The effectiveness of group-based gardening interventions for improving wellbeing and reducing symptoms of mental ill-health in adults: a systematic review and meta-analysis

Figures & data

Table 1. Risk of Bias table.

Figure 1. PRISMA flow diagram.

Table 2. Description of included studies.

Study	Study population		Intervention	Control	Outcomes	Scales	Follow up	Number of sessions	Length of sessions	Frequency of sessions	Total length (Hours)	Location	Facilitator	Theory
	Intervention	Control
Bay-Richter et al. (2012)	No information given		Garden rehabilitation programme in addition to treatment as usual.	Treatment as usual	Depression	Montgomery Asperg Depression Rating Scale MADRS	8 weeks	No information	No information	No information	No information	No information	No information	None mentioned
	No information given
	No information given
	No information about diagnosis, recruited from an outpatient psychiatric hospital
Brown et al. (2020)	n = 8	n = 12	Gardening on raised beds (Planning what to grow together, preparing, planting, and tending to vegetables) and semi-monthly gardening and food-related education sessions (n = 10).	Usual diabetes management	Mood	Profile of Mood States (POMS)	16 weeks	Participants tended to the raised beds at least once a week May – Sept	No info about how long they spent gardening- education sessions were 90 mins long	At least once a week. Two days a month of education sessions	Not possible to accurately determine total hours. 15 hours of education sessions	Outside tribal diabetes centre	Not specified	Community based participatory approach (CBPA) and Socio-ecological Model of health behaviour
	Mean age estimate = 49.5				Depression	Centre for Epidemiological studies depression Scale (CESD)
	80% female
	Diabetes patients				Quality of life	World health organisation quality of life questionnaire (WHOQOL-BRIEF)
Demark-Wahnefried et al. (2018); Cases et al. (2016)	n = 22	n = 20	Growing vegetables year-round in a raised bed in own garden with support from 'master gardeners’. All supplies needed provided for as part of intervention. Master gardeners contacted participants bimonthly with alternating home visits and telephone/emails.	Waitlist control group	Quality of life	Short-Form health survey-36 for health-related quality of life (SF-36)	52 weeks	No information	No information	85% of participants reported gardening 'several times a week’	No information	Own gardens	Master gardeners	Social ecological model and social cognitive theory
	Mean age =  70.4 (7.8)	Mean age= 69.7 (8.5)
	75% Female	63.3% Female			Stress	Perceived Stress Scale (PSS)
	Cancer Diagnosis, completed treatment
Detweiler et al. (2015)	n = 13	n = 12	Gardening in raised beds, general gardening activities and education about gardening; preparing beds, planting seeds, harvesting.	Occupational therapy – choice of crafts	Quality of life	Quality of Life Enjoyment and Satisfaction Questionnaire – Short Form(Q-LES-Q-SF)	3 weeks	15 sessions	60mins	Five days a week	15 hours	Courtyard garden of rehabilitation centre	No information	Horticultural therapy
	mean age = 46.4 (11.9)
	4.16% Female
	Comorbid substance abuse and mental illness				Depression	Centre for Epidemiological studies depression Scale (CESD)
Huang et al. (2018)	n = 33	n = 33	Horticultural therapy for hand function rehabilitation in addition to usual exercise rehabilitation. Involved, potting, caring for plants, planting herbs.	Routine exercise rehabilitation – treatment as usual	Depression	Beck Depression Scale	4 weeks	No information	No information	No information	No information	Rehabilitation hospital	No information	Horticultural therapy
	No information given
	No information given
	Postoperative hand trauma patients
Kam and Siu (2010)	n = 10	n = 12	Sessions followed same structure, warm up, gardening activities and then group sharing and each had specific themes and objectives.	Both control and intervention continued usual workshop training for work-related skills.	Depression	Depression, Anxiety and Stress scale (DASS21)	2 weeks	10 sessions	60 mins	10 consecutive days	10 hours	A rehabilitation farm with five themed gardens	A registered occupational therapist	Horticultural Therapy
	Mean age= 45.3 (10.38)	Mean age= 43.3 (11.7)			Anxiety
					Stress
	33% Female	25% Female
	Schizophrenia spectrum disorder, bipolar disorder, major depression. Attending rehabilitation services				wellbeing	Chinese personal wellbeing index (PWI-C)
Kim and Park (2018)	n = 18	n = 18	A set programme of horticultural therapy was followed with specific aims and approaches for each session. Various group gardening activities and crafts with plants e.g. flower arranging.	Pre and post-test questionnaires only.	Depression	Zung Self-rated depression scale (SDS)	6 weeks.	12 sessions	60 mins	Two days a week	12 hours	No information about the location	Two trained horticultural therapists	Horticultural Therapy
	Mean age estimate= 50.5
	100% Female	100% Female			Anxiety	State-trait anxiety inventory (STAI)
	No diagnosis
Kotozaki (2013a)	n = 15	n = 15	Group gardening intervention involving interactive lectures and practical horticultural training. Participants were also asked to garden for 15mins each day at their homes with kits provided by study.	Two groups; Gardening intervention performed individually and control with home gardening kits only	Depression	Centre for Epidemiological studies depression Scale (CESD)	4 weeks	4 sessions	60 mins	once a week	4 hours	University lab	Horticultural therapist and Clinical psychologist	Horticultural therapy
	Mean age 20.53 (2.45)	Mean age 21.60 (1.54)			Quality of life	WHO-QOL-26
					Affect	POMS
	51% female				Mental health	General Health Questionnaire (GHQ)
	No diagnosis
Kotozaki (2013b)	n = 20	n = 19	Group gardening intervention involving interactive lectures and practical horticultural training. Participants were also asked to garden for 15mins each day at their homes with kits provided by study.	Stress control psychoeducation group	Depression	Geriatric depression scale (GDS-15)	8 weeks	8 sessions	60 mins	once a week	8 hours	University lab	Horticultural therapist and Clinical psychologist	Horticultural therapy
	Mean age= 65.15 (3.65)	Mean age= 67.21 (5.18)			Quality of life	WHO-QOL-26
	100% female
	PTSD symptoms				PTSD	Clinician Administered PTSD Scale (CAPS)
Kotozaki (2014a)	n = 22	n = 23	Group gardening intervention. Participants were also asked to garden for 15mins each day at their homes.	Stress control psychoeducation group, 60 mins weekly for 8 weeks	Depression	Centre for Epidemiological studies depression Scale (CESD)	16 weeks	16 sessions	120 mins	once a week	32 hours	Community centre	No information	Horticultural therapy
	Mean age = 46.54 (8.40)				Mental health	General Health Questionnaire (GHQ)
	100% female
	No information given
Kotozaki (2014b)	n = 27	n = 27	Group gardening intervention involving interactive lectures and practical horticultural training. Participants were also asked to garden for 15mins each day at their homes with kits provided by study	No information	Depression	Centre for Epidemiological studies depression Scale (CESD)	8 weeks	8 sessions	60 mins	once a week	8 hours	University lab	Horticultural therapist and Clinical psychologist	Horticultural therapy
	Mean age= 42.48 (9.72)	Mean age= 44.22 (7.8)			Mental health	General Health Questionnaire (GHQ)
					Quality of life	WHO-QOL-26
					Affect	Positive and Negative Affect Scale (PANAS)
	100% female				PTSD	Clinician Administered PTSD Scale (CAPS)
	PTSD symptoms
Makizako et al. (2019); Makizako et al. (2015)	n = 20	n = 23 (Exercise) & n = 24 (Control)	Growing crops in a group setting. Planting, cultivating, growing, and harvesting in a public garden.	Two control groups – exercise and cognition classes & traffic safety + disaster prevention class.	Depression	Geriatric depression scale (GDS-15)	24 weeks, 52 weeks	20 sessions	60–90 mins	Once a week	25 hours	A Public Garden	Not specified	None mentioned
	Mean age = 73.1 (5.6)	Exercise = 73.1 (5.3)
		Control = 73.0 (5.9)
	46.7% Female	53.3% Female (Exercise)			Quality of life	Short-Form health survey-12 for health-related quality of life (SF-12)
		51.7% Female (Control)
	Depressive symptoms
Ng et al. (2018); Chan et al. (2017); Ng et al. (2016); Ng et al. (2019)	n = 26	n = 27	Horticultural therapy following a set session plan. Various gardening activities e.g. sowing, harvesting, garden maintenance. One week focused on indoor gardening and another on pressing flowers. Five of the weeks involved walks, locations included a nature reserve and botanical garden.	Waitlist control group	Depression	Zung self-rating depression scale (SDS)	12 weeks, 24 weeks	15 sessions	60 mins	Once a week for first three months, then once a month for last three months	15 hours	At selected parks/ gardens and a nature reserve	Not specified. The programme was designed by an 'experienced instructor’	Horticultural therapy
	Mean age= 67.21 (4.52)	Mean age= 67.00 (4.18)			Anxiety	Zung self-rating anxiety scale (SAS)
	79.3% Female	76.7% Female
	Schizophrenia, bi-polar disorder				Wellbeing	Ryff’s scale of psychological wellbeing
Okvat (2011)	n = 12 (Gardening)	n = 11	A range of gardening activities. 1.5h of gardening, planting, fertilising, composting, harvesting. Second hour allocated for socialising, chatting to gardener, having breaks. Two intervention groups, Gardening and Mindful gardening (same activities undertaken but in a different way – being fully present. 1h gardening and remaining time for mindfulness guidance and breaks).	pre and post-test measures only.	Affect	Positive and Negative Affect Scale (PANAS)	9 weeks	9 sessions	150 mins	Once a week	22.5 hours	A community garden	A garden Coordinator	Kaplan Attention Restoration Theory, Ecopsychology, Horticultural Therapy
	n = 16 (Mindful Gardening)
	Mean age G = 63.24 (5.60)	Mean age = 64.94 (5.46)			Quality of life	Quality of Life Enjoyment and Satisfaction Questionnaire – Short Form(Q-LES-Q-SF)
	Mean age MG = 62.18 (5.93)
	88% Female in both groups	75% Female
	No diagnosis
Odeh and Guy (2018)	n = 40 total		Horticultural therapy following a guidebook designed for the programme. All components were gardening related.	Art activity sessions twice weekly for 4 weeks	Mood	Profile of Mood States (POMS)	4 weeks	8 sessions	60 mins	Twice a week	8 hours	Greenhouse of a garden	Horticultural therapist	Horticultural therapy
					Stress	Perceived Stress Scale (PSS)
	Mean age= 33 (SD 5.7)	Mean age= 32.8 (5.6)			Depression	Beck Depression Inventory (BDI – 2nd edition)
	100% female				Anxiety	State-trait anxiety inventory (STAI)
	No information given				Quality of life	Short-Form health survey-36 for health-related quality of life (SF-36)
Pálsdóttir et al., 2020, 2015, 2016)	n = 48	n = 42	10-week structured programme of a range of gardening activities and guided exercise components in addition to usual stroke rehabilitation.	Control group continued their individualised programme of stroke rehabilitation.	Anxiety	Hospital Anxiety and Depression Scale (HADS)	32 weeks	20 sessions	210 mins	Twice a week	70 hours	Alnarp rehabilitation garden. 2-hectare garden	Occupational therapist, horticulturalist, psychotherapist, and physiotherapist	Horticultural Therapy
	Mean age= 67 (47–79)	Mean age= 66 (48–80)
	53% Female	66% Female			Depression
	Stroke				Quality of life	EQ-5D 3L
Siu et al. (2020)	n = 37	n = 36	Each session followed the same structure and had a specific theme and objectives. Non gardening activities included cooking and mindful eating, diaphragmic breathing technique and pressing flowers. Participants were encouraged to share experiences related gardening during reflection. Intervention group was released from normal programme to attend.	Control continued usual day centre attendance – work-related tasks, craft, manufacturing and job coaching.	Anxiety	Depression, Anxiety and Stress Scale (DASS21)	8 weeks, 10 weeks	8 sessions	75 mins. 50 mins of which was gardening	Once a week	10 hours total intervention time. 6.66 hours of gardening	Not specified	Therapists	Horticultural Therapy +  biopsychosocial and multidisciplinary perspective
	Mean age= 50.8 (10.5)	Mean age= 49.7 (8.7)
	46.7% Female	53.3% Female			Stress
	Mental illness, 76.8% had diagnosis of schizophrenia				Wellbeing	Warwick-Edinburgh Mental Wellbeing scale (C-WEMWBS)
Stigsdotter et al. (2018); Corazon et al. (2018); Nacadia Effect Study (NEST) (2013); Sidenius et al. (2017)	n = 39	n = 37	Narcadia Nature Based Therapy (NNBT). Sessions followed the same structure. All weeks had a theme in line with MBSR manual. Individuals could choose tasks undertaken. Most parts of intervention were carried out individually.	1:1 Cognitive Behavioural Therapy (CBT) programme for stress reduction. One hour sessions for 10 weeks	Wellbeing	Psychological general wellbeing index (PGWBI)	12 weeks, 24 weeks, 52 weeks	30 sessions	180 mins	Three days per week	90 hours	Therapy garden at the University of Copenhagen	Led by a clinical psychologist and a gardener	NNBT created with contributions from MBSR, CBT and attention restoration theory
	Mean age= 47.9 (7.8)	Mean age= 44.9 (8.8)
	79% female	73% female			Burnout	Shiron-Melamed Burnout Questionnaire (SMBQ)
	psychiatric diagnosis of adjustment disorder and reaction to severe stress
Vujcic et al. (2017)	n = 16	n = 14	Programme of Horticultural Therapy with specific aims and objectives. Introduction and preparation, then scheduled activities and group sharing. Activities included, potting, harvesting, walking through gardens, weeding. Also some art therapy and relaxation elements e.g. meditation outside and drawing.	Control group received occupational therapy and art therapy as well as conventional treatment in conditions without plants.	Depression	Depression, Anxiety and Stress Scale (DASS21)	4 weeks	12 sessions	60 mins	Three days per week	12 hours	Botanical Garden	No information about who led programme. Mentions it was created in collaboration with psychiatrists and mental health therapists	Horticultural Therapy. Stress reduction theory and Attention Restoration Theory
	Mean age = 45.35 (10.16)				Anxiety
	70% Female
	psychiatric diagnosis of an adjustment disorder and a reaction to severe stress, anxiety or depression disorders. 96% had diagnosis of depression.				Stress
Vujcic et al. (2021)	n = 15	n = 12	Programme of Horticultural Therapy with specific aims and objectives. Introduction and preparation, then scheduled activities and group sharing. Activities included, potting, harvesting, walking through gardens, weeding. Also some art therapy and relaxation elements e.g. meditation outside and drawing.	Control group received occupational therapy and art therapy as well as conventional treatment in conditions without plants.	Severity of mental illness	CGI – Clinical Global Impressions scale	5 weeks	15 sessions	60mins	Three days per week	15 hours	Botanical Garden	No information	Horticultural therapy
	43.92 (10.16)
	70% female
	Psychiatric diagnosis of an adjustment disorder and a reaction to severe stress, anxiety or depression disorders. 96% had diagnosis of depression.

Table 3. Available data from included studies.

Study	Outcomes	Scales	Group	Baseline			Post intervention			Effect estimate	95% CI	Statistical test	P value
				Mean	SD	N	Mean	SD	N
Bay-Richter et al. (2012)	Depression	Montgomery Asperg Depression Rating Scale MADRS	Gardening	No information, published only as abstract
			Control
Brown et al. (2020)	Mood	Profile of Mood States (POMS) – total mood disturbance	Gardening	Median 6.5	range −10 to 30	8	Median change −2	Range −16 to 18	8			Wilcoxon rank sum exact test	0.49
			Control	Median 9.5	range −6 to 46	9	Median change 9	Range −1 to 30	9
	Depression	Centre for Epidemiological studies depression Scale (CESD)	Gardening	Median 0	(range −6 to 2)	7	Median change 0	Range −6 to 2	5				0.38
			Control	Median 6	(range 3 to 15)	9	Median change 0	Range −4 to 18	9
	Quality of life	World health organisation quality of life questionnaire (WHOQOL-BRIEF) – psychological	Gardening	Median 17	(range 14 to 19)	7	Median change 0	Range −3.3 to 2	7				0.77
			Control	Median 16	(range 12 to 18)	11	Median change 0	Range −4 to 4.5	11
Demark-Wahnefried et al. (2018); Cases et al. (2016)	Quality of life	Short-Form health survey-36 for health-related quality of life (SF-36) – mental summary score	Gardening	75.46 (2.86)		24	68.8 (4.42)		22
			Control	74.01 (4.76)		22	75.95 (4)		20
		Short-Form health survey-36 for health-related quality of life (SF-36) – physical summary score	Gardening	72.45 (2.73)		24	67.69 (3.07)		22
			Control	66.14 (3.91)		22	74.67 (3.67)		20
	Stress	Perceived Stress Scale (PSS)	Gardening	13.14 (1.33)		24	13.67 (1.52)		22
			Control	11.37 (1.91)		22	11.46 (1.9)		20
Detweiler et al. (2015)	Quality of life	Quality of Life Enjoyment and Satisfaction Questionnaire – Short Form (Q-LES-Q-SF)	Gardening				Covariate-adjusted mean scores 71.05		n = 12	0.3		F test 1.758	0.201
			Control				Covariate-adjusted mean scores 61.22		n = 10
	Depression	Centre for Epidemiological studies depression Scale (CESD)	Gardening				Covariate-adjusted mean scores 15.61		n = 12	0.37		F test 2.521	0.13
			Control				Covariate-adjusted mean scores 21.31		n = 9
Huang et al. (2018)	Depression	Beck Depression Scale	Gardening			33	7.2	3.16					<0.05
			Control			33	10.25	3.68
Kam and Siu (2010)	Depression	Depression, Anxiety and Stress scale (DASS21)	Gardening	14.6	9.1	12	Change from baseline −9.20	9.15	10				0.04
			Control	9.3	8.9	12	Change from baseline −1.17	8.33	12
	Anxiety		Gardening	15	7.8	12	Change from baseline −9.0	7.62	10				0.01
			Control	9.8	8.7	12	Change from baseline 0.67	7.10	12
	Stress		Gardening	12.6	7.7	12	Change from baseline −6.6	5.30	10				0.05
			Control	11.3	10.8	12	Change from baseline −0.5	6.79	12
	wellbeing	Chinese personal wellbeing index (PWI-C)	Gardening	49.5	11.8	12	Change from baseline 0.6	14.21	10				0.84
			Control	53.2	14.9	12	Change from baseline 1.5	6.07	12
Kim and Park (2018)	Depression	Zung Self-rated depression scale (SDS)	Gardening	44.7	8.6	18	33.4	5.9	18			Paired t test	<0.001
			Control	43.2	6.6	18	43.5	6.8	18				0.9
	Anxiety	State-trait anxiety inventory (STAI)	Gardening	84.1	19.6	18	62.8	12.9	18				<0.001
			Control	85.3	15.3	18	87.5	15.7	18				0.67
Kotozaki (2013a)	Depression	Centre for Epidemiological studies depression Scale (CESD)	Gardening	13.53	10.32	15	7.67	3.64	15			One-way analysis of covariance
			Control	14	11.77	15	13.73	4.04	15
	Quality of life	WHO-QOL-26	Gardening	3.23	0.53	15	2.93	0.58	15
			Control	3.07	0.57	15	3.18	0.55	15
	Affect	POMS	Gardening	23.07	19	15	14.4	13.68	15
			Control	24.4	22.03	15	21.73	19.87	15
	Mental health	General Health Questionaire (GHQ)	Gardening	6	3.34	15	3.2	2.81	15				<0.05
			Control	4.73	2.79	15	5.47	5.79	15
Kotozaki (2013b)	Depression	Geriatric depression scale (GDS-15)	Gardening	3.25	3.37	20	1.85	2.06	20
			Control	3.11	2.64	19	3.42	2.67	19
	Quality of life	WHO-QOL-26	Gardening	3.19	0.24	20	3.43	0.3	20
			Control	3.07	0.39	19	2.98	0.36	19
	PTSD	Clinician Administered PTSD Scale (CAPS)	Gardening	23.5	6.03	20	6.6	5.25	20
			Control	21.84	4.83	19	10.63	8.9	19
Kotozaki (2014a)	Depression	Centre for Epidemiological studies depression Scale (CESD)	Gardening	7.59	4.62	22	4.41	4.34	22			One-way analysis of covariance	0.154
			Control	6.52	6.71	23	8.96	7.88	23
	Mental health	General Health Questionaire (GHQ)	Gardening	4.82	4.6	22	2.14	3.52	22				0.086
			Control	6.52	6.71	23	4.87	6.76	23
Kotozaki (2014b)	Depression	Centre for Epidemiological studies depression Scale (CESD)	Gardening	13.4	7.1	27	11.8	7.4	27			One-way analysis of covariance	0.934
			Control	14.6	6.9	27	12.5	5.2	27
	Mental health	General Health Questionaire (GHQ)	Gardening	7.1	5.1	27	4.4	4.2	27				0.248
			Control	6.8	5.7	27	5	4.7	27
	Quality of life	WHO-QOL-26	Gardening	52.5	5.8	27	53.9	6.5	27				0.297
			Control	52.3	6.3	27	51	5.9	27
	Positive affect	Positive and Negative Affect Scale (PANAS)	Gardening	20.5	6.4	27	23.3	7.4	27				0.011
			Control	23.6	7.8	27	21	7.2	27
	Negative affect	Positive and Negative Affect Scale (PANAS)	Gardening	18.9	7.7	27	15.1	6	27				0.071
			Control	21.8	7.1	27	18.5	6.4	27
	PTSD	Clinician Administered PTSD Scale (CAPS)	Gardening	31.5	6.5	27	10	7.1	27				<0.001
			Control	31.3	6.5	27	16.1	9.3	27
Makizako et al. (2019); Makizako et al. (2015)	Depression	Geriatric depression scale (GDS-15)	Gardening	6.9	4.7	26	4.7	2.7	26			Paired t test	0.744
			Control	6.4	2.5	28	5.1	3.1	28
	Quality of life	Short-Form health survey-12 for health-related quality of life (SF-12)	Gardening	50.8	7	30	51.9	7.7	26
			Control	52.4	6.2	29	50.1	7.5	28
Ng et al. (2018); Chan et al. (2017); Ng et al. (2016); Ng et al. (2019)	Depression	Zung self-rating depression scale (SDS)	Gardening	44.69 (3.75)		29						Repeated-measured analysis of variance (rANOVA) & paired t tests	0.68
			Control	45.31 (5.33		30
	Anxiety	Zung self-rating anxiety scale (SAS)	Gardening	35.14 (2.24)		29							0.81
			Control	34.23 (2.53)		30
	Wellbeing	Ryff’s scale of psychological wellbeing	Gardening	28.14 (4.87)		29							0.34
			Control	12.07 (4.75)		30
Okvat (2011)	Positive Affect	Positive and Negative Affect Scale (PANAS)	Gardening	38.8	3.61	15	39.53(5.70)	5.7	15
			Mindful gardening	36.41	4.56	15	38.13(3.81)	3.81	15
			Control	37	6.42	10	36.64	4.32	10
	Negative affect	Positive and Negative Affect Scale (PANAS)	Gardening	17.76	5.3	15	16.88(5.10)	5.1	15
			Mindful gardening	18.29	7.04	15	17.33(5.46)	5.46	15
			Control	17.81	4.76	10	16.55	5.66	10
	Quality of life	Quality of Life Enjoyment and Satisfaction Questionnaire – Short Form(Q-LES-Q-SF)	Gardening	69.43(5.12)	5.12	15	65.95(8.23)	8.23	15
			Mindful gardening	61.44(8.60)	8.6	15	62.78(11.13	11.13	15
			Control	62.72(9.30)	9.3	10	62.77(8.38)	8.38	10
Odeh and Guy (2018)	Mood	Profile of Mood States (POMS)	No numerical data in published paper
	Stress	Perceived Stress Scale (PSS)
	Depression	Beck Depression Inventory (BDI – 2nd edition)
	Anxiety	State-trait anxiety inventory (STAI)
	Quality of life	Short-Form health survey-36 for health-related quality of life (SF-36)
Pálsdóttir et al., 2020, 2015, 2016)	Depression	Hospital Anxiety and Depression Scale (HADS)	Gardening	5.37			4.33					Wilcoxon rank-sum test, 2-sided	0.31
			Control	5.86			4.68
	Anxiety		Gardening	7.63			6.27						0.42
			Control	7.94			7.39
	Quality of life	EQ-5D 3L	Gardening	0.57			0.6						0.94
			Control	0.56			0.61
Siu et al. (2020)	Anxiety	Depression, Anxiety and Stress Scale (DASS21)	Gardening	0.59	0.55	41	0.64	0.54	37			ANOVA	0.29
			Control	0.71	0.47	41	0.79	0.72	36
	Stress		Gardening	0.73	0.66	41	0.71	0.66	37				0.36
			Control	0.85	0.48	41	0.84	0.65	36
	Wellbeing	Warwick-Edinburgh Mental Wellbeing scale (C-WEMWBS)	Gardening	3.1	0.66	41	3.3	0.73	37				0.01
			Control	3.18	0.71	41	2.95	0.7	36
Stigsdotter et al. (2018); Corazon et al. (2018); Nacadia Effect Study (NEST) (2013); Sidenius et al. (2017)	Wellbeing	Psychological general wellbeing index (PGWBI)	Gardening	46,59	15,38	39	61,44	15,51	39	η2 = 0.144; ω2 = 0.125		Two way mixed design ANCOVA	<0.001
			Control	49,24	16,64	37	59,62	18,87	37	η2 = 0.088; ω2 = 0.067			<0.05
	Burnout	Shiron-Melamed Burnout Questionnaire (SMBQ)	Gardening									Freidman’s test	<0.001
			Control										<0.001
Vujcic et al. (2017)	Depression	Depression, Anxiety and Stress Scale (DASS21)	Gardening							Eta Squared = 0.037		Two factor analyses of variance	0.309
			Control
	Anxiety		Gardening							Eta Squared = 0.042			0.277
			Control
	Stress		Gardening							Eta Squared = 0.163			0.027
			Control
Vujcic et al. (2021)	Severity of mental illness	CGI – Clinical Global Impressions scale	Gardening	4.2	1.082	15	2.47	1.187	15	η2 = 0.313		Two factor analyses of variance	0.002
			Control	3.75	1.138	12	3.67	1.371	12

Table 4. Description of ongoing trials.

Ongoing trials	Study population		Intervention	Control	Outcomes	Scales	Follow up	Location
	Intervention	Control
Litt et al. (2018)	n = 156	n = 156	Community gardening	Waitlist	Wellbeing	Warwick-Edinburgh Mental Wellbeing scale (C-WEMWBS)	9 months	Community garden
					Anxiety	GAD-7
					Stress	Perceived stress scale (PSS)
A Dose of Nature: An Interdisciplinary Study of Green Prescriptions (2019)	n = 240		Gardening activities	No intervention	Depression	Patient Health Questionnaire (PHQ-9)	3–6 months	Greenspace pockets around GP surgeries
	Mild- moderate depression, 18+				Stress	Perceived stress scale (PSS)
					Wellbeing	Warwick-Edinburgh Mental Wellbeing (C-WEMWBS)
Assessing the Effect of Environmental Activity on Depressive Symptoms (2020)	n = 40	n = 40	Six-week intervention involving twice weekly vegetable and flower growing for 90 mins duration.	Educational worksheet on behavioural activation and relaxation techniques.	Depression	Beck depression inventory (BDI-II)	10 weeks	Park
	Mild – moderate depression, 18+				Quality of life	Short-Form health survey-36 for health-related quality of life (SF-36)
Harvest for Health in Older Cancer Survivors (2016)	n = 381		Gardening for 1 year in own gardens with support and supplies provided for by study	Waitlist	Quality of life	Short-Form health survey-36 for health-related quality of life (SF-36)	52 weeks	Own gardens
	Cancer survivors

Bay-Richter, C., Träskman-Bendz, L., Grahn, P., & Brundin, L. (2012). Garden rehabilitation stabilises INF-gamma and IL-2 levels but does not relieve depressive-symptoms. Neurology, Psychiatry and Brain Research, 18(2), 37. https://doi.org/10.1016/j.npbr.2012.02.002

 Google Scholar

Brown, B., Dybdal, L., Noonan, C., Pedersen, M. G., Parker, M., & Corcoran, M. (2020). Group gardening in a Native American Community: A collaborative approach. Health Promotion Practice, 21(4), 611–623. https://doi.org/10.1177/1524839919830930

 PubMed Web of Science ®Google Scholar

Demark-Wahnefried, W., Cases, M. G., Cantor, A. B., Fruge, A. D., Smith, K. P., Locher, J., Cohen, H. J., Tsuruta, Y., Daniel, M., Kala, R., & De Los Santos, J. F. (2018). A pilot randomized controlled trial of a home vegetable gardening intervention among older cancer survivors shows feasibility, satisfaction, and promise in improving vegetable and fruit consumption, reassurance of worth, and the trajectory of central adiposity. Journal of the Academy of Nutrition and Dietetics, 118(4), 689–704. https://doi.org/10.1016/j.jand.2017.11.001

 PubMed Web of Science ®Google Scholar

Cases, M. G., Fruge, A. D., De Los Santos, J. F., Locher, J. L., Cantor, A. B., Smith, K. P., Glover, T. A., Cohen, H. J., Daniel, M., Morrow, C. D., Moellering, D. R., & Demark-Wahnefried, W. (2016). Detailed methods of two home-based vegetable gardening intervention trials to improve diet, physical activity, and quality of life in two different populations of cancer survivors. Contemporary Clinical Trials, 50, 201–212. https://doi.org/10.1016/j.cct.2016.08.014

 PubMed Web of Science ®Google Scholar

Detweiler, M. B., Self, J. A., Lane, S., Spencer, L., Lutgens, B., Kim, D.-Y., Halling, M. H., Rudder, T. F., & Lehmann, L. (2015). Horticultural therapy: A pilot study on modulating cortisol levels and indices of substance craving, posttraumatic stress disorder, depression, and quality of life in veterans. Alternative Therapies in Health and Medicine, 21(4), 36–41.

 PubMed Web of Science ®Google Scholar

Huang, W. Z., Liu, L., Wang, Z. J., Mai, G. H., Cui, A. Y., & Yan, W. (2018). Effect of horticultural therapy on psychological factors of patients with hand functional rehabilitation. Basic & Clinical Pharmacology and Toxicology, 122(2), 50.

 Google Scholar

Kam, M. C. Y., & Siu, A. M. H. (2010). Evaluation of a horticultural activity programme for persons with psychiatric illness. Hong Kong Journal of Occupational Therapy, 20(2), 80–86. https://doi.org/10.1016/S1569-1861(11)70007-9

 Web of Science ®Google Scholar

Kim, K. H., & Park, S. A. (2018). Horticultural therapy program for middle-aged women’s depression, anxiety, and self-identify. Complementary Therapies in Medicine, 39, 154–159. https://doi.org/10.1016/j.ctim.2018.06.008

 PubMed Web of Science ®Google Scholar

Kotozaki, Y. (2013a). Comparison of the effects of individual and group horticulture interventions. Health Care: Current Reviews, 02(02). https://doi.org/10.4172/hccr.1000120

 Google Scholar

Kotozaki, Y. (2013b). The Psychological changes of horticultural therapy intervention for elderly women of earthquake related areas. Journal of Trauma & Treatment, 3(1).

 Google Scholar

Kotozaki, Y. (2014a). Horticultural therapy as a measure for recovery support of regional community in the disaster area: A preliminary experiment for forty five women who living certain region in the coastal area of Miyagi Prefecture. International Journal of Emergency Mental Health and Human Resilience, 16(2), 112–116.

 Google Scholar

Kotozaki, Y. (2014b). The psychological effect of horticultural therapy intervention of earthquake related stress in women of earthquake related areas. Journal of Translational Medicine & Epidemiology, 2(1)

 Google Scholar

Makizako, H., Tsutsumimoto, K., Doi, T., Makino, K., Nakakubo, S., Liu-Ambrose, T., & Shimada, H. (2019). Exercise and horticultural programs for older adults with depressive symptoms and memory problems: A randomized controlled trial. Journal of Clinical Medicine, 9(1), 99–112. https://doi.org/10.3390/jcm9010099

 PubMed Web of Science ®Google Scholar

Makizako, H., Tsutsumimoto, K., Doi, T., Hotta, R., Nakakubo, S., Liu-Ambrose, T., & Shimada, H. (2015). Effects of exercise and horticultural intervention on the brain and mental health in older adults with depressive symptoms and memory problems: Study protocol for a randomized controlled trial [UMIN000018547]. Trials, 16(1), 499. https://doi.org/10.1186/s13063-015-1032-3

 PubMedGoogle Scholar

Ng, K., Sia, A., Ng, M., Tan, C., Chan, H., Tan, C., Rawtaer, I., Feng, L., Mahendran, R., Larbi, A., Kua, E. H., & Ho, R. (2018). Effects of horticultural therapy on Asian older adults: A randomized controlled trial. International Journal of Environmental Research and Public Health, 15(8), 1705–1719. https://doi.org/10.3390/ijerph15081705

 PubMed Web of Science ®Google Scholar

Chan, H. Y., Ho, R. C., Mahendran, R., Ng, K. S., Tam, W. W., Rawtaer, I., Tan, C. H., Larbi, A., Feng, L., Sia, A., Ng, M., Gan, G. L., & Kua, E. H. (2017). Effects of horticultural therapy on elderly’ health: Protocol of a randomized controlled trial. BMC Geriatrics, 17(1), 192. https://doi.org/10.1186/s12877-017-0588-z

 PubMedGoogle Scholar

Ng, K. S. T., Chan, H. Y., Sia, A., Mahendran, R., Tan, H. C., Feng, L., Ng, M. K.-W., Tan, C. T. Y., Larbi, A., Ho, R. C.-M., & Kua, E. H. (2016). The effects of horticultural therapy on the psychological well-being and associated biomarkers of elderly in Singapore. Alzheimers and Dementia, 12(7), 1180. https://doi.org/10.1016/j.jalz.2016.07.117

 Google Scholar

Ng, K. S. T., Sia, A., Ng, M. K.-W., Kua, E., & Ho, R. C.-M. (2019). Horticultural therapy improves IL-6 and social connectedness differentially. Alzheimers and Dementia, 15(7), P1211–P1211. https://doi.org/10.1016/j.jalz.2019.06.3649

 Google Scholar

Okvat, H. (2011). A pilot study of the benefits of traditional and mindful community gardening for urban older adults’ subjective well-being [Doctoral dissertation, Arizona State University] ASU Digital Repository. https://repository.asu.edu/

 Google Scholar

Odeh, R., & Guy, C. (2018). Gardening and art study: Assessing biometric changes for healthy women in a randomized. Controlled Intervention. Proceedings of the Florida State Horticultural Society, 131, 224–227.

 Google Scholar

Pálsdóttir, A., Stigmar, K., Norrving, B., Grahn, P., Petersson, I., Åström, M., & Pessah-Rasmussen, H. (2020). The nature stroke study; NASTRU: A randomized controlled trial of nature-based post-stroke fatigue rehabilitation. Journal of Rehabilitation Medicine, 52(2), jrm00020. https://doi.org/10.2340/16501977-2652

 PubMed Web of Science ®Google Scholar

Pálsdóttir, A. M., Andersson, G., Grahn, P., Norrving, B., Kyrö-Wissler, S., Petersson, I. F., & Pessah-Rasmussen, H. (2015). A randomized controlled trial of nature-based post-stroke fatigue rehabilitation ("the nature stroke study" (NASTRU)): study design and progress report Paper presented at the ESO, Glasgow.

 Google Scholar

Pálsdóttir, A. M., Stigmar, K., Grahn1, P., Norrving, B., & Pessah-Rasmussen, H. (2016). The Nature Stroke Study (NASTRU), Nature-based rehabilitation of post stroke fatigue- A randomised controlled trial. Paper presented at the 2nd European Stroke Organisation Conference 2016.

 Google Scholar

Siu, A. M. H., Kam, M., & Mok, I. (2020). Horticultural therapy program for people with mental illness: A mixed-method evaluation. International Journal of Environmental Research and Public Health, 17(3), 711–710. https://doi.org/10.3390/ijerph17030711

 PubMed Web of Science ®Google Scholar

Stigsdotter, U. K., Corazon, S. S., Sidenius, U., Karlsson Nyed, P., Larsen, H. B., & Fjorback, L. O. (2018). Efficacy of nature-based therapy for individuals with stress-related illnesses: Randomised controlled trial. The British Journal of Psychiatry: The Journal of Mental Science, 213(1), 404–411. https://doi.org/10.1192/bjp.2018.2

 PubMed Web of Science ®Google Scholar

Corazon, S. S., Nyed, P. K., Sidenius, U., Poulsen, D. V., & Stigsdotter, U. K. (2018). A long-term follow-up of the efficacy of nature-based therapy for adults suffering from stress-related illnesses on levels of healthcare consumption and sick-leave absence: A randomized controlled trial. International Journal of Environmental Research and Public Health, 15(1), 137–147. https://doi.org/10.3390/ijerph15010137

 PubMed Web of Science ®Google Scholar

Nacadia Effect Study (NEST) (2013). Identification number NCT01849718. https://clinicaltrials.gov/ct2/show/NCT01849718

 Google Scholar

Sidenius, U., Karlsson Nyed, P., Linn Lygum, V., & Stigsdotter, U. K. (2017). A diagnostic post-occupancy evaluation of the Nacadia(R) therapy garden. International Journal of Environmental Research and Public Health, 14(8), 882. https://doi.org/10.3390/ijerph14080882

 PubMed Web of Science ®Google Scholar

Vujcic, M., Tomicevic-Dubljevic, J., Grbic, M., Lecic-Tosevski, D., Vukovic, O., & Toskovic, O. (2017). Nature based solution for improving mental health and well-being in urban areas. Environmental Research, 158, 385–392. https://doi.org/10.1016/j.envres.2017.06.030

 PubMed Web of Science ®Google Scholar

Vujcic, M., Tomicevic-Dubljevic, J., Tosevski, D. L., Vukovic, O., & Toskovic, O. (2021). Development of evidence-based rehabilitation practice in botanical garden for people with mental health disorders. Health Environments Research & Design Journal, 14(4), 242-257. https://doi.org/10.1177/19375867211007941

 Google Scholar

Litt, J. S., Alaimo, K., Buchenau, M., Villalobos, A., Glueck, D. H., Crume, T., Fahnestock, L., Hamman, R. F., Hebert, J. R., Hurley, T. G., Leiferman, J., & Li, K. (2018). Rationale and design for the community activation for prevention study (CAPs): A randomized controlled trial of community gardening. Contemporary Clinical Trials, 68, 72–78. https://doi.org/10.1016/j.cct.2018.03.005

 PubMed Web of Science ®Google Scholar

A Dose of Nature: An Interdisciplinary Study of Green Prescriptions (2019). Identification number NCT04175561. https://clinicaltrials.gov/ct2/show/NCT04175561?term=a+dose+of+nature&draw=2&rank=1

 Google Scholar

Assessing the Effect of Environmental Activity on Depressive Symptoms (2020). Identification number IRCT20181206041871N1. https://trialsearch.who.int/?TrialID=IRCT20181206041871N1

 Google Scholar

Harvest for Health in Older Cancer Survivors (2016). Identification number NCT02985411. https://clinicaltrials.gov/ct2/show/NCT02985411

 Google Scholar