Concrete jungles

On a hot summer’s day, I weave my way through throngs of Saturday shoppers on Brixton high street, South London. Turning onto a cooler side road, I reach a scruffy area behind the shops. This looks promising. On the walls, behind the waste bins and on the edge of the pavements, is a delightful selection of wild plants. My eye is first drawn to Capsella bursa-pastoris (shepherd’s-purse) rooted by a streetlight, its heart-shaped fruit instantly recognisable. Next I spot mauve-flowered Cymbalaria muralis (ivy-leaved toadflax), a Mediterranean native

A native plant is one that originated or arrived naturally in a particular place without human involvement. In the British Isles, native plants are those that were here during the last ice age or have arrived unaided since.

and a rock-garden plant, which has seeded itself on a wall. Down on the kerb, yellow Senecio squalidus (Oxford ragwort), a relative of our common ragwort, is blooming away by a bin. I kneel down next to the plant and a concerned passer-by asks if I’m okay. I reassure him I’m fine. Better than fine.

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Senecio squalidus (Oxford ragwort). From Mount Etna in Sicily to the Oxford Botanic Gardens, and then on to Oxford rail station, this consummate traveller has spread throughout the rail network and into most towns and cities in Britain

As an ecologist by training, I’m delighted by the diverse, ever-changing plant communities on our pavements and the nooks and crannies of our urban environments, and fascinated by the myriad features that enable them to thrive. I happily spend hours on urban backstreets, often on my knees, because laid out in front of me are an array of intriguing adaptions for living in a dry and nutrient-poor environment. Entire ecosystems are contained within the cracked concrete – there is beauty nestled within those inhospitable crevices. There are lessons to be found here too, and a world of stories.

Take Oxford ragwort which, despite its name, is of Sicilian origin. In his 2025 book Urban Plants, botanist Trevor Dines identifies it as a hybrid

A plant produced by crossing two distinct parents, often different species, to produce offspring that combine the characteristics of both. Hybrids can occur naturally, but crosses are often made deliberately by plant breeders to produce plants with better yield, improved flowering or vigour, or improved disease resistance.

of two ragwort species that grow on the volcanic slopes of Mount Etna and was brought to Britain in the 1600s by a plant collector and first recorded at Oxford Botanic Garden in the late 1700s. It then escaped the garden, spread along the city’s ancient walls, and reached Oxford railway station by the 1830s. There were reports at the time of its fluffy seeds swarming into train carriages and wafting along the tracks, and so the plant spread throughout the rail network, reaching London, records suggest, by 1867. It’s now a common sight alongside railway lines and on pavements across Britain.

Back in Brixton, a few steps on from the ragwort is native Hypochaeris radicata (cat’s ear), which is dandelion-like with a characteristic rosette of bristly leaves. I crouch down again and peer through my hand-lens at a tiny black pollen beetle hidden among the florets. As well as beetles, composite flowers like these attract wild bees and hoverflies – as I watch, a common carder bee duly arrives. The insect forages briefly, then flies off towards the pit around a nearby street tree where Senecio vulgaris (groundsel) and Stellaria media (chickweed) – both common garden weeds – are thriving. In the 1800s both of these plants were collected by the poor and sold to owners of caged birds, including goldfinches. It’s appropriate then, that I can hear goldfinches twittering from the treetops in a nearby car park.

I’ve come to Brixton to test out a route for a pavement-plant walk I’ll lead in a couple of days’ time. Doing my reconnaissance too far ahead is high-risk. In the intervening period a council’s street-cleaning team might swoop in and remove all of the fascinating plants I was hoping to point out. That would be a shame as today’s trip is proving productive. In the first 20 minutes of my ramble on the backstreets of South London, I record 30-plus species of wild plants. Some, like the chickweed and cat’s-ear, are native plants as common in the countryside as they are in town, while introduced Oxford ragwort occurs more in urban areas. A greyish tuft of downy leaves on a low wall reveals itself to be Laphangium luteoalbum (Jersey cudweed). Part of the daisy family, it’s one you’d be extremely lucky to find anywhere outside of an urban environment. While previously confined to the Channel Islands and eastern England, Jersey cudweed seeds are thought to have hitch-hiked to London in sand and aggregates imported from northern Europe. It has rapidly increased in the capital during the last 25 years and is starting to turn up in other towns and cities, too.

Laphangium luteoalbum (Jersey cudweed). Rare in the wild in Britain until 2000 but has increased 50-fold since, primarily in cities

Jersey cudweed may be an early arrival but there are other pioneering plants that usually beat it to a new pavement. Mosses and a tiny cushion-forming flowering plant with needle-thin leaves, Sagina procumbens (procumbent pearlwort), often pop up first and here they fill cracks between paving slabs below the cudweed. When seeds and spores arrive – whether wind-blown, transported on feet, in bird droppings or tyre treads – not all of them find what they need in the pavement cracks. But successful pioneers like these mosses and pearlworts appear to be able to germinate with the scarcest amount of moisture and nutrients

To grow well, plants need a wide range of nutrients in various amounts, depending on the individual plant and its stage of growth. The three key nutrients usually taken up from the soil are nitrogen, phosphorus and potassium. Plants also need carbon, oxygen and hydrogen to make carbohydrates — their main energy source. Carbon and oxygen come from the air as carbon dioxide, while hydrogen is drawn from water absorbed by the roots. Other important soil nutrients include magnesium, calcium and sulphur. Most garden soils contain enough of these nutrients to support healthy plant growth.

. As their tiny cushions form, a little more moisture is retained in the crevice and organic matter begins to collect, enabling a broader spectrum of plants to thrive. Invertebrates move in, both on the plants and in the soil beneath them. Within the space of a year or so, a whole new ecosystem is created.

Those plants lucky enough to escape the herbicidal efforts of street cleaning are able to form ephemeral ecosystems, such as this Epilobium species (willowherb), Conyza sumatrensis (Geurnsey fleabane) and Sonchus oleraceus (sowthistle)

I am endlessly drawn to these pavements and their assemblages of plants and animals. I’ll never stop marvelling at the fascinating species I find and how they may have arrived here. One street can host wild plants from continental Europe, the Middle East, Africa, South Asia, Southeast Asia and the Americas.

I cross to the opposite pavement where clumps of Corydalis lutea (yellow corydalis) dot the wall. I suspect it escaped from a garden nearby where it is growing in profusion. Like pavement cracks, wall crevices offer opportunities for plants. Walls provide warm dry habitats for ant colonies too, and corydalis seeds, rich in fats, attract ants. The insects haul them along the crevices to their colonies, discarding them, ready to germinate, once the fatty material has been consumed.

The surface of the wall is warm to touch. As well as scarce nutrients and water, pavement plants have elevated temperatures to contend with, as city centres can be up to nine degrees warmer than the surrounding countryside. This urban heat island effect is caused by a blend of factors, including hard surfaces absorbing and radiating heat. It’s probably this phenomenon alongside climate change that’s causing a shift to more Mediterranean species in London, not only in our gardens but on our streets. As well as long-established and deliberately introduced plants such as ivy-leaved toadflax and yellow corydalis growing wild, we’ve unintentionally imported newer arrivals – among them Urtica membranacea (Mediterranean nettle). Then there’s the cushion-forming Polycarpon tetraphyllum (four-leaved allseed), which is thought to be native in the Channel Islands and the south-west. These two species are both thought to have hitch-hiked to our cities in the pots of Mediterranean herbs and specimen trees imported from southern Europe and are now popping up on London’s streets.

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Polycarpon tetraphyllum (four-leaved allseed)

Many of the plants that grow – and thrive – in these unlikely locations have arrived on Britain’s streets in much the same way, as stowaways in imported soils. Further along the road I spot another example: a robust, thigh-high plant with inconspicuous chaffy groundsel-like flowerheads is growing on

Transferring young plants from one container to a slightly larger one, where they will have more room to grow and fresh potting compost. This encourages continuous, healthy growth.

the inside edge of the pavement. It’s one of several South American fleabanes on our streets. Close-up, I can see it’s Erigeron sumatrensis (Guernsey fleabane). A South American species, it was first recorded from Guernsey in 1961, and had made it to Essex by 1974. It is gradually spreading upwards but is still rare in northern Britain, Wales and Ireland.

Once wild plants – whether native, introduced, or hitchhikers – have reached our city streets and started to spread, survival is still a challenge. 

Not everyone is a fan of greenery between paving stones or along walls, and pavements up and down the country are regularly stripped of plant matter or inundated with herbicides. These little pavement plants are welcomed by botanists, but for some people they’re unfortunately perceived as a sign of urban decay. Responding to residents, local councils vary in their tolerance for wilder pavements beyond the essential removal of plants that block drainage or pose trip hazards. High streets tend to be scoured of greenery, but backstreets may receive less attention. It’s here I spend countless hours admiring these wonderfully resilient specimens.

Despite all the challenges faced by urban plant life, it rarely takes long to find interesting plants to point out to the groups I lead. They enjoy the diversity of plants and the stories behind them, regardless of how much they know in advance. I’d suggest, however, that it is gardeners who have the most to learn from the plants we find on our pavements. Greener streets provide a network linking our urban gardens with parks and other green spaces which is great for plant, animal and fungal diversity. The hoverflies and wild bees pollinating your fruit trees and ladybirds chomping aphids on your roses can make use of these green corridors to thrive and spread. Seeds from wild plants and associated invertebrates provide food for urban birds – the same birds that visit your garden to pluck caterpillars from your favourite plants.

The ecology of street plants can be informative and useful for gardeners. On an otherwise plant-free pavement, wild plants growing under a pub’s dripping hanging basket remind you to only water where you want plants to grow. Those that thrive on dry pavements suggest resilient choices for our warming climate. Plant communities around street trees illustrate the ecological principle that low levels of nutrients mean greater plant diversity – tree pits with shallow, low-nutrient substrates support a community of low-growing plants, whereas those regularly visited by dogs and doused in their nitrogen-rich excretions are often dominated by just one or two tall grasses. Translate this principle to your garden, and you have a useful reminder that to nurture a more sustainable wildflower

A term generally applied to non-woody, flowering plants that are natural to a particular area and grow there without human assistance. More accurately, British wildflowers normally applies to UK natives including plants introduced into the wild before 1500.

area, you’re best off with low-nutrient soil.

Looking out for street plants is a different – and thoroughly enriching – way to experience our cities, often against a backdrop of some of our most familiar man-made landmarks

Urban nature needs the help of gardeners, too. One plant I see in every British town and city is Buddleja davidii (butterfly bush), and as I finally make my way back to Brixton high street, I spot it growing on walls and roofs along the back of the shops. Brought to Britain as a garden plant from China in the 1890s it has since spread rapidly through urban environments. Good news for the bees and butterflies that enjoy its nectar

Sweet liquid mainly produced by flowers to attract pollinators. Honeybees make honey from nectar.

, less so for those tasked with maintaining our transport infrastructure. There’s a significant annual cost to removing it from buildings and our rail network, where it destroys masonry. This is also true of removing Reynoutria japonica (Japanese knotweed) from brownfield sites and Impatiens glandulifera (Himalayan balsam) from urban waterways. To help stop more species becoming invasive

Invasive plants are those that grow vigorously, spread rapidly and can out-compete other plants. Native, non-native and cultivated plants can all be invasive.

, gardeners can report early signs of invasiveness in ornamental plants to the citizen science project, Plant Alert. RHS members can also contact the RHS Advisory team for further advice on potentially invasive plants.

Gardeners have long known how important gardens are for wildlife, and entomologist Jennifer Owen helped to convince ecologists and conservationists of the value of urban gardens, too. She began recording everything in her Leicester suburban garden in 1972, and her RHS book Wildlife of a Garden – published in 2010 and reissued earlier this year – listed the 2,500 plants and animals she found, including 166 native flowering plants and 20 species of insects new to Britain. Recent horticultural trends – such as tolerating untidy corners, having naturalistic planting and introducing wildflower patches – could make our urban gardens more valuable and might inspire managers of verges, housing estate lawns, urban parks and cemeteries to follow suit. 

Using a hand-lens gives Amanda a glimpse into the microscopic world of some of the smaller street plants, such as this Parietaria judaica growing from the cracked pointing between bricks

As well as an increasing appreciation of the value of urban gardens, attitudes to wildlife on city streets seem to be changing, too. Legislation already requires local authorities to protect and enhance biodiversity

The variety of living organisms (plants, animals, fungi and microorganisms) in a particular environment. Boosting the biodiversity of your garden has many benefits, including supporting wildlife, improving soil health and reducing the likelihood of pest and disease problems.

. And in July 2025 Natural England, The National Lottery Heritage Fund and the National Trust launched Nature Towns and Cities, which aims to bring the benefits of nature and green space to everyone in the UK. A year on, there are 19 live funded projects in the UK, from Portsmouth to Bradford in England, to Fife in Scotland, Torfaen in Wales, and Belfast in Northern Ireland. Birmingham and Plymouth are now Nature Cities and Bournemouth, Poole and Christchurch are Nature Towns. Projects like these mean our urban environments could soon be greener and more varied. Good for plants, good for wildlife, and good for gardeners.

The plants I see when I visit an unfamiliar city reflect its climate, social and industrial history – even the tastes of local gardeners. Some of the plants I spot in London are common across England – shepherd’s-purse, for example – but visiting Belfast, I saw Senecio inaequidens (narrow-leaved ragwort) more often than Oxford ragwort. And Cardiff is the only city so far where I’ve noticed polypody ferns in branches of street trees, and in Edinburgh I found rare Viscaria vulgaris (sticky catch-fly) growing by a pavement in Holyrood Park. Talking with botanists from different parts of the country about urban plants, I’ve heard a cousin of red deadnettle – Lamium amplexicaule (henbit deadnettle) – is making inroads in Norwich. And a tiny relative of Galium aparine (goose grass) – pink-flowered Sherardia arvensis (field madder) – grows in pavement cracks in Merseyside. On top of everything else, these wild-growing plants enhance our understanding of a town and the communities who live there. They add colour and vitality to the tapestry that is a town’s history.

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Capsella bursa-pastoris (shepherd's-purse). A common pavement plant that's proto-carnivorous. The seeds produce a sticky mucus that captures and breaks down tiny invertebrates, thus releasing nutrients for the plant

Skills in identifying wild plants are key to valuing and protecting our urban biodiversity, and gardeners have a head start. Your garden is a great place to begin learning, before widening out to your street and neighbourhood beyond. Across these islands, amateur botanists already record urban plants to submit to the Botanical Society of Britain & Ireland, but there are areas where records of wild plants are scarce.

“This could change the way you see our cities for good,” I warn participants at the start of my pavement-plant walks. “Once you start noticing plants on streets it’s really hard to stop.” I suggest to the group that we can be depressed by consumerism, traffic and litter, or we can focus on and value the tenacious, fascinating and often attractive plants that have found a niche on our streets and contribute to caring for them, so that our wild pavements can be there for everyone to enjoy.