On a side street in the 11th arrondissement, just east of where the boulevards thin out into the working grain of the city, someone has been at the foot of a plane tree with a trowel. The square metre of earth that used to be bare and compacted — the dog-fouled, cigarette-stubbed default of a Parisian tree pit — is now a thicket of sage, hollyhock and something woody and self-seeded that nobody planted on purpose. A small enamel plaque, screwed to the bottom of the trunk by the Ville de Paris, says the bed is gardened under a permis de végétaliser — a “permit to make green”. It is a licence, in other words, to garden a piece of the public street.
The plaque is doing more work than it looks. It marks the point where the most photographed climate-adaptation idea in Paris — the headline forests, the 170,000 trees, the depaved squares — meets the part that does not photograph well at all: the slow, unglamorous business of getting a city of two million people to tend the thing once it is planted.
A permit to garden the street
The permis de végétaliser launched in the summer of 2015, under the first Hidalgo mandate, as a deliberately low-stakes instrument. Any resident could apply to plant and maintain a defined patch of public space — a tree pit, a strip of pavement, a wall base, a planter where open ground was impossible. The catch, and it is a revealing one, is that the licence is rarely granted to an individual. Most permits are issued to a collective: an association, a school, a neighbourhood council, a business, or simply a group of residents. The city, in effect, was not handing out gardening rights so much as outsourcing a maintenance contract to whoever would sign for it. The licence runs for a minimum of three years; the applicant supplies plans and photographs, the municipal teams run a feasibility check, and a plaque follows.
It is tempting to read the scheme as ornamental, and much of it is. But the logic underneath is the same logic driving the expensive end of the programme. Paris is one of the densest capitals in Europe, built in mineral — Haussmann’s stone, zinc roofs, sealed courtyards — and during a heatwave the city bakes harder and cools slower than the countryside around it. The urban heat island is not an abstraction here; it is the reason a flat under the zinc on the sixth floor becomes uninhabitable in July. Every square metre of unsealed, planted ground is a small withdrawal from that stored heat. The permit is the cheapest unit of the same campaign that, at the other extreme, costs ten million euros a square.
The forests that made the news
That expensive end is where the cameras went. Re-elected in 2020, Hidalgo committed the city to planting on the order of 170,000 trees by 2026, to converting a rising share of public space to green, and to a long-horizon target of roughly 40 per cent vegetated cover by 2040. The most legible promise was a handful of forêts urbaines, “urban forests”, to be dropped into emblematic mineral sites in the centre: the forecourt of the Hôtel de Ville, a square by the Gare de Lyon, the Place de la Bourse, the Place de Catalogne near Montparnasse, and others. The pitch was that a dense stand of trees could lower local summer peaks by several degrees where a roundabout or a forecourt now radiates heat.
The Place de Catalogne arrived first and roughly intact. A traffic roundabout was torn up and replaced, by the city’s own count, with around 470 trees — oaks, cherries, hornbeams — at a cost approaching ten million euros. It is a real depaving of a real piece of central Paris, and it is the kind of thing that visiting delegations are taken to see. But the full slate did not survive contact with the city. Several of the announced sites were quietly dropped or relocated; the Gare de Lyon and Opéra-area forests gave way to substitutes elsewhere. The headline number of forests turned out to be more provisional than the announcements implied.
Planting is the easy, photogenic half of the work. The hard half is the decade of watering, weeding and replacing that nobody cuts a ribbon for.
Permis de végétaliser programme, Ville de Paris
Where the Miyawaki method met the kerb
Some of the smaller plantings borrowed a fashionable technique: the méthode Miyawaki, named for the Japanese botanist Akira Miyawaki, in which native saplings are packed at high density so that competition drives fast, resilient growth. The method has become a kind of green shorthand across European cities, and Paris reached for it too. But botanists have been blunt about how loosely the label has been applied. A true Miyawaki micro-forest means very dense plantings of small native stock; several Parisian schemes that flew the name did not really meet the definition. At Porte de Montreuil, on the city’s eastern edge, a much-publicised micro-forest has struggled, with reports of dying stock and the spread of ailante, an invasive exotic, into the gaps.
This is the honest texture of the programme, and it is worth holding onto. A city can announce a planting target and hit it on paper, and still find that a meaningful share of what went into the ground does not thrive — because the soil under a Paris pavement is poor, because the watering regime slips, because the species was wrong, or because the political incentive ran out the moment the press release went out. Planting is the easy, photogenic half of the work. The hard half is the decade of watering, weeding and replacing that nobody cuts a ribbon for.
Which is exactly what the permit is for
Read against that, the modest permis de végétaliser starts to look less like decoration and more like the city’s answer to its own maintenance problem. A municipal team cannot water every tree pit in Paris through a heatwave. A resident with a key to the water and a stake in the hollyhocks can. The permit converts a passing enthusiasm into a three-year obligation and a plaque with a name on it — a way of distributing the dull, continuous labour that decides whether greening survives its second summer.
The limits show in the figures the city is candid about. By early 2022, some 2,500 permits had been issued across Paris — and by the programme’s own reckoning a large share, on the order of four in five, had since been abandoned. The volunteer gardener moves, tires, or simply stops; the bed reverts. That attrition rate is not a scandal so much as a description of how voluntary urban stewardship actually behaves. It is the same attrition the headline forests face, only visible at the scale of a single tree pit instead of a square.
The schoolyards as the steadier bet
The part of the Paris programme that may outlast all the others is the least street-level of them. Since 2018 the city has been running its cours oasis — “oasis schoolyards” — depaving and greening the playgrounds of its schools and reopening many of them to the neighbourhood during heatwaves as local cool islands. The stated ambition is to treat the bulk of the city’s roughly 650 schoolyards over a long horizon reaching toward mid-century, recovering on the order of seventy hectares of sealed ground. The scheme has been studied as a nature-based heat-adaptation case across Europe, and it has a structural advantage the volunteer tree pit lacks: a school is a permanent institution with a caretaker, a budget line and children who will still be there next July.
That contrast is the quiet lesson of the Paris decade. The forests photographed well and proved partly fragile. The permits scaled cheaply and shed most of their gardeners. The schoolyards, neither glamorous nor spontaneous, may be the durable core — because they attached the greening to an institution that has to keep showing up. A city can plant 170,000 trees. Whether it has 170,000 trees in 2036 is a different question, and the answer turns less on the planting than on who, years from now, is still holding the watering can.
What the plaque really promises
Back on the side street in the 11th, none of this is legible from the pavement. There is a tree, a thicket of sage gone slightly to seed, and an enamel plaque the colour of the city’s street furniture. The gardener is not named; the brief reportage temptation is to invent a retired couple out-planting City Hall, and the truth is duller and better. Somewhere is a collective, an association or five neighbours, who once filled in a form and now, more often than not, will keep at it through one more dry August — or won’t, in which case the bed will quietly go back to dust and the plaque will outlast the plants it was meant to protect.
That is the unromantic shape of citizen greening in a dense old capital: not a heroic substitution of volunteers for the state, but a negotiation about who carries the maintenance, settled one tree pit, one schoolyard, one ten-million-euro square at a time. Paris has been honest enough, in its own data, to show how much of it slips. The European cities now copying the permit would do well to copy that honesty too — and to budget, from the start, for the watering can rather than the ribbon.
Sources: Ville de Paris (paris.fr) — permis de végétaliser programme pages and open-data permit register (opendata.paris.fr); Ville de Paris tree-planting and forêts urbaines commitments 2020–2026; Place de Catalogne urban-forest project; cours oasis programme (Ville de Paris, since 2018) and European case-study coverage via the European Environment Agency and URBACT; reporting on the Porte de Montreuil micro-forest and the méthode Miyawaki; The Conversation, Actu-Juridique and France 3 Régions coverage of the urban-forest rollout.
