At 73, this former food industry executive describes himself as a "visionary" - even if he knows he has often been taken for a "madman".
With his own money, he built the first green belt in Sao Paulo, lining up dense rows of trees 3,2 km long and 100 metres wide in Penha, a district in the east of Latin America's largest city.
The green strip is wedged between two busy roads in Brazil's economic capital of 12 million people, in a previously abandoned area where crack users roamed.
She was completely transfigured by a white-haired man wearing thick, square-rimmed glasses who resembles Carl, the hero of the Pixar cartoon "Up" (2009).
He does not hesitate to hug tree trunks and even to speak to them, "in a whisper", so as not to be taken "once again" for a madman by passers-by.
Birds and native species
Originally from Promissao, a town located about 450 km from Sao Paulo, the former executive embarked on this adventure in November 2003, after a walk with his wife in his neighborhood of Penha, where gray was the dominant color.
"I wanted to leave a legacy to the city that welcomed me. I started planting trees and I never stopped," he told AFP.
The impromptu arboriculturist never asked for formal permission from the authorities, but the town hall inaugurated this new green space five years later, in 2008, naming it "Tiquatira Linear Park".
The park now has 32.000 trees, and Hélio da Silva has also planted 9.000 more in the surrounding area. More than 160 varieties are represented, most of them native species. He also makes sure to plant at least one fruit tree out of every twelve, to attract birds.
According to the city hall, 45 species of birds have been seen in this urban forest which is full of pau-Brasil (a tree with red wood emblematic of Brazil), palm trees and cedars.
"There are more than a thousand jequitibas, a Brazilian tree that lives for more than 3.000 years," says Hélio da Silva with pride, who devotes more than 6.000 euros a year to this passion. It takes him about ten minutes to plant each new cutting.
According to experts, green spaces in urban areas are fundamental to absorb heat and improve air quality.
And in Sao Paulo, a sprawling city that is already heavily polluted, the air quality has deteriorated dramatically in recent weeks, making it one of the worst in the world, due to smoke from the forest fires that are ravaging Brazil.
These fires are being fueled by extreme drought, particularly linked to climate change.
"Bringing life"
This oasis is therefore beneficial for the neighbourhood, who affectionately greet Hélio da Silva when he walks by, photo albums in hand to show curious onlookers the evolution of the place, from wasteland to green belt.
"Look how he has transformed this degraded area. It's splendid, I come here for walks all day long," rejoices Angela Maria Fiorindo Pereira, a 69-year-old retired teacher.
Himself retired since 2022, the septuagenarian spends a good part of his time surveying the places to identify new spaces. His objective: to reach 50.000 trees planted.
Volunteers sometimes come to lend a hand to this man who has had to undergo two shoulder operations, digging up the earth to plant new specimens.
"I want to bring life here," he says, determined to follow through with his vocation, which is written on his business card: "Hélio da Silva, tree planter."