In total 296 potential participants were approached (152 gardeners starting gardening in a community garden and 144 matched non-gardeners) and 141 were not included resulting in a final sample of 155 participants at baseline (response rate: 49.3% for gardeners and 55.6% for controls) (Fig. 1). We recruited gardeners from 19 different community gardens during the two gardening seasons: March-June (57.6%) and September-November (42.3%). The plots obtained were maintained either collectively (68.2%) or individually (31.8%). Gardens were rarely located next to gardeners' homes. Gardeners either walked/biked to the garden (72,7%, mean travel time: 8.6 min) or used car/public transportation (27.3%, mean travel time: 21.2 min). Only 14 participants were lost to follow-up between t0 and t1, and 66 matched pairs were included in the analysis.
Sociodemographic characteristics of the participants at baseline are shown in Table 1. The mean age of gardeners was 44.0 years. Most of them were women, subjects who held a university degree, and reported having no experience in gardening. There were some differences between the gardeners and the controls at baseline: gardeners had lower education level, lower BMI and gardeners’ households reported lower percentage of meals consumed outside of the home.
At t1, the quantity of fruit and vegetables harvested from the garden was 19.8 (SD 36.2) g/d per person (data not shown). No significant impact of participating in a community garden was observed neither on the main outcome variable (household fruit and vegetables supply) nor on any of the other outcomes, as shown by the lack of significance for the interaction terms (group*time) (Table 2). Even when removing the theoretical expenditure attributed to produce from the garden, there was no measurable impact of garden participation on total food expenditure and on food-group expenditure shares (data not shown).
At t1, 24% of the gardeners surveyed had dropped out the garden during the year. There was inter-individual variability in the frequency of garden attendance during the year, the majority of gardeners visiting the garden at least once a month throughout the year (56.1%) or over a period from 6 to 9 months (18.2%), while others visited the garden for shorter periods, from 3 to 6 months (16.6%) or only few times a year (9.1%). Sensitivity analyses performed on sub-samples including only active gardeners (who visited the garden at least once a month throughout the year, N = 37) or only those who did not drop out the garden during the year (N = 50) also showed a non-significant effect of participating in a community garden on outcome variables (Additional files 2 & 3). In the post-survey questionnaire, the majority of gardeners stated they did not perceive any change in their fruit and vegetables consumption, physical activity, life satisfaction and social relation due to gardening (Additional files 4).
Qualitative evaluation
The qualitative evaluation provided elements of answers that could explain the lack of change in gardeners’ lifestyles observed in the quantitative study. Of the 15 gardeners interviewed, the majority were active gardeners (N = 9), 4 visited the gardens over a period from 6 to 9 months and 2 less than 3 months.
Nine respondents perceived no change in their lifestyles after one year of gardening. This lack of benefit cannot only be explained by having a negative gardening experience, as one gardener described: "My life is the same as before [the garden], but it's true that it's a plus to have this garden anyway. It's among the positive things in my life, but after that it's not really changing my life actually” (Woman 1, age 54). A couple of respondents pointed out that participation in the garden was just part of their health and environmental consciousness: "I was already a nature enthusiast before. What I mean is that I have always been environmentally conscious, and caring about nature” (Man 1, age 34).
It is also possible that a follow-up period of one year is not sufficient to perceive changes. For example, one woman shared: “I hope I'll improve over time” (Woman 7, age 63).
The interview also highlighted several barriers to community garden participation the most mentioned being the lack of time to garden. Nine gardeners, mostly women, confessed facing greater challenges balancing the demands of gardening with their personal and professional lives, which could lead to feelings of guilt. One gardener mentioned:
At first, I didn't know if I would have enough time to invest myself in the garden […]. Indeed, it actually requires a lot of time. […] You see what time I get home from work and everything. I don't have time for this. I see them working. At first, I felt guilty, I thought, "Oh, now I see them and so on, and then I don't go there" I had no experience of gardening and how long it took. […] It's true that it's great, it's almost in a meditative state, it brings me a lot of well-being, but it takes a lot of time (Woman 2, age 42).
The demands of daily life are an important factor associated with participation, regardless of gardeners’ motivation:
My problem is to go there regularly. I said yes, I signed, and I thought I'm going to participate a lot. In the end, not that much, because I had a lot of events. My place of work changed. My husband was very ill. My father was very ill, while he’s in Toulouse, et cetera. My car is broken, there are things like that.... […] If it was in the same neighbourhood it would be easier. (Woman 3, age 61).
The distance between the garden and the house can be an additional source of discouragement outweighing benefits from the garden:
What’s difficult is not the time, it is the trip. It’s to organize the movement because you don’t come for 10 minutes, you come to stay longer than that. Therefore, the moving time, and the round trips make you sometimes not to always find the time to do it. If it was just next door, it would have been easier. (Woman 4, age 41).
These quotations underline how difficult it was for participants to make time in their busy lives to access the garden away from their homes. Other barriers mentioned by the gardeners were difficulties of gardening and the lack of experience (N = 3). One gardener explained that:
What I first noticed was that this work is not actually simple as people think. It’s not just planting and harvesting. You have to know what you’re planting. You have to know many plants. I know some of them. No, it’s not an easy job. You need to also know how to manage water because you can garden by putting a lot of water especially here in the South. It's a bit risky. It’s depends. Since we don't want to use pesticides, we want it to be as natural as possible. It’s not always an easy job. (Woman 5, age 65).
Lack of gardening knowledge, especially for beginning gardeners, can lead to a negative gardening experience if they are not helped or supervised by other more expert gardeners, as explained by this woman:
I had to make mistakes, I don't know which ones because we don't have– It's a garden where there aren't many people, so it's hard to get advice, it's hard to look at on the internet. That's not what I expect from a garden, that's the discussion, that's what I want to get tips, because there are people who have been doing this for a longer time. It didn't work for me. (Woman 6, age 60).
The difficulty of gardening, especially soil preparation and bending down can be a hindrance for people with fragile health such as the elderly: “After all, I’m 63 years old, and I don't have the corpulence, the physical resistance to mix the soil. Moreover, I sleep very badly because I feel pain everywhere. (Woman 7, age 63).
Although many gardeners mention the friendly moments in the garden, tension related to the management of garden can arise and lead to conflicts between gardeners. This was notably the case for one of the interviewed gardeners:
I refuse all fixed patterns of thinking. These people, unfortunately, behind their participatory democracy side, are oligarchs, sorry. I can't stand the oligarchy. Oligarchy is the power of a few behind a pseudo-democratic form. I don't want to be given orders, at least not in the garden, so I refuse to see them and leave. (Woman 8, age 48).