Horticultural Therapy

Abstract

Horticultural therapy, which MeSH classifies under psychotherapy, is the practitioner-guided use of gardening and plant-centred activity, dosed and directed at defined treatment goals for cognition, mood, and function. Its rationale rests on two theories of why nature restores rather than merely pleases: Attention Restoration Theory, on which natural settings replenish depleted directed attention through effortless soft fascination, and Stress Recovery Theory, on which natural scenes trigger a rapid, largely automatic recovery from stress. Controlled work links nature contact to measurable gains in attention and working memory and to reduced rumination. A clinical evidence base of systematic reviews and meta-analyses in depression, dementia, and well-being grounds the practice, though the trials are heterogeneous and often small. Three interactive demonstrations model attention recovery, the four restorative components, and the decay of stress in natural versus built settings.

Keywords: horticultural therapy, attention restoration theory, therapeutic gardening, restorative environments

Tending a garden after a taxing day is one of the oldest folk remedies for a tired mind, and the surprising finding of the last four decades is that the folk remedy has a measurable cognitive signature. People asked to walk in an arboretum, or merely to look at trees through a window, recover their capacity for concentrated mental work faster than people given a matched dose of the built environment, and they do so whether or not they believe the greenery is doing them any good (Berman, Jonides, & Kaplan, 2008; Ulrich, 1984). Horticultural therapy takes that regularity and turns it into a structured treatment: not gardening for its own sake but gardening prescribed, dosed, and directed at a clinical goal, on the premise that active contact with growing things restores attention and lifts mood in ways the laboratory can quantify.

What Horticultural Therapy Is

Horticultural therapy is the professionally guided use of plants and gardening activities to achieve specific therapeutic goals — cognitive, psychological, social, or physical — in a person referred for treatment. What distinguishes it from ordinary gardening is not the activity but the frame around it: a trained therapist sets individualised goals, structures the tasks to meet them, and documents progress, so that sowing, potting, and pruning become the medium of a treatment plan rather than a pastime. The field draws a working distinction between therapeutic horticulture, in which the gardening itself is designed to improve well-being, and horticultural therapy proper, in which that activity is embedded in a clinical process with defined objectives and a practitioner accountable for outcomes (Clatworthy, Hinds, & Camic, 2013).

The practice sits within the broader family of nature-based interventions, and MeSH indexes it under psychotherapy, alongside art, music, and dance therapy, as an allied treatment that works through structured engagement rather than talk. Its intellectual foundation, however, comes from environmental psychology, which supplies the two theories that explain why contact with nature should have any clinical effect at all. Both were developed to account for restoration in ordinary settings — a park, a view, a walk — and horticultural therapy is in large part the applied, dosed, goal-directed extension of that basic science (Kaplan, 1995; Ulrich et al., 1991).

Attention Restoration and Directed Attention

The cognitive engine of the field is Attention Restoration Theory, set out by Rachel and Stephen Kaplan. It begins from William James's distinction between two kinds of attention: an effortful, voluntary directed attention that must be aimed and held against distraction, and an effortless involuntary attention that inherently interesting stimuli capture on their own. Directed attention is the resource that flags with sustained mental work — the capacity that makes proofreading, planning, or resisting distraction possible — and because it depends on active inhibition of competing stimuli, it fatigues. The Kaplans' central proposal is that this fatigue is restored not by sleep alone but by settings that let the directed-attention system stand down while involuntary attention takes over (Kaplan, 1995).

Natural environments are held to do this uniquely well because they are rich in what the theory calls soft fascination: gently engaging stimuli — moving leaves, a shifting sky, the slow business of plant growth — that hold attention effortlessly yet leave enough mental room for reflection. A busy street also captures attention, but through hard fascination, demanding and depleting, offering no such respite. Gardening supplies soft fascination in abundance while adding purposeful, low-stakes activity, which is why it is a favoured medium for restoration. The first demonstration models this dynamic: a store of directed attention is depleted by demanding work and then recovers along different trajectories in a garden versus a built setting.

The strongest experimental support comes from Berman, Jonides, and Kaplan, who had participants perform a demanding working-memory task to fatigue their directed attention, then walk either in an arboretum or along city streets. After the nature walk, backward digit span — a stringent measure of working-memory capacity requiring directed attention — improved reliably; after the urban walk it did not, and the effect held even in winter when few found the nature walk more pleasant, ruling out a simple mood explanation (Berman, Jonides, & Kaplan, 2008). This is the finding that converts the theory from a claim about preference into a claim about cognition: time in nature restores a specific, measurable component of executive function.

The Four Components of a Restorative Setting

Attention Restoration Theory does not treat all nature as equally restorative. It specifies four properties a setting must have to replenish directed attention, and the degree to which an environment possesses them predicts how restorative it will be (Kaplan, 1995). Being away is a sense of psychological distance from the demands and routines that drain attention. Fascination is the presence of soft, effortlessly engaging stimuli. Extent is the feeling of a coherent, connected world large enough to occupy the mind and explore. Compatibility is the match between the setting and what the person wants to do in it — a garden one is invited to tend scores higher than one merely observed from behind glass.

A well-designed therapeutic garden is, in these terms, an environment engineered to maximise all four at once, which is what separates it from a token patch of greenery. The second demonstration lets the reader rate a setting on the four components and see the restorative potential the theory predicts, contrasting a designed garden with a desk by a window.

The framework also clarifies why the benefit is not merely relaxation. A person can be relaxed yet still spending directed attention — scrolling a phone, say — whereas restoration requires a setting that actively engages involuntary attention so the directed system can recover. This is the conceptual pivot on which horticultural therapy's cognitive claim rests: the garden works by giving attention somewhere effortless to go (Kaplan, 1995; Berman, Jonides, & Kaplan, 2008).

Stress Recovery and the Affective Route

The second mechanism runs faster and lower than attention. Roger Ulrich's Stress Recovery Theory holds that contact with unthreatening natural scenes triggers a rapid, partly innate recovery from stress — a drop in physiological arousal and negative affect that begins within minutes and does not wait on any deliberate appraisal of the view. On this account the response is evolutionarily old: for a species that evolved in natural surroundings, verdant, resource-rich scenes signalled safety, and the quick positive-affective shift they evoke is a built-in down-regulation of the stress response (Ulrich et al., 1991). This evolutionary framing is an instance of the biophilia hypothesis, the proposal that humans carry an innate affiliation with living things and natural forms; it supplies the ultimate, adaptive rationale for why nature specifically, rather than any restful setting, should quiet the body (Grinde & Patil, 2009).

Ulrich's founding evidence was clinical and simple. Surgical patients whose hospital windows looked onto a stand of trees had shorter postoperative stays, needed fewer strong analgesics, and drew fewer negative notes from nurses than matched patients whose windows faced a brick wall — a difference produced by nothing but the view (Ulrich, 1984). Later work put the recovery on a physiological footing: after a stressor, people shown natural scenes returned toward baseline on measures such as skin conductance, muscle tension, and heart activity faster than those shown urban scenes (Ulrich et al., 1991). Figure 1 shows the characteristic pattern, and the third demonstration lets the reader vary the recovery and compare the two settings.

The two theories are complementary rather than rival. Stress recovery is fast, affective, and largely automatic; attention restoration is slower, cognitive, and unfolds over a longer exposure. A garden session plausibly recruits both — an initial calming as arousal falls, followed by the gradual replenishment of directed attention over the minutes that follow — and the pair together explain why the effect touches mood and cognition at once (Bratman et al., 2015). The clearest bridge between them is the finding that a walk in nature reduces rumination, the repetitive self-focused thought that sustains low mood, and does so alongside reduced activity in the subgenual prefrontal cortex, a region implicated in rumination — a neural correlate for the affective benefit that no purely subjective report could supply (Bratman et al., 2015).

The Clinical Evidence Base

Moving from mechanism to treatment, the question is whether structured horticultural programmes produce reliable clinical benefit. The evidence is now substantial but uneven. A systematic review of randomised controlled trials found horticultural therapy effective across a range of conditions while noting that the trials were methodologically varied and often small, so the direction of benefit is clearer than its magnitude (Kamioka et al., 2014). In depression specifically, a prospective study isolated the active ingredients of a therapeutic-horticulture programme, linking clinical improvement to increased engagement and being-away rather than to gardening skill as such — a result that maps the clinical effect back onto the restoration mechanisms (Gonzalez et al., 2010).

The dementia literature is the most developed application. Reviews of therapeutic gardens and garden use in dementia care report reductions in agitation and improvements in mood and engagement, though again from a heterogeneous and methodologically mixed base (Detweiler et al., 2012; Whear et al., 2014). For cognition, the most directly relevant synthesis is a meta-analysis of controlled trials testing horticultural therapy for cognitive function, which found a positive overall effect (Tu & Chiu, 2020). Broader still, meta-analytic work on gardening in general populations finds consistent benefits for depression, anxiety, life satisfaction, and stress, and an umbrella review of that literature reaches the same conclusion while flagging the persistent limitations of the primary trials (Soga, Gaston, & Yamaura, 2017; Pantiru et al., 2024). Table 1 summarises the principal syntheses.

Worked Example

The two mechanisms become concrete when their recovery curves are worked, and the demonstrations reproduce this arithmetic. Take Stress Recovery Theory first, modelling residual stress after a stressor as exponential decay, S(t) = S0 times e raised to the power minus t over tau, where tau is the recovery time-constant and a smaller tau means faster recovery. Set the initial stress S0 = 100 units, with a natural setting giving tau = 2 minutes and a built setting tau = 6 minutes. At t = 4 minutes the natural setting leaves S = 100 times e raised to minus 4 over 2 = 100 times e to the minus 2 = 13.5 units, while the built setting leaves S = 100 times e raised to minus 4 over 6 = 100 times e to the minus 0.667 = 51.3 units. In four minutes the natural view has shed about 86% of the stress and the built view only about 49% — the gap Figure 1 draws and Ulrich's window study reported in clinical form (Ulrich, 1984).

Now attention restoration, modelling the fraction of directed attention recovered over a break as R(t) = 1 minus e raised to minus t over tau, which rises from zero toward full recovery. A restorative garden restores attention with a short time-constant, tau = 10 minutes; a busy street, offering little soft fascination, restores it slowly, tau = 30 minutes. After a 15-minute break the garden has recovered R = 1 minus e raised to minus 15 over 10 = 1 minus e to the minus 1.5 = 0.777, or about 78% of the depleted capacity, while the street has recovered only R = 1 minus e raised to minus 15 over 30 = 1 minus e to the minus 0.5 = 0.393, about 39%. The same fifteen minutes buys roughly twice the cognitive recovery in the garden — the quantitative shape of the digit-span advantage Berman and colleagues measured (Berman, Jonides, & Kaplan, 2008).

Discussion

Horticultural therapy is best understood as the applied edge of environmental psychology: a clinical practice whose credibility depends on the basic science of restoration that underwrites it. Two theories carry that weight. Attention Restoration Theory supplies the cognitive account — directed attention fatigues and is replenished by settings rich in soft fascination — and its strongest evidence is experimental, a measurable working-memory gain after nature exposure that survives controls for mood and weather (Kaplan, 1995; Berman, Jonides, & Kaplan, 2008). Stress Recovery Theory supplies the affective account — a fast, automatic down-regulation of stress — and its founding evidence is clinical, the shorter recoveries and lighter analgesia of patients with a view of trees (Ulrich, 1984; Ulrich et al., 1991). The rumination-and-subgenual-prefrontal finding ties the two together, showing that the affective benefit has a cognitive and neural signature rather than being mere self-report (Bratman et al., 2015).

What the field cannot yet do is state a dose. The intervention research is consistent in direction — benefits for depression, dementia agitation, well-being, and cognitive function recur across independent syntheses — but the primary trials are heterogeneous, frequently small, and rarely blinded, so the effective duration, frequency, and format of a horticultural-therapy programme remain unspecified (Kamioka et al., 2014; Tu & Chiu, 2020; Pantiru et al., 2024). This is the honest position: the mechanisms are well characterised and the direction of clinical benefit is reliable, while the precision a mature therapeutics would demand is still missing. Read this way, horticultural therapy is neither folk myth nor settled prescription but a mechanistically grounded intervention whose evidence base is maturing faster than its methodology.

Current Directions

The most active front is the tightening of the evidence from narrative review toward quantitative synthesis. The meta-analysis of controlled trials of horticultural therapy for cognitive function marks that shift, converting a scattered literature into a pooled effect and making cognition, not just mood, a measured endpoint (Tu & Chiu, 2020). The 2024 umbrella review goes further, aggregating the review-level evidence on gardening for well-being and mental health and making explicit what the primary trials still lack — adequate power, active control conditions, and standardised dosing — so that the open questions are now stated in the vocabulary of clinical-trial methodology rather than of enthusiasm (Pantiru et al., 2024).

A second direction reaches for mechanism at the neural level. The demonstration that a nature walk lowers both self-reported rumination and subgenual prefrontal activity points toward an imaging-based programme that could specify which populations and which exposures move the brain regions implicated in mood disorder, and how durably (Bratman et al., 2015). The two strands converge on the same target: a horticultural therapy specified precisely enough — in dose, in mechanism, and in the outcomes it moves — to sit inside mainstream evidence-based practice rather than beside it.

Common Misconceptions

Horticultural therapy is just gardening, rebranded.

The activity is gardening, but the therapy is the goal-directed clinical frame around it: individualised objectives set by a trained practitioner, tasks structured to meet them, and documented progress. The evidence that clinical improvement tracks engagement and being-away rather than horticultural skill shows the frame, not the pastime, is what treats (Gonzalez et al., 2010; Clatworthy, Hinds, & Camic, 2013).

The benefit is just relaxation, the same as any pleasant break.

Restoration is not the same as relaxation. A person can be relaxed while still spending directed attention, whereas attention restoration requires a setting that engages involuntary attention so the directed system can recover. The working-memory gain after a nature walk held even when participants did not find the walk more pleasant, dissociating the cognitive benefit from mood (Berman, Jonides, & Kaplan, 2008; Kaplan, 1995).

The evidence is anecdotal, so the effects are not real.

The effects are demonstrated in controlled experiments and pooled in meta-analyses, not merely reported anecdotally. What is genuinely limited is the precision of the intervention trials — their size, blinding, and dosing — which constrains how confidently a specific programme can be prescribed, not whether the underlying benefit exists (Kamioka et al., 2014; Tu & Chiu, 2020).

Glossary

Attention Restoration Theory.

The theory, due to Rachel and Stephen Kaplan, that directed attention fatigues with effortful use and is replenished by natural settings that engage involuntary attention through soft fascination.

Being away.

The first component of a restorative setting: a sense of psychological distance from the demands and routines that deplete directed attention.

Biophilia hypothesis.

The proposal, associated with Edward O. Wilson, that humans possess an innate, evolved affiliation with living things and natural forms; it is the ultimate rationale often invoked for why contact with nature is restorative rather than merely pleasant.

Compatibility.

The fourth component of a restorative setting: the fit between the environment and what a person wants or intends to do in it.

Directed attention fatigue.

The depletion of the capacity for directed attention after sustained effortful use, marked by lapses of concentration, distractibility, and irritability.

Directed attention.

Effortful, voluntary attention that must be aimed and sustained against distraction; the limited resource whose fatigue and restoration Attention Restoration Theory concerns.

Extent.

The third component of a restorative setting: the sense of a coherent, connected world of sufficient scope to occupy and engage the mind.

Fascination.

The second component of a restorative setting: stimuli that hold attention effortlessly. Soft fascination engages gently and leaves room for reflection; hard fascination is demanding and depleting.

Horticultural therapy.

The professionally guided use of gardening and plant activities to achieve defined therapeutic goals in a person referred for treatment.

Involuntary attention.

Effortless attention captured automatically by inherently interesting stimuli; its engagement in nature lets the directed-attention system rest and recover.

Restorative environment.

A setting that replenishes depleted psychological resources, especially directed attention; natural settings are the paradigm case.

Rumination.

Repetitive, self-focused negative thought that maintains and deepens low mood; nature exposure reduces it alongside reduced subgenual prefrontal activity.

Soft fascination.

Gently engaging stimulation — moving leaves, a shifting sky, plant growth — that holds attention without effort while leaving mental capacity for reflection; the mechanism by which nature restores.

Stress Recovery Theory.

Ulrich's theory that unthreatening natural scenes elicit a rapid, partly innate reduction in physiological and emotional stress, independent of deliberate cognitive appraisal.

Subgenual prefrontal cortex.

A prefrontal region implicated in the self-focused processing of sad affect; its activity falls, along with rumination, after a walk in nature.

Therapeutic garden.

A garden designed to maximise the restorative components — being away, fascination, extent, and compatibility — for use in a treatment or care setting.

Therapeutic horticulture.

The use of gardening activity to improve well-being, distinguished from horticultural therapy proper by the absence of an individualised clinical treatment plan.

Key Researchers

Marc G. Berman. University of Chicago (Environmental Neuroscience Laboratory); he provided the sharpest experimental test of Attention Restoration Theory, showing that a walk in an arboretum, but not one downtown, improved backward-digit-span performance, operationalising restoration as a measurable working-memory gain. Faculty Page - Google Scholar - ORCID

Gregory N. Bratman. University of Washington (Environment and Well-Being Lab); he linked nature contact to mental health at the neural level, showing that a walk in a natural setting reduced rumination and lowered activity in the subgenual prefrontal cortex, a region implicated in depressive rumination. Faculty Page - Google Scholar - ORCID

Terry Hartig. Uppsala University (Institute for Housing and Urban Research); a leading theorist of restorative environments who has tested and extended both Attention Restoration Theory and Stress Recovery Theory and helped isolate the active components of therapeutic horticulture in depression. Faculty Page - Google Scholar - ORCID

Rachel Kaplan. University of Michigan (Professor Emerita, School for Environment and Sustainability); co-developer, with Stephen Kaplan, of Attention Restoration Theory, the framework that explains why natural settings restore depleted directed attention. Faculty Page - Wikipedia

Stephen Kaplan (1936-2018). University of Michigan (Professor of Psychology and of Electrical Engineering and Computer Science); co-developer of Attention Restoration Theory and author of its integrative framework distinguishing effortful directed attention from involuntary soft fascination. Wikipedia

Masashi Soga. University of Tokyo (Graduate School of Agricultural and Life Sciences); he quantified the health returns of gardening across the literature, whose meta-analysis found consistent positive effects on depression, anxiety, life satisfaction, and stress. Faculty Page - ORCID

Roger S. Ulrich. Chalmers University of Technology (Professor of Architecture); founder of the evidence base for restorative healthcare environments, whose 1984 finding that surgical patients with a view of trees recovered faster grounds Stress Recovery Theory. Faculty Page - Google Scholar - ORCID

Frequently Asked Questions

What is horticultural therapy? Horticultural therapy is the professionally guided use of gardening and plant-based activities to reach defined therapeutic goals in a person referred for treatment. A trained practitioner sets individualised objectives, structures the gardening tasks to meet them, and documents progress, so the activity becomes the medium of a treatment plan rather than a hobby (Clatworthy, Hinds, & Camic, 2013).

How is horticultural therapy different from ordinary gardening? The activity is the same; the clinical frame is not. Horticultural therapy embeds gardening in an individualised process with treatment goals and an accountable practitioner, whereas gardening is undertaken for its own sake. A study of therapeutic horticulture in depression found that improvement tracked engagement and psychological distance rather than gardening skill, showing the frame is what treats (Gonzalez et al., 2010).

What is Attention Restoration Theory? Attention Restoration Theory, developed by Rachel and Stephen Kaplan, holds that the capacity for effortful directed attention fatigues with use and is replenished by natural settings. Such settings engage involuntary attention through soft fascination, letting the directed-attention system rest and recover (Kaplan, 1995).

Does time in nature actually improve cognition? Yes, under controlled conditions. Participants who walked in an arboretum after a demanding task improved on backward digit span, a stringent working-memory measure, while those who walked downtown did not, and the effect held even when the nature walk was not rated more pleasant (Berman, Jonides, & Kaplan, 2008).

How does nature reduce stress so quickly? Stress Recovery Theory proposes that unthreatening natural scenes trigger a rapid, largely automatic reduction in physiological and emotional stress that does not wait on deliberate appraisal. Surgical patients with a window view of trees recovered faster and needed fewer strong painkillers than those facing a brick wall (Ulrich, 1984).

Can horticultural therapy help people with dementia? The dementia literature is the most developed application. Reviews of therapeutic gardens and garden use in dementia care report reduced agitation and improved mood and engagement, though the primary studies are heterogeneous and methodologically mixed (Detweiler et al., 2012; Whear et al., 2014).

Is horticultural therapy an evidence-based treatment for depression? A systematic review of randomised controlled trials found horticultural therapy effective across conditions including depression, and a prospective depression study linked improvement to the restoration mechanisms, but the trials are often small and varied, so the direction of benefit is clearer than its precise magnitude (Kamioka et al., 2014; Gonzalez et al., 2010).

Why does nature reduce rumination? A walk in a natural setting reduces rumination, the repetitive self-focused thought that sustains low mood, and does so alongside lowered activity in the subgenual prefrontal cortex, a region implicated in that process. This gives the affective benefit a neural signature rather than resting on self-report alone (Bratman et al., 2015).

References