São Paulo nurseries bring the city’s rare and forgotten trees back to life

“One of the greatest pleasures I had when I came here was telling my friends, ‘Today I planted 5,000 fig tree seeds,’” says Yacov Kilsztajn. “Planting seeds here at the nursery is one of the actions that has the greatest impact when we think about urban afforestation. We’re working with seeds that are very small, but each one that germinates can become a huge tree.”

Kilsztajn is a biology student and intern at the Harry Blossfeld municipal nursery, in the São Paulo metropolitan region. He holds out a pot with seeds so small they look like grains of sand, and asks me how many seeds there are. Six hundred, I guess; he says there are 60,000. Not all of them will grow into trees.

“Species with lots of small seeds tend to have a lower germination rate than species with larger seeds,” he says. Each one that germinates, however, will have the potential to become a fig tree (Ficus organensis) up to 25 meters (82 feet) tall.

São Paulo’s municipal nurseries produce a combined 1.5 million seedlings a year; the Harry Blossfeld facility has been in operation since 1969.

Specializing in the native flora of the city of São Paulo, including trees from the Atlantic Forest and Cerrado biomes, the nursery cultivates an “Orchard of Delights,” featuring 39 species of fruit trees that produce cambuci (Campomanesia phaea), guabiju (Myrcianthes pungens) and other fruits that rarely make it onto the dessert platters of São Paulo residents.

Rare trees such as jacarandá-da-Bahia (Dalbergia nigra), Euplassa cantareirae and cambucá (Plinia edulis) — not to be confused with cambuci — are also a favorite of the nursery, which cultivates 22 species that are at threat of extinction.

With 190,000 seedlings available and a further 86,000 seedlings in tubes (smaller seedlings in the development phase), the nursery produces more than 200 species of trees that endure in the squares and streets of Brazil’s most urbanized city.

A nursery of solutions

“A tree nursery is a water nursery,” says Mariana Grimaldi as she walks through a boulevard of well-formed seedlings. An agronomist and one of the people in charge of the Harry Blossfeld nursery, Grimaldi says urban tree planting helps recharge aquifers and prevent erosion and flooding.

Her colleague and fellow agronomist, Guilherme Amaral, says public landscaping “combats heat islands, improves air quality, reduces noise pollution, contributes to emotional and physical well-being, connects green areas and attracts wildlife, among other benefits.”

São Paulo, the largest city in the Americas, has three municipal nurseries: the Manequinho Lopes nursery in Ibirapuera Park, the Arthur Etzel nursery in Carmo Park, and the Harry Blossfeld nursery in Cemucam Park — technically located in the municipality of Cotia, but part of the São Paulo metropolitan area.

The seedlings that these nurseries grow are used for landscaping squares and streets, for enriching the city’s parks, and also for urban reforestation initiatives, such as the Bosques de Conservação project, which grows mini-forests in areas with dense traffic, such as ring roads and areas close to the Marginal Tietê highway. The idea is to create up to 4.5 hectares (11.1 acres) of reforested land, each small patch named after a bird — such as the Tuim Forest, named for a tiny green parrot, and the Curicaca Forest, after a native ibis species — and specific trees to attract the chosen bird.

Through the municipal department of education, schools also benefit from the seedlings. The department’s partnership with the NGO Formigas-de-Embaúba has already coordinated the collaborative planting of almost 10,000 trees in São Paulo’s Unified Educational Centers, which serve underprivileged areas of the city.

Thinking about native species and biological diversity is fundamental when producing seedlings for urban tree planting. As well as restoring the ecosystem and rescuing the original species, it provides diverse food that attracts native wildlife, which in turn contribute to the reforestation effort.

“You can make this conversation about ecological corridors by working with public landscaping,” says Felipe de Oliveira, who oversees the municipal nurseries for the city’s environment department. He says these green corridors attract nocturnal fauna in particular: “At night, on major roads, you don’t have such a high flow of cars. So you’ll have small animals and small rodents.”

Oliveira says the movement of wildlife brings nature-based solutions to help restore the environment. Seeds that cling to an animal’s feather or fur can travel to another location, just as fruit can be ingested and their seeds dispersed elsewhere via the animal’s droppings, allowing the plants to spread across a wider area.

“I think the idea is to think of the city as a conservation area too,” says Kilsztajn, the biology student. “Urban afforestation isn’t just for beauty, it’s not just ornamental. It also has an ecological impact on both the city and the surrounding area: the impact of flora conservation.”

Rare and forgotten seeds

The work in the nursery comprises several stages. It all starts with the seeds: collecting, sorting, identifying and processing, which is the task of extracting the seed from the fruit. They’re then planted in trays, tubes, and finally pots as they grow bigger. The nursery workers care for them in greenhouses, then later put them through a period of so-called hardening, in which they’re exposed to more direct sunlight and weather, in order to strengthen them.

The Harry Blossfeld nursery spans 50 hectares (124 acres), of which 11 hectares (27 acres) are dedicated to growing seedlings. The rest of the area is forested and provides the seeds. Workers also collect seeds from the surrounding Cemucam Park and, in return, populate the park with native seedlings grown in the nursery.

Collecting seeds is an important part of the job, and field trips are appreciated. On their days off, at lunchtime, or even on a bike ride, the nursery workers have a keen eye for collecting seeds of new species. But not just any species: they have to be species native to the area of São Paulo.

“We map it out. Every collection we make, we mark a GPS point and note the phenological state: whether the tree has flowers, fruit, ripe seeds or green seeds,” Kilsztajn says.

The most sought-after seeds are those of native species that provide important environmental services but aren’t considered of high economic value or are threatened with extinction.

While commercial nurseries are necessarily focused on maximizing the economic value of their seedlings, municipal nurseries can focus on species that are relevant to the municipality’s biodiversity, valuing them and making them known, perhaps even generating new demand.

With this focus on rescuing forgotten flora, municipal nurseries end up being spaces for science, with privileged information on the collection, processing, planting, germination rates and behavior of various species.

“We’re in the process of finalizing a guide to seeds and seedlings that compiles all the work we do with germination tests. This way, people can get to know different species that are typical of the region and also see what is the best method for germinating them,” says Amaral, the Harry Blossfeld agronomist.

Canela-sassafrás (Ocotea odorifera), for example, was once heavily exploited for its timber and is today threatened with extinction. The idea is to test its germination in the nursery and work on producing seedlings to reintegrate it into urban forestry.

“It’s a species of historical use,” says João Carlos Candido Santos, a nursery intern and historian. “It was often used to make sea vessels. Its smell slows down rotting. It was also consumed as a drink. You would put the [bark] chips in brandy and the drink would have a high commercial value.”

Cambuci is another of the nursery’s experiments. Largely gone form the urban landscape today, the fruit is a symbolic species of the city that even has a neighborhood named after it. The aim is to produce an orchard of the species with genetic diversity from various places across São Paulo, so that the seedlings are resistant and can occupy the streets once again.

All those interviewed for this story agree that the intensive use of exotic, nonnative trees in urban areas isn’t the way to grow urban forests. “I can be in the north or I can be in the south of the country, and the tree planting is somewhat standardized,” Amaral says. “There are too many exotic species and not enough diversity.”

Just as each region has its own soundscape, governed by the local birds, the nursery team wants to invest in a floristic identity for São Paulo. They argue that it’s not only the birds, but also the trees that should mark the flowering of the local identity.

 
Banner image: Yacov Kilsztajn, an intern at the Harry Blossfeld Nursery, carries a fig tree seedling (Ficus organensis) that could potentially grow into 25-meter-tall (82-foot) tree someday. Image by Sibélia Zanon for Mongabay.

This story was reported by Mongabay’s Brazil team and first published here on our Brazil site on Oct. 16, 2023.