Plants & People

Does biodiversity make gardening less stressful?

There are a few studies saying a garden can improve wellbeing, but what if your garden is a source of stress? You’re not alone, but research gives some hints about what to change to help improve things.

There have been a few studies connecting urban gardens with increased wellbeing. But is having a patch of green space near you enough? Christopher Young and colleagues in Switzerland and Germany have been examining how gardeners benefit from gardens. Their study, published in Landscape and Urban Planning, suggests that increased biodiversity could improve the positive effect of a garden.

The research was an analysis of the responses of around 300 leisure gardeners in Zurich. The authors used the results to create a Structural Equation Model to see what factors correlated with increased restorative value. One of the interesting factors of the model was that it could take into account the type of garden that people garden in, so allotments could be compared to domestic urban gardens.

The team found that being an allotment gardener was associated with higher levels of restoration compared to domestic gardener. This does not surprise me, as you have to actively go and get an allotment to garden it. So the first result does look a bit like saying “the model found that people who make the effort to get more space to garden in, enjoy gardening.” However, the authors point out this result wasn’t found in a previous study by Cervinka et al. which seems a little odd. Young and colleagues point to another study that also stressed the importance of the social element of allotment gardening. So maybe the gardeners in Cervinka et al.’s study allotments all annoyed each other and so cancelled out the difference in benefit.

Another finding in the model is that biodiversity had a small but positive effect on the restorative power of gardens. I was sceptical of this finding. People who like gardening will go out and buy different plants, so is biodiversity in a garden a proxy measure of how much people like gardening? If so, then we have another “people who enjoy gardening get a benefit from a garden” result. However, this appears not to be the case.

“A higher number of plant species (with different colours, heights, leaf shapes etc.) should in general result in higher visual complexity and thus higher attention restoration,” Young and colleagues write in their article. “Our confidence in this mechanism is additionally supported by the control variable biodiversity preference. Thanks to this variable we can to a certain extent rule out the possibility of the number of plant species having a positive effect on gardeners’ restoration merely because it coincided with their preferences. As other studies describe, some gardeners gain much satisfaction from shaping the garden according to their preferences (Gross and Lane, 2007, Milligan et al., 2004). If gardeners actively aim to have a high number of plant species in their garden, achieving this could also have a positive effect on restoration. By controlling for biodiversity preference, we can argue that the association of the number of plant species with perceived restorativeness in our SEM was independent of gardeners achieving what they planned.”

So while biodiversity could be a sign of people aiming to collect and appreciate plants, the line, independent of gardeners achieving what they planned, shows that the biodiversity effect is not entirely a proxy.

A creative person can use their garden to create stress for others. Image: Canva.

As well as evaluating the benefits of gardening, the authors also consider gardens as a source of stress. The number of people stressed by their gardens is low, but still substantial, with 16% of gardeners saying they agreed or fully agreed with the statement that they often felt stressed by the garden. “As far as we know, this is the first quantitative appraisal of garden-related stress,” the authors write.

“Our data show that domestic gardeners were significantly more likely to experience garden-related stress than allotment gardeners, which is contrary to what we expected. We hypothesized that the strict formal rules of allotment associations would cause more garden-related stress among allotment gardeners if they feel more under pressure to keep their garden tidy. One reason for the contrary finding may be that these rules do not put additional pressure on allotment gardeners because they prefer tidy gardens anyway as our variable designed to capture the preference for a tidy garden suggested. On the other hand, informal garden norms in a neighborhood can also put domestic gardeners under pressure (Nassauer et al., 2009), blurring differences between the two garden types in respect to rules.”

I can sympathize with this view. I’ve followed no-mow May, with can’t-be-bothered June and who-cares-I-like-the-sound-of-grasshoppers July. My front lawn looks different to everyone else’s, and I am aware of that. So far laziness is beating peer-pressure, which is good news for the grasshoppers and crickets, and also for the hedgehogs that feed on them. However, the same peer-pressure will mean that next year the chaos out front will look a bit more planned.

Young and colleagues also return to the idea of self-selection in considering stress. Even if allotments and gardens have rules, they note that it’s a lot easier for allotment owners to stop their allotment being a source of stress. “Allotment gardeners may on average be more committed or enthusiastic gardeners than domestic gardeners, as allotment gardeners who cease to enjoy gardening can give up their allotment quite easily. For domestic gardeners, the garden is usually tied to their home. This means that giving up the garden would involve much greater effort than for allotment gardeners e.g. requiring moving into an apartment without a garden. This amounts to a negative self-selection process for allotment gardeners who do not enjoy gardening or feel stressed by it.”

One of the findings in the study that is a little glossed over in the discussion is that allotment gardeners were socio-economically less privileged than domestic gardeners. I am wondering if that is an aspect of Zurich or Swiss culture, or if it holds true more widely. The reason I find it interesting is that garden space could also be seen as a proxy for financial wealth. If that’s the case then the effect of gardens on wellbeing could be a kind of measurement of financial statues being correlated with wellbeing. However, given that allotment owners aren’t privileged in this study, but do get higher restoration, that would seem to torpedo the garden as wealth criticism.

The authors state there are limitations to the certainty of their conclusions due to the nature of the sampling they worked with. But their results do show there is definitely something interesting that deserves further investigation. The study of gardens as a source of stress as well as benefits is important. It would be good to see this develop further. Understanding what makes a less stressful garden, but still have restorative benefits would be extremely useful.

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