Abstract

Once a marginal practice, installing native plants on residential street verges is becoming increasingly common in the city of Perth, with a number of local governments (as well as state government entities) actively promoting and incentivising the practice. However, little information is available on the benefits and challenges of transforming the street verge to a native garden, from either the residents’ point of view, nor from key stakeholders with an interest in streetscape management. This paper presents selected results of social-ecological research on suburban street verges in Perth. We interviewed verge gardeners from 22 households to understand their motivations and sources of inspiration. Concurrently, we conducted plant surveys, and observations of pollinating insects in residents’ verge gardens. Most verge gardeners were motivated to reduce resource use, or improve the visual appeal of the verge. We also conducted an audit of Perth LGAs’ verge gardening policies, and conducted interviews with 30 stakeholders across State and local governments, horticulture and irrigation suppliers, peak bodies, environmental consultants, utility providers, developers, and champions of change. We used participatory social network mapping to understand how knowledge of the transformative practice of native verge gardening was shared. The prevalence of native verge gardening in Perth has risen dramatically in the last ten years, accompanied by changes in governance, practical knowledge and social norms. Both ‘top-down’ (government-led) and ‘bottom-up’ (community-led) initiatives have played a significant role in dissemination of verge gardening information and practices. 

Introduction

The vegetation alongside city streets and road corridors plays a key role in providing habitat for wildlife and green space benefits for people. Roadside vegetation occurs within the ‘road easement’, ‘nature strip’, or ‘street verge’. We will use the term ‘street verge’ throughout this paper, which can be defined as the area of land between the roadway and the front property boundary. These strips of land were originally conceived as fulfilling a largely utilitarian purpose, as designated space for services such as electricity, gas, water and telecommunications, and facilities such as footpaths and bus stops. Street verges can also play a key role in providing a wide range of social, economic and ecological services.

With increasing urban housing density and greater attention given to urban forests and canopy cover, the way that street verges are managed and used in Australian cities is a rapidly evolving area of policy change and community interest. To date, most existing research on urban roadside vegetation has focussed on the role of street trees. However, the lower vegetation strata are also part of the urban forest. Further, while street trees are managed by local authorities, the ground cover and lower vegetation strata are generally maintained by residents, making an interesting case study of the intersection of public and private interests in urban greening. In the city of Perth, many local government authorities now permit residents to convert street verges in front of their dwelling from ‘traditional’ verge treatments such as grass to low growing, native gardens, providing certain conditions are met (Figure 1). ‘Verge gardens’ are perceived to require less water and better reflect a local sense of place by using plants endemic to the Perth region.

In this research project, we set out to understand the socio-ecological benefits and challenges of planting native gardens on nature strips in Perth suburbs. Nature strip gardening is a form of citizen-led urban greening, involving residents planting and caring for understorey vegetation (and even trees) along the road verge.

Perth presents a particularly interesting case study for the research, due to its location in a biodiversity hotspot, and public policy initiatives to lower water consumption as a consequence of long-term declines in precipitation observed since the 1970s, which have placed pressure on water supply. Residential gardens consume a large proportion of domestic water supply. Many local governments now offer financial incentives and rebates to encourage verge conversions. Explicit social-ecological research in urban areas presents great potential for further our understanding of the impact of urban greening programs (Pauli et al. 2020).

Figure 1: Examples of street verge gardens in suburban Perth

There is a growing trend for households in Perth to install native and waterwise gardens on nature strips. Kangaroo paws (Anigozanthos spp.) are a popular choice (top L), and some gardeners mix native species with exotic species (top R). In the example across the centre, the gardener has installed a raised bed for growing herbs and vegetables. Some local governments organise ‘waterwise verge garden’ awards (lower L). Some native verge gardeners incorporate annuals amongst local endemics for a vibrant display in spring (lower R).

The overall aim of this research was to gather empirical data on the social and ecological values of street verge gardens in Perth, to better support decision making by local authorities and local residents. The major objectives of the research were to:

• Understand, the motivations and challenges for native verge transformations from the perspective of the residents, highlighting the potential social impacts of verge gardening activities.
• Quantify potential ecological values by sampling a selection of transformed verge gardens for plants, birds, and flower-visiting insects.
• Capture a snapshot of Local Government Authority (LGA) policies and perspectives on verge transformation with native species, as the primary stakeholder managing this land area.
• Understand the network of interactions between stakeholders, especially in terms of information sharing.

We developed recommendations for decision makers (including local authorities and local residents) to ensure that the social and ecological potential of native verge gardens can be realised, and highlight the particular challenges that are associated with this activity. Full details of the research results and recommendations are provided in Ligtermoet et al. (2021) and Pauli et al. (2021). 

Methods and results

Social and ecological values of verge gardens

A key element of the research involved understanding the social and ecological values of a range of different native verge gardens, established for different lengths of time, and in different parts of metropolitan Perth. The research team approached representatives of two suburban Perth LGAs which had long-established incentive programs promoting native verge gardens (City of Subiaco representing the inner city, and City of Stirling representing middle-ring suburbs), to ask them to distribute an invitation to residents to participate in the research. A strong initial response from residents demonstrated a high level of interest in participating in this kind of research.

We interviewed verge gardeners from 22 households to understand their motivations and sources of inspiration. Verge gardeners were selected to cover a range of socio-demographic variables, as well as a range of verge garden sizes and ages. Interview questions centred on the drivers, challenges and opportunities encountered during verge gardening. Concurrently, we conducted plant surveys, and observations of pollinating insects in residents’ verge gardens. Pollinator observations were conducted three times over the period October 2019-March 2020, during the period of maximum activity for native bees. Pollinator surveys identified the presence of at least eight species of native bees visiting verge gardens.

In terms of initial motivations for undertaking verge transformations, the most common reasons reflected practical motivations to reduce time, expense, water use and maintenance. Figure 2 highlights the major reasons given for converting verges to native gardens. There was limited overlap between residents nominating wanting to reduce water use, and residents wanting to improve the visual appeal of the verge. This suggests that aesthetic concerns and norms are a key driving factor for verge conversions, which has potentially been overlooked in research to date. While some respondents had an initial interest in native plants, most people interviewed had limited initial knowledge, and learnt more about native species and ecology through the process of verge gardening. This indicates that limited knowledge of native plants is not a barrier for residents wishing to commence a verge garden.

Households gain a variety of benefits from verge gardening, including personal satisfaction, shade and cooling, privacy from the street (if desired), connection to nature, and social interaction while out on the verge. The benefits vary widely by household, depending on individual preferences. A neighbourhood streetscape and network approach can help verge gardens act as connectors between neighbours, as well as appropriately develop habitat for small animals and invertebrates.

Figure 2: Initial impetus for verge transformation

Note that many respondents provided more than one reason for their initial decision to transform their verge. Excluded from the graphic are reasons with three or fewer responses. Responses were classified based on respondents’ answers to interview questions.

Plant surveys identified at least 265 distinct species from the 22 verge gardens. The geographic origins of species identified from verge gardens are shown in Figure 3. Around 41% of the species planted occur naturally on in the Perth subregion of the Swan Coastal Plain IBRA¹ region, and a further 28% of species originated elsewhere in Western Australia. In terms of choosing particular species, many residents wanted to have either Australian native plants, or endemic Swan Coastal Plain plants. The motivations behind this were multiple: some residents wanted to choose species that were likely to survive, being from the local area, whereas others wanted to provide habitat for local species in a miniature replica of remnant vegetation. The most commonly planted species closely reflect the species that were pre-selected for distribution to residents by local government authorities (about half of the respondents had received assistance from their local councils for the verge garden transformation, often in the form of free or subsidised plants). This close link demonstrates that verge species composition can be heavily influenced by local authorities.

Figure 3: Location of origin for species deliberately planted in native verge gardens

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¹ Interim Biogeographic Regionalisation of Australia

Based on interviews with residents, we developed a preliminary ‘typology’ of verge gardeners, which can be related to policy decisions (Figure 4). ‘Early Adopters’ are motivated by a combination of a sense of environmental responsibility and interest in ecology and conservation, and rarely access incentive programs, but could act as sources of inspiration. ‘On The Fence’ residents had toyed with the idea, but made the final decision to start because of incentive programmes. Residents in the ‘About Time’ category timed verge transformations with events such as retirement, moving, building and renovating.

Left – Figure 4: A typology of verge gardeners.
The categories at right are not exclusive – some residents would fit into multiple categories.

Verge garden policy audit

The research team undertook an audit of publicly available verge garden and urban forest policies for 31 LGAs in the Perth region. As of January 2021, all but two LGAs had a publicly available verge policy online, and all but one permit native verge gardens. Twenty of the 31 LGAs had Urban Forestry or Greening plans (including two in draft status). Of the 31 LGAs, only nine LGAs currently require residents to obtain permission to install a native verge, while 21 allow residents to install native verge gardens without special permission, providing that the LGA guidelines are followed. Plant height restrictions are variable, ranging between 50 cm to 75 cm, with some LGAs simply that plant height allows for clear lines of sight at all times. The full audit of LGA verge garden policies can be found on pages 21-24 of Ligtermoet et al. (2021) (publicly available report).

There has been a rapid increase in the development of verge garden policies in Perth over the last decade, and even in the last few years. A small number of LGAs have long-standing (i.e. 10⁺ years) policies on native verge gardens, while most have developed guidelines more recently. The increased visibility of verge garden policies may have been driven by a range of factors specific to the Perth context, including active community groups and promotion by influential actors at the state and local government level. Among these drivers may be that LGAs must have a waterwise verge policy in order to be certified as a ‘Waterwise’ Council by the state water utility, the Water Corporation (a government trading entity). An integral component of the research project was to understand how different stakeholders have interacted to disseminate knowledge on verge gardening in Perth, in terms of knowledge of both policies and guidance, and the technical knowledge of how to undertake verge conversions.

Mapping verge garden knowledge networks

The research team conducted interviews with 30 stakeholders across a broad range of categories, including State and local governments, horticulture and irrigation suppliers, peak bodies, environmental consultants, utility providers, developers, and champions of change. We used participatory social network mapping to understand how knowledge of the transformative practice of native verge gardening was shared. During interviews, each respondent was asked to draw a social network map of how they interacted with key stakeholders to share information, resources, labour and finances related to native verge gardening. The exercise resulted in 268 named entities or individuals within the collective stakeholder network, and almost 1000 separate directional flows of resources among entities in the network.

Network analysis using a measure of ‘betweenness centrality’ (an indicator of the degree to which an individual entity forms a link between other entities – and can therefore act as an important broker of information) uncovered a number of similar ‘communities’ in terms of the way that they share information. The different entities within each ‘community’ cover a range of different stakeholder types, which indicates that the knowledge network for sharing information and resources on verge gardens is diverse, with interaction and discussions across traditional ‘siloes’, and direct flows of information between community champions and elected officials in positions of influence.

The full network, coded according to the different communities, is shown in Figure 5. A more detailed breakdown of the stakeholders represented in the two central communities of ‘Promoters’ and ‘Enablers’ is presented in Figure 6, highlighting the close relationship that enables change to occur in streetscape vegetation policy and practice.

Figure 5: Graphical representation of social network analysis based on ‘betweenness centrality’ metric.

Social network analysis produced by Kirsten Martinus. Communities named based on commonalities in mode of operation, as defined by the author.

Figure 6: Breakdown of the stakeholders involved in each of two influential ‘communities’ in verge gardening.

‘Promoters’ provide the impetus for policy change to occur, advocating for native vegetation on streetscapes, and often providing incentives and knowledge that can aid ‘Enablers’. ‘Enablers’ respond to ‘Promoters’ by enacting the changes at a local level that need to occur for uptake of new/different streetscape vegetation policies. Each community is comprised of a particular number of specific entities, as identified in social network analysis. The pie chart shows the percentage of specific entities that have a primary affiliation with particular stakeholder types. For example, under ‘Promoters’, approximately one-third of all the entities from this community are State government stakeholders, and around one-fifth are from different Peak Bodies.

Key findings

This three-year program of research uncovered a diverse range of key findings relevant to the role of native verge gardens in urban greening. An expanded list of key findings are provided in Ligtermoet et al. (2021) and Pauli et al. (2021). From the overview results presented here, key findings include:

• Native verge gardens can showcase and normalize the use of local native plants in landscaping, as well as provide some additional habitat and foraging space for native fauna (including invertebrates). While individual front verge gardens are small patches, collectively they can add up to larger areas, particularly if linked with vegetated corridors in public green spaces and along arterial roads. Research in other places has found that verge gardening is ‘contagious’ along streets – as verge gardens appear, more and more residents are inclined to also take up the practice.
• Native verge gardens have shifted from a marginal practice to one that is sanctioned by most local government authorities in the city of Perth. Social norms have also shifted, with increasing uptake of verge conversion incentive programs by residents. The appearance of specialist verge landscaping firms and commercially-available nursery ranges of plants promoted as ‘verge-suitable’ highlights the increasing demand for native verge gardens.
• Residents who had taken part in incentive and rebate programs delivered by local governments were generally appreciative and espoused positive views of “the council”, often to their neighbours. Residents who had not taken part in incentive programs were often more wary or circumspect in their views as to “the council’s” approach and attitude towards verge transformations, sometimes being concerned about potential punishment or lack of acceptance of residents’ plans or ideas.
• Verge gardeners may be primarily interested in either saving water or in creating a more visually appealing street frontage. Those who are less interested in water conservation may still choose plants that require regular irrigation, or might overwater plants that are actually waterwise. To achieve both water conservation and aesthetic improvement, practical information and visual examples of how to achieve a beautiful, waterwise garden are required.
• Workshops, local government websites, booklets and ‘how-to’ videos are valuable sources of information for verge gardeners. Street verges present challenges that set them apart from other domestic garden zones, including poor soil, depleted nutrients, persistent weeds, higher temperatures and sometimes full shade. Many verge gardeners are novices with native plants, and require specific information on soil preparation, local endemic species and where to buy them, and watering needs.
• The prevalence of native verge gardening has risen dramatically in the last ten years, accompanied by changes in governance, practical knowledge and social norms. Stakeholder and social network analysis revealed a surprising diversity of stakeholders and the important role of both ‘top-down’ (government-led) and ‘bottom-up’ (community-led) initiatives in the dissemination of practical knowledge.

Our research provides a fascinating road map of how a once marginal social-ecological practice can become mainstream.

Acknowledgements

We would like to acknowledge that this research took place on Whadjuk Noongar Boodja (Country), metropolitan region of Perth. We respectfully acknowledge the sovereignty of all of Australia’s first peoples, their ancestors, and Elders, past, present and emerging and that their lands and waters of Australia have never been ceded.

The research presented here was supported by the Clean Air and Urban Landscapes Hub (https://nespurban.edu.au/). The Clean Air and Urban Landscapes hub was funded by the Australian Government’s National Environmental Science Program. We acknowledge the generosity of all our research participants in sharing their time, experiences and expertise with the research team.