of pertinence.
There are also other profound reasons to keep Art THerapy in sight, and thi has to do with how creativity works, as this article on wilderness and the creative mind suggests.
There is a vast academic research trail in this discipine which was formally recognized in 1991 in the UK (2011 in France) although being practiced formally for over a hundred years. Here is a general article
Here also is a survey of the art therapy literature from the medical standpoint
Play therapy and Recreational Therapy