Hong Kong (CNN) -- On the roof of a 21-story office building in Hong Kong's eastern district sits a grassy patch of hope that agriculture can thrive even in one of the world's most congested spaces.
The rooftop is managed by local entrepreneur Osbert Lam, who spends his afternoons amid the rows of planter boxes teaming with long beans, tomatoes and herbs that occupy his urban farm.
Juxtaposed with the Hong Kong skyline, his rooftop stands out like a dab of verdant paint on a canvas of concrete, and is just one of the growing numbers of farms sprouting atop the city's skyscrapers.
"There are a lot of empty, leftover rooftops that could easily be transformed into fields," said Lam, who started the Eco-Mama rooftop farm just six months ago.
For just $15 per month, Lam rents out toolbox-sized planter boxes to businessmen, elderly couples and families alike, and even runs horticulture classes. He uses imported soil from Germany to fill his planters and lets the humid, subtropical climate do the rest.
"I found that the veggies loved the environment on my rooftop," Lam, a 50 year-old father of two, said. "Here, there is good sun from the South, good air from the East and we're above the crowded streets."
And that's precisely the premise behind urban farming: integrating farming practices into the urban ecological and economic systems. This is done through direct interaction with the urban environment and incorporating resources, such as using organic waste for compost or utilizing portions of urban structures for farming projects.
Lam's farm -- a humble 2,000 square feet -- is one of an estimated 300 urban farming projects that now occupy Hong Kong's high-rises, joining the broader, global movement of food sustainability projects in densely populated urban settings.
"Twenty years ago, locals thought that the soil here was dirty," said Simon Chau, founder of the Produce Green Foundation, which manages Hong Kong's first urban farm in Tsuen Wan. "Now, after 20 years, people have started to realize that it is rewarding and meaningful to grow something themselves and to eat it."
But unlike the burgeoning urban farms of New York, Tokyo and Taipei, the city's budding urban agriculture movement continues to run into problems as it tries to expand, according to architecture and engineering professor Sam Hui of the Hong Kong University.
"If we really want to see the maximum benefits of urban farming here (in Hong Kong), we have to create more rooftop farms," said Hui, whose research focuses on sustainable agriculture and green roof use.
Hong Kong is one of the most densely populated cities in the world, with roughly 7 million residents living in an area of just over 400 square miles, according to government census data.
The population density makes it difficult to have urban farms anywhere other than on the rooftops of the city's soaring skyscrapers, Hui said. The city also has strict guidelines on development, allowing just 25% of the land to be built upon.
Urban agriculture's growing pains
Aside from the logistical challenges of planting crops in a city void of open space, many of Hong Kong's urban agriculture pioneers are frustrated by the local government's lackluster support toward urban farming.
Chan Choi-hi, a member of the Hong Kong district council, said the Hong Kong government must do more to build a viable urban agriculture policy.
"There is no policy, no vision (and) no idea of how to do urban farming in Hong Kong from the government. It's not even in the agenda," Chan said. "So first of all, we are trying to push this idea from an economic angle."
The economic angle, Chan said, may be the only way to convince top government officials to invest time and resources into bolstering Hong Kong's nascent urban farming movement.
But according to the numbers, that argument has proved to be a tough sell.
Farming makes up just a fraction of Hong Kong's current GDP and employs just 4,700 Hong Kong residents, less than one tenth of a percent of the population, according to Hong Kong's Agriculture, Fisheries and Conservation Department (AFCD).
The government has set up roughly 30 urban farm plots across the territory, but many are found in the middle of highways or in remote locations of the city, rendering them both unattractive and inconvenient for residents, Hui said.
Although a submitted statement to CNN by the AFCD said that they encourage "leisurely farming," support and services "are primarily geared for income-earning or food-producing local farmers."
The movement, therefore, has taken longer to catch hold in Hong Kong.
Outside of convincing politicians, Chau said Hong Kongers themselves have historically been resistant to the idea of farming as a suitable pastime.
"It is the lowest of our traditional caste system. In traditional Chinese culture, if you're good at nothing else, you work on the farm," Chau said. "Also, Hong Kong is a very money-minded place... land is also very expensive in Hong Kong, so people don't spend time worrying about growing their own food."
In light of the many challenges facing urban agriculture in Hong Kong, Lam is optimistic that his vision of a megacity capped with green gardens will be realized.
"I believe you can build a community of rooftop farmers here in Hong Kong," Lam said. "We can be very mobile, farming on rooftops across the city."